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Reported Side-effects and Safety Considerations for the Use of Blood Flow Restriction During Exercise in Practice and Research

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Reported Side-effects and Safety Considerations for the
Use of Blood Flow Restriction During Exercise
in Practice and Research
Christopher R. Brandner, PhD,* Anthony K. May, Bsc,Matthew J. Clarkson, MSc,
and Stuart A. Warmington, PhD
Summary: Blood ow restriction (BFR) exercise is seen as a potential
alternative to traditional training methods, and evidence suggests this is
being used with both healthy and clinical populations worldwide.
Although the efcacy of the technique regarding muscular adaptations
is well known, the safety of its use has been questioned. The purpose of
this review was: (i) provide an overview of the known reported side-
effects while using BFR exercise; (ii) highlight risks associated with the
cardiovascular system, and; (iii) suggest recommendations to minimize
risk of complications in both healthy and clinical populations. Overall,
reported side-effects include perceptual type responses (ie, fainting,
numbness, pain, and discomfort), delayed onset muscle soreness, and
muscle damage. There may be heightened risk to the cardiovascular
system, in particular increased blood pressure responses, thrombolytic
events, and damage to the vasculature. However, while these may be of
some concern there is no evidence to suggest that BFR exercise elevates
the risk of complications any more than traditional exercise modes.
Several modiable extrinsic factors for risk minimization include
selecting the appropriate BFR pressure and cuff width, as well as
completion of a preexercise safety standard questionnaire to determine
any contraindications to BFR or indeed the prescribed exercise. On the
basis of the available evidence, we are condent that the side-effects of
using BFR are minimal, and further minimized by the use of an
appropriate method of application in the hands of a trained practitioner.
Key Words: KAATSUsafetyside-effectsvascular occlusion
exercise.
(Tech Orthop 2018;33: 114121)
Exercise training with blood ow restriction (BFR) is a
technique whereby limb blood ow is reduced via external
compression that is typically applied with a pneumatic cuff or
tourniquet. More specically, it is expected that BFR results in
a partial restriction to arterial in-ow while occluding venous
outow. BFR is most commonly applied during resistance
exercise,1and is seen as a potential alternative to traditional
heavy-load resistance exercise (HLRE) [ 70% 1 repetition
maximum (1RM)] due to the light-loads prescribed (20% to
40% 1RM) that reduce the mechanical stress on the
musculoskeletal system, while providing gains in muscle
strength and mass that are greater than non-BFR equivalent
intensity exercise, and on occasion have been reported to be
similar to HLRE.24
The use of BFR in both healthy and clinical populations
has seen a rise in popularity over the past 2 decades, with many
of the original studies focusing on the efcacy of the use of
BFR with respect to muscle adaptations and performance. More
recently though, several papers have questioned the practicality
and safety of BFR in some human populations.513 However, it
would be expected that many of the purported risks and/or side-
effects may be avoided with well-controlled use of suitable
equipment to induce BFR, and when in the hands of trained
practitioners with knowledge of the technique.
To quantify the risk of BFR exercise for a specic pop-
ulation, it is important to compare the responses, side-effects,
and any adverse complications with that of traditional resistance
exercise with heavy-loads or light-loads, as well as high-
intensity and low-intensity aerobic exercise as these are the
current standards to improve muscle strength, mass, and
endurance. As an example, some populations are contra-
indicated to HLRE due to the risks associated with more
extreme elevations in blood pressure (BP), and thus the added
risk of a cardiovascular event.14 Others may be contraindicated
due to the mechanical strain placed on the musculoskeletal
system while lifting heavy-loads, such as low physical func-
tioning populations. Therefore, BFR exercise may be pre-
scribed as an alternative exercise method for populations con-
traindicated to traditional modes, provided that BFR confers
some benet to the risk of elevated BP or provides benet due
to the use of light-loads.
Therefore, the purpose of this review is to provide an
overview of the current literature associated with reported side-
effects while using BFR. In addition, to discuss factors that may
be considered important when examining the risks and con-
traindications of BFR. Lastly, we suggest several modiable
factors for risk minimization when using BFR in populations
that are often contraindicated or those that may be at greater risk
of adverse events during traditional modes of exercise.
REPORTED SIDE-EFFECTS WHILE PERFORMING
BFR EXERCISE
There have been reports of side-effects as a result of
performing BFR exercise. Even the original creator of the BFR
technique (referred to as Kaatsu in Japan), acknowledged that
he found it difcult to apply the appropriate pressure for him-
self and to other individuals during early experimentations, to a
point where his skin would turn pale and he was later diagnosed
with pulmonary embolism, although there is no evidence to
suggest that this was caused by BFR.15
From the *Sports Science Department, Aspire Academy for Sports
Excellence, Doha, Qatar; and Institute for Physical Activity and Nutrition
(IPAN), School of Exercise and Nutrition Sciences, Deakin University,
Geelong, Australia.
The authors declare that they have nothing to disclose.
For reprint requests, or additional information and guidance on
the techniques described in the article, please contact Christopher R.
Brandner, PhD, at chris.brandner@aspire.qa or by mail at Sports
Science Department, Aspire Academy for Sports Excellence, P.O. Box
22287, Doha, Qatar. You may inquire whether the author(s) will agree
to phone conferences and/or visits regarding these techniques.
Copyright © 2018 Wolters Kluwer Health, Inc. All rights reserved.
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As the technique was popularized in Japan, the largest
epidemiological study of BFR usage demonstrated particularly
low incidences of any adverse events for BFR exercise.5The
most common reported side-effect was subcutaneous hemor-
rhage (13%) followed by numbness (1.3%), and with occa-
sional reports of cerebral anemia, feeling cold, venous throm-
bus, pain, itch, and others. However, while some of these may
be considered more serious adverse outcomes, there is no
indication of any underlying medical conditions for those in the
survey who suffered adverse events, and given the occurrence
of these adverse outcomes was lower than the natural incidence
across the broader population, it is difcult to conclude that
these outcomes were a direct result of the BFR. However, it is
known that at the time of the survey, in Japanese centers BFR
was applied with relatively thin cuffs (3 cm) and high pres-
sures in excess of 160 to 200 mm Hg. As such, it is feasible that
this implementation of BFR may have been more likely to
produce adverse side-effects that are now rarely reported. A
more recent global survey of practitioners and researchers that
implement BFR in a wide variety of populations showed similar
reported incidence of subcutaneous hemorrhage/bruising (13%)
while numbness was more prevalent (19%). Again, there was
little evidence to directly align these outcomes with BFR, and
even less alignment with the method of BFR application (eg,
BFR pressure and cuff width). We are condent that the side-
effects of using BFR are minimal, and further minimized by
appropriate methods of application in the hands of a trained
practitioner.
Perceptual Type Responses
Fainting/Dizziness
One of the highest reported side-effects in a recent survey
of practitioners using the BFR technique was numbness and
fainting/dizziness, with almost 20% of respondents declaring
that they had observed this in their facility.1However, these
were only reported in <1% of cases by Nakajima and col-
leagues, and it is likely these reported incidences inate the true
representation of these side-effects given there are no data on
the number of users/participants of BFR within each facility,
and does not account for overlap between practitioners in the
survey that encountered the same event. In any case, it is likely
these participants experienced postexercise hypotension, or
even a vaso-vagal response associated with the application of
BFR and so is expected to be a somewhat random incidence
rather than being clearly denable, identiable, and predictable
in particular participants.
Numbness
The rst randomized control trial to comment on a sen-
sation of numbness in the quadriceps muscle during BFR
exercise used high pressures (230 mm Hg) combined with wide
cuffs (13 cm).16 These are important factors to consider, given
that the BFR pressure, duration of ination, and cuff width are
all modiable prescription variables that may reduce the risk of
these adverse responses. It is worth noting that numbness with
BFR likely occurs either due to pressure applied to peripheral
nerves, or more likely the development of ischemia in response
to the restriction to ow.17 In 1 study, sensory motor nerve
conduction was not altered following 4 weeks of lower body
resistance exercise with BFR,18 which is not surprising given
that BFR is typically only held for relatively short durations of
5 to 20 minutes. Even with experiments in which complete
occlusion is induced for upwards of 30 minutes, these do not
result in any long-term adverse effects or maladaptations and
these side-effects are rapidly reversed following the removal of
the BFR.17 In addition, being transient events without long-
term concerns, we do not expect these to be prohibitive for the
prescription of BFR when using an appropriate method and in
the hands of a trained practitioner.
Ratings of Perceived Exertion, Pain, and Discomfort
Most often BFR presents greater ratings of perceived
exertion (RPE), pain, and discomfort despite the use of light-
load resistance exercise (20% to 40% 1RM).1921 As such, one
might suggest that BFR remains unsuitable for populations with
low conditioning, poor motivation, and reduced adherence to
exercise programs. However, for these population, most forms
of exercise at least present with greater RPE. Therefore, if
undertaking structured exercise, BFR should form part of the
available repertoire. Indeed we have shown in older adults that
RPE was great in the initial stages of a BFR walking training
program, but this subsided over the rst few sessions to be
equivalent to that for non-BFR walking training.22
Importantly, some studies have shown that perceived
exertion and pain are lower with BFR exercise in comparison
with HLRE.23,24 However, this seems to be a contentious area
within the BFR literature with some opposing reports that are
likely due to different exercise protocols and BFR method-
ologies used between studies.19,21,25 Nevertheless, with these
perceptual responses subsiding after a few exercise sessions
with BFR,20,26 there appears an adaptive effect on these per-
ceptual responses that facilitates greater tolerance to BFR
exercise once participants gain some familiarity with the
experience.
Delayed Onset Muscle Soreness
Delayed onset muscle soreness (DOMS) seems to be
commonly reported following BFR exercise, and can persist for
24,27 48,28 and even 72 hours postexercise24 depending on the
exercise protocol and BFR methodology being used. BFR
exercise has been shown to result in greater DOMS in com-
parison with exercise with the same loads without BFR,24,27
whereas only 1 study has compared this response to HLRE and
found the DOMS response to be greater with BFR.24
It is imperative to note that an episode of DOMS is rela-
tively normal following unaccustomed exercise bouts, or due to
higher than expected increases in exercise intensity (ie, external
load) or volume (ie, total exercise volume).29 So while the
DOMS response peaks between 24 and 72 hours postexercise,
this is a transient response to the exercise stimulus and not to
BFR per se, before muscle soreness levels return to resting
levels.
Markers of Muscle Damage
Given that DOMS is often associated with several markers
of exercise-induced muscle damage, several different measures
for muscle damage have been examined following BFR exer-
cise. These are often measured as a time course response
postexercise in comparison with resting measurements. Overall,
the afliated markers of muscle damage appear only slightly
increased and/or rapidly return to resting levels. For example,
maximal voluntary contractile force is reduced immediately
postexercise30 and at 24 hours postexercise,27,31 whereas
changes in muscle swelling, circumference, and range of
motion all return to baseline levels within 24 hours of exercise
completion.28 Furthermore, although blood markers of muscle
damage have not been extensively examined, creatine kinase,
myoglobin, and interleukin-6 are not elevated following BFR
exercise in both young and older healthy adults.3234 Given that
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these observed markers are relatively low, it would appear that
the BFR exercise confers no more risk for muscle damage (and
perhaps even less so) than traditional training methods.
Of note, 1 paper observed reduced quadriceps muscle
cross-sectional area at the site of muscle origin following BFR
training.16 However, this was likely due to the application of
wide cuffs in combination with suprasystolic restriction pres-
sures (230 mm Hg) resulting in high compression and shear
stress to the tissue under the cuff. There have also been case
study reports of BFR-inducing rhabdomyolysis,35,36 which is a
condition in which damaged skeletal muscle breaks down
rapidly and myoglobin is released into the circulation. The
patient in the rst reported case study presented to hospital with
elevated creatine kinase levels following just a single bout of
BFR knee extension exercise. However, this patient was dis-
charged from hospital after 3 days, and 18 days after the inci-
dent continued BFR exercise without further (reported) inci-
dent. The patient in the more recent case study36 was a 30-year-
old overweight man (body mass index, 28.1 kg/m
2
) diagnosed
with rhabdomyolysis within 24 hours following a single BFR
exercise session. This was the rst training session after a
period of inactivity. Physical inactivity, and the early intro-
duction of squats to a training program, which he performed
with a BFR (pressure and load not listed), are both considered
risk factors for rhabdomyolysis.37 In addition, before any
diagnosis of rhabdomyolysis, a high fever and pharyngeal pain
(diagnosed as tonsillitis) were reported after the session and
resulted in a local clinic prescribing a number of medications,
which may have further promoted the later onset/diagnosis and
treatment of rhabdomyolysis.38 Therefore, this case of rhab-
domyolysis seems to be more a result of a combination of
factors, and probably not a result of the BFR. The large epi-
demiological study conducted by Nakajima and colleagues
reported only 1 of 12,642 persons diagnosed with rhabdo-
myolysis following BFR exercise. More recently, of 115
practitioners surveyed in a questionnaire using BFR with their
clients/patients, 3% reported an incident of rhabdomyolysis
while using BFR.1However, 1 potential limitation of these
studies is that it is not clear how rhabdomyolysis was deter-
mined, while a large range of populations with possible con-
traindications to exercise/BFR were captured, making it dif-
cult to relate the adverse effects to BFR when so few
occurrences have been noted. Overall, muscle damage seems to
be a minor risk following BFR exercise.
Other Reported Side-Effects
There have been few other side-effects described in the
current literature, but case studies have reported acute loss of
vision,39 and a series of complications including brain hemor-
rhage, petechial hemorrhage, and venous injury.40 Although
future studies are encouraged to report any side-effects that may
occur during BFR exercise, it is somewhat difcult to elucidate
if the complication was caused solely by BFR, the exercise
stimulus, or via any underlying complicating physiology/path-
ology. Furthermore, the potential risk of using BFR either with
or without exercise, and frequency of side-effects, should not be
any higher than what is typically seen following traditional
resistance or aerobic exercise.
POTENTIAL RISKS WHEN USING BFR DURING
EXERCISE
Before prescription of any traditional mode of exercise,
consideration is needed with regard to the potential risks of
adverse events. This is typically undertaken through standard
screening procedures to evaluate certain risks. Factors such as
age, training history/habits, evidence of chronic disease (dia-
betes, hypertension, obesity, etc.), genetic/family medical his-
tory, current/prior musculoskeletal injury, etc., all play a role.
However, often the focus is largely on BP and the associated
complications that may arise as a result, and which vary
between populations. These factors inform the practitioner of
the risk of prescription of HLRE as well as intense aerobic
exercise, yet despite BFR exercise prescribing the use of light-
loads, similar considerations must be given these common
contraindicators that confer added risk of adverse events to
undertaking any exercise type. Therefore, in the sections below,
we describe and discuss some of the potential contraindicators
to BFR exercise to characterize their signicance in the context
of HLRE, given HLRE is considered the most likely exercise
type to confer a signicant risk of an adverse event. In addition,
we review some other areas of focus that have previously been
raised as a concern when considering prescription of BFR
exercise.
Hemodynamics
For resistance exercise, the BP response increases in line
with the resistance load, volume, and mass of skeletal muscle
recruited for the action. Although this is normal for any exer-
cise, BP may be exacerbated during HLRE with maximal val-
ues for mean arterial pressure being reported upwards of
250 mm Hg.41 As such, BFR with light-loads is seen as a
potential alternative.
A large body of the current literature has focused on the
acute hemodynamic responses to BFR, both with and without
exercise, and a systematic review of these responses was pub-
lished recently.42 It seems that when matched for the same
external load (% 1RM) and total exercise volume (sets×repe-
titions), BFR resistance exercise typically elicits slightly higher
acute increases in heart rate (HR), BPs, and cardiac output, with
reductions in stroke volume, in comparison with non-BFR
exercise.23,4347 However, when exercise is performed until
muscle failure, these acute hemodynamic responses are similar
between light-load BFR and non-BFR exercise.16,48 The mode
of exercise is also important to note, with BFR walking pro-
ducing comparably lower elevations in BPs, HR, and cardiac
output in comparison with BFR resistance exercise in both
healthy young and older populations.23,43
Comparisons with heavy-load exercise are less frequent
but in the context of risk assessment, probably the most
important. Nevertheless, the hemodynamic responses with BFR
exercise are generally shown to be similar,23,44 and in some
cases lower than for HLRE.47,48 For example, evidence from
our laboratory with both young and older healthy populations
has shown that HR, BP, and cardiac output responses are
similar to HLRE when utilizing high-pressure BFR exercise
(150 mm Hg), yet more similar to light-load resistance exer-
cise when the BFR pressure is reduced (90 mm Hg).44 Myo-
cardial workload (measured as the product of HR and BP) is
also lower with BFR exercise in comparison with HLRE49 or at
least not any greater than traditional HLRE.44,47 This is espe-
cially important to consider, given that increased muscle
strength and mass may be derived though BFR exercise in
conjunction with a reduction in exercising hemodynamic stress,
and so may alleviate some of the risk associated with HLRE for
populations that may be contraindicated.
Vasculature
There is growing interest in the effect of BFR exercise on
vascular function.48,5057 In particular with respect to muscular
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endurance, with current evidence suggesting that BFR exercise
promotes postexercise blood ow, oxygen delivery, and capil-
larization (angiogenesis), resulting in an overall improvement in
microvascular function.53,58 The main stimuli for inducing
skeletal muscle angiogenesis include intramuscular hypoxia,
changes in vascular wall tension/shear stress, and mechanical
overload produced during muscle contraction. The result is an
increase in expression of several angiogenic factors. However,
despite the low mechanical tension associated with BFR exer-
cise in comparison with HLRE, results from a study by Larkin
et al59 showed that BFR exercise also increases the expression
of several angiogenic factors, including vascular endothelial
growth factor, hypoxia-inducible factor-1 α, and neuronal-nitric
oxide synthase. Importantly, these responses were shown to
be elevated immediately postexercise and up to 24 hours post-
exercise, which is similar to observations seen following HLRE60
and early BFR research.61 However, BFR exercise training
[4 weeks of knee extension; with BFR (30% 1RM) or without
(80% 1RM)] has not demonstrated any effect on measures of
pulse wave velocity in healthy young adults,18 andsothisneeds
further investigation.
This potential effect of BFR on vascular function may
prove particularly benecial in populations that are more
susceptible to endothelial dysfunction as a result of progressive
atherosclerosis across the lifespan (eg, older adults). However,
this raises some degree of caution given that BFR is more likely
to produce turbulent arterial ow that can lead to vascular
damage, thus placing populations like older adults at greater
risk of a vascular event during BFR.9,62 Although, recent evi-
dence has demonstrated a positive effect on vascular endothelial
function and peripheral blood circulation in healthy older adults
without any reported contraindications.57 Again, there is little
evidence to support BFR being any more deleterious in pop-
ulations susceptible to vascular injury, but provides an element
of concern and certainly an area for future research.9,62
Thrombolytic Events
Given the nature of the application of BFR, there may be a
concern associated with obstruction of blood ow producing
conditions that may promote coagulation at sites of vascular
damage and atherosclerosis. Fortunately, as mentioned above,
there have yet to be any reports of deleterious effects of BFR on
the vasculature within well-designed research studies. The
epidemiological questionnaire conducted by Nakajima et al5
reported thrombolytic complications at 0.055% (7 cases) in
their large study sample, whereas only 0.8% of practitioners
reported thrombolytic events with their clients in a more recent
questionnaire, although the health and age of these participants
was not able to be determined.
One way to measure the effect of BFR exercise on
thrombolytic events is by examining the acute and training-
related changes in blood markers for coagulation (eg, brinogen
and D-dimer). Nakajima et al63 were the rst to show that BFR
resistance exercise did not alter prothrombin time or markers of
coagulation, whereas Madarame et al64 also showed that blood
markers of thrombus formation and thrombin production are
not elevated following a single bout of 4 sets of leg press with
BFR. Similar results were found in a follow-up study by the
same authors in patients with stable ischemic heart disease
who were not currently treated with anticoagulant drugs.65
Although these studies examined the effects of BFR following
a single training session, Clark et al18 did not observe any acute
changes in brinolytic or coagulation markers following an
initial exercise session with either BFR or heavy-loads, or
following the nal training session after 4 weeks of training in
healthy young adults. This seems to be similar in healthy older
adults (60 y and above), with 12 weeks of BFR resistance
exercise of both the lower-body66 and upper-body67 showing
no deleterious changes in coagulation factors such as brinogen
degradation product or D-Dimer.
In contrast to the negatively associated effects of BFR
exercise on thrombus formation, it would appear that resistance
exercise without BFR68 as well as BFR without exercise69 have
been shown to stimulate the brinolytic system. Importantly as
well, the combination of BFR and light-load resistance exercise
helps to promote a brinolytic state,63,64 which inhibits
thrombus formation. Therefore, while most of the afore-
mentioned studies were conducted in healthy populations, it
would appear that BFR exercise does not activate the coagu-
lation system.
MINIMIZING RISK FACTORS WHEN
PRESCRIBING BFR
There are several intrinsic and extrinsic factors that should
be considered before conducting BFR exercise. Intrinsic factors
can include an individualsmedical history, and are considered
contraindications to BFR exercise (Table 1). These are some-
what less modiable than extrinsic factors. Other intrinsic
factors that are not contraindicators but should be considered
before prescription of BFR exercise can include age, lifestyle
TABLE 1. Possible Contraindications to Use of BFR
Cardiovascular disease
Coronary heart disease
Unstable hypertension
Peripheral vascular disease
Venous thromboembolism
Hypercoagulable states (blood clotting disorders)
Cardiopulmonary conditions
Atherosclerotic vessels causing poor blood circulation
Silent myocardial ischemia
Left ventricular dysfunction
Hemophilia
Vascular endothelial dysfunction
Varicose veins
Induration/Marfan syndrome
Musculoskeletal injury
Recent muscle trauma or crush injuries
Postsurgical excess swelling
Open fractures
Open soft tissue injuries
Skin graft
Lifestyle
Age
Smoking
Body mass (eg, obesity)
Pregnancy
Uncontrolled diabetes mellitus
Dyslipidemia
Dehydration
Family medical history
Clotting disorders
Sickle cell anemia
Atrial brillation or heart failure
Cancer
Medications
Those known to increase blood clotting risk
On the basis of authors review of the literature and in consultation
with medical professionals.
BFR indicates blood ow restriction.
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factors, blood vessel size, limb size, muscle and adipose tissue
thickness, and current strength capacity.15 As such, the mod-
ication of extrinsic factors such as the nal BFR pressure,
duration of applied pressure, and the width of the cuffs or
tourniquets is required to prescribe BFR exercise in an effective
and safe manner.
Considerations on Patient Selection and Possible
Contraindications
The majority of data available on healthy young pop-
ulations suggests that BFR is a safe alternative to traditional
modes of exercise; however, possible contraindications to the
use of BFR are listed in Table 1. Over the past decade there has
been an increase in adoption of BFR exercise in clinical pop-
ulations such as older adults at risk of sarcopenia,67,70 pregnant
women,71 following musculoskeletal injury,72 patients with
metabolic syndrome,73 hypertension,7476 cardiovascular
disease,65,77 as well as obese clients.78 Importantly, no adverse
risk responses have been reported in published randomized
control trials in these clinical populations, and while there have
been some reported side-effects to BFR, it remains difcult to
suggest whether BFR should be avoided in any special
populations.
All populations should be assessed for possible risks and
contraindications before performing BFR in research and
practice. Therefore, thorough clinical judgement is required by
the practitioner to determine if the individual is an appropriate
candidate to perform BFR. For all research studies involving
BFR (either with or without exercise), approval from the
Institutional Research Review Board and signed informed
consent from the study participants should be obtained.
Although it may not be necessary for the lead investigator of a
BFR research study to be a licensed physician, it would be
expected that this person should be an expert in BFR with
knowledge about principles, physiology, prescription, and
potential side-effects or adverse reactions to the technique. In
addition, it should be essential that before any use of BFR in
research or the eld that a standard prequestionnaire screen
should be completed by all BFR candidates. An easy to use risk
assessment tool was recently published.10
Providing that screening is administered, and the
researcher/practitioner has knowledge of BFR and its applica-
tion, there is potential for the use of BFR with broader clinical
populations, provided the researcher/practitioner is well-versed
in exercise responses in those populations or protocols are
devised with a collaborator that is. For example, while uncon-
trolled hypertension may prohibit BFR use in the same way it
prohibits HLRE, those medicated for hypertension may still be
eligible for BFR exercise given that BP and BP responses may
still fall within normalranges seen during and following
exercise.79 Diabetes is often strongly associated with hyper-
tension, and additionally requires strict monitoring of blood
glucose.80 However, both factors are easily measured and
controlled by medication, meaning BFR exercise may not be
contraindicated provided BP and blood glucose are monitored.
Diabetes may still be contraindicated to BFR in the presence of
symptomatic neuropathy or active retinal hemorrhage.80 Thie-
baud et al81 highlighted the potential benets of BFR exercise
for chronic obstructive pulmonary disorder. Providing consid-
erations to underlying cardiovascular concerns are well man-
aged, and the prescription accounts for impaired respiratory
capacity, BFR may be valuable for chronic obstructive pulmonary
disorder. Pilot data (Stuart A Warmington and Matthew J Clarkson;
Data collected, 2016) from our research group indicates that
BFR applied during cycling exercise is appropriate for patients on
hemodialysis. Neither BP, HR, nor dialysis adequacy were affected
with low-to-moderate intensity BFR cycling compared with
equivalent intensity non-BFR cycling, which is already a recom-
mended prescription for dialysis patients.82 Although these sug-
gestions represent a range of clinical populations that may benet
from BFR with additional considerations, it is by no means a
comprehensive list, and for most conditions further research is still
required to conrm the suitability of prescribing BFR exercise.
BFR Recommendations for Practitioners and
Research
It seems that the area of main concern regarding the use of
BFR relates to the equipment being used (in particular the width
of the restrictive cuff) and the nal BFR pressure used during
exercise and how this may initially be determined. Early
research studies (eg, between 1998 and 2012) often prescribed
arbitrary and excessive BFR pressures. However, this method is
limited in that it does not account for interindividual differences
in limb size (ie, both muscle and adipose tissue content), vas-
cularization, and BP, which may not only decrease the efcacy
of BFR with regard to functional adaptations, but may also be a
safety concern if prescribed exercise pressures are excessive.
The major focus for prescribing a pressure during BFR exercise
should be to nd the lowest possible pressure that remains
effective for the individual. Loenneke et al83 rst proposed a
standardization method to account for interindividual differ-
ences when using BFR. It was suggested that the pressure that
produces a complete cessation of arterial blood ow, or the
individual arterial occlusion pressure (AOP) be determined
using Doppler Ultrasound at rest, and practitioners are
encouraged to use a set percentage of that measurement for the
BFR pressure.84 Methodology for determining the AOP using
Doppler Ultrasound has been provided previously,85 whereas
other devices utilize in-built technology to similarly determine
the maximal limb occlusion pressure (LOP). Importantly, time
of day also has an effect on the maximal AOP, thus practi-
tioners should endeavor to measurement of AOP immediately
before undertaking BFR exercise, or at least at the same time of
day as previous measurements of AOP.86 Furthermore, given
that pressure transmission from the cuff to the underlying tissue
is dependent on cuff width (discussed below), the cuff width
used to determine AOP must be the same as that used to restrict
blood ow during a BFR exercise bout.
Following on from the determination of AOP, the practi-
tioner must decide what percentage of AOP to prescribe for the
BFR user. The nal restriction pressure used has varied widely
(50 to 300 mm Hg) depending on the individual and exercising
limb. However, similar increases in elbow exion muscle
strength, mass, and endurance have been observed between
BFR pressures equal to 40% AOP (53 ±7 mm Hg) and 90%
AOP (116 ±17 mm Hg), suggesting that lower pressures could
be useful to avoid any deleterious responses to higher
pressures.87 There still is no consensus within the literature as
to the most optimal BFR pressure, and utilization of AOP/LOP
methods for BFR exercise is still low (11.5% of 115 surveyed
practitioners).1In addition, it is unknown whether different
BFR pressures may be required for prescription in different
populations. For example, athletes versus nonathletes, older
adults versus young adults, and a host of other populations. As
such, despite limited information on safe yet effective BFR
pressure prescription, we recommend use of a BFR pressure in
the range of 40% to 80% AOP for both the upper-body and
lower-body, with lower pressures perhaps just as efcacious as
higher pressures while minimizing the risk of contraindications
to BFR during exercise. It may also be prudent to begin training
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programs at lower percentages and progressively increase the
restriction pressure each exercise session while monitoring
physiological and perceptual responses.
Restrictive cuffs can range from 3 to 15 cm in width.
However, wider cuffs likely occlude arterial blood ow at lower
overall pressures in comparison with narrow cuffs.88,89 When
using the same percentage of maximal AOP (80%), no differ-
ences in muscle strength or mass were observed following 12
weeks of training with either wide (10 cm) or narrow (5 cm)
cuffs.90 However, when matched for the same relative pressure
(determined as a percentage of systolic BP), wider cuffs have
been shown to induce a greater cardiovascular response in
comparison with narrow cuffs,91 and this may be seen as a
potential concern, particularly for those with underlying car-
diovascular issues. Overall, wide cuffs (8 to 10 cm for upper-
body, 10 to 14 cm for lower-body) should provide a more
effective transmission of pressure through the underlying tissue
and vasculature in comparison with narrow cuffs (5 and 3 cm
for upper-body and lower-body, respectively), and thus lower
relative restriction pressures can be prescribed. It may be more
likely that narrow cuffs and subsequently higher restriction
pressures increase the risk of adverse responses in bruising,
nerve compression, and numbness. Finally, contoured cuffs
induce occlusion at lower pressures than commonly used
straight cuffs.92 As such, this should also be considered when
prescribing BFR pressures.
BFR AND ORTHOPEDIC CONSIDERATIONS
The majority of the BFR-published literature has been
conducted on nonclinical populations. However, clinicians have
begun to apply BFR as part of a rehabilitation program after
injuries and orthopedic surgery.72 A number of published
studies have assessed the effects of BFR after anterior cruciate
ligament reconstruction without adverse events.93,94 Time
frames ranged from days 3 to 14 and weeks 2 to 16 post-
operative. One trial included measurements of joint laxity via
knee ligament arthrometry (KT2000) and found no signicant
difference between groups. The potential for thrombus for-
mation has only been assessed in 1 postoperative BFR trial. In
that study, 6 weeks of BFR after knee arthroscopy found no
signs of thrombus formation on Duplex Ultrasound imaging.95
Currently, there are registered orthopedic trials assessing
the effects of BFR after joint arthroplasty, anterior cruciate
ligament surgery, femur fractures, and wrist fractures.96 As
more large robust clinical trials are completed the safety of BFR
and appropriate clinical populations will be better understood.
Orthopedic surgeons have adopted the use of surgical grade
medical tourniquets in the operating room with minimal com-
plications. In the clinical setting, applying BFR following the
same safety principals utilized during surgery may help reduce
potential tourniquet complications.97
CONCLUSIONS
The purpose of this review was to briey discuss the
reported side-effects of performing BFR either with healthy or
clinical populations, to present some possible contraindications
to BFR exercise, and to provide recommendations to minimize
risk when using BFR in populations that are often contra-
indicated or those that may be at greater risk of adverse events
during traditional modes of exercise.
On the basis of the current literature, it seems that BFR
exercise can be used safely in most populations without sig-
nicant risk of complications, provided that BFR is prescribed by
trained practitioners that have knowledge of appropriate protocols
(ie, restriction pressure application and durations, and their
interaction with different cuff widths), and the possible contra-
indications to the use of occlusive stimuli. It is recommended that
the nal restriction pressures used during exercise should be
calculated as a percentage of each individuals maximal AOP,
with lower pressures (ie, 40% to 80% AOP) perhaps conferring a
reduction in risk, making BFR safer and just as efcacious as
higher pressures for improving musculoskeletal mass and
strength, cardiovascular tness, and functional abilities. The
current data examining the safety aspect of BFR is in its relative
infancy, although tourniquet safety has long been examined.
Therefore, before performing BFR it is recommended that prac-
titioners use a preexercise safety standard questionnaire that
accounts for listed contraindications to BFR exercise (as well as
traditional exercise modes) to determine any contraindications,
and future studies should report and discuss any side-effects
observed when using BFR exercise to improve our understanding
of any arising issues with respect to safety.
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... The study participant below believed that he had the will to do the physical activity but believed the wrong information that people with hypertension could not do it because their blood pressure would rise if they did the physical activity ( Figure 10). Regular physical activity by itself lowers blood pressure [49]. Although physical activity has a positive effect on blood pressure, regardless of medication, the older adults in this study did not participate in physical activity due to the acquisition of insufficient and distorted information. ...
... Numbness, pain, discomfort, and muscle aches are the side effects that hypertensive patients can have after participating in physical activity [49], and various side effects can appear when exercising at an appropriate level or higher. However, physical changes caused by physical activity can be a great fear for older adults when they do not know these facts. ...
... Through news and other indirect experiences, negative aspects of physical activity are recognized, which leads to avoidance of physical activity [57]. Furthermore, if the risk of accidents from physical activity due to other chronic diseases is significantly low, then older adults with hypertension should be encouraged to engage in physical activity by the current guidelines [49]. It has been noted that highintensity physical activity has more disadvantages than significant advantages for older adults with hypertension, as compared to moderate-intensity physical activity [20]. ...
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This study attempted to explore the barriers to physical activity of older patients with Hypertension. It aimed to provide robust evidence produced through their eyes. First, through the data analysis of the accelerometer and the decision of the research team, 10 out of the 30 applicants were invited to participate in a photovoice study. Photovoice is one example of participatory action research. Photovoice participants can communicate their unique experiences through photographs, providing a highly realistic and authentic perspective that is not possible to be understood with traditional qualitative research. This study inductively identified four main themes; health illiteracy, distortion of health information, fear of physical activity, and rejection of any life changes. Based on a specific understanding of the population’s perception of physical activity, this study attempted to provide evidence of why many elderly Korean patients with Hypertension stay inactive.
... BFRT consist of exercising using a surgical grade pneumatic cuff or tourniquet that partially restricts arterial inflow, and fully restricts venous outflow from the working musculature during exercise. 15,16 The clinical value of BFRT that has been suggested in the literature is that it allows increased muscle adaptation and hypertrophy with LL-RT, 17 making BFRT a potentially advantageous tool to implement in the early post-operative population. The utilization of BFRT in conjunction with current rehabilitation standards of care has shown potential with respect to muscle adaptations and performance. ...
... Possible concerns include the effects of BFRT on the cardiovascular system such as blood pressure responses, potential thrombolytic events and damage to the vascular system. 16 Despite these concerns, there have been several extensive reviews published demonstrating that the side effects are minimal, 18,19 and BFRT when compared with traditional methods of strength training shows no greater risk in adults. 20 Hughes et al. described BFRT to be as effective at improving strength and more effective at improving function, pain, and swelling compared to HL-RT in ACLR patients, 13 as well as more comfortable for patients during the early phases of post-surgery rehabilitation. ...
... 20 Prior authors have reported on adverse events after BFRT with the use of narrow diameter cuffs (∼3 cm) and with high pressures (160 to 200 mm Hg). 16 A higher rate of adverse side effects were reported utilizing a narrow diameter cuff and high pressures, consistent with Estebe et al. who concluded that a 14 cm cuff needed significantly less pressure to occlude blood flow compared to a 7 cm cuff that caused significantly more pain after reaching arterial occlusion. 30 Additionally, LOP was calculated for each limb individually at every training session. ...
Article
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Background: Blood flow restriction training (BFRT) has gained popularity in rehabilitation due to its benefits in reducing muscle atrophy and mitigating strength deficits following anterior cruciate ligament reconstruction (ACLR). While the effectiveness and safety of BFRT has been well studied in healthy adult subjects, there is limited information about the use of BFRT in the adolescent population, specifically related to patient tolerance and reported side effects post ACLR. Purpose: To investigate and record reported side effects and patient tolerance to BFRT during ACLR rehabilitation in adolescents. Study design: Prospective Cohort Study. Methods: Patients between 12 and 18 years of age who underwent ACLR at Connecticut Children's were included. Patients utilized an automatic personalized tourniquet system and followed a standardized BFRT exercise protocol over 12 weeks starting 8.72 ± 3.32 days post-op. Upon completion of exercise while using BFRT, patients reported side effects and any adverse events were logged. Descriptive statistics were used to describe the reported side effects and adverse events associated with BFRT and calculate the frequencies of those events over a 12-week period. Results: Five hundred and thirty-five total BFRT sessions were completed between 29 patients (15.39 ± 1.61 years of age). There were zero reports of subcutaneous hemorrhage (SubQ hemorrhage) and deep vein thrombosis (DVT). Reported minor side effects to BFRT included itchiness of the occluded limb (7.85%), lower extremity paresthesia (2.81%), and dizziness (0.75%). A total of 10.47% of BFR treatment sessions were unable to be completed due to tolerance, and 3.5% of sessions required a reduction in limb occlusion pressure (LOP). Conclusion: These preliminary data suggest that BFRT is safe with only minor side effects noted in the adolescent population after ACLR. Further investigations are warranted to continue to evaluate patient tolerance and safety with BFRT, because while these preliminary results suggest a positive safety profile and good tolerance in the adolescent population after ACLR, they represent the experiences of only a small sample. Level of evidence: Level 3.
... Few studies in the literature have been concerned with analyzing variables which could verify the safety of pBFR training [30,47]. In analyzing muscle damage, Wilson et al. [19] demonstrated that soreness, power and muscle swelling were similar between low-load resistance exercise with and without pBFR; in addition, Behringer et al. [38] demonstrated that after 6 weeks of sprint training, the heart-type fatty acid-binding protein (h-FABP) was significantly lower in the group that trained with pBFR than in the control group, with similar responses between groups regarding cortisol. ...
... These findings lead us to think that pBFR training in healthy individuals is safe, and it seems that side effects or adverse events are minimal, with risks being minimized when the practitioner or researcher is well trained using appropriate methods in applying the elastic wrap or cuff. According to Brandner et al. [47], most often the side effects caused by traditional BFR training seem to be associated with high pressure applied by the cuff (~ 200 mmHg) or when thin cuffs (~ 3 cm) are used. Previous studies have reported that wider cuffs require a lower pressure to occlude blood flow compared with narrower cuffs [34,36,48,49]. ...
Article
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Most studies with blood flow restriction (BFR) training have been conducted using devices capable of regulating the restriction pressure, such as pneumatic cuffs. However, this may not be a viable option for the general population who exercise in gyms, squares and sports centers. Thinking about this logic, practical blood flow restriction (pBFR) training was created in 2009, suggesting the use of elastic knee wraps as an alternative to the traditional BFR, as it is low cost, affordable and practical. However, unlike traditional BFR training which seems to present a consensus regarding the prescription of BFR pressure based on arterial occlusion pressure (AOP), studies on pBFR training have used different techniques to apply the pressure/tension exerted by the elastic wrap. Therefore, this Current Opinion article aims to critically and chronologically examine the techniques used to prescribe the pressure exerted by the elastic wrap during pBFR training. In summary, several techniques were found to apply the elastic wrap during pBFR training, using the following as criteria: application by a single researcher; stretching of the elastic (absolute and relative overlap of the elastic); the perceived tightness scale; and relative overlap of the elastic based on the circumference of the limbs. Several studies have shown that limb circumference seems to be the greatest predictor of AOP. Therefore, we reinforce that applying the pressure exerted by the elastic for pBFR training based on the circumference of the limbs is an excellent, valid and safe technique.
... Potential adverse events that could reflect thrombosis, ischaemia, or rhabdomyolysis [15] were monitored (Table 1), with participants instructed to record and report any response that was atypical for them post-exercise. Participants completed a safety questionnaire after each BFR session and attended a weekly virtual meeting with a researcher (BD/EM) to report any adverse events that occurred during the preceding week. ...
... No signal of important harm was identified when garment-integrated BFR was applied to the upper limb of healthy adults, reflected by the minimal presence of adverse events and confirmation of sub-occlusive pressure. Muscle soreness is a common side effect of low load resistance exercise combined with BFR [1], which may persist for up to 72 h [15]. Two participants (8%) in this study reported excessive muscle pain post-exercise. ...
Article
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Background Blood flow restriction training (BFR) has been demonstrated to increase muscle hypertrophy and strength, but has logistical and cost barriers. Garment-integrated BFR has the potential to reduce these barriers by lowering equipment demands and cost. The primary aim of the study was to explore the feasibility of garment-integrated BFR in the upper limb of healthy adults, with a secondary aim of exploring safety and efficacy. Methods Physically active and otherwise healthy participants with no previous experience with BFR were sought. Eligible participants completed a five-week garment-integrated BFR programme that involved completing two sessions per week. Feasibility was determined by a priori defined thresholds for recruitment, adherence to the garment-integrated BFR programme, and data collection. Safety was determined by recording adverse events and by monitoring for total arterial occlusion pressure using a fingertip pulse oximeter. Efficacy was determined by measuring push-ups to volitional failure, arm girth, and number of prescribed repetitions completed. Feasibility and safety outcomes were reported descriptively or as a proportion with associated 95% confidence intervals (95% CI). Mean change, 95% CIs, and associated effect sizes were calculated for efficacy outcomes. Results Twenty-eight participants were included (15 men, 13 women; mean age 31.6 years [±9.1]) and 27 successfully completed the study. Participants were successfully recruited within three months and 278/280 sessions were successfully completed (adherence=99.3%, 95% CI 97.4%, 99.9%). Minimal adverse events were reported; one incident of localised bruising (0.36%, 95% CI 0.06%, 2.0%) and three incidences of excessive pain during or post-exercise from two separate participants (1.07%, 95% CI 0.03%, 3.1%). 82/2240 pulse oximeter readings were not recorded (3.7%, 95% CI 2.9%, 4.5%). Mean push-ups to volitional failure increased by 40% (mean change=8.0, 95% CI 6, 10, d=1.40). Mean arm girth and number of prescribed repetitions completed were unchanged. Conclusions Garment-integrated BFR is feasible and has no signal of important harm in the upper limb of healthy adults, and could proceed to a future trial with stop/go criteria for randomisation. Further work is required to investigate the efficacy of garment-integrated BFR and determine its equivalence or superiority compared to existing BFR methods.
... Potential adverse events that could re ect thrombosis or ischaemia (20) were monitored (see table 1). ...
... Garment-integrated BFR was identi ed to be safe for use in the upper limb of healthy adults, re ected by the minimal presence of adverse events and con rmation of sub-occlusive pressure using perceived compression stimulus. Muscle soreness is a common side effect of low load resistance exercise combined with BFR (1), which may persist for up to 72 hours (20). Two participants (8%) in this study reported excessive muscle pain post-exercise. ...
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Background Blood flow restriction training (BFR) has been demonstrated to increase muscle hypertrophy and strength, but has logistical and cost barriers. Garment-integrated BFR has the potential to reduce these barriers, by lowering equipment demands and cost at point of access. The primary aim of the study was to explore the safety and feasibility of garment-integrated BFR in the upper limb of healthy adults, with a secondary aim of exploring efficacy. Methods Participants who were active, otherwise healthy and had no previous experience with BFR, were sought. Eligible participants completed a five-week garment-integrated BFR programme that involved completing two sessions per week. Safety was determined by recording adverse events and by monitoring arterial occlusion pressure using a pulse oximeter. Feasibility was determined by measuring recruitment, adherence to the garment-integrated BFR programme and data collection. Efficacy was determined by measuring push-ups to volitional failure, arm girth, and number of prescribed repetitions completed. Adverse events were counted and reported as a percentage of the cohort. Adherence was calculated as a percentage of successfully completed sessions of the prescribed total. Mean change, 95% confidence intervals and associated effect sizes were calculated for efficacy outcomes. Results 28 participants were included and 27 successfully completed the study. Minimal adverse events were reported; one incident of localised bruising (0.36%) and three incidences of excessive pain during and post-exercise from two separate participants (1.07%). 3.7% of pulse oximeter readings were not recorded (82/2240). 278/280 sessions were successfully completed (adherence=99.3%). Mean push-ups to volitional failure increased by 40% (mean change=8.0, 95% CI 5.7, 10.3, d=1.40). Mean arm girth and mean number of prescribed repetitions completed were unchanged. Conclusions Garment integrated BFR is a safe and feasible option in the upper limb of healthy adults, with a secondary increase in push-ups to volitional failure also observed. Further studies are required to determine the efficacy of garment integrated BFR compared to other training methods, and the use of garment integrated BFR in other populations.
... This would allow for the LOP to be measured as a relative value in relation to individual arterial pressure and the use of a certain percentage of the arterial occlusion pressure (AOP) to ensure individual safety (13,20). Setting this AOP too high (.80% occlusion) can increase the risk of suffering an adverse event (e.g., subcutaneous hemorrhage or numbness), whereas too low (,40% occlusion) pressures may not guarantee an adequate stimulus to generate desired adaptations (5,30). Moreover, high pressures are more likely to cause discomfort and pain in the individual, potentially leading to a reduction in training adherence (31). ...
Article
Research suggests that healthy eating and exercise decrease the likelihood of developing osteoarthritis (OA) with age. Despite this, OA is a prevalent chronic condition that typically causes joint pain at rest and during exercise, making it difficult to develop effective training programs. Recently, blood flow restriction (BFR) training has shown to be a beneficial alternative to traditional resistance training to improve muscle function. In this article, we provide a rationale as to how BFR may be a beneficial resistance training alternative that would allow individuals with osteoarthritis to experience similar improvements in muscle function compared with traditional resistance training using lower relative intensities.
... Evaluation of the individual patient for BFRT represents a potentially complex medical screening problem. A list of individual risk factors that are associated with adverse responses to BFRT has already been discussed and proposed elsewhere to aid in the screening process (Nakajima et al., 2011;Kacin et al., 2015;Brandner et al., 2018;Bond et al., 2019;Rolnick et al., 2021). However, a considerable amount of information regarding their impact on health is scattered throughout the literature and not compiled in a BFR-specific resource. ...
Article
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Blood flow restriction training (BFRT) is a modality with growing interest in the last decade and has been recognized as a critical tool in rehabilitation medicine, athletic and clinical populations. Besides its potential for positive benefits, BFRT has the capability to induce adverse responses. BFRT may evoke increased blood pressure, abnormal cardiovascular responses and impact vascular health. Furthermore, some important concerns with the use of BFRT exists for individuals with established cardiovascular disease (e.g., hypertension, diabetes mellitus, and chronic kidney disease patients). In addition, considering the potential risks of thrombosis promoted by BFRT in medically compromised populations, BFRT use warrants caution for patients that already display impaired blood coagulability, loss of antithrombotic mechanisms in the vessel wall, and stasis caused by immobility (e.g., COVID-19 patients, diabetes mellitus, hypertension, chronic kidney disease, cardiovascular disease, orthopedic post-surgery, anabolic steroid and ergogenic substance users, rheumatoid arthritis, and pregnant/postpartum women). To avoid untoward outcomes and ensure that BFRT is properly used, efficacy endpoints such as a questionnaire for risk stratification involving a review of the patient’s medical history, signs, and symptoms indicative of underlying pathology is strongly advised. Here we present a model for BFRT pre-participation screening to theoretically reduce risk by excluding people with comorbidities or medically complex histories that could unnecessarily heighten intra- and/or post-exercise occurrence of adverse events. We propose this risk stratification tool as a framework to allow clinicians to use their knowledge, skills and expertise to assess and manage any risks related to the delivery of an appropriate BFRT exercise program. The questionnaires for risk stratification are adapted to guide clinicians for the referral, assessment, and suggestion of other modalities/approaches if/when necessary. Finally, the risk stratification might serve as a guideline for clinical protocols and future randomized controlled trial studies.
Article
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This review paper outlines the effect of blood flow restriction exercise on hemodynamics from the biomechanical perspective. Blood flow restriction exercise is a kind of exercise methods that maximizes the effectiveness of exercise by applying specific pressure to block vein flow while allowing flow of arteries by wearing portable pneumatic cuffs in the upper and lower parts of the body prior to exercise. In various existing literature, the effect of blood flow restriction on exercise has been revealed based on lots of field including elite sports, recreation, and rehabilitation. This study will establish the concept of blood flow restriction on exercise by integrating the contents of such research. Therefore, the purpose of this study is to provide information based on scientific evidence on blood flow restriction exercise by introducing the concept and principle of blood flow restriction, physiological mechanisms and effects, actual application cases, and precautions.
Article
INTRODUCTION: During spaceflight missions, astronauts work in an extreme environment with several hazards to physical health and performance. Exposure to microgravity results in remarkable deconditioning of several physiological systems, leading to impaired physical condition and human performance, posing a major risk to overall mission success and crew safety. Physical exercise is the cornerstone of strategies to mitigate physical deconditioning during spaceflight. Decades of research have enabled development of more optimal exercise strategies and equipment onboard the International Space Station. However, the effects of microgravity cannot be completely ameliorated with current exercise countermeasures. Moreover, future spaceflight missions deeper into space require a new generation of spacecraft, which will place yet more constraints on the use of exercise by limiting the amount, size, and weight of exercise equipment and the time available for exercise. Space agencies are exploring ways to optimize exercise countermeasures for spaceflight, specifically exercise strategies that are more efficient, require less equipment, and are less time-consuming. Blood flow restriction exercise is a low intensity exercise strategy that requires minimal equipment and can elicit positive training benefits across multiple physiological systems. This method of exercise training has potential as a strategy to optimize exercise countermeasures during spaceflight and reconditioning in terrestrial and partial gravity environments. The possible applications of blood flow restriction exercise during spaceflight are discussed herein.Hughes L, Hackney KJ, Patterson SD. Optimization of exercise countermeasures to spaceflight using blood flow restriction. Aerosp Med Hum Perform. 2021; 93(1):32-45.
Thesis
Introdução: Desordens musculoesqueléticas são comuns e podem comprometer a função, o desempenho físico e a qualidade de vida. Dentre as intervenções utilizadas no manejo de desordens musculoesqueléticas, as modalidades de restrição de fluxo sanguíneo (RFS) vêm ganhando espaço na literatura científica. Objetivos: Essa tese teve o propósito de investigar os aspectos fisiológicos, os métodos de prescrição e as aplicações clínicas de modalidades de RFS em diferentes desordens musculoesqueléticas. Métodos e resultados: As modalidades de RFS consideradas foram a RFS passiva (sem exercício concomitante), o pré-condicionamento isquêmico (PCI) e a RFS combinada ao exercício. Como desordens musculoesqueléticas foram consideradas condições que causassem prejuízo funcional, tais como perda de força e de massa muscular, dano muscular induzido por exercício, fadiga muscular e osteoartrite (OA) de joelho. A presente tese é composta por introdução, três capítulos referentes às modalidades de RFS, e considerações finais. Os capítulos 1, 2 e 3 versam, respectivamente, sobre RFS passiva, PCI e RFS combinada ao exercício, e são compostos de sete artigos científicos envolvendo três desenhos de estudo: revisão sistemática (com e sem meta-análise), revisão narrativa e ensaio clínico aleatorizado. O capítulo 1 é uma revisão sistemática (artigo 1) sobre os efeitos da RFS passiva para minimizar perdas de força e de massa muscular (hipotrofia por desuso) em indivíduos submetidos a restrições na descarga de peso em membros inferiores. No capítulo 1 observamos que embora potencialmente útil, o alto risco de viés apresentado nos estudos originais limita a indicação de RFS passiva como modalidade eficaz contra a redução de força e de massa muscular induzida por imobilismo. O capítulo 2 é um ensaio clínico controlado e aleatorizado (artigo 2) que investigou os efeitos do PCI na proteção contra o dano muscular induzido por exercício (DMIE) em pessoas saudáveis. O artigo 2 apontou que o PCI não foi superior ao sham para proteger contra o DMIE. O capítulo 3 aborda aspectos fisiológicos, metodológicos e clínicos da RFS combinada ao exercício físico. O primeiro manuscrito do capítulo 3 (artigo 3) é uma revisão sistemática com meta-análise que analisou a excitação muscular (por eletromiografia de superfície) durante exercício resistido com RFS. O artigo 3 indicou que a excitação muscular durante o exercício de baixa carga com RFS foi maior que durante exercício de carga pareada sem RFS somente quando a falha muscular não foi alcançada. Adicionalmente, exercício de baixa carga com RFS apresentou menor excitação muscular que exercício de alta carga, independentemente de alcançar ou não a falha voluntária. O segundo manuscrito do capítulo 3 (artigo 4) é uma revisão sistemática com meta-análise que mostrou uma viii antecipação da falha muscular durante exercícios de baixa carga com altas pressões de RFS, mas não com baixas pressões. O terceiro manuscrito do capítulo 3 (artigo 5) é uma revisão narrativa que discute a possível necessidade de ajustar a pressão de RFS ao longo das semanas de treinamento. No artigo 5 observamos que a literatura é contraditória, o que dificulta recomendar se tais ajustes na pressão de RFS são necessários. O artigo 6 é um protocolo de ensaio clínico aleatorizado proposto para investigar os efeitos do exercício de baixa carga e volume total reduzido com RFS versus treinamento de alta carga sem RFS no tratamento da OA de joelho. O artigo 7 é o ensaio clínico aleatorizado que apresenta os resultados do protocolo (artigo 6) e mostrou que o treinamento de baixa carga com volume total reduzido e com RFS teve efeito similar ao treinamento de alta carga sem RFS na dor no joelho, desempenho muscular, função física e qualidade de vida de pacientes com OA de joelho, embora a magnitude nos ganhos de força tenha sido maior após treino de alta carga. Conclusões: De forma geral, com exceção do PCI para proteger contra o DMIE, as modalidades de RFS são potencialmente úteis no manejo das disfunções musculoesqueléticas aqui estudadas. Adicionalmente, concluímos que é necessário avançar no entendimento dos mecanismos fisiológicos e no estudo dos métodos de prescrição das diferentes modalidades de restrição de fluxo sanguíneo.
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Objectives: The progressive age-related declines in muscle health and physical function in older adults are related to muscle size and strength. Walking with an applied blood flow restriction is an alternative to maintain muscle volume in older adults to increase the value for time spent walking. Therefore, the aim of this study was to examine the effect of adding blood flow restriction to low-intensity walking on clinical measures of physical function. Design/methods: Sedentary older men and women were randomised to either a low-intensity blood flow restriction walking group (BFRW; n=10), or a non-blood flow restriction walking control group (CON; n=9). Participants were assessed at baseline, three-weeks and six-weeks for the 30second sit to stand, six-minute walk test, timed up and go, and a modified Queen's College step test. While a rating of perceived exertion (RPE) for training sessions at baseline, three-weeks and six-weeks. Results: BFRW typically resulted in a 2.5-4.5 fold greater improvement in performance on all measures of physical function compared with CON among these older adults. However, RPE was greater for BFRW at all time points (for baseline, three-weeks, six-weeks: 14±0; 11±0; 11±0) compared with CON (8±0; 7±0; 8±0), despite declining across the study for BFRW. Conclusions: The greater improvement in physical function with blood flow restriction demonstrates how this addition can increase the quality of simple walking exercise for populations that may be contraindicated to heavy-load resistance training.
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The hemodynamics of light-load exercise with an applied blood-flow restriction (BFR) have not been extensively compared between light-intensity, BFR, and high-intensity forms of both resistance and aerobic exercise in the same participant population. Therefore, the purpose of this study was to use a randomized crossover design to examine the hemodynamic responses to resistance and aerobic BFR exercise in comparison with a common high-intensity and light-intensity non-BFR exercise. On separate occasions participants completed a leg-press (resistance) or treadmill (aerobic) trial. Each trial comprised a light-intensity bout (LI) followed by a light-intensity bout with BFR (80% resting systolic blood pressure (LI+BFR)), then a high-intensity bout (HI). To characterize the hemodynamic response, measures of cardiac output, stroke volume, heart rate and blood pressure were taken at baseline and exercise for each bout. Exercising hemodynamics for leg-press LI+BFR most often resembled those for HI and were greater than LI (e.g. for systolic blood pressure LI+BFR = 152 ± 3 mmHg; HI = 153 ± 3; LI = 143 ± 3 P < 0.05). However, exercising hemodynamics for treadmill LI+BFR most often resembled those for LI and were lower than HI (e.g. for systolic pressure LI+BFR = 124 ± 2 mmHg; LI = 123 ± 2; HI = 140 ± 3 P < 0.05). In conclusion, the hemodynamic response for light aerobic (walking) BFR exercise suggests this mode of BFR exercise may be preferential for chronic use to develop muscle size and strength, and other health benefits in certain clinical populations that are contraindicated to heavy-load resistance exercise.
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The purpose of the study was to investigate the current use of blood flow restriction (BFR) by practitioners during exercise/training. A questionnaire was developed and data were obtained from 250 participants, with 115 stating that they had prescribed BFR as an intervention. The most common exercise intervention used in combination with BFR was resistance exercise (99/115), followed by during passive (30/115) conditions, and during aerobic exercise (22/115). The main outcome measure for using the technique was to increase muscle mass (32.6%) followed by rehabilitation from injury (24.2%). Over half of respondents (57.4%) reported that they did not use the same cuff widths for the lower body and upper body, with varying final restriction pressures also being utilised during each different exercise modality. Most practitioners performed the technique for ~10 min each training session, 1–4 times per week. Eighty percent of practitioners rated the use of BFR as very good-excellent. The incidence rate of side effects was largest for delayed onset muscle soreness (39.2%), numbness (18.5%), fainting/dizziness (14.6%) and bruising (13.1%). These results indicate that the use of BFR training is widespread amongst practitioners; however, care should be taken to ensure that practice matches current research to ensure the safety of this technique.
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The purpose of this study was to determine the perceptual responses to resistance exercise with either heavy-loads (80% 1 repetition maximum [1-RM]), light-loads (20% 1-RM), or light-loads in combination with blood flow restriction (BFR). Despite the use of light-loads, it has been suggested that the adoption of BFR resistance exercise may be limited due to increases in delayed onset muscle soreness (DOMS) and perceived exertion. Seventeen healthy untrained males participated in this balanced, randomized cross-over study. Following four sets of elbow-flexion exercise, participants reported ratings of perceived exertion (RPE), with DOMS also recorded for seven days following each trial. DOMS was significantly greater for low-pressure continuous BFR (until 48 h post-exercise) and high-pressure intermittent BFR (until 72 h post-exercise) compared with traditional heavy-load and light-load resistance exercise. In addition, RPE was higher for heavy-load resistance exercise and high-pressure intermittent BFR compared with low-pressure continuous BFR, with all trials greater than light-load resistance exercise. For practitioners working with untrained participants, this study provides evidence to suggest that in order to minimize the perception of effort and post-exercise muscle soreness associated with BFR resistance exercise, continuous low-pressure application may be more preferential compared with intermittent high-pressure application. Importantly, these perceptual responses are relatively short-lived (∼2 days) and have previously been shown to subside after a few exercise sessions. Combined with smaller initial training volumes (set x repetitions) this may limit RPE and DOMS to strengthen uptake and adherence, and assist in program progression for muscle hypertrophy and gains in strength.
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Introduction: Quadriceps strength after arthroscopic knee procedures is frequently diminished several years postoperation. Blood flow restriction (BFR) training uses partial venous occlusion while performing submaximal exercise to induce muscle hypertrophy and strength improvements. The purpose of this study was to evaluate BFR as a postoperative therapeutic intervention after knee arthroscopy. Methods: A randomized controlled pilot study comparing physical therapy with and without BFR after knee arthroscopy was conducted. Patients underwent 12 sessions of supervised physical therapy. Subjects followed the same postoperative protocol with the addition of 3 additional BFR exercises. Outcome measures included thigh girth, physical function measures, Knee Osteoarthritis Outcome Score (KOOS), Veterans RAND 12-Item Health Survey (VR12), and strength testing. Bilateral duplex ultrasonography was used to evaluate for deep venous thrombosis preintervention and postintervention. Results: Seventeen patients completed the study. Significant increases in thigh girth were observed in the BFR group at 6-cm and 16-cm proximal to the patella (P = 0.0111 and 0.0001). All physical outcome measures significantly improved in the BFR group, and the timed stair ascent improvements were greater than conventional therapy (P = 0.0281). The VR-12 and KOOS subscales significantly improved in the BFR group, and greater improvement was seen in VR-12 mental component score (P = 0.0149). The BFR group displayed approximately 2-fold greater improvements in extension and flexion strength compared with conventional therapy (74.59% vs 33.5%, P = 0.034). No adverse events were observed during the study. Conclusions: This study suggests that BFR is an effective intervention after knee arthroscopy. Further investigation is warranted to elucidate the benefits of this intervention in populations with greater initial impairment.
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This study systematically reviewed the available scientific evidence on the changes promoted by low-intensity (LI) resistance training (RT) combined with blood flow restriction (BFR) on blood pressure (BP), heart rate (HR) and rate-pressure product (RPP). Searches were performed in databases (PubMed, Web of Science(™) , Scopus and Google Scholar), for the period from January 1990 to May 2015. The study analysis was conducted through a critical review of contents. Of the 1 112 articles identified, 1 091 were excluded and 21 met the selection criteria, including 16 articles evaluating BP, 19 articles evaluating HR and four articles evaluating RPP. Divergent results were found when comparing the LI protocols with BFR versus LI versus high intensity (HI) on BP, HR and RPP. The evidence shows that the protocols using continuous BFR following a LIRT session apparently raise HR, BP and RPP compared with LI protocols without BFR, although increases significantly in BP seem to exist between the HI protocols when compared to LI protocols. Haemodynamic changes (HR, SBP, DBP, MBP, RPP) promoted by LIRT with BFR do not seem to differ between ages and body segments (upper or lower), although they are apparently affected by the width of the cuff and are higher with continuous BFR. However, these changes are within the normal range, rendering this method safe and feasible for special populations.
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Abstract The development of non-pharmacological approaches to hypertension (HA) is critical for both prevention and treatment. This study examined the hemodynamic and biochemical responses of medicated hypertensive women to resistance exercise with blood flow restriction (vascular occlusion). Twenty-three women were randomly assigned to one of three groups: High intensity strength training (n = 8); low-intensity resistance exercise with occlusion (n = 8); and control (n = 7). The first two groups underwent eight weeks of training performed twice a week, including three series of wrist flexion exercises with or without vascular occlusion. The exercised with occlusion group showed pre- to post-test reduction in systolic and diastolic blood pressure, mean arterial pressure, and double product, whereas the other groups showed no significant hemodynamic changes. In conclusion, resistance exercise during 8 weeks was effective in lowering blood pressure in medicated hypertensive subjects.
Article
Background and objective Low-load exercise training with blood flow restriction (BFR) can increase muscle strength and may offer an effective clinical musculoskeletal (MSK) rehabilitation tool. The aim of this review was to systematically analyse the evidence regarding the effectiveness of this novel training modality in clinical MSK rehabilitation. Design This is a systematic review and meta-analysis of peer-reviewed literature examining BFR training in clinical MSK rehabilitation (Research Registry; researchregistry91). Data sources A literature search was conducted across SPORTDiscus (EBSCO), PubMed and Science Direct databases, including the reference lists of relevant papers. Two independent reviewers extracted study characteristics and MSK and functional outcome measures. Study quality and reporting was assessed using the Tool for the assEssment of Study qualiTy and reporting in EXercise. Eligibility Search results were limited to exercise training studies investigating BFR training in clinical MSK rehabilitation, published in a scientific peer-reviewed journal in English. Results Twenty studies were eligible, including ACL reconstruction (n=3), knee osteoarthritis (n=3), older adults at risk of sarcopenia (n=13) and patients with sporadic inclusion body myositis (n=1). Analysis of pooled data indicated low-load BFR training had a moderate effect on increasing strength (Hedges’ g=0.523, 95% CI 0.263 to 0.784, p<0.001), but was less effective than heavy-load training (Hedges’ g=0.674, 95% CI 0.296 to 1.052, p<0.001). Conclusion Compared with low-load training, low-load BFR training is more effective, tolerable and therefore a potential clinical rehabilitation tool. There is a need for the development of an individualised approach to training prescription to minimise patient risk and increase effectiveness.
Article
Objectives: To investigate the influence of time, within and between days, on arterial occlusion pressure and to determine whether the variability resembles the oscillatory pattern of bSBP. Design: Test-retest. Methods: Twenty-two participants completed four testing sessions at 08:00 and 18:00h, 48h apart. Arm circumference, bSBP, and brachial diastolic blood pressure (bDBP) were measured at rest. Arterial occlusion pressure was determined using a cuff inflated on the proximal portion of the upper arm, with a Doppler probe placed over the radial artery. Results: Significant differences [mean (SD)] were observed for arterial occlusion pressure between Morning Day 2 [132 (14) mmHg, p<0.05], and all other visits [Morning Day 1: 138 (16); Evening Day 1: 139 (17); Evening Day 2 138 (14) mmHg]. A time effect was observed for bSBP, with a post-hoc test revealing that Morning Day 2 was different from all other visits. Conclusions: Our findings suggest that arterial occlusion pressure is influenced by the time of day. As such, multiple occlusion measurements across an experiment may be necessary in order to account for potential oscillations in pressure and provide the intended relative restrictive stimulus.
Article
The purpose of this study was to examine the effects of a Vasper™ workout on healthy adults. The use of the Vasper™ machine in current clinical settings is similar to blood flow restriction (BFR) exercise in safety profile and in benefits. The Vasper™ machine delivers blood flow restriction through the use of cool water pressure and delivers a 20-min high intensity interval training (HIIT) program. The study outcome measure, safety, is established by successful subject completion of the program with no associated adverse events in measured parameters. The tested null hypothesis is that there is no adverse response in measured parameters associated with increasing cuff pressure (40 to 85 mmHg) as compared to control (no pressure). We conclude that Vasper™ HIIT BFR exercise, with concomitant cooling, is safe in a cross section of the general population of regular exercises. An IRB approved trial appears to be warranted to evaluate if Vasper™ is safe and offers enhanced benefits to a cardiac rehab population in a conventional rehab program.