ArticlePDF Available

Recommendations for Future Post-mission Neuro-musculoskeletal Reconditioning Research and Practice Post-mission Exercise (Reconditioning) Topical Team Report

Authors:
  • KBR for European Space Agency

Abstract and Figures

This report outlines the work undertaken by the ESA Post-Mission Exercise (Reconditioning) Topical Team to ascertain and provide details of evidence based postflight reconditioning programmes, looking beyond current practices in readiness for future longer duration missions. The report covers gaps in knowledge and proposes how terrestrial rehabilitation practices, and research and development, may have lessons for post-space mission reconditioning. Information is presented to help protect astronauts from the potential long-term effects of their occupation, i.e. periodic but regular deconditioning and exposure to microgravity, and how these factors might impact the long-term risk and incidence of osteoporosis, osteoarthritis, and other conditions related to deconditioning or premature ageing. The report culminates in conclusions and recommendations for the future activities that the European Space Agency and the wider space community might pursue in preparation for long duration exploration missions.
Content may be subject to copyright.
Post-mission Exercise (Reconditioning) Topical Team Report
1
30th June 2016 (updated 11th Feb 2017)
European Space Agency
‘Post-mission Exercise (Reconditioning)’ Topical Team
FINAL REPORT
Recommendations for Future Post-mission Neuro-musculoskeletal
Reconditioning Research and Practice
Topical Team Members
Maria Stokes PhD GDPhys FCSP (Co-Editor of TT Report and Co-Chair of TT)
Simon Evetts PhD FRAeS (Co-editor of TT Report)
Joern Rittweger PhD MD (Co-Chair of TT)
Tobias Weber PhD (Secretary of TT)
Nick Caplan PhD
Lieven Danneels PhD
Dorothee Debuse PhD MSCP
Julie Hides PhD MPhty St BPhty FACP
André Kuipers MD
Gunda Lambrecht Dip Physio
Nora Petersen Dipl.-Sportwiss
Jonathan Scott PhD
Andrew Winnard BSc BSc MSc MCSP
Jochen Zange PhD
External Expert Authors
Daniel Barry MD PhD
David Beard GDPhys MCSP MA MSc, DPhil
Jacob Bloomberg MD
Dieter Blottner PhD
Filippo Castrucci MD PhD
Jonathan Cook PhD BSc GradStat
Rebecca Cusack MD FFICM
Anna-Maria Liphardt PhD
Carly McKay PhD
Anja Niehoff PhD
Gita Ramdharry PhD MCSP
(see Appendix A for author affiliations)
Post-mission Exercise (Reconditioning) Topical Team Report
2
Contents
EXECUTIVE SUMMARY (page 3-7)
Chapter 1. Introduction (pgs 8-10)
Chapter 2. Objectives (pg 11)
Chapter 3. Current Knowledge of the Effects of Time in Space and Countermeasures on the
Neuro-Musculoskeletal System and Fluid State (pgs 12-24)
Chapter 4. Astronaut and operations expert perspectives on effects of microgravity influencing
postflight reconditioning (pgs 25-33)
Chapter 5. Knowledge Gaps (pgs 34-43)
Chapter 6. Filling the Knowledge Gaps Reconditioning Research on Astronauts and
Microgravity Analogues (pgs 44-51)
Chapter 7. Filling the Knowledge Gaps Lessons from Parallels with Terrestrial Rehabilitation
and Challenging Environments (pgs 52-59)
Chapter 8. Research Methodology (pgs 61-67)
Chapter 9. Conclusions (pgs 68-70)
Chapter 10. Recommendations (pgs 71-72)
APPENDICES
Appendix A Topical Team and Report Authors, and Acknowledgments (pg 73)
Appendix B - Standard ESA international space station exercise countermeasures programme
(pg 75)
Appendix C Astronaut Perspective Case Reports (pg77)
Appendix D Papers from Report published in Supplement of Musculoskeletal Science and
Practice journal (pg 83) updated 11th February 2017
Appendix E List of Abbreviations (pg 84)
BIBLIOGRAPHY (pg 86)
Post-mission Exercise (Reconditioning) Topical Team Report
3
EXECUTIVE SUMMARY
Scope
This report outlines the work undertaken by the ESA Post-Mission Exercise (Reconditioning)
Topical Team to ascertain and provide details of evidence based postflight reconditioning
programmes, looking beyond current practices in readiness for future longer duration missions.
The report covers gaps in knowledge and proposes how terrestrial rehabilitation practices, and
research and development, may have lessons for post-space mission reconditioning.
Information is presented to help protect astronauts from the potential long-term effects of their
occupation, i.e. periodic but regular deconditioning and exposure to microgravity, and how these
factors might impact the long-term risk and incidence of osteoporosis, osteoarthritis, and other
conditions related to deconditioning or premature ageing. The report culminates in conclusions
and recommendations for the future activities that the European Space Agency and the wider
space community might pursue in preparation for long duration exploration missions.
Objectives
The Topical Team aimed to produce recommendations for future post-space mission
reconditioning research and practice. Inflight countermeasure (CM) programmes do not prevent
deconditioning completely and structural and functional deficits in many of the body’s
physiological systems are still present on return from long duration spaceflight. The
musculoskeletal and neuromuscular (neuro-musculoskeletal, including neuromotor control)
systems are especially affected and have a strong relevance to the practice and effectiveness of
reconditioning. Until an inflight solution is found that prevents space deconditioning entirely, the
need exists to optimise post-mission reconditioning to correct neuro-musculoskeletal changes
and reduce the risk of musculoskeletal problems, and promote return to preflight function, as
well as ensure good long-term health.
The objectives of the work to be pursued by the Topical Team were as follows:
1. Identify acute and chronic neuro-musculoskeletal problems experienced by astronauts as a
result of undertaking short and long-term space missions.
2. Identify risk factors affecting successful reconditioning following spaceflight.
3. Identify and document existing strategies for correcting deconditioning related to neuro-
musculoskeletal problems.
4. Anticipate challenges to reconditioning likely to result from longer (exploration) missions.
5. Document potentially useful reconditioning strategies to prevent and/or treat these long
duration mission-derived challenges.
6. Produce a report including recommendations for research prioritisation to enhance
postflight reconditioning of ESA astronauts.
The approach taken to achieve these objectives and produce the deliverable, this report,
involved developing a collaborative team of scientists, medical operations experts and
astronauts. Tasks involved identifying knowledge gaps, including a systematic literature review
and consulting with those who experience and witness effects on astronauts, and then exploring
ways to fill these gaps, using optimal research methodologies for optimal designs and outcome
measures in astronaut research studies. The report also indicates how evidence based
terrestrial practices could be adopted directly for the benefit of postflight reconditioning, given
that some research questions are not possible to test in the astronaut population.
Post-mission Exercise (Reconditioning) Topical Team Report
4
Science / Operations Collaboration
The breadth of expertise of the authors of this report spans several scientific and clinical
disciplines, including physiotherapy, medicine, sport and exercise science, physiology,
psychology, statistics and research methodology. Patient and public involvement (PPI) is
fundamental to the feasibility and success of terrestrial medical research. Therefore, the
involvement of astronauts and operations experts was considered integral to this report, as well
as to future research aimed at improving the efficiency, effectiveness and impact of
reconditioning activities. Astronaut experiences and views provide valuable insight into how their
care might be optimised, and aids decision making concerning research priorities. The pre-, in-
and postflight medical issues reported in this document illustrate aspects where past crew
health management was lacking and that current and future practice can benefit from
considering the perspectives of astronauts themselves and those working closely with them.
Knowledge Gaps
Responses to microgravity, inflight CM and postflight reconditioning after missions to the
International Space Station (ISS) are better understood for some of the body’s systems and
functions than others. For example, aerobic performance can be well maintained with effective
CM and can recover rapidly postflight but muscle weakness, particularly of postural muscles
protecting the back, is still a significant problem on return to Earth.
The gaps in knowledge which will need to be ‘spanned’ to adequately embark upon Long
Duration Exploration Missions (LDEM) involving planetary surface excursions, e.g. on Mars, are
explained (Chapter 3) and specific research questions posed (Chapter 5). A potential new
challenge is a reduced CM programme during transit (e.g. due to limited equipment space;
need to conserve resources; reduced motivation for compliance with exercise on prolonged,
isolated missions than current ISS missions etc.). Crewmembers may therefore be required to
undertake a reconditioning (preconditioning) programme specifically to prepare for planetary
surface excursions, either in orbit or on the surface, to ensure safe, effective performance of
tasks. It is expected, therefore, that the challenges to the human body and effects of micro- and
reduced gravity will be greater after longer duration missions, but the magnitude, duration and
emphasis of effects on the different systems and specific parameters are difficult to anticipate.
It is also not possible to know whether any cumulative effects will occur after repeated long
duration missions, which could compromise the long-term health of the astronaut, so research
will be vital to understand recovery processes after reconditioning between missions.
Filling Knowledge Gaps
Solutions proposed for filling the knowledge gaps focus on reversing musculoskeletal deficits
and improving performance using physical and psychological strategies. Accurate, routine
reporting and monitoring of musculoskeletal and psychological status will be vital to understand
the body’s adaptations to long duration spaceflight and postflight recovery. Delphi studies are
suggested to capture practices of medical operations specialists and to determine future study
designs from experts in different areas of terrestrial rehabilitation research. Long-duration bed
rest offers an opportunity to conduct exercise reconditioning research more systematically.
Translation of evidence-based clinical and research practices from terrestrial rehabilitation and
sports settings, which are not possible to investigate in astronauts, may provide valuable
lessons for postflight reconditioning. Parallels with terrestrial populations include clinical
Post-mission Exercise (Reconditioning) Topical Team Report
5
conditions involving deconditioning (e.g. low back pain, neurological disorders and critical care
patients) and elite sports training (preconditioning and reconditioning exercise programmes to
optimise performance, prevent injury (including overuse microtrauma and acute trauma) and
promote musculoskeletal health, and psychological strategies to enhance motivation and
adherence to exercise programmes). The benefits of exchanging knowledge and expertise
between the space and terrestrial environments are reciprocal. Terrestrial scenarios are
discussed briefly in this report, whilst more detailed accounts will be published in a Supplement
of the Musculoskeletal Science and Practice rehabilitation journal (Appendix D).
Potential solutions to the difficulties in human space medicine research are proposed by
considering methodologies that can draw from robust terrestrial designs and practices, and
alternative approaches to address the unique aspects of space science which demand special
consideration (e.g. small numbers and the need for accurate, reliable outcome measures).
Conclusions
The identified effects of microgravity and factors that affect the efficacy of post-mission
reconditioning include:
Loss of muscle mass and strength, as well as neuromuscular changes.
The vulnerability of the muscles of the lumbopelvic region.
Risk of bone fractures and spinal injuries due to bone loss and changes in spinal
structures.
Effects on cartilage, which are unknown and have yet to be explored (research in
progress)
The effect of the Advanced Resistive Exercise Device (ARED). This CM has reduced
declines in physiological and physical function but not entirely mitigated them, e.g.
muscle strength can still be reduced by 20%; orthostatic tolerance and neuromuscular
control are still poor for the first few days and performance of functional tasks requiring
dynamic control is adversely affected.
Motivation to comply with the exercise programme and adhere to exercise after
supervised reconditioning.
Continued access to reconditioning facilities and support during the postflight period.
Competing commitments and available time for reconditioning.
A systematic review of exercise CM during bed rest, focusing on the lumbopelvic muscles
showed that:
Lack of consistency in outcome measures limited the ability to make meaningful
comparisons between studies and between CM interventions
No CM intervention has thus far been successful in limiting or preventing all
musculoskeletal changes seen in the lumbopelvic region, including spinal morphology,
muscle physiology and function.
The current ESA postflight reconditioning programme is based on principles from the best
evidence available from space (currently minimal) and terrestrial research:
Early intervention is centred on retraining motor control, balance and posture
Exercises progress to trunk strengthening once lumbar postural control is restored
More strenuous general resistance and cardiovascular training follow.
Post-mission Exercise (Reconditioning) Topical Team Report
6
Potential reconditioning strategies need to be investigated to prevent and/or treat the effects
of longer duration exploration missions (LDEMs), involving surface planetary excursions,
e.g.:
Knowledge is needed of short-term effects of LDEMs to determine factors that will
influence the ability to perform postflight reconditioning and the effectiveness of
exercise programmes
Programmes are required that use physical and psychological strategies for postflight
reconditioning are required upon return to Earth
Preconidtioning to prepare for planetary surface excursions are also needed.
Intelligence on any long-term effects of repeated LDEMs, (e.g. osteoporosis,
osteoarthritis) must be gathered.
RECOMMENDATIONS
The following recommendations for future post-mission reconditioning research and practice are
presented in relation to the objectives and are detailed further in Chapter 10. Research priorities
will need to be determined by involving relevant space and terrestrial communities of scientific
experts (basic and rehabilitation sciences) and users (astronauts and Medical Operations
specialists) in an initial Delphi study. The Delphi research method involves gaining consensus
on a specific topic from relevant experts through a series of surveys (Section 8.2.6).
It is recommended that research be conducted on:
1. Effects of spaceflight on neuro-musculoskeletal function (Objective 1)
More crew focused research is needed;
o on adaptation processes to improve inflight CM and postflight reconditioning strategies
o on the possible long-term effects of space travel (e.g. osteoporosis, osteoarthritis)
2. Postflight effects (Obj 1) and risk factors impacting on reconditioning (Obj 2)
Routine (anonymised) systems are required to capture data on musculoskeletal problems
Use astronaut-specific personalised outcome measures
Use novel technologies to assess muscle status inflight to help improve inflight CM to
reduce postflight deficits.
3. Improving existing reconditioning strategies after ISS missions (Obj 3)
Multi-agency studies (quantitative and qualitative) are required for international consensus
and guidance on reconditioning practice, and future research priorities
Develop optimal reconditioning programmes - account for safe reloading; exercise dose,
duration, rest periods, timing; functional activities of daily living; psychological factors.
Obtain views of astronauts (using qualitative methods)
Synthesise and build on existing evidence from relevant terrestrial populations in clinical
specialties (e.g. back pain, neurology) and elite sports training
Evaluate effectiveness of current and new post-ISS programmes.
Post-mission Exercise (Reconditioning) Topical Team Report
7
Minimise injury and ensure safe exercise for postflight reconditioning programmes
o Establish re-loading protocols that minimise tissue damage (e.g. joint cartilage,
intervertebral discs, muscle injuries)
o Use movement screening tools to assess quality of movement pre- in-and postflight
o Develop tailored exercise programmes to re-educate movement control to protect joints
from abnormal or excessive loading during exercise.
Improve functional performance evaluation in postflight reconditioning
o Include functional tests relevant to activities of daily living.
Improve motivation strategies for complying with and adhering to postflight reconditioning
o Investigate links between behaviours preflight, inflight, and postflight
o Utilise astronaut experiences to inform motivation enhancement strategies
o Understand the therapeutic alliance to enhance reconditioning outcomes
o Draw from motivation and adherence strategies in elite sports.
4. Anticipating challenges to reconditioning from longer (exploration) missions (Obj 4)
and developing reconditioning and preconditioning strategies in preparation for
planetary surface explorations (Obj 5)
Develop inflight exercise CM that are less time-consuming, functional, enjoyable and
target multiple physiological systems simultaneously
Establish inflight monitoring procedures to inform preconditioning programmes and
determine readiness for safe and effective planetary surface excursions.
Develop equipment/hardware for inflight preconditioning programmes.
Bed rest studies to develop inflight preconditioning exercise programmes
Develop non-technology based preconditioning exercise programmes
Develop technologies for inflight monitoring of e.g. orthostatic intolerance, sensorimotor
function and functional performance using sensors with feedback to astronauts
Develop non-technology based exercises as contingency for equipment failure
Develop optimal postflight reconditioning exercise programmes
Identify and prevent potential barriers to ongoing health behaviours for designing mission
specifications and generating policies
Post-mission Exercise (Reconditioning) Topical Team Report
8
CHAPTER 1: INTRODUCTION
1.1. The Goal of Postflight Reconditioning is:
For future exploration class missions, an additional phase of postflight reconditioning will be
required following deep space cruise to destination, to enable surface exploration. Such
reconditioning will need to incorporate specific functional exercises to prepare crewmembers
for safe and effective undertaking of mission objectives. Hence, this aspect of conditioning is
termed preconditioning (Figure 1.1). Optimal reconditioning and preconditioning
programmes have yet to be established.
Figure 1.1: Optimal conditioning of astronauts over one long duration mission cycle
involving surface exploration
NMSK = Neuro-musculoskeletal System
PC = Preconditioning; ICM = Inflight Countermeasures;
SPE = surface planetary excursion
1.2 Purpose and Content of the Report
The negative effects of microgravity on neuro-musculoskeletal structures, physiology and
function are well documented for space missions up to six months (Buckey 2006; Clément
2011; Smith et al. 2012). Advances in technology and inflight exercise programmes have largely
mitigated these effects but not entirely, as impairments are still present on return to earth, e.g.
loss of muscle strength can be as much as 20% (Gopalakrishnan et al. 2010). As missions
increase in duration and extend to unfamiliar environments beyond Low Earth Orbit (LEO) and
involve planetary surface excursions (Long Duration Exploration Missions; LDEM) e.g. on Mars,
challenges to the human body and requirements for effective postflight reconditioning need to
be better understood by learning from existing knowledge and further research.
To trigger and complete physical re-adaptation processes to Earth gravity
after long-term exposure to reduced gravity during space flight, to return
astronauts to their preflight status.
Post-mission Exercise (Reconditioning) Topical Team Report
9
The term reconditioning is used rather than rehabilitation, as astronauts are not patients with
pathology but rather have made normal physiological adaptations in response to exposure to
time in space (adaptation occurs in these circumstances as an aspect of muscle plasticity which
is the ability of a tissue or organ to adapt to a given environment e.g. 1G or µG). Indeed,
feedback from an astronaut was that rehabilitation implied recovery from addictive behaviours,
whereas reconditioning was a more appropriate term.
Whilst normal adaptation takes place in space, on returning to Earth (or landing on the Moon or
Mars), these changes could be seen as “maladaptation” and thus need to be minimized by
inflight CM. Postflight recovery requires the astronaut to readapt to gravity on Earth to achieve
normal function as safely and as rapidly as possible. Reconditioning therefore needs to consider
both the short-term requirements to return the astronaut to activities of daily living and readiness
for future missions (Figure 1.1), as well as the astronaut’s long-term health (Figure 1.2).
Figure 1.2: Potential long-term neuro-musculoskeletal (NMSK) function and health of
crewmembers over repeated long-duration mission cycles
PC = Preconditioning; ICM = Inflight Countermeasures
PFR = Postflight reconditioning
The present Topical Team for Post-mission Exercise (Reconditioning) was tasked with setting
priorities for research to develop optimal postflight reconditioning programmes for astronauts
returning from future long duration exploration space missions. Both the short-term and longer-
term reconditioning requirements for crewmember health have been considered.
Gravity plays a fundamental role in physiotherapy, particularly in re-educating posture and its
control through antigravity muscle activity (Massion 1998), and use of gravity in graded manual
muscle strength testing methods (Hislop et al. 2013). The acceleration levels experienced by
astronauts range from up to 9Gx (felt briefly, horizontally through the chest) during Soyuz
ballistic re-entry, to 1Gz (9.81 m/s²) on Earth (feetward) to 0G (microgravity) in orbit with
variable reduced gravity experienced on planet surfaces, e.g. lunar gravity 0.17Gz (1.63 m/s²)
or on Mars 0.38Gz (3.71 m/s²). Effective and safe performance during surface planetary
excursions on Mars following long duration flights at 0G will require preparation through specific
exercise programmes on board prior to landing, which the authors of this report have termed
preconditioning (a term also used in sport, as are prehabilitation and preactivation).
Post-mission Exercise (Reconditioning) Topical Team Report
10
The ability to conduct definitive studies of postflight reconditioning using conventional research
designs, such as randomised controlled trials (RCTs), is restricted by factors such as insufficient
numbers, availability of astronauts (which can be restricted for follow-up testing for reasons
such as distance of home base from study location) and the use of non-standardised exercise
programmes between agencies. Knowledge is largely gleaned from bed rest studies and by
drawing on similarities with conditions seen in terrestrial populations, e.g. low back pain (LBP),
where the distribution of trunk muscle atrophy is similar to that in microgravity (Hides et al. 2007;
Pool-Goudzwaard et al. 2015). Another field suitable for comparison with the effects of
microgravity is that of ageing (Biolo et al. 2003) but the greater challenges ahead that result
from longer missions and new environments may benefit from drawing on challenges faced by,
and rehabilitation strategies used in, other terrestrial clinical conditions involving deconditioning,
such as neurological and intensive care conditions. At the other end of the spectrum,
reconditioning of astronauts may benefit from adopting the physical and psychological strategies
for achieving optimal performance used by athletes in elite sports. To enable these parallels to
be drawn and broaden the knowledge base relevant to postflight reconditioning, the Topical
Team recruited additional experts in relevant fields to contribute as authors of this report (see
authors in Appendix A). More detailed accounts of the reciprocal benefits of these parallels are
published in a Special Edition of the rehabilitation journal Musculoskeletal Science and Practice,
including a systematic review conducted as a basis for this report in relation to lumbopelvic
rehabilitation (Winnard et al, 2017a in Appendix D).
An advantage of drawing on evidence from terrestrial populations is that knowledge is typically
more advanced than that from space research, due to availability of larger study populations
and more stable environments, enabling robust research designs. However, the present report
explores research methodologies for optimal designs and outcome measures in astronaut
studies as well. It also indicates how evidence based terrestrial findings could be adopted
directly for postflight reconditioning practice, given that some research questions are not
possible to test in the astronaut population, due to the difficulty in employing complex designs
requiring large numbers to test dose (intensity) effects of exercise over different postflight time
periods.
A key feature of the present report is the involvement of astronauts and Medical Operations
specialists in the Topical Team to gain their unique perspectives of the challenges that influence
postflight reconditioning. Throughout the report, the need for input from astronauts and
operations specialists at all stages of future research is stressed, mirroring the practice of PPI
now considered vital in terrestrial research in some countries
(http://www.nihr.ac.uk/funding/pgfar-patient-and-public-involvement.htm). This approach
ensures research questions are relevant to users (astronauts and those involved in their care)
and that studies are designed to develop protocols that are feasible to produce findings that will
have an impact on everyday practice and the long-term health of astronauts.
This report therefore proposes recommendations for future research and practice for postflight
reconditioning based on current knowledge from scientific literature on astronaut and bed rest
studies, and relevant terrestrial populations, as well as insights from the perspectives of
astronauts, space Medical Operations and terrestrial clinical experts. The content of the report
is intended to inform priority setting for research, provide information that could be used in the
calls for research and provide a useful resource for researchers investigating those topics.
Post-mission Exercise (Reconditioning) Topical Team Report
11
CHAPTER 2: TOPICAL TEAM OBJECTIVES
The objectives of the work to be pursued by the Topical Team were as follows:
2.1 Identify acute and chronic neuro-musculoskeletal problems experienced by astronauts
as a result of undertaking short and long-term space missions.
2.2 Identify risk factors affecting successful reconditioning following spaceflight.
2.3 Identify and document existing reconditioning strategies for correcting deconditioning
related to neuro-musculoskeletal problems.
2.4 Propose the anticipated challenges to reconditioning likely to result from longer
(exploration) missions.
2.5 Document potentially useful reconditioning strategies to prevent and/or treat these long
duration mission-derived challenges.
2.6 Produce a report including recommendations for research prioritisation to enhance
postflight reconditioning of ESA astronauts.
Post-mission Exercise (Reconditioning) Topical Team Report
12
CHAPTER 3
CURRENT KNOWLEDGE OF THE EFFECTS OF TIME IN SPACE AND COUNTERMEASURES ON THE
NEURO-MUSCULOSKELETAL SYSTEM AND FLUID STATE
3. Introduction
The environment at the surface of the Earth is highly distinctive. It has nurtured the evolution
of life over millions of years and in turn life has refined itself to thrive in these exclusive
conditions. Therefore, since the beginning of human exploration above and below the surface
of the Earth, the primary goal has been the provision of conditions that approximate those
normally provided by nature. In space, this is provided by life-support systems which keep the
astronaut alive and by deconditioning CM which attempt to maintain terrestrial physical and
physiological function.
The human body does, however, adapt to novel environments. This capability is such that the
physical structure and function of many of the body’s tissues, organs and systems alter to
enable life to proceed in microgravity in an efficient and economical manner. The primary
systems affected are the skeletal, muscular, neuromotor, neurovestibular, cardiovascular,
endocrine and immune systems. Adaptations occur within hours to days for some systems,
but can take weeks to months or even longer for others. Inflight exercise CM programmes
mitigate these effects to an extent but deficits are still present on return to Earth and need to
be better understood to inform effective reconditioning.
Details are provided hereafter concerning the effects of exposure to the space environment on
the physiological systems that are pertinent to post-mission reconditioning. Findings from a
Systematic Review of the topic are incorporated into the chapter. The effects of microgravity
have been reported widely in the literature and in other ESA Topical Team reports (ESA
SP1281, 2005, Belavy et al 2016), and as such are only summarised here. This chapter
focuses on what is known about the status of the body after prolonged microgravity with and
without CM, in both the postflight period (after short and long duration space missions) and
after bed rest studies. The limited research on reconditioning after bed rest is then outlined.
3.1 Skeletal Muscle
In the absence of adequate CM, the decreased stimulus experienced during exposure to
microgravity causes muscles to atrophy and alters muscle morphology, with a resulting loss of
contractile mass and performance capability (Fitts et al. 2010). This loss reduces the speed
and strength of muscular contraction and thus leads to detriments in overall force and power
(Widrick et al. 1999). Alterations in muscle morphology for some muscles (e.g. soleus) are
characterised as a transition from Type I slow twitch to Type II fast twitch fibre types, a shift
away from aerobic and towards anaerobic capabilities (Fitts, Trappe 2010). This is similar to
the fibre-type conversion that occurs in spinal cord injury patients (Lotta et al. 1991). Most of
the muscle losses occur in anti-gravity muscles of the lower back, pelvis and lower limbs, with
a predominance of effect on extensors over flexors throughout the body (Danneels et al. 2000;
Hides et al. 2007).
Post-mission Exercise (Reconditioning) Topical Team Report
13
3.1.1 Lower Limb Muscles
Strength reductions may be 2 to 5% per week depending on the site and function of the
muscle, and CM use (Narici et al. 1989; Tesch & Berg 1998). Reductions in knee extensor
maximum strength of 15% have been found after 2 weeks of spaceflight (Gopalakrishnan,
Genc 2010) and 16% reductions in knee flexion strength are evident after ISS missions even
with today’s extensive CM programmes (English et al. 2015). Soleus peak power has been
reported to be 32% lower after 6 months on the ISS (Trappe et al. 2009).
Bed rest studies suggest that, in addition to morphology and function changes, prolonged
disuse in bed rest without CM resulted in altered molecular composition of the soleus
neuromuscular synapse (Salanova et al. 2011). They have also shown an imbalance in redox
mechanisms of postural skeletal muscle fibres (oxidative stress), which is a potential cause
of the disuse-induced muscle stiffness and fatigue seen after extended muscle inactivity in
various clinical settings (e.g., intensive care units; see Section 7.5), in bed rest, and also in
astronauts in space (Blottner & Salanova 2015; Salanova et al. 2013). Reconditioning of
redox mechanisms in skeletal muscle and neuromuscular properties (recovery of Homer
signal proteins involved in synaptic transmission), as well as global changes in the disuse-
sensitive skeletal muscle proteome (contractile to metabolism to signalling) and related gene
transcripts (transcriptome) have been achieved by resistive vibration exercise (RVE) during
and after bed rest (Salanova et al. 2015; Salanova et al. 2014). The novel findings from such
ground-based spaceflight analogue studies may help to find optimal CM protocols for
functional and structural (close-to-normal physiological) recovery postflight to nearly preflight
conditions.
Bed rest studies also indicate that for some muscles, in particular postural, a return to normal
function may take some time despite a return to normal activity and upright gravitational
loading (Belavy et al, 2008). The composite data from Skylab, Mir and Shuttle flights suggest
that the loss of lower limb muscle mass is exponential with the duration of flight (Fitts et al.
2000); however, with the addition of recent ISS findings it appears that this loss can be
minimised for some crew during six months on ISS with the current on-board exercise CM
programmes that incorporate ARED and the most recent treadmill, T2 (English, Lee 2015).
3.1.2 Paraspinal and abdominal muscles of the trunk.
Spinal extensor volume decreases have been reported to be greater than hip flexor (psoas
muscle) decline in astronauts (LeBlanc et al. 1995). A single case study by Hides and
associates (Hides et al. 2016a) revealed that the deep lumbopelvic muscles (transversus
abdominus and lumbar multifidus) were atrophied after a six month mission on the ISS. These
data are consistent with the findings of ESA operational measurements of crew on their return
from ISS missions (personal communication Lambrecht, ESA Physiotherapists). Although
bed rest is not a perfect model for spaceflight where astronauts can move freely, similar
patterns of muscle imbalance in the trunk muscles appear to occur in response to both
conditions (Hides et al. 2016a; Adams et al. 2003; Pavy-Le Traon et al. 2007). While some
muscles undergo the expected response of atrophy, such as the lumbar multifidus, erector
spinae and Transversus Abdominis, other trunk muscles, such as the psoas, rectus
abdominis and anterolateral abdominal muscles increase in size (Hides et al. 2007).
Overactivity of the abdominal muscles was verified in a bed rest study (First Berlin Bed Rest
Study [BBR-1}) using electromyography and activation of spinal extensor muscles changed
from tonic activation to a more phasic pattern that persisted for at least six months after re-
ambulation. These changes in muscle may impact the ability of the spine to distribute loads
Post-mission Exercise (Reconditioning) Topical Team Report
14
appropriately. Selective atrophy of spinal extensors and preservation of the flexors is also
seen in terrestrial individuals with low back pain (LBP) when compared to healthy controls
(Section 7.2.1). A recent study showed that 70% of astronauts suffered LBP inflight and for
those with a history of LBP prior to spaceflight, inflight prevalence was 100% (Pool-
Goudzwaard et al 2015). Most of this inflight LBP occurs early in the mission during acute
adaptation and resolves within 710 days. This separates the short-lived adaptive back pain
from the chronic degradative condition that can occur. The persistence of LBP postflight and
the associated muscle deficits are not well documented. It is unknown how far the results of
bed rest studies can be translated when interpreting microgravity-induced changes after
spaceflight.
3.2 Bone
Bone is lost in space and individuals can lose as much as a quarter of their bone mineral
density at selected skeletal sites within a 6-month mission (Vico et al. 2000). Bone is also lost
in unloading paradigms that are used as ground based space-analogues, such as experimental
bed rest (Rittweger et al. 2005) and experimental limb suspension (Rittweger et al. 2006). The
greatest bone losses, notably, have been observed after spinal cord injury (Wilmet et al. 1995).
The skeletal system is weakened through this demineralisation and atrophy, primarily in the
bones that are normally weight bearing on Earth e.g. the pelvis, femur and lower vertebrae
(Lang et al. 2004). The dynamic turnover of bone is altered towards a predominance of bone
resorption by the absence of the static loading present in 1G (Smith, Heer 2012), and by
reductions in the dynamic loading applied by impact and muscular contraction (Yang et al.
2015).
During a meta-analysis of the effects of spaceflight on bone Sibonga and colleagues (Sibonga
et al. 2007) highlighted that astronauts who participated in long duration flights aboard Mir and
ISS showed consistent loss of regional bone mineral content, with 92% experiencing a
minimum 5% loss in at least one skeletal site (e.g. the calcaneous or pelvis) and over 40%
experiencing a 10% or greater loss in at least one site (e.g. lumbar spine or femoral neck).
These losses occurred in spite of exercise regimens aboard the space stations (Sibonga,
Evans 2007). More recently with the advent of the ARED on ISS, losses of bone mineral density
in orbit have been reduced to acceptable levels in some subjects (Smith, Heer 2012) and in
experiments incorporating bisphosphonates a prevention of loss has been reported (Leblanc
et al. 2013). What still remains to be ascertained, however, is how bone structure is affected
and what bearing this has on bone strength characteristics.
Without or with minimal CM, however, early spaceflight findings indicate that load bearing
bones may lose 1 to 2% of their density per month for extended periods leading to clinically
relevant conditions in less than a year or two (Lang, LeBlanc 2004; LeBlanc et al. 2000). Bone
atrophy increases the hypothetical risk of fracture when returning to gravity conditions (return
to Earth, planetary exploration or hyper gravity flight conditions) and the time of post-mission
convalescence on Earth can be significant without the certainty of complete recovery
(Carpenter & Carter 2010).
If recovery from bone loss is not complete it could lead to osteoporosis, which is known to be
a predisposing factor for fractures (Kanis et al. 1994). The question arises whether bone loss
incurred during spaceflight will recover on Earth (LeBlanc & Schneider 1991). For the femoral
neck it has been demonstrated that bone mass recovers 1 year after space flight (Lang,
LeBlanc 2004; Lang et al. 2006), albeit with greater bone diameter, and thus with structurally
reduced energy absorbing capacity. In the distal tibia, recovery is in-complete at 1 year
postflight (Personal communication, L Vico, University St Etienne), and it is currently being
Post-mission Exercise (Reconditioning) Topical Team Report
15
studied whether full recovery is reached at later stages. Evidence from clinical observations,
however, suggests that full recovery of bone is linked to full functional reconditioning (Lang,
LeBlanc 2004; Lang, Leblanc 2006; Rittweger et al. 2011). Moreover, full recovery of tibial
bone loss has been demonstrated after 3-months of experimental bed rest (Rittweger &
Felsenberg 2009).
Taken together, the available evidence suggests that bone loss in astronauts will recover as
long as full functional reconditioning is achieved. Risk of fractures may not be substantially
increased in bone-deficient astronauts when they are relatively young; however, enhanced risk
of fracture must be expected when space-related bone loss persists into old age.
3.3 Stature
Reports from Shuttle and Skylab missions reveal that astronaut body-length may increase up
to six centimetres during missions (Sayson et al. 2013) . Increases in stature are also noted
during and after current ISS missions (Young & Rajulu 2011). This can have operational
impacts as EVA suits and capsule seats are individually tailored using stature as measured on
Earth. There may also be health impacts due to morphological changes, and it has been noted
that many astronauts suffer from LBP for a period of time on return to Earth (English et al.
2015).
Due to the absence of gravitational loading in space, the intervertebral discs, particularly the
nuclei pulposi, absorb more water than on Earth. This lengthens the spine and flattens its
curves, and is associated with moderate to severe LBP in the early stages of space flight
(Belavy et al. 2016; Kerstman et al. 2012). Reports of astronauts experiencing back pain in
space have been consistent with Wing and colleagues (1991) reporting incidence proportins
up to 68% and Pool-Goudzwaard et al (2015) reporting pain in 70% of those without a history
of LBP and 100% of those with a history of LBP. It has recently been postulated (Belavy et al.
2016) that the condition of overhydrated discs comprises a major risk factor for herniated discs
in astronauts on their return to earth, as illustrated by one of the astronaut case histories in this
report (Section 4.2.1). In order to relieve acute LBP in space, astronauts apply different
strategies, such as tucking themselves into a foetal position, taking pain killers, stretching
themselves or trying to compress the spine through loaded exercise on the treadmill or ARED
(Belavy et al. 2016; Kerstman et al. 2012).
Johnston et al. (2010) found that astronauts had a four-fold increased incidence of herniated
disc pulposus within the first year following spaceflight, compared with matched controls.
Sayson and Hargens (2008) suggested that LBP and disc injury in astronauts could be caused
by a range of factors linked to spinal lengthening and reduced loading. Belavy et al. (2016)
argued that the increased lumbar intervertebral disc herniation risk in astronauts was most
likely caused by long term disc tissue deconditioning which results from swelling of the discs
due to unloading during spaceflight.
3.4 Cartilage
Articular cartilage provides joint congruency and transfers and distributes forces, allowing for
normal joint movement. Cartilage is presumed to respond to mechanical loading and this
mechanism may play a key role in maintaining cartilage health (Andriacchi et al. 2004), 2004).
Although the effects of microgravity on bone and muscle have been studied extensively, little
is known about the effects of immobilization on human articular cartilage morphology and
composition in humans in response to a longer stay in microgravity. However, the question of
whether joints are still fully functional after several months in microgravity is essential for
astronauts’ health during space travel and especially for reconditioning after space flight.
Post-mission Exercise (Reconditioning) Topical Team Report
16
Current knowledge of immobilization effects on articular cartilage are based on a few studies
which have investigated the influence of mechanical unloading on articular cartilage in patient
cohorts (Hinterwimmer et al. 2004; Hudelmaier et al. 2006; Owman et al. 2014; Vanwanseele
et al. 2004; Vanwanseele et al. 2003).Unloading after spinal cord injury, ankle fractures or knee
surgeries provides an opportunity to analyse the effects of no or absent/reduced cartilage
loading on tissue integrity. In paraplegic patients after spinal cord injury, cartilage thinning of
up to 25% after 24 months has been observed (Vanwanseele, Eckstein 2004; Vanwanseele,
Eckstein 2003). Hinterwimmer and colleagues investigated the effect of 7 weeks of partial load
bearing after an ankle fracture on articular cartilage morphology in different knee
compartments (Hinterwimmer, Krammer 2004). The reported changes in articular cartilage
thickness for the different compartments ranged from -2.9 ± 3.2 % for the patella to -6.6 ± 4.9%
for the medial tibia. Hudelmaier and associates detected a reduction in patellar cartilage
thickness of 14 % but no changes at the tibia in a patient affected by 6 weeks of immobilization
after knee joint surgery (Hudelmaier, Glaser 2006).
Cartilage health of the lower limb joints has been investigated in microgravity analogue bed
rest studies. Fourteen days of bed rest reduced cartilage thickness at the knee, as well as
serum oligomeric matrix protein (COMP) concentrations (Liphardt et al. 2009). Furthermore, it
has been shown that COMP, matrix-metalloprotease-3 (MMP
1
-3) and matrix-metalloprotease-
9 (MMP-9), were sensitive to 5- and 21-days of bed rest. These results indicate that a cartilage
response to unloading can be seen after as little as 1 to 2 weeks of immobilization (Liphardt
2015) Applied CM in bed rest studies, such as vibration training with (Liphardt 2015) or without
(Liphardt et al. 2009) additional resistive exercise have not successfully compensated for the
effects of immobilisation on cartilage metabolism. The effects of microgravity on cartilage
health in humans are only just being investigated in ISS experiments.
3.5 Cardiovascular system.
With inactivity the cardiovascular system deconditions resulting in reductions in muscle mass,
metabolic enzyme levels, and the size and quality of capillary beds and mitochondria.
Decreases of circulating blood volume and ventricular stroke volume are also prevalent (Neufer
1989). The main effects of such deconditioning during spaceflight where exercise CM are sub-
optimal, include decreases in maximal aerobic capacity, increased heart rate for any given
level of exertion and orthostatic intolerance (Moore et al. 2014). The ISS CM programme
appears to be relatively effective, however, in preventing significant in- and postflight changes
of cardiovascular stability under low intensity physical conditions (Hughson et al. 2012).
Nine to 14 days of space flight have shown a 22% reduction in VO2max (maximum aerobic
capacity) (Levine et al. 1996). Reports of 80% of astronauts returning from ISS experiencing
greater than 6% loss of VO2max despite a rigorous CM programme are typical (Moore et al.
2010). These temporal cardiovascular fitness responses are typical of a 6 month ISS mission,
as outlined below (Section 3.8.7). The loss of oxygen carrying capacity contributes to the
observed limitation of exercise and work capacity seen under microgravity conditions
(Convertino & Sandler 1995).
1
MMPs are matrix degrading proteins
Post-mission Exercise (Reconditioning) Topical Team Report
17
3.5.1 Fluid Shifts
On entry to microgravity body fluids, principally the blood, move from the lower to upper
body. This shift leads to immediate changes in venous pressures across the body and
minor, possibly transitory, alterations in arterial pressure where for instance reductions of
between 8 and 10 mmHg for systolic, diastolic and mean arterial pressure have been noted
(Norsk et al. 2015). Stroke Volume is increased (+35%) by an augmented preload to the
heart, which when coupled with a relatively stable heart rate, can cause increases in cardiac
output (+41%) (Norsk et al, 2015). Within days blood volume becomes substantially
decreased. Some of these effects in the short to medium term may be linked with space
adaptation syndrome, in particular space motion sickness and mild cognitive impairment.
Although mean arterial blood pressure and central venous pressures (Buckey et al. 1993 &
1996) appear to be only mildly less than terrestrial standing values, microgravity induced
pressure equilibration across the body results in pressures in the upper body which are
greater in space than experienced when standing on Earth. It is becoming increasingly
evident that the association some of these changes have with intracranial pressure has the
potential to indirectly affect intraocular pressure and vision (Mader et al. 2011).
Postflight alterations in baroreflex response slopes correlate with reductions in
parasympathetic activity to the heart, an effect which is indicative of cardiovascular
deconditioning (Hughson, Shoemaker 2012) and may play a role in orthostatic intolerance.
Over a period of months in space the structure and function of the blood vessels of the lower
body and the heart alter (i.e. decondition), resulting in a poorer ability to react to stress
hormones and aid blood perfusion, contributing to excessive blood pooling in the lower body
and thus also to orthostatic intolerance on a return to Earth (Verheyden et al. 2010).
3.5.2 Orthostatic intolerance.
The inability to assume and retain the standing position under +1Gz is a multifactorial
consequence of cardiovascular deconditioning. Due to the risk of syncope (temporary loss
of consciousness due to fall in blood pressure), it is a major risk specifically during re-entry
in the Gz alignment through the atmosphere. The incidence of orthostatic intolerance
increases with space mission duration (Lee et al. 2015), and has been seen to be as high
as 64% for short missions (Buckey, Gaffney 1996) and up to 90% after long duration
missions (Vorobyov et al. 1983). Factors that may be involved in the aetiology of this
condition are blood volume (and the related reduction in red blood cell mass), baroreceptor
function and cardiac and smooth muscle structure and function (Lee, Feiveson 2015).
3.6 Neurovestibular and Sensorimotor Deconditioning
The neurovestibular/muscular systems are acutely affected by the loss of the gravity vector
resulting in transitory space motion sickness, decrements in oculomotor control, hand-eye
coordination, spatial orientation, and cognition during space flight missions and a
deconditioning of the proprioceptive system and associated structures for most crew (Center
2008). The systems decondition due to a chronic alteration in stimuli causing balance and gait
control detriments (Carpenter et al. 2010), and motion sickness for many, immediately on
return to a gravity environment.
Post-mission Exercise (Reconditioning) Topical Team Report
18
NASA’s Human Research Roadmap states that given that there is an alteration in
vestibular/sensorimotor function during and immediately following gravitational transitions,
manifested as changes in eye-head-hand control, postural and/or locomotor ability, gaze
function, and perception (https://humanresearchroadmap.nasa.gov/risks/risk.aspx?i=88 X).
There is a possibility that crew will experience impaired control of the spacecraft during gravity
transitions and during landing or decreased mobility during gravity transitions and following a
landing on a planetary surface (Earth or other) after long-duration spaceflight.
Astronauts can also suffer from disorientation, a loss of sense of direction and loss of postural
stability (Miller et al. 2010). Upon return astronauts must readjust to gravity and can experience
problems standing up, stabilizing their gaze, walking and turning, and retaining posture
(Clement et al. 2013; Bloomberg & Mulavara, 2003; also Section 4.2.2 , 4.2.1 and Appendix
C). The magnitude of sensorimotor disturbances after gravity transitions increases with
microgravity exposure, which is of particular relevance to long duration spaceflight (Reschke
et al. 1998). Such disturbances can impact operational activities including approach and
landing, docking, remote manipulation, extravehicular activity and egress (both normal and
emergency), and thus if not adequately handled, compromise crew safety, performance and
mission success (Paloski et al. 2008). It is believed that this sensorimotor deconditioning
results from inflight adaptive changes in central nervous system processing of information from
the visual, vestibular, and proprioceptive systems (Paloski et al. 1992). The absence of
muscular and joint proprioception has been shown to affect performance in several ways, and
plays a key role in determining the spatial motor frame of reference (Bard et al. 1995). The
loss in postural control has also been attributed to atrophy of the antigravity extensor muscles
and spindle sensitivity (Forth & Layne 2008).
Some interesting novel findings suggest that the neurovestibular system is also linked via
vestibulosympathetic reflexes to the musculoskeletal system (shown in an experimental animal
model lacking neurovestibular input and ß-adrenergic receptor signalling). This could be an
additional inflight CM protocol to ameliorate muscle and bone loss to circumvent impaired
performance control observed in astronauts during spaceflight (Levasseur et al. 2004; Luxa et
al. 2013; Ray 2001; Vignaux et al. 2015) and thereafter.
These changes, seen over hours, days, weeks and months, are a positive response to the
space environment, in particular the absence of gravity. However, they are problematic if
gravity is re-imposed during planetary excursions (increasing risk of injury), when Earth related
achievement standards are necessary inflight e.g. during emergencies, or on return to Earth.
3.7 Current International Space Station Exercise Countermeasures Programme
3.7.1 The current inflight exercise CM programme followed by ESA is delivered primarily
through the use of three exercise devices: a cycle ergometer, a treadmill and a
resistance training machine, supplemented by the addition of other CM such as isotonic
saline fluid loading immediately before departing ISS. The programme is divided into
three phases; an Adaptation Phase (1430 d), a Main Phase (120 d) and the
Preparation for Return Phase (1430 d) immediately before un-docking for re-entry.
The Adaptation Phase provides the crew with the opportunity to familiarise themselves
with the on-board exercise equipment and their programme. The Main Phase aims to
provide a regular and appropriate physiological stimulus in an attempt to maintain
aerobic capacity, muscle strength, neuromuscular control and bone mass/strength at
preflight levels. The Preparation for Return Phase emphasises neuromuscular control
and functional movement patterns to ease the transition back to a gravity environment.
More details on the ISS inflight CM programme can be found in Appendix B.
Post-mission Exercise (Reconditioning) Topical Team Report
19
3.8 Physiological systems positively affected by countermeasures in the ISS exercise
programme and bed rest studies
The goal of postflight reconditioning is to correct any physiological deficits incurred during
space travel and thus return a crewmember to their preflight status. As such, the focus of
current reconditioning is driven by the deficits astronauts present with postflight, the presence
and magnitude of which reflect the summation of the well-documented adaptive responses
to long-duration spaceflight and the efficacy of the current inflight CM.
3.8.1 The Musculoskeletal System
3.8.1.1 Major Muscle Groups
In ground-based analogues of microgravity, exercise CM have proven to be largely
effective in preventing deleterious changes in skeletal muscle during unloading,
while nutritional interventions in isolation offer little protection (Blottner et al. 2014).
Early inflight studies of skeletal muscle during ISS LDM, where crew had access to
the TVIS, CEVIS and the iRED exercise devices suggested that, in combination,
these devices resulted in better maintenance of muscle mass than the systems used
on the Shuttle-Mir missions (LeBlanc, Schneider 2000). Despite this, they still
observed a loss of muscle volume at the thigh (4-7%) and calf (10-18%), with greater
losses in the soleus muscle compared with the gastrocnemius (Gopalakrishnan,
Genc 2010; Trappe, Costill 2009), although some of this loss was as a result of
cephalad fluid movement on entry to microgravity. During recovery from flight,
Trappe and colleagues reported approximately 50% of the loss of muscle volume
was restored by R+19, whereas overall reduction in muscle performance was
sustained, and in several cases exacerbated on R+13 (Trappe, Costill 2009).
Comparable detailed studies of muscle function after LDM when crew have had
access to a treadmill (T2), cycle ergometer (CEVIS) and, importantly the ARED, are
limited, but published data suggest further improvements in muscle volume/function
protection with the current CM programme:
Gains (compared to previous losses in the pre-ARED era) in lean body mass
(Smith, 2012);
Less reduction in total body mass (Smith, Heer 2012);
Smaller magnitude of losses in knee muscle strength vs. pre-ARED era (-7 to -
15% vs. -9 to 20%, (Center 2008; English, Lee 2015).
Despite these improvements, however, there has been minimal positive effect on
ankle and trunk strength (English, Lee 2015) and, on an individual level, many
crewmembers continue to lose in excess of 20% muscle strength, which fails to meet
the current permissible outcome limit for returning crewmembers.
3.8.1.2 Postural Muscles
As demonstrated by the sensitivity of the soleus muscle to space flight, postural
muscles are considered to be particularly sensitive to prolonged unloading due to
their tonic, continuous activation for normal function in gravity. Muscle atrophy is
known to occur around the lumbar spine during spaceflight, but not in the cervical
extensor muscles (LeBlanc, Schneider 2000) and crewmembers with access to
ARED show marginally less decrease in spinal muscle extensor strength compared
with the iRED era (Center 2008). However, despite this apparent improvement using
Post-mission Exercise (Reconditioning) Topical Team Report
20
ARED, the most recent published data (albeit with small subject numbers) from ISS
suggests that atrophy of key spinal stabilising muscles is still evident after LDMs
(Hides et al. 2016a).
3.8.2 Bone Mineral Density
Although the combination of suitable aerobic training devices on ISS and appropriate
CM programmes has been largely successful at countering the loss of aerobic capacity
which occurs during LDMs, it has not been successful at countering inflight bone loss
and despite the inclusion of weight-bearing exercise (T2) and moderate intensity
resistance exercise (iRED), (Lang, LeBlanc 2004; Sibonga, Evans 2007). However, with
the transition to ARED, recent preliminary evidence suggests that some crewmembers
with access to ARED and with adequate energy and vitamin D intake display little or no
difference between pre- and postflight measures of bone health (Smith, Heer 2012), with
no difference between male and female astronauts (Smith et al. 2014). More recently
still, ARED use has been seen to be associated with significantly less bone loss
measured at the trochanter, total hip and pelvis than during the pre-ARED era, with a
trend for better preservation at the lumbar spine and femoral neck (Sibonga et al. 2015).
3.8.3. The Spine
Ground-based analogues of prolonged microgravity in which the spine is no longer
subjected to an axial load have provided evidence of an increase in stature, changes in
spinal curvature and an increase in volume of the intervertebral discs (IVD) (Belavy et
al. 2011; Cao et al. 2005). These changes may persist for a prolonged period following
re-loading (Belavy et al. 2012; Belavy et al. 2011). In comparison, however, there is little
inflight data to corroborate this. Stature certainly increases, but no differences in sagittal
plane disc area or lumbar spine length are reported (LeBlanc et al. 1994) and only now
are inflight studies of the effect CM programmes have on IVDs underway
2
. Considering
initial data from these experiments, Sayson and colleagues (Sayson 2015) report the
following observations:
Variable (between crew and different spinal levels) IVD water content changes, but no
significant changes in disc height;
Decreased functional extensor endurance and decreased (-14 to -17%) cross-sectional
area of lumbar and cervical muscles;
Increased spine stiffness in flexion and increased spine straightening due to 11%
reduction of lumbar lordosis;
No reductions in the negative effects (e.g. lower glycosaminoglycan concentration), on
quality and/or anterior wedging of vertebral bodies, or endplate irregularities.
2
http://www.nasa.gov/mission_pages/station/research/experiments/944.html and
(http://www.nasa.gov/mission_pages/station/research/experiments/872.html).
Post-mission Exercise (Reconditioning) Topical Team Report
21
3.8.4. Cartilage
Since the risk of cartilage degeneration as a result of prolonged immobilization and
microgravity is not known, the potential for exercise to counteract the initiation of cartilage
degeneration in a healthy joint can only be estimated at present. Furthermore, cartilage
tissue has not been properly examined during postflight reconditioning, thus leading to the
current scarcity of data. Inflight studies of human cartilage health are only now in progress
(CARTILAGE
3
) so the postflight status of astronauts’ articular cartilage health remains
unknown and cartilage status is not considered in the current CM programme.
3.8.5. Aerobic Capacity
Following ISS flights, crewmembers exhibit elevated heart rate responses to submaximal
exercise initially, with a return to preflight levels occurring 1 month after return to Earth
(Moore et al. 2014; Moore, Lee 2010). With the current inflight CM exercise programme,
VO2peak decreases on average to 82% of pre- flight levels by Flight Day 15, but partially
recovers during the remainder of the mission (Moore, Downs 2014). As such, on return to
Earth, VO2peak is typically only 15% below preflight levels immediately after flight and
recovered by approximately 50% after 10 d and completely after 30 d back on Earth
(Moore, Downs 2014; Moore, Lee 2010). This is comparable to previous investigations
from short (814 d) duration flights (Levine, Lane 1996) and illustrates that how unlike
bone loss in space, aerobic capacity does not continue to degrade (with adequate CM)
and is probably related to subacute CV changes and possibly biomechanics, etc. Although
those with a higher preflight VO2max appear more susceptible to inflight deconditioning
(despite following the same CM programme), their postflight absolute level of aerobic
capacity remains both acceptable and still greater than those who were less fit preflight.
In addition, a closer examination of the individual crewmember data indicates that 50%
actually maintain or even increase their aerobic capacity during their missions, and that
those who attained higher exercise intensities during CM sessions were less susceptible
to a loss of function (Moore, Downs 2014).
3.8.6. Functional Performance
To understand how physiological changes affect functional performance, a pre- and
postflight testing regimen, the Functional Task Test (FTT), was developed. (Arzeno et al.
2013; Ryder et al. 2013; Spiering et al. 2011). It was found that for Shuttle, ISS and bed rest
(control and exercise) subjects, functional tasks requiring a greater demand for dynamic
control of postural equilibrium (i.e. fall recovery, seat egress/obstacle avoidance during
walking etc.) showed the greatest decrement in performance after microgravity. Functional
tests with reduced requirements for postural stability (i.e. hatch opening, ladder climb,
manual manipulation of objects) showed little reduction in performance. These changes
were paralleled by similar decrements in sensorimotor tests designed to specifically assess
postural equilibrium and dynamic gait control. Bed rest subjects who performed an
integrated high intensity interval-type resistance and aerobic training programme while in
bed showed significantly improved lower body muscle performance compared to bed rest
controls and spaceflight subjects. However, resistive and aerobic exercise alone was not
sufficient to mitigate decrements in functional tasks that require dynamic postural stability
3
http://www.nasa.gov/mission_pages/station/research/experiments/872.html
Post-mission Exercise (Reconditioning) Topical Team Report
22
and mobility, and point to the need for the addition of balance/sensorimotor adaptability
training to current CM systems.
Bed rest subjects experienced similar deficits as spaceflight subjects, both in functional tests
with balance challenges and in sensorimotor tests designed to evaluate postural and gait
control, indicating that body support unloading and proprioceptive alterations plays a central
role along with vestibular disturbances postflight. Additionally, ISS crewmembers who
walked on the treadmill with higher pull-down loads had enhanced postflight performance
on tests requiring mobility. Taken together, the spaceflight and bed rest data point to the
importance of supplementing current inflight exercise CM with balance training that requires
coordination and integration of proprioceptive feedback i.e. motor control training
(exercises for performance of controlled, good quality movement), and body loading
information. This suggests that other systems responsible for balance and postural control
(proprioception, mechanical loading, muscle afferents, etc.) may be suitable targets for
inflight CM development. Therefore, preflight sensorimotor adaptability training (as in injury
prevention programmes in elite sport; see Section 7.4.2) can be supplemented with inflight
balance and treadmill training to enhance overall adaptability of balance and gait control
enabling rapid recovery of function postflight.
Crewmembers who exercised on the ARED on ISS have shown less decrement in postflight
postural stability and agility scores compared to subjects using the Intermediate Resistance
Exercise Device (iRED) (Wood et al. 2011), which offered less resistance than ARED. The
Functional Fitness Tests (FFT; not part of the FTT) includes practical exercise tests such
as push-ups, pull-ups, bench press, and leg press, and, for all but one measure,
crewmembers with access to ARED fared better than their iRED counterparts, with either
small postflight decrements or even improvements after spaceflight (Center 2008).The
increased body loading during ARED exercises may have provided greater postural
challenges during exercise improving postflight balance performance. Another key factor in
performance training is motor control training and warrants attention in all phases of
astronaut training (see Sections 4.2.2, and 7.2.2).
3.8.7. Orthostatic Intolerance
As mentioned in section 3.5.2, crewmembers undertaking long duration mission (LDM),
such as 6 month ISS missions, have a significantly greater chance of experiencing postflight
orthostatic Intolerance (OI) than those undertaking Short Duration Missions (SDM) (4-18
days), and their cardiovascular response to an orthostatic challenge recovers more slowly
(Lee, Feiveson 2015). The true rate of landing day OI is likely higher still, as crewmembers
who are very ill on landing are either not tested (and thus not included in calculations) or
testing is delayed until they are sufficiently well to participate. Whilst LDM crewmembers
appear highly susceptible to landing day OI, the most recent data suggest that the majority
(89%) recover sufficiently to pass the 10 minute tilt test after two days of recovery, and all
are recovered by day three (Meck et al , 2004) (Lee, Feiveson 2015). Although the exact
magnitude of inflight CM programme effect on OI is unknown, anecdotally crew report a
positive effect in particular as a result of the pre-landing fluid loading regimen (Appendix B)
and the use of lower body anti-G garments (Buckey, 2006).
Post-mission Exercise (Reconditioning) Topical Team Report
23
3.8.8 Sensorimotor Function
Despite the large body of sensory-motor and psychological research data obtained from
space flight experiments over the years, there is little published information specifically
concerning pre- to postflight changes with LDMs and advanced exercise CM. The time to
complete a functional mobility test walking at a self-selected pace through an obstacle
course on a base of 10-cm-thick, medium-density foam is increased by 48% and is
estimated to take up to 15 d postflight to return to preflight levels (Mulavara et al. 2010).
Likewise, performance of a sensory organization test using sway-referenced support
surface motion with eyes closed is decreased after LDMs (Cohen et al. 2012). Disruptions
in lower limb kinematics leading to reduced toe clearance have also been reported, but this
decrement corrects by the 1st day postflight (Miller, Peters 2010). The most recent data from
NASA utilising a computerised dynamic posturography protocol indicates the presence of
postflight decrements, which vary considerably between individuals (Wood et al. 2011).
However, these data also suggest improvements in some aspects of postural performance
since the introduction of ARED, including sensory organisation and motor control.
Although studies of the magnitude and recovery of sensorimotor symptoms following return
to Earth after LDMs are limited, Clément and colleagues (Clément et al. 2016) undertook a
review of available data and concluded that recovery of function takes an average of 15 days
to return to within 95% of preflight performance levels. It is noted that the subjects and
populations from which this conclusion is drawn did have varying exercise countermeasure
programmes and operational circumstances (Clément et al 2016).
3.9 Reconditioning following prolonged simulated microgravity
An intervention programme post bedrest (Bed Rest Study BBR-2), which incorporated motor
control training and graduated weight bearing (with special attention to maintenance of spinal
curves) has been shown to be effective in restoring the size of the spinal and abdominal muscles
to their pre-bed rest size and relationship to each other (Hides et al. 2011). Postflight
reconditioning programmes in current practice are outlined in Chapter 4, which have yet to be
evaluated for their effectiveness.
Post-mission Exercise (Reconditioning) Topical Team Report
24
3.10 Conclusions
This chapter has highlighted the physiological changes experienced by the human body during
space missions which have a bearing on post mission reconditioning. The musculoskeletal,
neurovestibular and neuromuscular control systems are especially affected and require
substantial CM in an attempt to ameliorate the changes. Positive responses to CM used on ISS
have been detailed to help provide an understanding of the status of astronauts as they start
their reconditioning on return from space.
MUSCLE: With access to the current exercise CM devices, and specifically ARED, in
general, the magnitude of inflight atrophy of the major muscle groups has been reduced
in comparison to the pre-ARED era. However, on an individual level, some crew members
continue to lose muscle strength of clinical proportions. Recent evidence from a small
number (<10) of crew members with access to ARED indicates that the deep spinal
muscles are still subject to marked atrophy;
BONE: Recent preliminary evidence suggests that, compared with the pre-ARED era,
some crew members with access to ARED display little or no change in BMD during LDM,
however, variability between crew indicates that the issue is not yet fully addressed;
OI: Whilst LDM crewmembers appear highly susceptible to landing day OI, the majority
recover sufficiently to pass the 10 minute tilt test after two days and indications are that all
may recover by day three. However, due to use of other pre-landing CM (i.e. fluid loading)
the exact magnitude of inflight CM programme effect on OI is unknown;
CARTILAGE: There is insufficient knowledge of changes to human cartilage as a result of
LDMs for adequate conclusions at present, although studies have begun;
SPINE: Preliminary inflight data suggests that the effect of LDMs on the spine is variable
(between crew and different spinal levels). IVD water content changes with no significant
changes in disc height, but increased spine stiffness and straightening occur;
AEROBIC CAPACITY: With access to the current exercise CM devices, it appears that as
many crewmembers maintain or increase their aerobic capacity during their mission as
those who experience losses. Those who attain higher exercise intensities during CM
sessions appear less susceptible to a loss of aerobic function;
FUNCTIONAL PERFORMANCE: In postflight functional tests, including postural stability
and agility push-ups, pull-ups, bench press, and leg press, crewmembers with access to
ARED showed less decrement in performance compared to those from the pre-ARED era;
SENSORIMOTOR FUNCTION: Sensorimotor function, as measured using computerised
dynamic posturography, indicates improvements in some aspects of postural
performance since the introduction of ARED, although with considerable inter-individual
differences in performance. A number of measures of sensorimotor function suggest
that preflight performance is recovered by around 15 days postflight.
The following Chapter provides a small number of personal insights from astronauts and
Medical Operations specialists on the topics covered in the present chapter and documents
their proposed recommendations for future improvements in the field.
Post-mission Exercise (Reconditioning) Topical Team Report
25
CHAPTER 4:
ASTRONAUT AND OPERATIONS EXPERT PERSPECTIVES ON EFFECTS OF MICROGRAVITY
INFLUENCING POSTFLIGHT RECONDITIONING
4.1 Introduction
An Astronaut/Operations Experts Sup-group of the Post-Mission Exercise (Rehab) Topical
Team (TT) was set up to enable their perspectives to be captured. Engaging these experts is
analogous to PPI in terrestrial research (see Section 8.2.6). The purpose was to gain
valuable insights into the challenges they face to help ensure the research priority areas for
postflight reconditioning proposed by the TT were feasible. For example, are the right
questions being asked to solve challenges for effective reconditioning? If a research
project/programme was developed and funded, would it be workable on a practical level?
Aspects during preflight and inflight exercise that impact on postflight reconditioning have
been considered, and the NASA and ESA postflight reconditioning programmes are outlined
in Section 4.2. The experiences and challenges of astronauts and operations teams are
reflected in this chapter, which are reported in full in Appendix C.
4.2 Postflight Reconditioning Practices
Despite rigorous inflight CM exercise programmes, postflight reconditioning after return to
Earth is still required (Chapter 3) and implemented by space agency reconditioning
specialists. Strategies differ between agencies, and common practice guidelines do not yet
exist, and thus reconditioning practices vary between crew member and space agency.
4.2.1 NASA Postflight Reconditioning
In 2003, Chauvin et al (Chauvin et al. 2003) reported (in a conference abstract) that
reconditioning of United States crewmembers to full functional preflight status following
flights on the Russian Mir Space Station had required more than six months. Chauvin et al
(2003) also reported findings of the postflight reconditioning for crew members returning
from the ISS, which lasted 45 days (2 hours per working day). Phase 1 began on landing
day and placed an emphasis on ambulation, flexibility, and muscle strengthening. Phase 2
added proprioceptive exercise and cardiovascular conditioning. Phase 3 (the longest
phase) focussed on functional development. Programmes were tailored for each astronaut
according to their test results (of functional fitness, agility, isokinetic strength, and
submaximal cycle ergometer performance) and preferred recreational activities. Most
crewmembers reached or exceeded their preflight test values 45 days postflight. Since
2003 the ARED device has been introduced to the ISS and reconditioning has emphasised
functional fitness/agility and proprioception (Section 3.8.5 and 3.8.6). Wood et al (2011)
describe an individualised sensorimotor reconditioning programme that challenges
multisensory integration with an increasing level of difficulty.
4.2.2 The ESA Postflight Reconditioning Programme
Since 2006, the ESA reconditioning team has managed the CM programme of eight long
duration (6-month ISS) crewmembers. One Physiotherapist and three Exercise Specialists
are now responsible for developing and conducting the ESA reconditioning programme.
The ESA Exercise Specialists are sports scientists who give CM support to ESA
crewmembers by providing exercise prescriptions based on interfacing with flight surgeons
and biomedical engineers. This programme also includes the preflight training and the
inflight prescription and monitoring of exercise performance on the ISS, as these phases
Post-mission Exercise (Reconditioning) Topical Team Report
26
are related and cannot be managed in isolation. A brief overview of the programme follows.
Operational challenges are also outlined (Sections 4.4 & 4.5).
The objective of the ESA reconditioning programme is to trigger and enable the complete
recovery process, comparable with preflight status, using an individualised, efficient and
functional reconditioning approach. The unique combination of physiotherapy and sport
scientific methods leads to a comprehensive and efficient recovery programme over the first
21 days after return from space (Lambrecht et al 2017 & Petersen et al 2017 in Appendix
D).
4.2.2.1 Principles of the ESA postflight reconditioning programme
a) Reorganisation of postural control, muscle control and muscle balance the
stabilizing muscular system, which enables an optimal upright posture, is first re-
educated (soleus, vastus medialis, deep lumbopelvic muscles). Functional exercises,
progressing from simple to complex movement patterns, are used to retrain postural
control and to balance the activity between the stabilizing and mobilizing muscular
systems. To retrain muscle balance, it is essential to avoid using the wrong muscles
or compensation movements, and to integrate and consolidate the readjusted
movement quality into functional exercise during the reconditioning phase.
b) Use of motor learning principles - motor control exercises, training of proprioception,
balance and coordination are used to reorganize the astronaut’s motor capabilities
and functional fitness. Optimized motor skills are fundamental for pain and injury
prevention.
c) Respect the centre of gravity the Gravity Line is the optimal line of load transfer
through the human body, which enables the body to use the positive effect of
pressure to reduce stress on weight-bearing joints and optimize muscle function. The
centre of gravity is at the 3rd lumbar vertebra (L3). Both the centre and line are lost
after a period of microgravity exposure and have to be retrained to produce economic
movement and to avoid long lasting additional stress on the musculoskeletal system.
Exercises during the reconditioning period focus on paying close attention to
movements respecting the gravity line and posture.
d) Apply appropriate stimuli at the right time - through a careful combination of
physiotherapy interventions and physical exercise that is gradually intensified to
respect individual adaptation capabilities, avoiding injury yet stimulating functional re-
adaptation.
e) Strength and endurance training following motor control training building on the
basis of stable motor control, posture and movement patterns, physical exercises are
determined and progressed to enable not only functional but also structural recovery
processes, requiring higher intensities later in the reconditioning process.
4.2.2.2 Objectives of the ESA postflight reconditioning programme
a) Initiate and complete an efficient postflight reconditioning programme, beginning within
24h of landing, independent of location of crewmember on return
b) Prevent short and long-term pain (e.g. LBP) and mission-induced physical health
problems
Post-mission Exercise (Reconditioning) Topical Team Report
27
c) Return the astronaut to their preflight physical capabilities as assessed in preflight
medical and physical assessment defined in Medical Operation Document (MED B
4
),
Astronaut Functional Fitness Assessment (AFA
5
). The aim is to achieve full recovery
without risking the development of pain or injuries associated with readaptation and to
enable the resumption of loading (relevant to joint health and preventing osteoarthritis
in longer-term; see sections 6.2.1.3 and 6.2.1.4).
d) Support physical recovery to allow crewmember flight recertification
e) Support resumption of unimpaired activities of daily life and preferred physical activity
(such as sports)
f) Encourage astronaut self-management of exercise after postflight recovery
g) Minimise long-term effects of space flight on the musculoskeletal system (as far as
possible)
4.2.3.3 Structure of the ESA reconditioning programme
The ESA postflight programme combines physiotherapy, sports science and exercise
methods in sequential order. It uses good communication techniques to ensure that a
highly coordinated programme can be operated by a small, well trained team in different
locations within 21 days. This period can be extended up to 45 days if required. To be
able to adapt to individual crew conditions, and short and long-term exposure to external
conditions (such as mission duration or profile), an interdisciplinary and individualized
programme tailored to each crewmember is implemented. The programme consists of
three phases:
A. Back to gravity (first week)
B. Back to function (second week)
C. Back to work i.e. return to duty (third week)
Return to duty involves high performance flight, EVA training in Neutral Buoyancy Lab
(NBL) and other activities that differentiate the astronaut job from the typical work place.
Full return may take up to 45 days, depending on the individual’s progress with recovery.
Programme conditions and considerations include:
a) Daily, supervised implementation of 2-hour reconditioning programme for 21 days,
using facilities either at the host agency or at the European Astronaut Centre.
Unsupervised reconditioning exercise sessions continue after completion of the initial
reconditioning phase of 21 days.
b) Consideration of tight schedules and medical and experimental constraints associated
with post-mission Baseline Data Collection (BDC), which impacts the reconditioning
intervention programme (e.g. frequency or intensity).
c) Daily programme adjustment to crewmember’s physical condition and rate of progress
d) Close interaction between astronaut and reconditioning team and within the team,
between physiotherapist and Exercise Specialist, and with medical doctors, schedulers,
and management.
e) Implementation of daily reconditioning programme in available gym facilities, applying
training principles established by ESA exercise and reconditioning specialists.
4
Med B - Medical Evaluation Documents (Med) Volume B, preflight, inflight, and postflight medical evaluation
requirements for long-duration ISS crewmembers, SP 50667.
5
AFA Astronaut Fitness Assessment used by the ESA Medical Operations office.
Post-mission Exercise (Reconditioning) Topical Team Report
28
The programme involves progressive development of complexity and intensity,
beginning with motion quality developed through motor control and postural control
exercises, merging into an individualized functional fitness conditioning programme,
which can be implemented without continuous supervision. Preliminary service
evaluation (i.e. documenting effectiveness of the programme) indicates that the
programme is effective (Petersen et al. 2017 in Appendix D).
4.2.2.4 Conclusions
The ESA programme was developed using evidence from extensive terrestrial studies and
limited studies on postflight and post-bed rest reconditioning research, as well as
experience in working with astronauts. Developing optimal postflight reconditioning
programmes and evaluating their effectiveness in astronauts is a major research
challenge within this relatively small field. Research designs and methods appropriate for
space research need careful consideration (Chapter 8). Studies of reconditioning post-
bed rest could contribute to the evidence base for reconditioning but are lacking (Section
6.3.3). The unknown challenges with longer missions are discussed from the medical and
operations team perspectives below (Sections 4.4 & 4.5).
4.3 Astronaut Perspective Case Reports
Space flight experiences of two astronauts are outlined below and detailed in Appendix C.
4.3.1 Astronaut Case Report 1
Astronaut 1 flew three short duration space missions with the Shuttle Transportation
System (STS). Personal trainer availability for consultation and treatment was appropriate,
as was their skill and knowledge. The astronaut perceived trust in physiotherapists and
trainers to be crucial to good working relationships and to feeling supported.
4.3.1.1 First Flight (9 days duration)
Astronaut 1 suffered from mild low back pain (LBP) early inflight which resolved within a few
days. His stature increased inflight by about 5cm placing pressure on his shoulders during
EVA. Post-mission he felt mild orthostatic intolerance when upright during the first few
hours on Earth and had balance and orientation difficulties for the first few days. He began
running three days postflight and suffered from a large cervical disc extrusion which
progressed in severity from the 2nd week and it was treated successfully with surgery and
recovered within 3 months of return. There had been no pre-existing neck pain or injury.
Key Messages in brief
Close monitoring of postflight effects is important and may have prevented the post-mission
injury suffered after this flight.
Gradual re-loading during reconditioning is crucial to minimise the risk of injury.
Appropriate levels of assessment are necessary to prevent medical complications
Standardized assessments of relevant functional activities can enable the efficacy of pre, in
and postflight programmes to be better assessed and monitored.
4.3.1.2 Second Flight (3 years later 10 days)
Astronaut 1’s postflight experience was an improvement over the first mission. Minimal
orthostatic intolerance was felt, which lasted for only an hour or so on return. Ccoordination
and orientation issues were much less severe and aspects of recovery that took days after
the first flight only took one day after the second.
Post-mission Exercise (Reconditioning) Topical Team Report
29
Key Messages
The nature and enjoyment of inflight exercise is seen as important to maintain motivation.
Group activities inflight were seen as more enjoyable and may enhance exercise compliance
Increase post-mission weight-bearing exercise duration and intensity very gradually.
4.3.1.3 Third Flight (2 years later 12 days)
Astronaut 1 had no conditioning or strength issues and felt that post-mission effects were
less than in previous flights, for instance not needing any pressure in his anti-G suit during
entry and experiencing normal feelings of orthostasis within an hour postflight. A pressure
and friction wound was, however, suffered during his first EVA which extended to the bone
of the 5th metacarpal. Although this injury did hurt a little during the second EVA, it did not
interfere with overall performance and healed without complications.
Key Message
Some adaptation to the effects of microgravity on orthostasis from undertaking repeated
missions might be evident, or exercise CM programme of the 3rd mission may have been
more effective (included bike, treadmill, iRED).
4.3.1.4 Recommendations from Astronaut 1
1) Focus on functional tasks postflight as well as preflight. Understand the specific areas of
strength and conditioning needed to accomplish the tasks and train with these in mind to
make the routines shorter, less boring, and to increase compliance.
2) If possible, use techniques that use multiple aspects of function, e.g. strength, co-
ordination etc, for exercise in flight. For example, create routines like flying exercises
(described in Appendix C) to maintain the required combination of coordination, impact,
strength, and conditioning needed. They are also much more enjoyable, and therefore
contribute to the crew’s mental well-being. [However, the space available for current
missions would not allow as much freedom to move around the space station and future
long-duration missions are likely to have even more space restrictions.]
4.3.2 Astronaut Case Report 2
Astronaut 2 undertook two missions, both using Soyuz to fly to the International Space
Station. The first mission was an 11 day flight and the second was for 6.5 months.
4.3.2.1 Flight 1 (11 days)
Astronaut 2 had three musculoskeletal issues during the preparation phase. The first
involved pain over the patella and tendon of the right knee, which impacted his postflight
reconditioning. Although the issue resolved sometime after the first mission it returned (on
the left knee) during the Soyuz simulations in preparation for the 2nd flight. The second
issue was acute LBP pre-mission, which local physiotherapy and electro-stimulation
resolved. The third issue was Plantar Fasciitis on the left side, probably caused by running,
which was painful when standing on the heel of the foot after sitting still or when getting up
out of bed. It was treated successfully with special shoe soles in daily and running shoes.
Neuromuscular coordination was adversely affected on return, requiring aid from medical
staff during the first day but resolving by week 2 post-mission.
4.3.2.2 Flight 2 (6.5 months)
Astronaut 2 noted an inflight increase in stature of 23 cm, but with no back pain. A mild
back injury was, however, suffered with associated pain during an early ARED session,
which affected physical performance for approximately one week thereafter.
Post-mission Exercise (Reconditioning) Topical Team Report
30
Neuromuscular coordination was also adversely affected on return and required longer to
return to preflight levels (Appendix C). Orthostatic intolerance was felt during the first few
days post-mission. A near fainting (syncope) episode was experienced after a maximal
exercise test. Aching muscles were noted for about 3 months on return.
Key Messages in brief
Recreational videos can make exercise more enjoyable and help with motivation
Real-time feedback from the ground support team when exercise is performed in space is
important and may prevent crew injuries.
The ergonomics of spacecraft design needs to be considered in more detail to prevent crew
discomfort bordering on injury (e.g. prolonged sitting in cramped conditions, see below).
4.3.2.3 Recommendations from Astronaut 2
1) Special attention to physiotherapy/flexibility etc. to deal with the prolonged sitting position
in the Soyuz simulator (where space is restricted and the knees are bent for hours and
cannot be stretched out), in order to prevent stress injuries (particularly in tall
astronauts). The discomfort can be distracting during the simulation/flight, difficult to
recover from and may persist.
2) Direct video AND voice contact is needed with fitness instructors during several ARED
sessions, early, midway and later in the mission, for effective exercise and to prevent
injuries due to incorrect body positions and movements.
3) It is useful to have access to video clips of each ARED exercise, easily accessible before
the session, with warnings for wrong positioning.
4) DEXA monitoring sufficient to document return to preflight bone density.
4.4 Flight Surgeon Perspective
This section is a personal perspective from an experienced ESA Flight Surgeon.
One of the primary concerns for a Flight Surgeon (FS) is to protect the astronaut during the very
busy post-mission phase. The first few weeks after a mission include an intensive schedule of
postflight medical assessments, baseline data collection for scientific studies, Public Relations
and media activities, space agency briefings and other calls upon the crewmember’s time. The
FS is the astronaut advocate and must try to enable post-mission reconditioning in the face of
an aggressive postflight schedule.
The preflight exercise programme is very important too. The busy pre-mission schedule makes
it difficult for crew to accurately follow their fitness programme, and yet we need them to be as
fit/healthy as possible as they start their mission. Preconditioning needs to be as structured as
inflight training (although this is very challenging).
The TT recommendations in this report might help the Medical Operations team to know:
- The R+1-21 period evolved as a compromise with competing demands on astronauts’ time.
What evidence exists to support postflight reconditioning programme in the first 21 days?
- What evidence supports the prescription used to bring crew back to an appropriate level of
well-being?
- Are astronauts being pushed too hard? Is the rigidity of the postflight schedule dictating the
nature of the reconditioning programme?
Post-mission Exercise (Reconditioning) Topical Team Report
31
4.4.1 What are the most common problems observed by flight surgeons that impact on
postflight reconditioning of astronauts?
Astronauts are typically tired and dehydrated when they first return to Earth but
‘blossom’ by R+2.
The physical impairment of crew returning is, at present, reasonable given the nature of
6 month ISS missions. What evidence exists to allow us to state what is ‘good enough’
for an astronaut to be released, for example, for a transatlantic flight?
Upon returning from a six-month flight most astronauts face various medical conditions,
some of which are acute but others require longer recovery times.
o The major challenges the astronaut faces upon landing is re-adaptation to gravity. In
particular fatigue and neurovestibular symptoms make unaided reambulation on
landing day extremely difficult, fatiguing and provocative. Although it is reasonable to
believe that orthostatic hypotension may play a role, in my personal experience this
has not been the case as no fainting episodes have been observed in my presence.
Dizziness and emesis were often linked to sudden head or body movements, thus
assumed to be neurovestibular in nature. Currently, astronauts typically pre-medicate
before landing to mitigate neurovestibular symptoms on landing. This improves their
performance in the immediate post-landing period. Within 24 hours of landing,
unaided ambulation is usual; however, an incomplete neurovestibular re-adaptation
(turning corners, unstable balance in absence of visual cues, etc) persists for 10 to 15
days after landing.
o In my experience, I have not witnessed significant evidence of orthostatic
hypotension; however, some mild oedema of the ankles observed in some
astronauts, in the early postflight period (days-weeks) is testimony that the interstitial
tissues gradients are still re-adapting to the gravity-induced increase in hydrostatic
pressure in the lower body areas.
o Fatigue, both physical and mental, is a chronic symptom that persists for longer
periods of time and beyond the current 21 days acute rehabilitation phase. Recovery
from fatigue and the lingering muscloskeletal discomforts (weeks to months) is not
supported by the intense pace of the postflight activities, making adherence to
physical rehabilitation difficult beyond the first 21 days postflight. At this time, both
physically and psychologically, the astronaut is nearly exhausted, after six months of
enduring work and spaceflight-induced environmental and physical challenges. The
astronaut realises that the months ahead will be possibly more intense and less
structured than those on ISS with postflight testing, public relations, travelling and
debriefings. This holds the potential to delay optimal physical and psychosocial
rehabilitation and a proper re-integration into private life, until much later than desired,
in the postflight phase.
4.4.2 Perceptions for exploration length missions
Preliminary informal comments from the 1 year mission crew flown on ISS indicated
that postflight effects are much more marked after 12 months than 6. When considering
2 year missions, although exercise countermeasures programmes for 6 & 12 month
missions appear efficient, we probably need better ways of exercising so that crew do
not need to exercise for 2 hrs every day for 2 years. This might come in the form of
better equipment but also less conventional activities such as motor imagery, which is
Post-mission Exercise (Reconditioning) Topical Team Report
32
known to improve physical skill and muscle strength, possibly using video/computer
games.
With respect to space vehicles and engineering processes there is a need to not see
human needs as constraints but as requirements around which engineering solutions
are centred. Space habitats need to be developed with humans more fully in mind so
that a ‘human compatible environment’ results. For example, more thought is needed
behind where exercise equipment is placed and how it is designed, e.g. treadmill
harness and loading devices.
Space vehicle design needs to fit the needs of astronauts to keep them healthy inflight
by more closely mimicking the Earth environment without imposing non-physiological
effects e.g. avoiding high CO2 content within the space environment.
Future mission architects need to take into account postmission rehabilitation needs (as
reflected by inflight CM efficacy) and build post-mission schedules with these needs in
mind, rather than the reconditioning programme being ‘shoe horned’ into the schedule.
Exercise countermeasures may never be able to totally prevent the effects of
microgravity, so technological solutions are needed in the long-term (e.g. artificial
gravity) to better create a human environment that is compatible with the need to
maintain Earth physical standards.
4.5. Operations team (physio/exercise specialist) perspectives
4.5.1 Operational challenges in postflight reconditioning
Postflight reconditioning of astronauts is implemented within a very compact post-
mission schedule, accompanied by medical checks, social and public relations (PR)
commitments, debriefings and experimental baseline data collection. Daily reconditioning
exercise needs to be individually tailored, requiring daily 2 hr sessions and appropriate
and focused adjustment of the programme. Differences in available equipment and
facilities will depend on the location of the returning astronauts, so these need to be
considered and the programme tailored accordingly. Large intra-individual differences
and diverse mission profiles do not allow simple implementation of a standard protocol,
but reconditioning principles (section 4.2.2.1) can be interpreted for the individual and
the surrounding conditions.
4.5.2 Future reconditioning challenges after longer missions
Discussion with the ISS CM Working Group (CMWG) indicates that operational experts
generally agree on the nature of the problems typically seen after long duration space
flight and that these need to be addressed and further understood, especially for mission
durations longer than 6 months. The emphasis of intervention for reconditioning of
astronauts after 1-year missions might be more focused on neuromuscular training than
is currently carried out after six month ISS missions.
Greater understanding is needed to identify tailored and efficient intervention strategies
for the individual. A scoping exercise, via survey or focus groups, may be a useful
research activity to capture the views of operations experts. Specifically, it would be
useful to hear what challenges might be anticipated after longer duration missions (> 12
months) based on those currently experienced after 6-month missions.
Post-mission Exercise (Reconditioning) Topical Team Report
33
Inflight preconditioning during deep space cruise will be required to prepare for planetary
exploration after a period in which physical deconditioning has occurred. There will also
be a need for autonomous treatment effective enough to ensure mission operations can
be undertaken quickly and safely. Furthermore it can be envisaged that future
exploration missions will be followed by intensive media interest, so it will be important
not to allow this to impact the post-mission reconditioning programme.
4.6. Conclusions
4.6.1 The astronauts and operations specialists consulted perceived that:
Trust in reconditioning specialists is crucial to good working relationships;
The nature and enjoyment of inflight exercise is important to maintain motivation to follow
the programmes provided.
Postflight reconditioning of astronauts is implemented within highly demanding post-
mission schedule of 3 to 4 weeks, and must be co-ordinated with medical checks, social
and public relations commitments, debriefings and postflight tests required for scientific
experiments for which astronauts serve as volunteers;
Large inter-individual differences and diverse mission profiles do not permit
implementation of a standard reconditioning programme. As such, programmes provided
by ESA specialists are individually-tailored during daily, two hour sessions, and can be
influenced by differences in equipment and the facilities at the location to which the
astronaut returns.
A key feature of the success of the ESA Reconditioning Programme is the close
collaboration between the physiotherapists and Exercise Specialists.
4.6.2 There will be a wide variability of crew experiences and operations expert views, so
those reflected in this report only provide a small perspective and wider involvement is
needed:
Patient and public involvement (PPI) is fundamental to the feasibility and success of
terrestrial research, so involvement of astronauts and operations experts needs to
become integral to human space research.
Such involvement includes participating in setting research and operational evaluation
priorities, and conducting associated projects, as appropriate. These activities require the
training of representatives in research processes and governance procedures.
The astronaut case histories are of value (Appendix C) and have highlighted aspects of
spaceflight and post-mission challenges that are important to them that may not be
considered as important to those responsible for their health. Gaining astronauts’ views
provides insights into how their care might be improved, what might increase adherence to
exercise and also aid decisions on research priorities. An effective system is needed to
capture views from serving and retired astronauts but it must be anonymised so as not to
compromise their trust (see Section 7.8.4). An example is the NASA Crew Comments
Data Base, which logs all debriefs and is searchable on terms and topics in a non-
attributable fashion.
Recommendations related to these conclusions are summarised in Chapter 10. The report
thus far has discussed the effects of microgravity on the neuro-musculoskeletal system and
the challenges faced on return to Earth, with the postflight reconditioning programmes from
two agencies (ESA & NASA) outlined. The next chapter identifies what is unknown and
requires research to develop optimal postflight reconditioning programmes for current and
future longer duration missions.
Post-mission Exercise (Reconditioning) Topical Team Report
34
CHAPTER 5:
KNOWLEDGE GAPS
5.1. Introduction
As stated in Chapter 1 (Section 1.1), the goal of postflight reconditioning is to correct any
physiological and functional deficits incurred during exposure to the space environment, thus
returning crew to their preflight status. Knowledge gaps and research priorities are, therefore,
related to the presence and magnitude of the deficits:
1. Currently observed, in medical tests and by re-conditioning specialists, and experienced
by crew members, returning from nominal 6-month missions to ISS;
2. Likely to be observed in, and experienced by, crewmembers returning from future
missions, including those of longer duration, those outside Low Earth Orbit (LEO) and
those involving planetary surface excursions (Long Duration Exploration Missions
LDEM).
In the case of the LDEMs, the two most likely destinations for surface explorations will be Moon
and Mars, both of which have partial gravity (> µG and < 1G) environments (moon: 0.16 G;
Mars 0.38 G). As such, LDEMs will consist of time in µG (transit out), time in partial gravity
(surface exploration) and further time in µG (transit back). Human adaptation to prolonged µG
has been well-documented, but currently little is known about the adaptation that will occur in
partial gravity. The extent of adaptation will depend on the forces acting on the body during
surface locomotion and, although these have yet to be quantified, they are likely to be
substantially less than those routinely experienced by the body in Earth’s gravity. It is likely,
therefore, that exercise CM, consisting of both novel exercise programmes and novel exercise
devices, will also be required to support crew living and working in partial gravity environments
as part of LDEMs.
5.2 Knowledge gaps for current six-month missions
The knowledge gaps in postflight reconditioning for current missions to the ISS are listed
below in Table 5.1.
Post-mission Exercise (Reconditioning) Topical Team Report
35
Table 5.1. Postflight re-conditioning Knowledge Gaps for crewmembers returning from nominal 6-month missions to ISS.
Parameter
Knowledge Gap(s)
Rationale
Report
Section
Reference
Musculoskeletal
System
Major Muscle
Groups
How can the residual loss of
muscle mass and strength on
return to Earth be recovered
as rapidly and effectively as
possible by postflight
reconditioning?
What is the nature of
changes at the
neuromuscular junction?
Are alternative CM protocols
helpful to support re-
adaptation postflight ?
What are the adaptation
mechanisms of the
neurovestibular system
affecting skeletal muscle
structure and bone density,
and how can postflight re-
conditioning protocols make
use of such novel findings ?
The response of the major muscles of the lower limbs to space flight is
well documented in Chapter 3. Although inflight CM are more effective
than ever, they do not completely prevent the loss of muscle
volume/force production. Some crew continue to lose in excess of 20%
muscle strength in some muscles.
Knowledge of these links is important for understanding afferent and
efferent signal transmission, and subsequently the nature of muscle
deconditioning/reconditioning.
Recent findings show that short-term resistive vibration (RVE)
mechanostimulation as a CM in bed rest is well tolerable, less time
consuming than others (resistive exercise), highly effective in outcome,
and acceptable to bed rest participants (works via neuroreflexive
activation independent from motivation) and effectively support a close-
to-normal muscle fiber microstructure, molecular composition and
function in disused human skeletal muscle (soleus).
As suggested by animal studies, impaired vestibulosympathetic reflexes
affect skeletal muscle structure (myofiber type pattern) as well as bone
density with potential risk of injury in crew during spaceflight and
thereafter. One pharmacological target could be administration of ß-
adrenergic receptor agonists in microgravity to mimic
sympathoadrenergic activation in spaceflight. More knowledge is
needed to better understand such highly unique linking mechanisms
(systems cross-talk) in the body
Section 3.1.1
and 3.8.1
Section 3.6
Section 3.1.1
Section 3.6
Post-mission Exercise (Reconditioning) Topical Team Report
36
Postural muscles
What is the condition of the
postural muscles on return
from LDMs?
What are the adaptation
processes of the lumbopelvic
muscles during inflight CM
and postflight reconditioning?
Little is documented about the postural muscles postflight but preliminary
evidence suggests the muscles that support the trunk are particularly
vulnerable, similar to LBP patients. The postural hip and leg muscles
(gluteus, adductors, soleus/gastroc, anterior tibialis) and others involved
in gait control at 1G and not in use in µG (such as plantar foot short
muscles) are also important to consider. Changes in these muscles on
return to Earth are likely to influence many functional tasks, including
those requiring spinal stability, which need addressing/accounting for
during re-conditioning activities.
Research on the adaptation processes of lumbopelvic muscles during
microgravity and post-microgravity reconditioning has been limited to
bed rest studies, but it is unknown how far these findings can be
translated to astronauts. More crew-focused research is needed to help
improve spine-specific inflight CM and postflight reconditioning
strategies.
Section 3.1.2,
3.3 and 3.8.1.2
Section 3.1.2
and 3.8.1.2
Cartilage
What is the effect of LDM on
human cartilage and what is
the significance of these
changes for the days/weeks
after landing?
Little is known about the effects of LDM on human cartilage but ground-
based analogue studies point to a loss of tissue thickness and possible
sensitivity to re-loading, which could directly impact re-conditioning
strategies.
Section 3.4
and 3.8.4
What are the long-term
effects on cartilage and
implications for development
of osteoarthritis (OA)?
CM in bed rest studies have not been able to compensate for the effects
of immobilisation on cartilage metabolism. Effects of microgravity on
cartilage could have implications for OA in later life in a similar way that
overuse of joints in young athletes causes greater incidence and earlier
onset of OA than in the general population. The occurrence of OA in
astronauts is unknown.
Post-mission Exercise (Reconditioning) Topical Team Report
37
Bone Mineral
Density
What is the short and long-
term significance of postflight
decreases in BMD that
persist in some crew
members despite the recent
improvements in
effectiveness of inflight CM?
The current inflight CM Programme results in some crew maintaining
their BMD inflight, but some crewmembers continue to display
decreases. Given the evidence of delayed recovery of BMD postflight,
such changes may need specific management during re-conditioning
activities for affected individuals. Long-term reduced BMD has
implications for osteoporosis. Also see neurovestibular effects on BMD
(Section 3.6)
Section 3.2
and 3.8.2
Spine
What is the condition of the
spinal structures, including its
shape, BMD and the
intervertebral discs on return
from LDMs?
Spinal elongation and changes to the IVDs occur during bed rest, and
crewmembers’ spines elongate during space-flight, potentially
increasing risk of postflight IVD herniation. Little is known about inflight
changes to the IVDs, particularly with the chronic use of ARED, and thus
the condition of the spine at the onset of re-conditioning activities,
although variable (between crewmembers and between spinal levels)
water content changes have been observed with no change in disc
height.
Section 3.3
and 3.8.3
Injury
Is µG exposure a factor in
inflight exercise-related
musculoskeletal injuries and
are the residual effects of
these injuries still evident on
landing/during
reconditioning?
Inflight exercise-related injuries are relatively rare, but they are the most
frequent source of injuries in astronauts living aboard the ISS. Treadmill
and/or resistive exercise equipment accounts for 85% (12 of 14) of
reported musculoskeletal injuries.
Section 4.3.2.2
Post-mission Exercise (Reconditioning) Topical Team Report
38
Orthostatic
Intolerance
Do orthostatic symptoms
continue to affect
crewmembers in the
days/weeks after landing,
and what, if any, is the
functional impact?
Although highly susceptible to orthostatic intolerance (OI) on landing
day, most LDM crew recover sufficiently to pass the 10 minute tilt test
after only one day of recovery, which suggests that OI symptoms are not
an issue for the re-conditioning activities. However, qualitative research
with astronauts and crew surgeons is needed to confirm this.
Section 3.5.1,
3.5.2 and 3.8.7
Sensorimotor
Function
Do sensorimotor symptoms
continue to affect
crewmembers in the days
after landing and what, if any,
is the functional impact?
Recovery of function appears to take an average of 15 days to return to
within 95% of preflight performance levels. A collaborative experiment
between NASA and Russia is currently conducting sensorimotor Field
Tests on astronauts and cosmonauts returning from ISS
http://www.nasa.gov
/mission_pages/station/research/experiments/1768.html
Recovery in relation to activities of daily living beyond the early postflight
period has yet to be determined and comments from astronauts suggest
that qualitative studies would be useful in documenting challenges
experienced in everyday activities.
Section 3.6
and 3.8.8
Functional
Performance
What exercises are effective
for restoring dynamic control
of movement?
To what degree and for how
long does a LDM affect
crewmembers’ ability to
perform functional tasks in
the days/weeks after
landing?
Reduction in Functional Task Test (FTT) performance is greater for tasks
requiring high dynamic postural control than those requiring less postural
stability
Functional tasks requiring a greater demand for dynamic control of
postural equilibrium (i.e. fall recovery, seat egress/obstacle avoidance
during walking) show the greatest decrement in performance. Functional
tests with reduced requirements for postural stability (i.e. hatch opening,
manual manipulation of objects and tool use) show little reduction in
performance.
Section 3.8.6
Section 3.8.6
and 7.8
Post-mission Exercise (Reconditioning) Topical Team Report
39
Aerobic Capacity
What is the functional impact
of postflight decreases in
aerobic capacity that persist
in some crewmembers,
particularly those who have
low/moderate preflight
values?
The present inflight CM programme results in some crew maintaining, or
even increasing, their aerobic capacity inflight, but some crewmembers
continue to display decreases. Such decrements are of little significance
in those who display high values, but might have a functional impact on
return to Earth that needs addressing/accounting for during re-
conditioning activities.
Section 3.5
and 3.8.5
Psychological
Status
How motivated are
astronauts to continue with
self-guided reconditioning
once the supervised element
is complete, and what effect
does this have on adherence
and efficacy?
Whilst for most astronauts the nominal 3-4 week supervised element of
postflight reconditioning programme is sufficient to completely correct
many of the residual effects of spaceflight, several partially remain (
including reduced muscle volume/force production capacity, BMD and
VO2max). Such parameters are known to change more slowly, even with
active reconditioning, so complete restoration of preflight status requires
longer and self-guided reconditioning, and against a backdrop of
competing demands from other postflight requirements, many of which
require international travel.
5.3 Knowledge gaps for future missions
The knowledge gaps for future missions fall into two categories:
5.3.1 Those that directly affect the delivery and effectiveness of post-mission reconditioning on Earth by re-conditioning specialists
following longer missions in LEO (e.g. the recently initiated One Year missions) and LDEMs;
5.3.2 Those that are related to preparation for, and execution of, surface activities during LDEMs that include planetary surface (low
gravity) excursions.
In the case of the latter:
a) Crewmembers may be required to undertake a reconditioning/preparation (preconditioning) programme prior to performing
excursions, either in flight and/or on the surface. The gravity environment will be novel, e.g. 1/3 G on Mars, and the normal
CM and reconditioning programmes are already oriented toward planetary surface excursions, e.g. on Earth, but the support
from reconditioning specialists that occurs after return to Earth will be absent. It is highly likely that reconditioning specialists
Post-mission Exercise (Reconditioning) Topical Team Report
40
will be called upon to advise on the design and implementation of these preparatory programmes to ensure they are safe to
conduct (i.e. minimise injury risk) and task specific, to both ensure safety and maximise productivity during subsequent
excursions;
b) LDEM vehicles will be far smaller than ISS and likely contain only a single exercise CM device. As such, it might not be
possible to maintain the current efficacy of the ISS inflight exercise CM programme during these missions;
c) In an attempt to conserve resources (e.g. oxygen, food) and minimize undesirable effects that could compromise the mission
(e.g. production of moisture, heat and carbon dioxide, and excessive wear and tear to exercise devices), it is possible that
mission planning will require crew to partially abstain (e.g. during the early stages) from exercise during transit, which would
further impact on the efficacy of the CM programme. Given the known negative effects of microgravity on the body and the
fact that current CM do not mitigate these entirely, such reduction in exercise would need to be introduced with caution after
calculating the risks. For instance, sound evidence would be needed to indicate that negative effects of reduced exercise
could be reversed through preconditioning CM in space, prior to vital tasks during planetary surface excursions, and would
not cause irreversible impairment in the longer-term. These suggestions are speculative but nonetheless necessary to
consider;
d) The effectiveness of an inflight exercise countermeasure programme is heavily reliant on an individual’s compliance with its
prescription, which itself, is strongly influenced by personal motivation. In a NASA report from 1986, astronauts indicated that
exercise counteracted stressful aspects of the inflight period by maintaining morale and providing a source of enjoyment
(Stuster 1986). The mental health benefits of exercise are well documented and, given the general level of crew satisfaction
with inflight training programmes, adherence is likely to remain high during the ISS mission phase. There is only limited
evidence from LDEM mission analogue studies on the effects of prolonged confinement/isolation on voluntary physical activity
and motivational state (Belavý et al. 2013), but the high level of compliance with inflight exercise CM currently observed on
ISS cannot be assumed during longer and more isolated missions, particularly where contact for support from ground will be
less available. Monotony is a potential problem and staying motivated over a two year period with limited variety could be a
challenge. The stress and different priorities of planetary exploration could also make adherence more tenuous. It is only
possible to speculate on these issues at this stage, but evidence from terrestrial analogues suggests that adherence might
suffer in these situations, and prevention strategies will be needed.
It is expected that the challenges to the human body and effects of microgravity will be greater after longer duration missions but
the magnitude, duration and emphasis of effects on the different systems and specific parameters are difficult to anticipate.
Post-mission Exercise (Reconditioning) Topical Team Report
41
Research questions aimed at addressing these gaps in knowledge about longer missions in LEO will need to be developed and
tested. In particular, the effects on crewmembers during the days after landing and the functional impact of these effects will be
important to know. Table 5.2 focuses on knowledge gaps specific to future missions that relate to factors other than greater
mission duration, such as challenges from missions beyond LEO and those involving planetary surface excursions.
Table 5.2. Postflight re-conditioning Knowledge Gaps for crewmembers participating in future long-duration missions, primarily those outside Low
Earth Orbit and those involving planetary surface excursions.
Parameter
Knowledge Gap(s)
Report Section
Reference
Musculoskeletal
System
Major Muscle
Groups
Will losses in muscle volume/force production during transit impair planetary surface
excursions? What magnitude of effect can be considered acceptable, in terms of impacting on
functional performance of tasks and safety?
Section 3.1 and 3.8.1
Will the postflight decreases in muscle volume/force production that persist in some
crewmembers following LDM be exacerbated (i.e. suffered by all crewmembers and/or suffered
more profoundly by some), if the inflight exercise CM programme is less effective?*
Section 3.7 and App B
Functional
Performance
To what degree and for how long will crew members’ ability to perform functional tasks in the
days/weeks after return to Earth be affected if the inflight exercise CM programme is less
effective?*
Section 3.8.6 and 3.7
How will crewmembers’ ability to perform functional tasks during planetary surface exploration
be affected?
Section 3.8.6
Postural muscles
Will potential decrements in postural muscle volume/function impair planetary surface
excursions?
Section 3.1.2 and 3.8.1.2
Cartilage
What will be the magnitude of changes in human cartilage with µG exposure during the
reloading that will occur during preconditioning for planetary surface excursions, and with re-
loading during excursions themselves?
Section 3.4 and 3.8.4
Section 3.1.2, 3.3 and
3.8.3
Post-mission Exercise (Reconditioning) Topical Team Report
42
Spine
What will the condition of the spinal structures be on return to Earth following LDEMs?
What will be the significance of the condition of the spinal structures during the reloading that
will occur during preconditioning for planetary surface excursions, and with re-loading during
excursions themselves?
Injury
Will there be an increased risk of musculoskeletal injury on return to Earth if the inflight exercise
CM programme is less effective?*
Will prolonged microgravity during LDEM transit increase the risk of musculoskeletal injury
during preconditioning for planetary surface excursions, and with re-loading during excursions
themselves?
Section 4.3.1.1
Preparation for
planetary surface
excursions
Contingency
exercise
programmes for
equipment failure
What inflight preconditioning exercise programmes will be effective for preparing astronauts to
perform functional tasks safely and efficiently during surface excursions?
Quantification required of the physical demands of planetary surface excursions.
What exercise programmes / low specification technologies could be used in the event of
equipment failure
Section 6.3.2 and 4.3.1.4
Section 6.3 and 4.3.1.4,
Table 6.1
Orthostatic
Intolerance
How much worse will OI symptoms be on return to Earth if the inflight exercise countermeasure
programme is less effective?*
Will OI symptoms be significant when conducting planetary surface excursions?
Section 3.8.7 and 3.5.2
Sensorimotor
Function
To what extent will sensorimotor symptoms affect crew members in the days after landing on
Earth if the inflight exercise countermeasure programme is less effective*, and what, if any, will
be the functional impact?
Section 3.6 and 3.8.8
Will sensorimotor symptoms associated with µG exposure impair planetary surface
excursions?
Aerobic Capacity
How much worse will losses in aerobic capacity be on return to Earth if the inflight exercise CM
programme is less effective?*
Section 3.5 and 3.8.5
Post-mission Exercise (Reconditioning) Topical Team Report
43
Will losses in aerobic capacity associated with µG exposure impair planetary surface
excursions?
Bone Mineral
Density
Will the postflight decreases in BMD that persist in some crewmembers following LDM be
exacerbated (i.e. suffered by all crewmembers and/or suffered more profoundly by some) if the
inflight exercise CM programme is less effective?*
Section 3.2 and 3.8.2
Will losses in BMD associated with µG exposure be operationally significant during
preconditioning for planetary surface excursions, and with re-loading during excursions
themselves?
Psychological
Factors
How will prolonged confinement and isolation affect inflight mood state, motivation to exercise
and adherence to inflight exercise countermeasures and preconditioning for planetary surface
excursions?
Section 4.3.1.2
* if inflight exercise CM programme is less effective due to (in isolation or in combination) a planned reduction in exercise volume, a reduction in
device effectiveness, hardware failure, reduced exercise adherence.
5.4 Summary
Several questions have been posed in this chapter to address unknown factors that could influence the outcome of postflight
reconditioning and preconditioning during LDEMs prior to planetary surface excursions.
The following two chapters propose ways of filling these knowledge gaps identified. The first (Chapter 6) concerns research
opportunities for astronauts and microgravity analogues. Chapter 7 then proposes how parallels with terrestrial situations, including
clinical conditions and challenging environments, could be exploited by implementing strategies from current evidence based exercise
programmes and adopting similar designs used in relevant terrestrial rehabilitation research.
Post-mission Exercise (Reconditioning) Topical Team Report
44
CHAPTER 6:
FILLING THE KNOWLEDGE GAPS RECONDITIONING RESEARCH IN ASTRONAUTS
AND MICROGRAVITY ANALOGUES
6.1 Introduction
This chapter proposes solutions for filling the knowledge gaps identified in the previous
chapter, focussing on reversing neuro-musculoskeletal deficits and improving performance
using physical and psychological strategies. The chapter also covers factors that may impact
on the effectiveness of reconditioning, and therefore must be considered for future research,
as well as practical and operational situations. Specifically, it is important to consider that
inflight CM on long duration missions may be less effective due to possible planned reduction
in exercise volume, reduced effectiveness or failure of exercise equipment (compared with that
currently available on ISS), and reduced exercise adherence (Chapter 5, Table 5.2), and these
factors may impact postflight reconditioning.
6.2. Research to address knowledge gaps
6.2.1. Musculoskeletal system
6.2.1.1. Major muscle groups
Studies of optimal exercise protocols (Section 6.3.1) for increasing muscle strength and
endurance would determine the most efficient methods for regaining muscle function as
soon as possible postflight. In relation to preparation for surface planetary exploration, we
need to understand the dose-response to inflight exercise CM to inform preconditioning
programmes, e.g. what is the threshold (minimum effort) required to stimulate muscle
development (not just maintain it) in microgravity?
A novel non-invasive digital palpation device (MyotonPRO), for the measurement of
biomechanical properties (stiffness, tension, elasticity) in disused human skeletal muscle,
(MYOTON in ESA´s RSL Study at DLR: envihab, 2015-2016, PI Blottner) has been
successfully used in parabolic flight (Schneider et al. 2015) and, more recently, in LDBR
to monitor the overall muscle status and training efficacy in several major muscle groups
(including postural muscles) following reactive jumping as a CM (Blottner D et al.,
manuscript in preparation). Myometric measurements on human subjects with
MyotonPRO are planned to be performed on ISS (D. Blottner, PI Myotones, ILSRA-2014-
0015). In addition to existing inflight monitoring systems (i.e., cardiovascular, sympathetic,
neuromotor behaviour), the outcome of individual myometric monitoring of the muscle
status during all mission phases will potentially be very helpful to assess the overall
neuromuscular status; it may be even more important to monitor during re-loading within
24 h post-landing.
6.2.1.2 Postural muscles
The postural muscles of the trunk that protect the lumbar spine appear to be particularly
vulnerable and further research is needed to confirm preliminary evidence (Hides et al.
2016a). Studies of strategies used in terrestrial rehabilitation of LBP patients could be
conducted on astronauts, e.g. use of rehabilitative ultrasound imaging to provide feedback
of optimal muscle contraction to treat muscle imbalance (Section 7.3), screening of
movement control (Section 7.8) and motor control exercises (Section 7.3.2). The ESA
reconditioning programme already incorporates ultrasound imaging and motor control
retraining (Section 4.2.2), but the effectiveness needs to be evaluated. Ultrasound
imaging has only been used to monitor the effects of the programme on trunk muscles in
one astronaut (Hides et al. 2016a). An example of novel, innovative apparatus that may
augment reconditioning is the Functional Readaptive Exercise Device (FRED), which
targets the lumbopelvic muscles (Caplan et al. 2015; Winnard et al. 2017b in Appendix D).
Post-mission Exercise (Reconditioning) Topical Team Report
45
6.2.1.3 Postflight reloading for health of cartilage and bone
Studies are needed to determine safety guidelines to minimise risk of injury to cartilage
and bones, whilst ensuring adequate loading to stimulate tissue recovery.
a) Re-loading protocols for minimizing damage to cartilage
Since the effect of microgravity on articular cartilage is unknown (Section 3.8.4) postflight
reconditioning might best be guided by what is known about excessive loading and
cartilage damage, and risk of osteoarthritis (Maly 2008). A priority for postflight research
is to investigate the status of cartilage, to address the problem if it exists.
b) Re-loading protocols for bones
It is currently unknown which factors predispose astronauts to incomplete recovery of
bone loss (Section 3.2). Lack of mechanical loading or endocrine alterations may play a
role. Establishing such factors would fill an important research gap. Research is needed
to systematically monitor the time course of recovery of bone loss and to understand the
inter-individual variability of loss during unloading and gain during reloading. For the time
being,astronauts and participants from bed rest studies are probably well-advised to
attempt resumption of the original habitual loading patterns as fast as reasonably
possible, until evidence is provided to guide a more specific reloading strategy. Notably,
the cervical spine disc prolapse described by the astronaut in Chapter 4 (Case history 1)
appears to have been caused by a premature return to running (3 days postflight), so
caution is needed. Studies using the anti-gravity treadmill
6
may help establish guidelines
for safe return to more strenuous load-bearing activities during postflight reconditioning.
6.2.1.4 Longer-term effects of spaceflight on bone and joint health
a) Osteoporosis
Bone losses incurred during spaceflight and bed rest (Section 3.2) generally appear to
recover after return to Earth and after re-ambulation, respectively (Lang, Leblanc 2006;
Rittweger & Felsenberg 2009). However, recovery may not be complete in all individuals
(personal communications by D Felsenberg and by L Vico to Jörn Rittweger). The long-
term effects of spaceflight on bone in astronauts is unknown and warrants studies to
monitor bone mineral density, both to map the time course of recovery in the first few
months postflight, as well as periodically throughout the life of the astronaut, although
the latter may be contentious, as DEXA involves radiation.
b) Osteoarthritis (OA)
The incidence of OA in astronauts is unknown but NASA’s Lifetime Surveillance of
Astronaut Health (LSAH) database provides the opportunity to compare astronauts of
different ages with matched groups in the general population.
6.2.1.5 The spine
The condition of spinal structures was recently reported on by the ESA Intervertebral
Disc Herniations in Astronauts Topical Team (Belavy et al. 2016). Their report was
based on bed rest studies and an increased risk of postflight IVD injury, so the priority is
to learn more about the effects of LDMs on spinal structures to enable their impact on
postflight reconditioning to be understood.
6
Treadmill with air-tight positive pressure system surrounding the lower body, decreasing foot impact on running/walking.
Post-mission Exercise (Reconditioning) Topical Team Report
46
6.2.1.6 Musculoskeletal injury
Accurate reporting of exercise-related injuries during spaceflight and their persistence
postflight is needed to determine the prevalence of such events and any association with
mission duration and activities. This would help to develop strategies to manage injuries
during postflight reconditioning. Safe exercise is vital to minimise injury risk, as relatively
minor injuries could cause life threatening situations postflight and during planetary
surface excursions. Exercise concepts that involve potential risk of injury, such as those
with high loads and/or high loading rates, need to be evaluated carefully before being
implemented as inflight CM for astronauts. The problem of confidentiality could be
overcome by anonymised reporting (Table 6.1).
6.2.2 Orthostatic intolerance
Studies of efficient and accurate ways of monitoring orthostatic intolerance (OI), both
inflight to prepare for planetary surface excursions, and during the postflight period will
help determine the effect of OI on the effectiveness and risks of preconditioning and
reconditioning, to inform exercise programmesInflight testing requires the development of
technologies for sensors that would provide feedback to crew and ground medical
operations staff, to tailor the exercise programme. An interactive system would be needed
for use without direct input from reconditioning specialists on the ground. . Knowledge is
also needed concerning the likelihood of OI in lunar and Martian gravity following a
prolonged period in microgravity, although operationally OI is likely to have minimal impact
and not warrant high priority for research.
6.2.3 Sensorimotor function
As with OI, studies to monitor sensorimotor function during the postflight period will help
inform reconditioning. Knowledge of sensorimotor function in lunar and Martian gravity is
also needed. Tests suitable for inflight monitoring need to be developed to inform exercise
programmes for preconditioning to prepare astronauts for planetary surface excursions.
Tests could also be developed for planetary post-landing assessment of performance
prior to an EVA, e.g. simple tests of postural stability could be performed after landing in a
gravitational environment to provide a go/no decision for EVA.
6.2.4 Functional performance
The Functional Task Test (FTT) battery being developed for astronauts described in
Chapter 3 (Section 3.8.6) requires further development to include activities of daily living
relevant to the postflight period. This, together with the more aerobic Functional Fitness
Test (FFT), would help determine the extent and duration of effects of spaceflight on
ability to perform functional tasks and thereby inform the design of reconditioning
programmes relevant to the astronaut’s life on Earth. The FTT will enable assessment of
performance risks and inform the design of CM for exploration class missions. Other
forms of movement screening and exercise programmes to improve quality of movement
(control) used in terrestrial populations (Section 7.4) may also be useful to incorporate into
the preparation (preconditioning) and reconditioning of astronauts.
6.2.5 Aerobic capacity
The exact exercise prescription for the maintenance or improvement of aerobic fitness in
weightlessness is still under investigation. Work is underway to ascertain the correct
elements of such a programme and a systematic and statistically appropriate programme
of work is required to elucidate the nature of the issue. Some analysis of the field is being
pursued by the International Association for the Advancement Study Group of Space
Safety (IAASS) Multilateral Exercise Countermeasures Working Group (personal
communication J Scott, Wyle GmbH). The findings of this work will inform and aid the
Post-mission Exercise (Reconditioning) Topical Team Report
47
development of postflight reconditioning programmes. Based on recent ISS data, aerobic
capacity is maintained well in crewmembers and is not a high priority for reconditioning
research.
6.2.6 Psychological Factors
Adherence and motivation strategies to help astronauts maintain physical activity levels
beyond the supervised phase of postflight reconditioning need to be investigated.
Psychological factors will become more important for long-duration missions, both for
mitigating the effects of long periods in microgravity and for inflight preparation
(preconditioning) for planetary surface excursions (Table 5.2). Recommendations have
been made by Kanas et al (2009) for preparing to deal with psychological factors during
long periods of isolation in future missions but these do not make specific reference to
inflight or postflight exercise. It is unknown whether the benefits of exercise reported for
reducing stress and maintaining morale during pre-ISS missions (Stuster, 1986) will
translate to long duration missions of 1-2 years. Psychological research in the astronaut
population has not focussed on health behaviours, which is necessary to achieve good
adherence and self-motivation but extensive terrestrial research provides a basis for
developing these aspects of space research and promoting good practice (Section 7.8).
6.3 Considerations for research unique to postflight reconditioning
When reviewing the knowledge gaps and identifying strategies to address them (and
subsequently producing recommendations), it is important to consider factors that are unique
to postflight reconditioning and how these may influence the effectiveness of reconditioning.
Several key factors are outlined below in Table 6.1, with some areas explored in further detail
in subsequent sections.
Table 6.1. Considerations for research into postflight exercise re-conditioning
Consideration
Rationale
Programme Focus
Unlike terrestrial rehabilitation which may focus on one or a small number of systems
(e.g. aerobic capacity) or specific parts of that system (e.g. the knee after injury),
postflight exercise re-conditioning must aim to correct changes in many different
systems simultaneously and thus must be designed accordingly.
Accurate reporting of
symptoms and injuries
Research Questions
Problems can only be addressed effectively if the medical operations team are alerted
to them. As in elite sport, where athletes may withhold the presence of injuries and
symptoms so as not to threaten their selection for the next competitive event, openness
in reporting by astronauts is inhibited by the concern of not being deemed medically
certified for the next flight (Harrison 2005). Anonymised reporting of postflight
conditions using mixed methods research in active astronauts would provide a more
complete picture of postflight problems. Effective management of individuals pre- and
postflight requires the astronaut to be open with medical operations, so research to
enhance the therapeutic alliance and operations procedures would be beneficial.
Accurate reporting impacts on all the knowledge gaps identified in Tables 5.1 and 5.2,
to establish the presence and effects of various factors on postflight status of
musculoskeletal structures and function, and planetary surface task performance.
Research questions driven by astronauts and operations teams
(physiotherapists/Exercise Specialists/Flight Surgeons) are important (Section 4.1).
Their involvement at all stages of research is equivalent to PPI in terrestrial research
(section 8.2.6) and needs to begin when developing research questions, to ensure
research is relevant to the needs of astronauts and that the studies are feasible.
Post-mission Exercise (Reconditioning) Topical Team Report
48
Programme Design
Postflight constraints
Supervised postflight exercise reconditioning must take place within a relatively narrow
timeframe (approximately 21-28 days; Section 4.2) and crewmembers typically have
other commitments during this early postflight period including: standard operational
postflight medical testing, testing for human physiology science experiments, and media
commitments for both their Space Agency and home nation, as well as vacations. The
optimal reconditioning period is unknown and research would reveal whether this should
be extended.
Optimal programmes
Links between phases of
astronaut cycle
Optimal postflight reconditioning programmes are needed to maximise function in the
most efficient and effective way (Section 6.3.1).
Effective postflight reconditioning cannot be achieved in isolation. Preflight preparation
and inflight CM will impact its success. As well as preflight strength and conditioning
status affecting subsequent phases, movement quality preflight may affect inflight and
postflight functional performance and injury risk, as poor movement patterns can involve
abnormal loading on joints and cause damage (repeated microtrauma, possibly leading
to osteoarthritis), as in sports (Section 7.4). Close links between the three phases not
only applies to research but also to management of the astronaut. Preferably, the same
team would follow individual astronauts throughout the cycle, as in the ESA Programme
(Section 4.2.2).
Surface activities during
Long Duration
Exploration Missions
Human surface exploration is not new, with experience gained from the Apollo
programme. What will be new with LDEMs is the need to undertake activities following
prolonged periods in microgravity in novel (e.g. Martian) low gravity environments.
Preparation for such activities will be vital (see Section 6.3.2).
Contingency exercises
for equipment failure
In the event of failure of exercise equipment, backup exercise programmes are required
to preserve cardiovascular and musculoskeletal function. Programmes using simple,
low mass and volume devices are needed, e.g. use of high resistance therabands as a
replacement for a resistance training device. Motor imagery to improve strength and
motor skills (Section 6.3.1) could potentially play a role in the absence of equipment.
Electrical stimulation of muscles is another option but the efficacy of use in astronauts
would need to be investigated (Sections 7.5 and 7.6.4).
Research
Opportunities
Existing evidence across
Agencies
With astronauts
Multi-agency collaboration to map current reconditioning practices would enable the
best available evidence to be implemented and inform research to improve practice.
Delphi studies of medical operations specialists would capture practices and future
study designs could involve experts in different areas of terrestrial rehabilitation
(musculoskeletal, sports, neurorehabilitation etc.). A Delphi study involves asking
specific questions to panels of experts to reach consensus statements or
recommendations (Section 8.2.6).
Opportunities for postflight exercise re-conditioning research are limited by the small
number of astronauts and the low frequency with which they return from missions (due
to standard LDMs being of 6-months duration). This issue may, in part, be addressed
by collaborative investigations with the other ISS Partners, which would require
overcoming specific challenges relating to between-Agency coordination to deliver
standardised protocols.
With microgravity
analogues
Long-duration best rest (LDBR) is currently considered the ‘Gold Standard’ ground-
based analogue for prolonged exposure to microgravity for musculoskeletal issues. As
such, it offers an opportunity to conduct exercise reconditioning research (Section
6.3.3); however, to date, this is an opportunity that has not been exploited fully.
Post-mission Exercise (Reconditioning) Topical Team Report
49
6.3.1 Optimal reconditioning programmes
The effectiveness of exercise programmes to restore muscle and functional performance is
multifactorial. The ISS Countermeasure Working Group (CMWG) is an international group of ISS
partners, which forms part of the Multilateral Medical Operations Panel (MMOP). Itconstituent
specialists discuss pre-, in- and postflight exercise matters. It will be important to engage this group
in considering future research about optimal reconditioning programmes. Addressing all factors for all
scenarios in a single research project would require too complex a design to be feasible. The desired
effects of exercise vary, e.g. strength, power, local muscular endurance, cardiovascular fitness, motor
control for quality of movement, vestibular function, performance of specific tasks etc., so will require
different approaches. Development of optimal reconditioning programmes requires studies to
determine the various components:
Dose (frequency and intensity or load)
Duration (within sessions and length of reconditioning period)
Recovery - rest periods within and between sessions to minimise muscle damage and fatigue
Timing of intervention prior to planetary excursions and during postflight period
Tailored to account for inter-individual variability
Strategies to maximise effectiveness and minimise exercise time warrant investigation, for both
inflight and postflight programmes. For example, motor imagery of muscle contractions and
functional tasks can, without the person moving, improve strength (Ranganathan et al. 2004) and
motor skills (Nyberg et al. 2006), and can select the type of contraction (Guillot et al. 2007).
6.3.2 Surface activities during Long Duration Exploration Missions (LDEMs)
6.3.2.1 Preparation for surface activities in microgravity: on-board ‘preconditioning’
The requirement to undertake surface exploration activities following prolonged periods in microgravity
means that the performance effects on crew must be taken into account in the planning phase. Recent
data from ISS suggests that with current knowledge and access to a range of complex exercise CM
devices, some crewmembers are able to largely resist the characteristic changes to musculoskeletal
and cardiovascular systems. However, in relation to surface exploration activities during LDEMs,
several important factors must be considered:
a) The individual response to microgravity and inflight exercise CM is highly variable, and despite
progress, some crewmembers still experience marked losses in muscle volume/strength, BMD and
VO2max (Chapter 3). Even larger changes can be expected following long transits in microgravity;
b) The effectiveness of the ISS exercise CM programme relies on a range of large, highly complex
devices that must be used on a regular basis to achieve CM efficacy (see Section 3.7). However,
the vehicles for LDEMs will be much smaller than ISS and likely contain only a single, far simpler
(for more reliability and lower maintenance needs) exercise CM device. Although further
advancements in CM technologies exercise and otherwise will be made prior to the
commencement of LDEMs, it is possible that, within the constraints of a LDEM vehicle, the current
efficacy cannot be maintained or improved;
c) Due to the constrains of an LDEM vehicle, attempts to conserve resources (e.g. oxygen, food) and
minimize undesirable effects that could compromise the mission (e.g. production of moisture, heat
and carbon dioxide, and excessive wear and tear to exercise devices), mission planning may
require crew to abstain, either partially or completely, from exercise during the early part of a transit,
increasing the volume only shortly before surface exploration and landing on Earth. This scenario is
only hypothetical but needs to be considered.
Alone or in combination, these factors may result in some or even all crew experiencing marked
physiological deconditioning when arriving in orbit around the body to be explored. Crew may therefore
Post-mission Exercise (Reconditioning) Topical Team Report
50
be required to undertake a reconditioning (or preconditioning) programme prior to landing and
commencing planetary surface excursions. This preparation is analogous to the prehabilitation
programmes used in sport to optimise performance and minimise injury risk (see Section 7.4.2) and
research will be needed to develop appropriate programmes for astronauts. As ESA’s current postflight
reconditioning programme is instructor-led, requires a number of intensive face-to-face sessions, and is
conducted in Earth’s gravity, the need for on-board preconditioning presents a range of novel
challenges that must be resolved. It is likely that current reconditioning specialists will be called upon to
advise on the design and implementation of these programmes to ensure crew safety on return to
Earth, and both ensure safety and maximise productivity during surface activities.
6.3.2.2 Performance in low (Lunar and Martian) gravity environments
Surface explorations during the Apollo programme demonstrated that humans can operate effectively
in Lunar (0.16 G) gravity, with no crew reporting disorientation or vestibular illusions (Homick 1975).
Based on these reports, it was concluded that lunar gravity is sufficient for the otolith organs to sense
gravity and to distinguish up from down. This conclusion is supported by data from a recent centrifuge
study, which found that 0.15 G is the critical acceleration threshold where perceived upright and the
‘real’ upright coincide (Harris et al. 2014). Future LDEMs that visit Moon or Mars (0.38 G), will likely
require greater duration surface explorations than the Apollo programme (three days during Apollo 17),
and will thus impose novel physiological and biomechanical demands.
Virtually nothing is known about the physiological effects of prolonged exposure to reduced (< 1G)
gravity. Terrestrial models of reduced gravity includes parabolic flights, supine centrifugation, vertical
body weight support systems (e.g. lower-body positive pressure ‘anti-gravity’ treadmills), tilt tables,
supine suspension systems with sagittal loading and exoskeleton devices. Whilst all these models are
sufficient to reduce the gravitational force acting on the centre of mass, none are capable of, or
practical in, mimicking the physiological effects of prolonged reduced gravity exposure. However, short-
term studies using these models suggest that Lunar and Martian gravity will significantly alter gait
kinematics, muscle activation and muscle coordination patterns during locomotion (Ivanenko et al.
2002). These are likely to translate to changes (reductions) in loading on bones and muscles which, as
suggested by animal studies, might be insufficient to maintain BMD and muscle mass (Swift et al.
2013). This prognosis is reinforced by a theoretical model assuming that bone follows a similar
adaptation pattern to < G as it does to increased loading, and predicts a weekly bone loss of 0.39% in
lunar gravity (Keller 1988).
As demonstrated by studies of astronauts and bed rest subjects, complete gravitational unloading
eliminates the demands on the cardiovascular system to support and transport the weight of the body,
and results in a marked decrease in aerobic capacity (Section 3.5). In contrast to microgravity,
however, crew will experience bodyweight and ground reaction forces during surface explorations, and
the latter will likely increase as a result of the EVA suits and portable life support systems necessary to
conduct activities. In addition, the cardiovascular system will adapt favourably to long periods of
relatively low intensity aerobic exercise. However, whether the loading and associated
cardiorespiratory demand during surface activities will be sufficient to maintain aerobic capacity within
acceptable limits is unknown. Studies with anti-gravity treadmills suggest that cardiorespiratory
demand decreases with reductions in effective body weight, although this decrease is non-linear, with
the change in oxygen consumption becoming significantly smaller as bodyweight support increases
from 0 to 40% (McNeill et al. 2015). Whilst this might suggest that locomotion in low (0.38 or 0.16 G)
gravity could still demand reasonable respiratory effect, particularly with EVA suits and portable life
support systems, this assumes the maintenance of normal terrestrial locomotion. As demonstrated
during the Apollo programme, however, where astronauts adopted a two-footed skipping technique to
optimise O2 use/CO2 production (Kuehnegger et al. 1966), normal locomotion might not be the
preferred method of surface movement in reduced gravity (Minetti 1998).
Post-mission Exercise (Reconditioning) Topical Team Report
51
Should future investigations suggest that the forces acting on the human body during normal
locomotion in partial gravity will most likely be insufficient to maintain musculoskeletal and
cardiovascular function within acceptable limits, exercise CM will also be required during prolonged
periods of surface activity. When and how intensively such CM need to be undertaken will depend on a
number of factors, including the extent of adaption during transit out, the length of stay on the surface
and the nature of operations whilst there.
6.3.3 Reconditioning after bed rest studies
Best rest studies are an under-exploited opportunity to develop effective reconditioning programmes
after deconditioning. The focus of LDBR is on the effects of bed rest itself and only very infrequently
(e.g. Hides et al., 2011) have they been used to study reconditioning after bed rest. An advantage of
bed rest studies is that they typically contain a Control Group that does not participate in any
intervention and thus experiences marked deconditioning. However, control-only groups in bed rest
studies have already generated a knowledge base and the ethical justification for control groups in
future studies needs to be considered. Active control groups to compare interventions would be
justified.
There are important considerations for exploiting the reconditioning research opportunity post-
LDBR:
a) The ethical requirement to perform post-bed rest reconditioning this is not universal across
different nations:
b) Participant numbers typically not large to start with (less than 20) and will reduce further if the
control group is divided into two for comparative studies. Alternatively, if all subjects are used, the
intervention group and control group will likely differ markedly in their physical condition at the end
of bed rest;
c) Participant availability after spending a long period of time at a bed rest facility, if not required for
ethical reasons, participants may not be willing to prolong their stay to take part in supervised re-
conditioning research. If unsupervised re-conditioning research is planned, participants may
disperse widely throughout a country (or even several countries) following bed rest, which creates
its own specific challenges for experimental teams.
d) The study investigating the reconditioning process should not interfere with the research question
of the bed rest study.
e) A bed rest study design that allows post-bed rest reconditioning research to be conducted would
be optimal
A strategy could be implemented across Space Agencies to enter participants into large
multinational randomised controlled trial (RCTs) of reconditioning, using standardised protocols,
once the bed rest component of the study is completed. This approach would be an efficient use of
resources already being invested in the bed rest phase. Exclusions to entering a reconditioning trial
immediately post-bed rest would be studies that aim to monitor lasting effects of interventions
administered during bed rest but reconditioning research could still be built into such studies at a
later stage of recovery.
6.4 Conclusions
Ways to fill knowledge gaps through astronaut and analogue studies have been proposed in relation to
each of the areas identified in Chapter 5 and recommendations are listed in Chapter 10. Considerations
specific to postflight reconditioning research have also been outlined and the design of such studies are
considered further in Chapter 8. Parallels drawn with terrestrial research, where these may be beneficial
for postflight reconditioning research and practice, are expanded upon in the next chapter.
Post-mission Exercise (Reconditioning) Topical Team Report
52
CHAPTER 7
FILLING THE KNOWLEDGE GAPS LESSONS FROM PARALLELS WITH TERRESTRIAL
REHABILITATION AND CHALLENGING ENVIRONMENTS
7.1 Introduction and Relevance
This chapter considers how the identified knowledge gaps in post-mission reconditioning (Chapter 5)
could be partially filled using evidence from terrestrial research. Translation of practices from terrestrial
rehabilitation, which are not possible to investigate in astronauts, may provide valuable lessons for
postflight reconditioning (Section 4.2). Similarly, drawing on knowledge from research where the
reconditioning needs are similar to those of astronauts could inform the designing of robust studies.
Whilst microgravity induces well-documented changes in the neuromuscular system (Chapter 3),
interesting parallels can be seen with various populations on Earth. Examples include responses to
exposure in elite sports (increased activity and muscle imbalances), prolonged bed rest (decreased
activity) and clinical conditions involving deconditioning, such as muscle atrophy following
immobilisation or low back pain (LBP) and neurological disorders. Other aspects associated with sport
that could inform postflight reconditioning include preconditioning exercise programmes to prevent
musculoskeletal injury and promote for example, neuromuscular responsiveness (motor unit
recruitment) and joint health, and psychological strategies to enhance motivation and adherence.
Some terrestrial environments pose specific challenges to conducting research, e.g. on the sports field
and in intensive care units, where the conditions are difficult to control and numbers of participants are
relatively small. Parallels between changes seen in astronauts and terrestrial populations also allow
researchers to pose questions and conduct experiments involving astronauts which can inform and
underpin applications that can benefit all of these populations. The benefits of exchanging knowledge
and expertise between the two environments are therefore reciprocal. Key aspects of terrestrial
scenarios are discussed briefly (Hides et al 2017 in Appendix D).
7.2 Parallels with low back pain (LBP)
7.2.1 Trunk muscle function and impairments in people with LBP
As mentioned in Section 3.1.2, the pattern of atrophy of the lumbopelvic muscles in astronauts is
similar to that in patients with LBP and therefore these patients represent an appropriate population to
learn lessons from. In addition to testing changes in muscles, such as atrophy using imaging
techniques (ultrasound or MRI), control of muscles can be examined using neurophysiological
techniques, such as electromyography to record electrical activity and transcranial magnetic stimulation
to test cortical representation of spinal muscles in the brain. Low back pain (LBP) is known to have
wide-ranging effects on the neuromuscular system. In acute LBP, muscles such as the lumbar
multifidus can decrease rapidly in size (Hides et al. 1994). In contrast, other trunk muscles may
increase their activity (Geisser et al. 2005; Radebold et al. 2000) , which may represent a strategy of
the neural control system to stiffen the spine. Interestingly, the cortical representation of spinal muscles
like the multifidus muscle is discretely organised (Tsao et al. 2011). This, as well as the muscle’s
segmental innervation, may explain the ability of the multifidus muscle to provide precise control of the
segmental spinal segments, which allows control of the position of the lumbar lordosis. The
representation on the cortex has been shown to be altered in people with chronic LBP, where the
cortex is “smudged” (Tsao et al. 2011). It is possible that exposure to microgravity could also influence
sensory feedback from the muscle system to the brain and result in changes in the neuromuscular
system which parallels those seen in people with LBP. It is important to understand these changes, as
these factors are modifiable and could inform the development of interventions. Future research could
investigate whether cortical representation is altered following exposure to microgravity. Strategies to
improve processing of sensory information (such as training two point discrimination of the trunk) in
people with chronic LBP could be trialled and assessed on astronauts postflight. Transcranial magnetic
stimulation could be used to see if “smudging” of the cortex occurs in astronauts, and if it does, if “de-
smudging” is possible in this population through reconditioning.
Post-mission Exercise (Reconditioning) Topical Team Report
53
7.2.2 Motor control retraining in rehabilitation of people with LBP
Despite high levels of fitness, elite athletes are not immune to LBP. For example, elite cricketers with
LBP showed alterations of trunk muscle size and function when compared with asymptomatic
cricketers (Hides et al. 2008). Motor control training (MCT) is a broad term which can include
consideration of all sensory and motor aspects of spinal motor function. A MCT programme
demonstrated effectiveness at decreasing LBP and restoring trunk muscle size and function after
prolonged bed rest (Hides et al. 2012). As outlined in Section 3.3, and in an ESA TT report on inflight
CM for LBP (Snijders & Richardson 2005), LBP is an important consideration in the reconditioning of
astronauts postflight and MCT is a vital part of early ESA postflight reconditioning (Section 4.4.2) but
research is needed to provide evidence of the effectiveness of MCT in astronauts.
7.3 Muscle imbalances in elite athletes
Muscle imbalance is not just about symmetry between the two sides of the body but about imbalances
between muscles within the same movement segment of the body, e.g. agonists and antagonists,
flexors and extensors etc. Also, undertaking apparently symmetrical exercises using ARED does not
guarantee symmetrical muscle activation or movement patterns. In certain sports, the principles of
training and skills required to perform the sports can lead to development of muscle imbalances. For
example in sports which are flexor dominant in nature, the size of extensor muscles can decrease
(Hides & Stanton 2012). Within a group of muscles, such as the anterolateral abdominal muscles, the
effects may vary between muscles that have different roles and are controlled independently by the
neural system. A major torque producing muscle, such as the internal oblique muscle, may increase
over a football playing season, whereas the deep transversus abdominis muscle may decrease in size
over the same period of time (Hides, Stanton 2012). In line with different activities, muscles may
change function between sides of the body in response to functional demand. In summary, muscle
imbalances can occur between muscle groups, within muscle groups and between sides of the body. It
is important to consider rehabilitation strategies for muscle imbalances, as they can be related to
injuries. Such imbalances need to be examined in astronauts and managed with exercise programmes.
Rehabilitation of muscle imbalances using a motor control training programme has been shown to
decrease injury rates in footballers, and was associated with increases in the size of lumbopelvic
muscles and improved ability to draw in the abdominal wall (Hides et al. 2012; Mendis & Hides 2016).
Because stability and protection of the lumbopelvic region involves dynamic trunk control to allow
production, transfer, and control of forces and motion to the distal segments of the kinetic chain (Kibler
et al. 2006), good control of the lumbopelvic area is likely to be required to meet the high demands
imposed on the body in sports such as football.
7.4. Movement control strategies for functional performance and joint health
Controlled movement is not only important for optimal performance of functional tasks but also for
healthy loading on joints (e.g. good alignment and distribution of load (within and between joints in the
kinetic chain). The specific effects of microgravity on functional performance were highlighted in
Section 3.8.6, with tasks requiring more dynamic postural control being more negatively affected than
those requiring less postural stability. Ways of assessing movement control and functional
performance, as well as exercise strategies for improving them, are gaining attention in terrestrial and
space research, but optimal tools and exercise programmes have yet to be established.
It is recognised that despite high levels of athletic performance, poor movement patterns may increase
the risk of injury (Teyhen et al. 2014), e.g. control of the response of the trunk muscles to trunk
perturbation is predictive of lower limb injuries in athletes (Zazulak et al. 2007). Assessment of injury
risk using movement screening tools is translating from elite sport to amateur sport and occupational
groups, including military personnel (Teyhen et al. 2014), fire fighters (McGill et al. 2013) and
astronauts (Bloomberg et al. 2015a). Injury does not just refer to acute trauma but also to repeated
Post-mission Exercise (Reconditioning) Topical Team Report
54
microtrauma, e.g. abnormal loading of joints through poor alignment can lead to osteoarthritis and can
be reduced by motor control exercises to correct movement patterns (Bennell et al. 2012). Exercise
programmes using motor control exercises to improve movement quality are used in sport to optimise
performance and prevent injury (prehabilitaiton or preactivation) but research is in the early stages (see
below).
7.4.1 Movement quality (control) and functional performance screening
Movement screening comprises two types of tests: physical performance tests, which assess
function, e.g. Triple Single Leg Hop, Star Excursion Balance Test (Hegedus et al. 2014; Hegedus et
al. 2015), and movement control tests, which assess quality of movement. Movement quality tests
involve identifying and rating functional compensations, asymmetries, impairments or efficiency of
movement control through transitional (e.g. single knee bend, squat, lunge) or dynamic (hopping,
walking, landing) movements tasks. Several movement control screening tools exist, e.g. the
functional movement screen or FMS (Frohm et al. 2012; Kiesel et al. 2007) and the Performance
Matrix (Mottram & Comerford 2008). However, consensus is needed to harmonise terminology and
definitions used for both types of tools (Hegedus, McDonough 2014; Hegedus, McDonough 2015;
Teyhen, Bergeron 2014). Evidence of the robustness of tools (reliability, validity) is emerging but
further research is needed to determine which tool is most appropriate for a given situation. An
International Movement Screening Group led by the Arthritis Research UK Centre for Sport,
Exercise and Osteoarthritis is co-ordinating efforts by movement screening researchers across the
globe to reach consensus and share protocols to advance the field in research and clinical practice
(http://tinyurl.com/IntMovScrGrp). The ESA Physiotherapist (Lambrecht) recently joined the group.
An example of how a simple observational screening test of movement quality can be used to correct
poor movement control is the small single knee bend test (Botha et al. 2014). Poor alignment of the
knee is illustrated (left picture in Figure 7.1), which causes higher loading and microtrauma on the
medial (inside) aspect of the knee and there is evidence that this results in greater loss of articular
cartilage in the medial compartment of the knee joint (Bennell et al. 2011). The findings of this test
would then be used to inform the exercises needed to retrain the muscles and improve movement
control and alignment of joints (motor control retraining), as in the right hand picture. It is not just
about ability to perform a task but the quality with which the task is carried out as well.
Figure 7.1. The small
knee bend test used to
assess quality of
movement during a
simple semi-squat and
inform motor control
exercises needed to
improve joint alignment
(reproduced from
Botha et al 2014, with
permission from Nadine
Booysen)
Post-mission Exercise (Reconditioning) Topical Team Report
55
As outlined in Sections 3.8.6 and 6.2.4, a movement screen of functional performance introduced by
NASA, the Functional Task Test (FTT), could be complemented with other tests of movement control.
Movement control testing in the immediate post-landing period, when motor control changes rapidly,
may help to inform intervention.
7.4.2 Prehabilitation in sport
Bed rest and spaceflight studies (Section 3.8) highlight the importance of supplementing current
inflight exercise countermeasures with balance training that requires coordination and integration of
proprioceptive feedback and body loading information. This suggests that other systems responsible
for balance and postural control (proprioception, mechanical loading, muscle afferents, etc.) may be
suitable targets for inflight and postflight countermeasure development. The FIFA 11+ used as a
warm-up by football (soccer) players is perhaps the most widely implemented neuromuscular
exercise injury prevention programme (Soligard et al. 2010). More targeted preventive training
programmes aimed at correcting specific movement impairments identified by screening tools are
now being developed for specific sports and occupations (Padua et al. 2014). Astronaut
preconditioning (Bloomberg et al. 2015b) and reconditioning may also benefit from this approach, as
suggested in relation to the performance tests mentioned above (Bloomberg et al 2015a).
The relatively new concept of using exercises to protect joints from overuse injury and abnormal
loading warrants consideration across pre-to-postflight phases, to protect long-term joint health in
astronauts at all times (Figure 1.2). Consultation with elite athletes and coaches reveals that the
motivation for prehabilitation exercises is to optimise sport performance rather than prevent injury,
which they see as a secondary benefit (personal communication, Maria Stokes). Optimising
performance may be an appropriate way to view preconditioning for astronauts, as injuries are
relatively few, although prevention of microtrauma and long-term effects, such as osteoarthritis are
important to consider.
7.5 Parallels with rehabilitation in intensive care
Survivors of critical illness experience significant deconditioning which can have detrimental effects on
quality of life for years after recovery (Herridge et al. 2011). The well-known consequences of bedrest
are compounded in critically ill patients by systemic inflammation associated with sepsis resulting in up
to 12% muscle loss within the first week of illness (Puthucheary et al. 2013). Further heavy sedation
and use of neuromuscular blocking drugs can induce complete ‘mechanical silence’ of the muscles. It is
now recognised that rehabilitation physiotherapy in critically ill patients needs to start early to prevent
deconditioning. Evidence-based choice of therapy depends primarily on the patient’s level of
consciousness as to whether they are able to follow instructions. If so the patients engage in
increasingly demanding active interventions and if not the patients receive passive interventions, often
delivered by therapist or new technology (Gosselink et al. 2008; Sommers et al. 2015) in an effort to
maintain joint range of movement and prevent muscle loss.
The recent application of very early rehabilitation (within 2-5 days of critical illness) in an attempt to
attenuate this rapid deconditioning has focused on non-volitional mobility therapy. Studies applying
unilateral continuous passive movement (daily for 9-10 hours over 7-10 days) in sedated critically ill
patients can preserve muscle architecture, reduce protein loss (Griffiths et al. 1994) and help preserve
force generation capacity of muscle (Llano-Diez et al. 2012). The introduction of cycle ergometry into
Intensive Care Units (ICU) means that both passive and active cycling can be implemented from the
very early stages of illness ((Pires-Neto et al. 2013) with improved functional outcomes (Burtin et al.
2009).
Neuromuscular electrical stimulation (NEMS) creates passive contraction of skeletal muscle using low
voltage electrical impulses delivered through electrodes attached to the skin. Its use increases muscular
blood flow, oxidative capabilities and maximal force generation capacity (Bax et al. 2005). Similar effects
are seen in the critically ill with preserved muscle mass (Gerovasili et al. 2009), improved function and
improved microcirculation (Gerovasili et al. 2009) which interestingly has been shown to have both local
and systemic effects (Routsi et al. 2010). In chronically ventilated patients mobility therapy with NEMS
Post-mission Exercise (Reconditioning) Topical Team Report
56
results in significantly improved muscle strength compared to those who receive standard mobility
therapy alone (Zanotti et al. 2003), although these effects have not yet been reproduced in the critically
ill (Kho et al. 2015). A potential alternative to NEMS is functional electrical stimulation (FES) which
differs from NEMS in that it stimulates muscles in functional patterns in an effort to mimic ‘normal’
contraction under volitional control. FES in conjunction with cycle ergometry may be potentially
beneficial to patients who are not able to partake in volitional exercise (Parry et al. 2014). Investigations
as to whether this is beneficial alone or in conjunction with applied resistance are in development.
Notably, much work in the critically ill is confounded by the heterogeneity of the population, absence of
baseline assessment of function of patients prior to their illness and lack of consensus on outcome
measures.
Deconditioning after six months on the ISS is not severe due to successful countermeasures. However,
effects of longer duration missions are unknown but may present with more severe changes in
neuromuscular tissues that are more difficult to reverse, which would resonate more with the challenges
in managing deconditioning in intensive care patients. Lessons from the latest evidence in such patients
may therefore be useful to draw on when the effects of longer duration missions become apparent.
Moreover, similar intervention strategies may be appealing in these situations, given that non-volitional
training (particularly in conjunction with resistance) may improve compliance and be considered time
efficient, if 2-3 hours of training per day are required. There is also the possibility to train while doing
other tasks.
7.6 Lessons from Rehabilitation of Muscle Wasting Diseases (Neuromuscular Diseases)
A number of the changes in the musculoskeletal and vestibular systems seen after spaceflight or bed
rest (Chapter 3) are similar to the secondary deconditioning effects seen in people with neurological
disorders. Strategies used in neurological rehabilitation, particularly for people with neuromuscular
diseases (NMDs), may have relevance to space reconditioning and some of the key aspects are
considered here.
7.6.1 Muscle atrophy
There has been a recent upsurge in MRI studies exploring primary and secondary muscle atrophy in
NMDs that has enabled greater understanding of the mechanism of weakness and muscle function in
this group. In primary muscle atrophy, due to muscle fibre necrosis or long term denervation, there is
replacement with fat tissue (Morrow et al. 2016). Similar fatty infiltration also occurs with aging (Hogrel
et al. 2015). People with NMDs tend to be sedentary and volume loss is observed in muscles not
affected by the primary disease, with associated reduced muscle strength (Morrow, Sinclair 2016). This
is thought to be secondary disuse atrophy and is a key focus of rehabilitation programmes in conditions
where there is no reversal or treatment of the disease process (Ramdharry 2010). Secondary atrophy
tends to be chronic and long term, so may be a good model for comparison with microgravity induced
deconditioning in astronauts.
7.6.2 Sensory impairment
People with polyneuropathies commonly experience sensory impairment, particularly of proprioception
(van der Linden et al. 2010). Transcranial magnetic stimulation suggests that NMDs with sensory
impairment may have reduced central activation, implying central changes to the sensory pathways
where there has been limited feedback (Schillings et al. 2007). This has implications for astronauts who
may experience similar central changes due to altered sensory feedback during space flight (see
Section 3.6). Sensory impairment has been found to impact gait and balance performance. Altered
proprioceptive feedback can impact joint moments and power generation during gait, and altered
postural stability is observed in people with NMDs, often with increased visual dependency (Mazzaro et
al. 2005; van der Linden, van der Linden 2010).
7.6.3 Fatigue and fatigability
Fatigue and fatigability have specific definitions according to the different experiences and structures
affected. Types of fatigue are commonly described using the following categories: physiological
(peripheral) and central fatigue (Taylor & Gandevia 2008) though experienced fatigue has also been
described in relation to people with NMDs and refers to the overwhelming feeling of tiredness that is
Post-mission Exercise (Reconditioning) Topical Team Report
57
unrelated to the number of muscle contractions and amount of work done, and tends to be pathological
(Schillings, Kalkman 2007). Fatigue in NMDs and other neurological conditions is known to be multi-
factorial (Kalkman et al. 2007; Schillings, Kalkman 2007) and may be of more concern for astronauts in
long duration missions than current ISS missions.
7.6.4 Reconditioning strategies: methods and timescales
NMDs that are “single incident” and undergo full or partial recovery provide some parallels with
deconditioning in astronauts, e.g. Guillain Barre syndrome (GBS), critical illness polyneuropathy (CIP)
and critical illness myopathy (CIM). Recovery from these conditions, however, also relies on recovery
from a pathological process that can take several months, so direct application to astronauts may be
limited. However, parallels with space reconditioning may become more relevant for longer missions, as
recovery may take longer.
A more relevant comparison will be rehabilitation of chronic secondary disuse and deconditioning in the
less affected muscles groups/ sensory systems of people with lifelong NMDs. A number of studies have
investigated both strength and cardiovascular training protocols for a spectrum of nerve and muscle
diseases. For strength training, significant effects were observed with 16 to 24 week programmes using
standard protocols recommended by the American College of Sports Medicine (Lindeman et al. 1995;
Ramdharry et al. 2014). It is worth considering that the effect sizes to achieve functional improvement in
these chronic, long term conditions may be a lot smaller than those required by astronauts to get back to
preflight levels. The optimal time scale for full recovery may be longer than that required by some
muscle groups not so well maintained by inflight CM. An additional inflight CM that could be considered
for such muscle groups is electrical stimulation. It has been explored in critical illness polyneuropathy
and critical illness myopathy (Section 7.5), and is available in the Russian space programme, however
its efficacy is yet to be fully established (Hermans et al. 2014).
Rehabilitation strategies to challenge the sensorimotor control systems have also been explored in
polyneuropathies. Approaches that may be most applicable to astronauts are ways of challenging
stability to improve the coordination of balance responses. Small exploratory studies of moving and
vibrating platforms show some potential in patients with neuropathy (Yoosefinejad et al. 2015) and
vestibular dysfunction (Nardone et al. 2010). Vibrating insoles have also shown improvements in
balance parameters in people with diabetic peripheral neuropathy (Ites et al. 2011).
Functional and exercise training have also shown benefits in patients with neuropathy, including Tai Chi
showing improvements in balance (Ahn & Song 2012), proprioceptive balance training as part of mixed
programmes that include lower limb strengthening (Ites, Anderson 2011) and improvements in
laboratory based balance measures after multi-sensory balance training (Missaoui & Thoumie 2013).
When considering the timescales, it would appear that functional training requires several weeks to
demonstrate change, but some of the higher tech approaches may give faster results. The studies are
small, however, and we must still consider the differences in effect size required for people with NMDs to
show functional improvement, and the effect size required for astronauts to return to preflight function.
7.7 Rehabilitation in Musculoskeletal Ageing
The most extensively explored parallel between microgravity and terrestrial musculoskeletal health is in
ageing, so this is not covered in depth in the present report. Simulated microgravity in bed rest studies
has been used widely in research as a model for ageing (Gianni et al. 2003). An ESA Topical Team
report made reference to ageing in effects on muscle physiology (Wilson & Elmann-Larsen 2005). It
may be that greater effects from longer duration missions result in changes that resemble ageing more
closely in terms of ability to reverse physiological changes and declines in function.
Post-mission Exercise (Reconditioning) Topical Team Report
58
7.8 Psychological aspects of postflight reconditioning
7.8.1. Introduction
Compliance with the reconditioning programme and adherence beyond the supervised phase are
affected by personal and environmental characteristics, as well as previous cognitions and behaviours.
Therefore, preflight, inflight, and postflight factors must all be considered together. Preconditioning
programmes undertaken during mission preparation and inflight will provide the basis for postflight
reconditioning by setting goals, outcome expectations, relationships with the medical team,
motivational climates, barrier mitigation strategies, and behavioural routines.
7.8.2. Compliance and Adherence
There is limited understanding of postflight barriers/resources affecting reconditioning. In terrestrial
populations, poor understanding of medical conditions or prescribed rehabilitation is a key factor in
treatment non-compliance (Marshall et al. 2012), , whereas achieving recovery milestones and
realising anticipated outcomes are positive determinants of ongoing adherence (Bauman et al. 2002).
Similar to elite athletes, astronauts may adopt aggressive reconditioning regimens to promote rapid
recovery (Brewer et al. 2000), but the consequences of over-adherence include risk of injury and
decreased motivation over time (Frey 2008).
Compliance with clinic-based treatment, with supervision and feedback, is generally better than home-
based programmes in patient populations (Granquist et al. 2014) and the ESA reconditioning
programme follows this evidence-based practice. Other facilitators include individualized programmes
(also used by ESA), reference materials (e.g., videos) (Marshall, Donovan-Hall 2012), treatment diaries
or activity monitors, (Levy et al. 2006), accurate outcome expectancies, social support, exercise
enjoyment (Bauman et al. 2012;) and self-selection of exercise types and intensities (Williams 2008).
Similar strategies may be applied with astronauts. On extended missions or between missions, these
strategies may become crucial, as barriers and resources are likely to be situational and could change
rapidly, necessitating both self- and external monitoring to maintain behaviour. Access to resources in
such cases would be essential, and environmental factors (e.g. temperature, clothing requirements,
absence of feedback) will likely present novel barriers during extended missions.
7.8.3. Motivation
During supervised early postflight reconditioning, astronaut motivation and compliance are typically
high. Based on operational experience, self-motivation is likely to be most challenging preflight and
following supervised postflight reconditioning. Two primary motives for astronauts to comply with
reconditioning are the recovery/maintenance of functional health and the desire to return to preflight
status (and thus qualify for future missions). These powerful drivers do not exist in isolation. Astronauts
are likely motivated more globally by extrinsic (e.g. policy or performance requirements) and intrinsic
(e.g. enjoyment of exercise, challenge, professional and personal identity) factors. Extrinsic motivation
has consistently been implicated in poor adherence to rehabilitation and exercise programmes (Ng et
al. 2012), whereas intrinsic (self-determined) motivation predicts adherence (Brewer, Van Raalte
2000).
Self-reliance and self-efficacy (perceived competence) are essential factors for behavioural
maintenance (Wilson et al. 2008), and practitioner support for patient autonomy and competence is
directly related to treatment outcomes in rehabilitation settings (McGrane, Galvin 2015). Therefore,
during preflight and inflight phases, supporting these needs will be crucial in promoting intrinsic motives
for programme compliance. The importance of such support was stressed in the astronaut case
histories in Section 4.3. During postflight reconditioning, the balance between autonomy and medically
necessitated interventions will change along with the transition from acute reconditioning to health
maintenance, but should be considered in the design of long-term exercise plans.
7.8.4. Therapeutic Alliance and Trust
The therapeutic alliance (the relationship between patient and therapist) is positively associated with
treatment compliance, treatment satisfaction, physical function, and depressive symptoms (Hall et al.
2015). Provision of emotional support and allowing patient involvement in decision making are key in
Post-mission Exercise (Reconditioning) Topical Team Report
59
both athlete (Clement et al. 2013) and clinical populations (Pinto et al. 2012). It is important for
therapists to understand patient preferences and priorities in order to tailor reconditioning programmes
that will be acceptable and feasible on a case-by-case basis (Dean et al. 2005).
Similar to elite athletes, astronauts are often reluctant to report medical symptoms or health problems
for fear it will result in disqualification (Flynn 2005). Developing trust in medical staff is therefore a
critical component of preflight and inflight care that will translate to postflight reconditioning. Trust was
highlighted as a key factor in the astronaut case history in Section 4.3.1. A positive relationship with
the therapist will lead to better decision-making and will likely provide a foundation for more realistic
outcome expectations, more meaningful feedback, and better astronaut buy-in to long-term exercise
programming.
7.8.5. Recommendations for practice
For astronaut care, there is a need to routinely monitor psychosocial factors that may influence
reconditioning compliance and treatment outcomes (Foster & Delitto 2011). Considering common
postflight medical concerns, symptoms are likely the largest barrier to compliance in the acute
reconditioning phase, but personal motivations and social/physical environment factors will play a
larger role with adherence over time. Addressing these issues will assist therapists in making
appropriate decisions and tailoring programmes to fit individual needs, ultimately enhancing treatment
results (Seefeldt et al. 2002). Creating autonomy-supportive climates will be challenging within the
constraints of existing training procedures and mission requirements, but building astronaut self-
efficacy and providing detailed information to allow for realistic outcome expectations is feasible.
Additionally, given the norms of confidentiality within the astronaut corps (Harrison 2005), developing
strong therapeutic alliances can help to mitigate concerns related to health care and provide necessary
social support (Slade et al. 2009).
7.8.6. Future research on psychological aspects
Most behavioural health research within the space exploration domain has focused on psychiatric
problems rather than social psychology, and there has been no investigation of health behaviours
either inflight or post-mission (Brady 2005). Therefore, recommended areas of research include
examination of astronaut experiences to inform the design of multifactorial barrier mitigation and
motivation enhancement strategies, and investigation of the links between preflight, inflight, and
postflight behaviours. Understanding the nature of the therapeutic alliance would allow maximization of
existing personnel resources and enhance reconditioning outcomes, and could lead to better uptake of
evidence-based recommendations (Palinkas et al. 2005). Finally, with a view to longer duration and
exploration missions, investigating potential barriers to ongoing health behaviours will become
important in designing mission specifications and generating policies (Pascoe et al. 1994).
7.9 Spin-offs for terrestrial rehabilitation from space research and vice versa
The reciprocal benefits of terrestrial and space research to aid recovery from deconditioning have been
alluded to throughout this chapter. Back pain and risk of back injury are very relevant to astronauts, so
research in this area may be applied directly. Training in elite sports is also directly applicable, as
astronauts are healthy, but, due to microgravity derived deconditioning could exist at the opposite end
of the activity spectrum at the culmination of a LDM. Rehabilitation research into deconditioning
associated with clinical conditions, such as neurological disorders, intensive care for critical illness and
ageing, can provide useful lessons for astronaut reconditioning. Psychological approaches to
motivation and adherence to exercise may be particularly effective in astronaut reconditioning.
The advantage of translating research on astronauts to terrestrial rehabilitation is that changes to the
neuromuscular system which may take a long time to develop on Earth develop at an accelerated rate
in microgravity. Also, the adaptations in response to microgravity occur without the complications of
specific pathologies which may be associated with clinical conditions on Earth; e.g. a clearer picture of
deconditioning is seen. Some of the spin-offs may be technological advances, an example from space
research being the anti-gravity treadmill, now used in terrestrial sports training and rehabilitation.
Post-mission Exercise (Reconditioning) Topical Team Report
60
7.10 Conclusions on lessons from terrestrial rehabilitation
There are several parallels between the deconditioning effects of microgravity on astronauts and those
on Earth, associated with different environments, activities and clinical conditions. Understanding the
effects on the neuromuscular system is important, as this system is plastic and interventions can
therefore be planned based on observed modifiable changes identified. For example, if specific
muscles are atrophied, exercises can be planned to target the group/muscle, leading to potential
development of better and more effective interventions for astronauts and the wider community.
Recommendations proposed from these terrestrial parallels to fill knowledge gaps in postflight
reconditioning are listed later in Chapter 10. Specific challenges faced in astronaut and microgravity
analogue studies are now addressed in Chapter 8, which suggests ways of applying different research
designs to provide non-conventional yet robust solutions.
Post-mission Exercise (Reconditioning) Topical Team Report
61
CHAPTER 8
RESEARCH METHODOLOGY
Research methodology for space medicine can, for the most part, draw from established designs and
practices (as described in standard literature), yet there are unique aspects to space science which
demand special consideration. The challenge is to identify which aspects of terrestrial methodology remain
robust for space science, identify which aspects are inappropriate and then present solutions.
8.1 Study design challenges in existing literature/knowledge
The methodological considerations unique to space travel and reconditioning are described in brief.
The overall objective is to create or enhance the body of space travel related knowledge, particularly
with regard to efficacy of reconditioning treatment. Whilst evidence on treatment efficacy is preferably
generated from randomised controlled trials (RCTs) and meta-analyses of such studies, the space
science environment with its extremely small population restricts the relevance and applicability of such
a design. Randomised N = 1 trials may have a limited role to play in this area although they cannot
address final rehabilitative outcomes. Alternative and hybrid methods or modifications are required to
generate a body of knowledge (see Fig 8.1), including;
1. Assimilation, extraction and summation from existing studies (specifically on space reconditioning).
However, there will be very few to reference.
2. Translation from existing observational studies from the realms of physiology and psychology.
3. Evidence from directly related terrestrial studies of similar problems in relation to
deconditioning/pathology.
4. Indirect evidence from corollary studies of hostile environments (these may have similar limitations
to space travel science)
5. New tailored and specifically designed interventional studies (accepting the small study sizes and
the restrictions inherent in the environment).
Designing new studies will be the most challenging and the majority of the chapter is given over to this
topic (Beard & Cook, 2017 in Appendix D). Little detail is provided in terms of reconditioning content,
as this has been covered in Chapters 4, 6 & 7).
Figure 8.1: Schema of information source for reconditioning science and efficacy
Body of
Knowledge
Existing
Knowledge
Observational
Studies
(Physiology,
Psychology)
Interventional
Studies
[Counter
Measures]
(Efficacy)
Terrestrial Non
Space
Evidence
Translational
Corollary
Environment
Translational
Post-mission Exercise (Reconditioning) Topical Team Report
62
8.1.1 First in human characteristics of interventions
Interventions for space medicine, including reconditioning, share similar characteristics with “first
in [hu]man studies”
7i
, particularly with the surgical specialities. These studies are the first time
the device or drugs have been used in/for human subjects and are usually tested in very small
controlled sample sizes. The very low ceiling on available participants (of astronauts) with the
associated reduction in statistical precision to detect differences is of particular note and
suggests that formal statistical analyses are not likely to be appropriate, except in very restricted
and modified (accepted a much lower level of certainty than is commonly used) sense.
With this in mind it is recommended that an ordered and systematic approach to prospective data
collection is pursued, similar to that of IDEAL (Idea, Development, Exploration, Assessment,
Long-term follow-up) recommendations for surgical sciences (McCulloch et al. 2009; McCulloch
et al. 2013). The IDEAL is a systematic approach to the introduction of surgical innovation which
consists of the five phases and the first two (idea and development), in particular, may lend
themselves to postflight reconditioning. The first part of the IDEAL approach does not involve
inferential statistics.
Realistically, the majority of studies will have low numbers of participants and may span sever