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The Performance Benefits of Training with a Sauna Suit: A Randomized, Controlled Trial

Authors:
Samuel Van de Velde at University of Montana
Samuel Van de Velde
Bryant Byrd at Western Colorado University
Bryant Byrd
Jennifer S Fargo
Jennifer S Fargo
Jennifer S Fargo
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Christina A Buchanan at Western Colorado University
Christina A Buchanan
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Abstract and Figures

Purpose: The purpose of this study was to quantify the performance-related benefits to training with a sauna suit. It was hypothesized that training with a sauna suit would elicit better improvements in maximal oxygen uptake (VO2max), ventilatory threshold, and 5km time trial performance (in temperate and simulated hot environments). Methods: Apparently healthy and endurance-trained men and women (n=14) were match paired according to sex, VO2max, and 5km personal best times and subsequently randomized to a control group and treatment group. Participants in both groups completed usual volume and intensity of training for 14 days with the treatment group performing all training sessions in a sauna suit. Participants performed a maximal exercise test and 2 x 5km time trials (in temperate and simulated hot environments) at baseline and post-training. Weight was obtained before and after time trial performances to quantify sweat rate. Additionally, body core temperature was monitored continuously throughout each time trial performance in both environmental conditions. Results: After 14 days of training with a sauna suit there were significant (p < 0.05) improvements in VO2max (+9.1%) and ventilatory threshold (4.6%). The 5km time trial performances in both hot (52 sec) and temperate conditions (38 sec) were significantly faster (p < 0.05) in the sauna suit treatment group after 2wks of training. Relative to the control group, sweat rate and thermoregulation improved (p < 0.05) during the 5km heat time trial after 14 days of training with a sauna suit. Conclusions: Findings from the present study support the utility of training with a sauna suit as a novel form of heat acclimation. Indeed, the present study demonstrated that 14 days of training with a sauna suit elicited improvements in VO2max, ventilatory threshold, and time trial performances. A greater sweat rate and lower core temperature likely mediated improved time trial performances following training with a sauna suit.
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[Year]
1
Van de Velde et al. (2017) Int J Res Ex Phys. 13(1):1-11.
Sponsored by:
Exercise and Sport Science Program
Western State Colorado University
The Performance Benefits of Training with a Sauna Suit:
A Randomized, Controlled Trial
Samuel S. Van de Velde1, Bryant R. Byrd1, Jennifer S. Fargo1, Christina A. Buchanan1, Lance C. Dalleck1
1High Altitude Exercise Physiology Program, Western State Colorado University, Gunnison, CO, USA
Abstract
Purpose: The purpose of this study was to quantify the performance-related benefits to training with a
sauna suit. It was hypothesized that training with a sauna suit would elicit better improvements in
maximal oxygen uptake (VO2max), ventilatory threshold, and 5km time trial performance (in temperate
and simulated hot environments). Methods: Apparently healthy and endurance-trained men and
women (n=14) were match paired according to sex, VO2max, and 5km personal best times and
subsequently randomized to a control group and treatment group. Participants in both groups
completed usual volume and intensity of training for 14 days with the treatment group performing all
training sessions in a sauna suit. Participants performed a maximal exercise test and 2 x 5km time trials
(in temperate and simulated hot environments) at baseline and post-training. Weight was obtained
before and after time trial performances to quantify sweat rate. Additionally, body core temperature
was monitored continuously throughout each time trial performance in both environmental
conditions. Results: After 14 days of training with a sauna suit there were significant (p < 0.05)
improvements in VO2max (+9.1%) and ventilatory threshold (4.6%). The 5km time trial performances in
both hot (52 sec) and temperate conditions (38 sec) were significantly faster (p < 0.05) in the sauna suit
treatment group after 2wks of training. Relative to the control group, sweat rate and thermoregulation
improved (p < 0.05) during the 5km heat time trial after 14 days of training with a sauna suit.
Conclusions: Findings from the present study support the utility of training with a sauna suit as a novel
form of heat acclimation. Indeed, the present study demonstrated that 14 days of training with a sauna
suit elicited improvements in VO2max, ventilatory threshold, and time trial performances. A greater
sweat rate and lower core temperature likely mediated improved time trial performances following
training with a sauna suit.
Key Words: Heat Acclimation, Hyperthermic Conditioning, Maximal Oxygen Uptake, Time Trial
[Year]
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Van de Velde et al. (2017) Int J Res Ex Phys. 13(1):1-11.
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Exercise and Sport Science Program
Western State Colorado University
INTRODUCTION
Endurance-performance can be drastically
impacted by various environmental
stressors, including hot and/or humid
conditions. Within the last several decades
there has been an abundance of research
looking at the physiological adaptations
that take place with consistent heat
exposure and how that might impact
endurance performance10. Competing in
hot environments (35C) places an added
environmental stressor on the human
body25. Research in the field of
thermoregulation has revealed that heat
stress can impair performance during
prolonged endurance exercise6,12,23. In
some cases, time to exhaustion has been
shortened due to increased body core
temperature6. Therefore, a proposed
mechanism for an early onset of fatigue
during endurance performance in hot
environments is elevated body core
temperatures3,6. Indeed, it has previously
been demonstrated that fatigue
corresponds with body core temperatures
of ~40 C11,13. To compensate for an
increased body core temperature, heart
rate and cardiac output for the same
relative workload, all rise and increase
burden on the cardiovascular system as
blood flow is modulated to accommodate
for the necessary heat loss1.
Athletes and coaches are continuously
seeking innovative ways to improve
performance. One strategy for optimal
performance is being adapted to the
environment on competition day. For
instance, if an individual is adapted to an
environmental stressor like heat, and has
consistently been exposed to the given
environment, on the day of competition,
the likelihood that environmental stressor
will impact performance is minimized.
Many championship events take place in
hot environments in the middle of the day,
such as the recent summer Olympics in
Brazil. If individuals are not accustomed to
performing in the heat, homeostasis will be
disrupted quickly and performance will be
compromised. Preparing the body to better
cope with heat stress is a fundamental
strategy to help optimize performance in
heat4. Heat acclimation is the process of
positive physiological adaptations occurring
after an individual is exposed to repeated
bouts of heat stress. Hallmark adaptations
of heat acclimation have been revealed to
produce: earlier onset of sweating,
decreased heart rate, plasma volume
expansion, and decreased body core
temperature9,14,19-20,25. Endurance-trained
individuals can begin to exhibit full heat
acclimatization adaptations as quickly as 7-
14 days upon consistent heat exposure
during exercise25. For instance, it has been
demonstrated that 10 days of repeated
bouts of cycling at ∼50% VO2max in a room
set to 40° C improved both cool (6%) and
hot (8%) time trial performances9.
Overall, the impact of heat acclimation to
improve cardiovascular stability during
exercise under heat stress has been well
studied9-10,18,20,24,26. However, to our
[Year]
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Van de Velde et al. (2017) Int J Res Ex Phys. 13(1):1-11.
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Exercise and Sport Science Program
Western State Colorado University
knowledge, no studies have investigated
the effects of exercise training with a sauna
suit on heat acclimation and performance.
It is plausible that exercise training with a
sauna suit may provide coaches and
athletes with a practical and portable heat
acclimation alternative when compared to
other traditional strategies (i.e., relocation
to hot climates or exposure to chamber-
based artificial heat stress). Therefore, the
purpose of this study was to quantify the
performance-related benefits to exercise
training with a sauna suit. It was
hypothesized that exercise training with a
sauna suit would elicit better improvements
in maximal oxygen uptake (VO2max),
ventilatory threshold, and 5km time trial
performance (in temperate and simulated
hot environments).
METHODS
Participants
Fourteen (men n=12, women n=2)
consented to participate in the study.
Physical attributes of participants are
presented in Table 1. Participants were
eligible for inclusion into the study if they
were low risk17. Exclusionary criteria
included evidence of cardiovascular
pulmonary, and/or metabolic disease.
Participants had >6 yrs of endurance-
training and competition experience and
maintained weekly training loads ranging
from 7 to 12 hrs. The study was conducted
during a training phase when no
competitions were planned. All participants
were fully acclimatized to an altitude of
2350m. This study was approved by the
Human Research Committee at Western
State Colorado University in accordance
with international standards and all
participants gave their written informed
consent.
Table 1. Physical attributes of participants.
(Values are mean SD).
Measure
Treatment
(n=7)
Control
(n=7)
Age (yrs)
27.0 7.6
31.6 12.1
Height (cm)
174.3 3.4
171.0 7.9
Weight (kg)
68.4 6.7
70.6 5.8
Experimental design
Participants completed a battery of
physiological and performance assessments
at baseline and post-program as shown in
Figure 1. On the first visit participants
performed a maximal exercise test to
measure VO2max The next visit was a 5km
time trial performed on a treadmill in a
simulated hot environment (~35° C). The
third visit entailed a 5km time trial
performed on a treadmill in temperate
conditions (~18° C). All baseline and post-
program measurements were obtained
from each participant at similar times of the
day ( 2 hours). All tests at baseline and
post-program were separated by at least 48
hours. The order of testing for each
participant was randomized to prevent an
order effect. Participants were instructed to
avoid consumption of alcohol or caffeine for
at least 24 hours before each physiological
measurement baseline and post-program.
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Van de Velde et al. (2017) Int J Res Ex Phys. 13(1):1-11.
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Exercise and Sport Science Program
Western State Colorado University
Figure 1. Flow chart of experimental procedures for each of the two groups (control and treatment).
KW-SS, Kutting Weight sauna suit; VO2max, maximal oxygen uptake.
After the completion of baseline testing,
participants were initially match paired
according to sex, VO2max, and 5km
personal best times and subsequently
randomized to a control group and
treatment group. Participants in both
groups completed usual volume and
intensity of exercise training for 14 days.
Participants were instructed to log and
maintain their usual training volume and
intensity throughout the intervention. The
treatment group was instructed to perform
all training for the 14 day intervention
wearing a sauna suit (Kutting Weight, LLC.,
Los Angeles, CA).
Protocols
Physical measurements
All physical measurements were obtained
using standardized guidelines. Briefly,
participants were weighed to the nearest
0.1 kg on a medical grade scale and
measured for height to the nearest 0.5 cm
using a stadiometer.
Maximal exercise test
Participants completed a modified-Balke,
pseudo-ramp graded exercise test (GXT) on
a power treadmill (Powerjog GX200,
Maine). Participants ran at a self-selected
pace. Treadmill incline was increased by 1%
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Exercise and Sport Science Program
Western State Colorado University
every minute until the participant reached
volitional fatigue. Participant heart rate was
continuously recorded during the GXT via a
chest strap and radio-telemetric receiver
(Polar Electro, Woodbury, NY, USA).
Expired air and gas exchange data were
recorded continuously during the GXT using
a metabolic analyzer (Parvo Medics
TrueOne 2.0, Salt Lake City, UT, USA).
Biological variability in VO2max was not
quantified7.
Gas exchange and data analysis
Prior to each maximal exercise test, the
metabolic cart (TrueOne 2400, Parvo
Medics, Sandy, UT) was calibrated with
gases of known concentrations (16.02% O2,
4.00% CO2) and with room air (20.93% O2
and 0.03% CO2) as per the manufacture
guidelines. Calibration of the
pneumotachometer was done via a 3 Litre
calibration syringe (Hans-Rudolph, Kansas
City, MO). Throughout the maximal exercise
test continuous pulmonary gas exchange
data was obtained. In order to determine
VO2max from the maximal exercise test, the
final 15 seconds of data were averaged
constituting the final data point. The next
closest data point was calculated by
averaging the data during the 15 seconds
prior to the final 15 seconds. The VO2max
was represented by the mean of the 2
processed data points provided a plateau
was exhibited (VO2 < 150 mL/min).
Determination of both the first ventilatory
threshold (VT1) and second ventilatory
threshold (VT2) were made by visual
inspection of graphs of time plotted against
each relevant respiratory variable
(according to 15 second time-averaging).
The criteria for VT1 was an increase in
VE/VO2 with no concurrent increase in
VE/VCO2 and departure from the linearity
of VE. The criteria for VT2 was a
simultaneous increase in both VE/VO2 and
VE/VCO2. Overall ventilatory threshold was
recorded as the mean of VT1 and VT2. All
assessments were done by two experienced
exercise physiologists. In the event of
conflicting results, the original assessments
were reevaluated and collectively a
consensus was agreed upon.
Temperate 5km time trial
Participants performed a 5km time trial on a
treadmill at 1% grade in a temperate
environment of ~18° C. Participants were
instructed to give a maximal effort and pace
was initially set to their 5k personal best
pace to set the tone. Participants were
instructed to arrive well-hydrated and
consume 1L of water in the previous hour.
Participants ingested CorTemp sensor pill 2-
3 hours prior to the 5km time trial as
suggested by the user manual. A resting
body core temperature was first recorded
then a near nude body weight (down to
shorts) was recorded. Participants all
performed self-selected pace 5-minute
warm-up in a temperate condition on a
treadmill prior to commencing the time
trial. During the time-trial pace was self-
selected by the subject throughout the
whole time trial and they had access to
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Van de Velde et al. (2017) Int J Res Ex Phys. 13(1):1-11.
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Exercise and Sport Science Program
Western State Colorado University
adjust the speed. Total elapsed time was
blinded to the participant throughout the
time trial. No verbal feedback was provided
throughout the time trial. Heart rate, rating
of perceived exertion (RPE), body core
temperature, and time was recorded every
400 meters, and at 5,000 meters. Near
nude body weight was recorded
immediately post time-trial.
5km time trial in simulated heat
Participants performed a 5k time trial on a
treadmill at 1% grade in a simulated hot
environment of 35° C. Participants were
instructed to give a maximal effort and pace
was initially set to their 5k personal best
pace to set the tone. Participants were
instructed to arrive well-hydrated and
consume 1L of water in the previous hour.
Participants ingested CorTemp sensor pill 2-
3 hours prior to the 5km time trial as
suggested by the user manual. A resting
body core temperature was first recorded
then a near nude body weight (down to
shorts) was recorded. Participants all
performed self-selected pace 5-minute
warm-up in a temperate condition on a
treadmill prior to commencing the time trial
in the hot environment. During the time
trial pace was self-selected by the subject
throughout the whole time trial and they
had access to adjust the speed. Total
elapsed time was blinded to the participant
throughout the time trial. No verbal
feedback was provided throughout the time
trial. Heart rate, RPE, body core
temperature, and time was recorded every
400 meters, and at 5,000 meters. Near
nude body weight was recorded
immediately post time-trial.
Statistical analyses
All analyses were performed using SPSS
Version 23.0 (Chicago, IL) and GraphPad
Prism 6.0. (San Diego, CA). Measures of
centrality and spread are presented as
mean SD and percentage (%) change from
baseline to post-program. Paired t-tests
were used to compare the mean
performance measures (VO2max,
ventilatory threshold, and 5km time trial
performances) from baseline to post-
program within each group (control and
treatment). Independent t-tests were used
to compare changes in performance
measures between control and treatment
groups. Repeated measures ANOVA were
used to examine possible differences in
body core temperature and heart rate
responses throughout 5km time trial
performances at baseline and post-program
between treatment and control groups.
When appropriate, main effects significance
was examined using post hoc comparisons
by Bonferroni-corrected t-tests. The
probability of making a Type I error was set
at p ≤ .05 for all statistical analyses.
RESULTS
The intervention was well tolerated for all
14 participants. Each of the 14 participants
completed 10-14 training sessions across
the 2 week intervention. Moreover, there
were no adverse events experienced in the
[Year]
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Van de Velde et al. (2017) Int J Res Ex Phys. 13(1):1-11.
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Exercise and Sport Science Program
Western State Colorado University
treatment group (i.e., sauna suit) across all
exercise training sessions and all
physiological responses remained within
normal ranges. There were no within-group
changes from baseline to post-program in
training volume and intensity. Additionally,
there were no between-group differences
in training volume and intensity.
Performance outcomes
The performance outcomes for participants
at baseline and 2wk post-training in both
control and treatment groups are shown in
Table 2. After 2wk, there were significant
improvements (p < 0.05) in VO2max,
ventilatory threshold, and 5km heat and
temperate time trials in the treatment
group. All performance outcomes in the
control group were unchanged (p>0.05)
after the 2wk intervention.
Physiological responses to time trial
performances
The weight changes (mean ± SD) to all 5km
time trial performances at baseline and 2wk
for control and treatment groups are
presented in Table 3. Weight change in the
sauna suit treatment group was significantly
greater (p<0.05) in the post-program 5km
heat time trial. Repeated measures ANOVA
showed that body core temperature
responses (Figure 2-upper panel)
throughout the 5km heat time trial were
significantly lower (p<0.05) following 2wk of
training in the sauna suit treatment group.
Repeated measures ANOVA demonstrated
that heart rate responses (Figure 2B-lower
panel) throughout the 5km heat time trial
were similar (p>0.05) after 2wk of training
in the sauna suit. These similar heart rate
responses existed despite the significantly
faster 5km heat time trial performance
post-training (Table 2).
Table 2. Performance variables at baseline and 2wk. (Values are mean SD).
Control group (n=7)
Variable
Baseline
2wk
Baseline
2wk
VO2max (mL/kg/min)
52.0 7.0
52.5 6.9
52.8 7.3
57.6 6.3*†
Ventilatory threshold (% VO2max)
67.4 4.9
67.7 5.2
66.7 5.9
71.3 5.2*†
5km heat time trial (sec)
1344 286
1355 264
1322 188
1270 183*†
5km temperate time trial (sec)
1325 220
1318 263
1308 193
1270 181*
* Within-group change is significantly different from baseline, p < 0.05. † Change from baseline is
significantly different than control group.
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Van de Velde et al. (2017) Int J Res Ex Phys. 13(1):1-11.
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Exercise and Sport Science Program
Western State Colorado University
Table 3. Weight changes during time trials at baseline and 2wk. (Values are mean SD).
Control group (n=7)
Treatment group (n=7)
Variable
Baseline
2wk
Baseline
2wk
5km heat time trial
Weight change (kg)
-0.61 -0.27
-0.60 -0.19
-0.64 -0.27
-1.01 -0.33*†
5km temperate time trial
Weight change (kg)
-0.46 -0.24
-0.51 -0.21
-0.56 -0.10
-0.74 -0.30
* Within-group change is significantly different from baseline, p < 0.05. † Change from baseline is
significantly different than control group.
Figure 2. Physiological responses of the treatment group at baseline and post-training to the 5km heat
time trial. Body core temperature responses are presented in the upper panel (A) while heart rate
responses are highlighted in the lower panel (B).
[Year]
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Exercise and Sport Science Program
Western State Colorado University
DISCUSSION
The primary finding of the present study is
that short-term training with a sauna suit
improves heat acclimation and endurance
performance. Although heat acclimation
using a variety of methodologies has been
well studied, to our knowledge, the training
adaptations to exercise training with a
sauna suit has not been scientifically
explored in a randomized, controlled
fashion. As such, the results of this novel
study are encouraging and support use of a
practical and portable sauna suit as a form
of heat acclimation to enhance aerobic
capacity and endurance performance.
Improvements in VO2max (+ 9.1%) in the
treatment group in the present study are
comparable to those previously reported in
the literature with heat acclimation. Heat
acclimation elicits an increase in overall
plasma volume which subsequently benefits
stroke volume and maximal cardiac output9.
The 5km time trial performances in the
treatment group improved between 2% and
3% across temperate and hot conditions,
respectively. This improvement in
endurance performance is comparable to
past literature which has demonstrated a
1.9% improvement in 5km time trial
performance following heat acclimation9.
The treatment group improvements were
likely attributed to favorable heat
acclimation adaptations9-10,21. Specifically,
improved time trial performance in the
treatment group was likely underpinned by
a combination of improved VO2max and an
increased capacity for
thermoregulation2,16,27. For instance, sweat
rate (as evidenced by increased time trial
weight loss) was increased during the 5km
heat time trial following 14 days of training
in a sauna suit. This favorable adaptation
permitted individuals in the treatment
group to dissipate heat more effectively and
maintain a lower body core temperature
throughout the 5km heat time trials post-
intervention (Figure 2). Overall, these
adaptations resulted in faster 5km time trial
performance in both hot and temperate
conditions following sauna suit training.
Heat acclimation has been well researched
and it has been well-established that
physiological adaptations from heat
acclimation improve performance in the
heat5,22. Therefore, sauna suit training
provides a feasible alternative to simulate
heat stress for individuals who plan to
compete in hot environments. However, in
the past, individuals wishing to heat
acclimate have needed to relocate to a hot
environment or exercise in an
environmental chamber that simulates a
hot environment15,19-20. Both of these
options are expensive and may not be
pragmatic for most individuals wishing to
prepare for performance in the heat. In
contrast, sauna suits are more practical as
they can be applied to varying indoor or
outdoor environments and only require a
nominal initial investment. Furthermore, it
has been demonstrated that heat
acclimation decay is also quite slow after
[Year]
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Van de Velde et al. (2017) Int J Res Ex Phys. 13(1):1-11.
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Exercise and Sport Science Program
Western State Colorado University
full heat acclimation is obtained with a
decay rate of 1-3 weeks depending on
fitness levels and further heat exposure14.
Therefore, it is possible for coaches and
recreational enthusiasts to front load
training 1-2 months in advance of
competition in a hot environment
performance and gradually taper sauna suit
sessions to 1 session per week as the
scheduled competition approaches. In
summary, sauna suit training prior to
competition can be sensibly applied.
Possible limitations to the present study
merit discussion. We recruited a
convenience sample and findings may not
necessarily be applicable to a wider
population. Thermal stress from sauna suit
use was not directly quantified with thermal
skin sensors which is an important topic for
future research. Last, it is unknown whether
the improved endurance performance
observed in the present study in a
laboratory-based setting would be
transferable to a real world competition.
CONCLUSIONS
Findings from the present study support the
utility of exercise training with a sauna suit
as a novel form of heat acclimation. Indeed,
the present study demonstrated that 14
days of exercise training with a sauna suit
elicited improvements in VO2max and time
trial performances. A greater sweat rate
and lower core temperate likely mediated
improved time trial performances following
exercise training with a sauna suit.
Competing interests
This investigation was supported financially by
the American Council on Exercise (ACE). The
American Council on Exercise (ACE) was not
involved in development of the study design,
data collection and analysis, or preparation of
the manuscript. There are no other potential
conflicts of interest related to this article.
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Western State Colorado University
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Sauna use as a lifestyle practice to extend healthspan
Article
  • Aug 2021
  • EXP GERONTOL
Sauna use, sometimes referred to as “sauna bathing,” is characterized by short-term passive exposure to high temperatures, typically ranging from 45 °C to 100 °C (113 °F to 212 °F), depending on modality. This exposure elicits mild hyperthermia, inducing a thermoregulatory response involving neuroendocrine, cardiovascular, and cytoprotective mechanisms that work in a synergistic fashion in an attempt to maintain homeostasis. Repeated sauna use acclimates the body to heat and optimizes the body's response to future exposures, likely due to the biological phenomenon known as hormesis. In recent decades, sauna bathing has emerged as a probable means to extend healthspan, based on compelling data from observational, interventional, and mechanistic studies. Of particular interest are the findings from large, prospective, population-based cohort studies of health outcomes among sauna users that identified strong dose-dependent links between sauna use and reduced morbidity and mortality. This review presents an overview of sauna practices; elucidates the body's physiological response to heat stress and the molecular mechanisms that drive the response; enumerates the myriad health benefits associated with sauna use; and describes sauna use concerns.
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Effects of Heat Acclimation and Acclimatisation on Maximal Aerobic Capacity Compared to Exercise Alone in Both Thermoneutral and Hot Environments: A Meta-Analysis and Meta-Regression
Article
Full-text available
  • Apr 2021
  • SPORTS MED
Background Heat acclimation and acclimatisation (HA) is typically used to enhance tolerance to the heat, thereby improving performance. HA might also confer a positive adaptation to maximal oxygen consumption ( VO2max⁡V{\text{O}}_{2\max } V O 2 max ), although this has been historically debated and requires clarification via meta-analysis. Objectives (1) To meta-analyse all studies (with and without control groups) that have investigated the effect of HA on VO2max⁡V{\text{O}}_{2\max } V O 2 max adaptation in thermoneutral or hot environments; (2) Conduct meta-regressions to establish the moderating effect of selected variables on VO2max⁡V{\text{O}}_{2\max } V O 2 max adaptation following HA. Methods A search was performed using various databases in May 2020. The studies were screened using search criteria for eligibility. Twenty-eight peer-reviewed articles were identified for inclusion across four separate meta-analyses: (1) Thermoneutral VO2max⁡V{\text{O}}_{2\max } V O 2 max within-participants (pre-to-post HA); (2) Hot VO2max⁡V{\text{O}}_{2\max } V O 2 max within-participants (pre-to-post HA); (3) Thermoneutral VO2max⁡V{\text{O}}_{2\max } V O 2 max measurement; HA vs . control groups; (4) Hot VO2max⁡V{\text{O}}_{2\max } V O 2 max measurement, HA vs . control groups. Meta-regressions were performed for each meta-analysis based on: isothermal vs . iso-intensity programmes, days of heat exposure, HA ambient temperature (°C), heat index, HA session duration (min), ambient thermal load (HA session x ambient temperature), mean mechanical intensity (W) and the post-HA testing period (days). Results The meta-analysis of pre–post differences in thermoneutral VO2max⁡V{\text{O}}_{2\max } V O 2 max demonstrated small-to-moderate improvements in VO2max⁡V{\text{O}}_{2\max } V O 2 max (Hedges’ g = 0.42, 95% CI 0.24–0.59, P < 0.001), whereas moderate improvements were found for the equivalent analysis of hot VO2max⁡V{\text{O}}_{2\max } V O 2 max changes (Hedges’ g = 0.63, 95% CI 0.26–1.00, P < 0.001), which were positively moderated by the number of days post-testing ( P = 0.033, β = 0.172). Meta-analysis of control vs . HA thermoneutral VO2max⁡V{\text{O}}_{2\max } V O 2 max demonstrated a small improvement in VO2max⁡V{\text{O}}_{2\max } V O 2 max in HA compared to control (Hedges’ g = 0.30, 95% CI 0.06–0.54, P = 0.014) and this effect was larger for the equivalent hot VO2max⁡V{\text{O}}_{2\max } V O 2 max analysis where a higher ( moderate-to-large ) improvement in VO2max⁡V{\text{O}}_{2\max } V O 2 max was found (Hedges’ g = 0.75, 95% CI 0.22–1.27, P = 0.005), with the number of HA days ( P = 0.018; β = 0.291) and the ambient temperature during HA ( P = 0.003; β = 0.650) positively moderating this effect. Conclusion HA can enhance VO2max⁡V{\text{O}}_{2\max } V O 2 max adaptation in thermoneutral or hot environments, with or without control group consideration, by at least a small and up to a moderate–large amount, with the larger improvements occurring in the heat. Ambient heat, number of induction days and post-testing days can explain some of the changes in hot VO2max⁡V{\text{O}}_{2\max } V O 2 max adaptation.
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Effects of Exercise Training with a Sauna Suit on Cardiovascular Health: a Proof-of-Concept Study
Article
Full-text available
  • Mar 2016
Abstract Introduction: Cardiovascular disease (CVD) is the leading cause of death worldwide, accounting for 17.3 million deaths per annum, a figure that is projected to grow to more than 23.6 million by 2030. It has been estimated that 80% of premature heart disease can be prevented through positive modification of CVD risk factors. It has been demonstrated that systemic thermal therapy by regular administration of heat through a variety of methodologies, such as sauna or taking a warm bath, can induce a number of advantageous responses in terms of cardiovascular health. However, no studies have investigated the effects of exercise training with a sauna suit, a practical and portable alternative to other thermal treatments, on cardiometabolic risk factors. The purpose of this study was to determine the effectiveness of exercise training with a sauna suit at positively modifying cardiometabolic risk factors. Methods: Twelve men (mean ± SD: age, height, weight, percentage body fat, and VO2max = 25.3 ± 7.3 yr, 179.6 ± 5.7 cm, 78.6 ± 7.6 kg, 14.6 ± 3.3 %, and 50.4 ± 8.8 mL/kg/min, respectively) completed a 6wk exercise training program (30min sessions performed 5 days/wk at a moderate-intensity of 55-60% heart rate reserve) while wearing a sauna suit. Cardiometabolic risk factors were measured at baseline and post-program. Results: After 6wk of exercise training with a sauna suit there were significant (p < 0.05) improvements in the following cardiometabolic risk factors: percentage body fat (relative Δ -1.5%), systolic (relative Δ -1.4%) and diastolic (relative Δ -3.1%) blood pressure, triglycerides (relative Δ -15.5%), HDL cholesterol (relative Δ +6.4%), and maximal oxygen uptake (relative Δ +8.5%). Conclusions: Findings from the present study support the feasibility of exercise training with a sauna suit to improve cardiovascular health. Indeed, the present study demonstrated that regular moderate-intensity exercise training with a sauna suit elicited improvements in cardiorespiratory fitness and positive modification to several key CVD risk factors. Key Words: Heart Disease, Hyperthermic Conditioning, Physical Activity, Prevention
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Self-paced exercise in hot and cool conditions is associated with the maintenance of %VO2peak within a narrow range
Article
Full-text available
  • Mar 2015
This study examined the timecourse and extent of decrease in peak oxygen uptake (VO2peak) during self-paced exercise in HOT (35ºC and 60% RH) and COOL (18ºC and 40% RH) laboratory conditions. Ten well-trained cyclists completed four consecutive 16.5 min time trials (15 min self-paced effort with 1.5 min maximal end-spurt to determine VO2peak) interspersed by 5 min of recovery on a cycle ergometer in each condition. Rectal temperature increased significantly more in HOT (39.4 ±0.7ºC) than COOL (38.6 ±0.3ºC; P<0.001). Power output was lower throughout HOT compared with COOL (P<0.001). The decrease in power output from trial one to four was ~16% greater in HOT (P<0.001). VO2 was lower throughout HOT than COOL except at 5 min and during the end-spurt in trial one (P<0.05). In HOT, VO2peak reached 97, 89, 85 and 85% of pre-determined maximal oxygen uptake, whereas in COOL 97, 94, 93 and 92% was attained. Relative exercise intensity (%VO2peak) during trials one and two was lower in HOT (~84%) than COOL (~86%; P<0.05), decreasing slightly during trials three and four (~80% and ~85%, respectively; P<0.05). However, heart rate was higher throughout HOT (P=0.002) and ratings of perceived exertion greater during trials three and four in HOT (P<0.05). Consequently, it appears that the regulation of self-paced exercise occurs in conjunction with maintaining %VO2peak within a narrow range (80-85 %VO2peak). This range widens under heat stress however, when exercise becomes protracted and a disassociation develops between relative exercise intensity, heart rate and ratings of perceived exertion. Copyright © 2015, Journal of Applied Physiology.
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Heat acclimation responses of an ultra-endurance running group preparing for hot desert-based competition
Article
Full-text available
  • Jan 2014
Heat acclimation induces adaptations that improve exercise tolerance in hot conditions. Here we report novel findings into the effects of ultra-marathon specific exercise load in increasing hot ambient conditions on indices of heat acclimation. Six male ultra-endurance runners completed a standard pre-acclimation protocol at 20°C ambient temperature (Tamb), followed by a heat acclimation protocol consisting of six 2 h running exercise-heat exposures (EH) at 60% O2max on a motorised treadmill in an environmental chamber. Three EH were performed at 30°C Tamb, followed by another three EH at 35°C Tamb. EH were separated by 48 h within Tamb and 72 h between Tamb. Nude body mass (NBM), blood and urine samples were collected pre-exercise; while NBM and urine were collected post-exercise. Rectal temperature (Tre), heart rate (HR), thermal comfort rating (TCR) and rating of perceived exertion were measured pre-exercise and monitored every 5 min during exercise. Water was provided ad libitum during exercise. Data were analysed using a repeated measures and one-way analysis of variance (ANOVA), with post hoc Tukey's HSD. Significance was accepted as P< 0.05. Overall mean Tre was significantly lower during 30°C EH3 and 35°C EH3 compared with their respective EH1 (−0.20 and−0.23°C, respectively; P
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Heat acclimation improves aerobic performance
Article
Full-text available
  • Oct 2010
  • J APPL PHYSIOL
This study examined the impact of heat acclimation on improving exercise performance in cool and hot environments. Twelve trained cyclists performed tests of maximal aerobic power (VO2max), time-trial performance, and lactate threshold, in both cool [13°C, 30% relative humidity (RH)] and hot (38°C, 30% RH) environments before and after a 10-day heat acclimation (∼50% VO2max in 40°C) program. The hot and cool condition VO2max and lactate threshold tests were both preceded by either warm (41°C) water or thermoneutral (34°C) water immersion to induce hyperthermia (0.8-1.0°C) or sustain normothermia, respectively. Eight matched control subjects completed the same exercise tests in the same environments before and after 10 days of identical exercise in a cool (13°C) environment. Heat acclimation increased VO2max by 5% in cool (66.8 ± 2.1 vs. 70.2 ± 2.3 ml·kg(-1)·min(-1), P = 0.004) and by 8% in hot (55.1 ± 2.5 vs. 59.6 ± 2.0 ml·kg(-1)·min(-1), P = 0.007) conditions. Heat acclimation improved time-trial performance by 6% in cool (879.8 ± 48.5 vs. 934.7 ± 50.9 kJ, P = 0.005) and by 8% in hot (718.7 ± 42.3 vs. 776.2 ± 50.9 kJ, P = 0.014) conditions. Heat acclimation increased power output at lactate threshold by 5% in cool (3.88 ± 0.82 vs. 4.09 ± 0.76 W/kg, P = 0.002) and by 5% in hot (3.45 ± 0.80 vs. 3.60 ± 0.79 W/kg, P < 0.001) conditions. Heat acclimation increased plasma volume (6.5 ± 1.5%) and maximal cardiac output in cool and hot conditions (9.1 ± 3.4% and 4.5 ± 4.6%, respectively). The control group had no changes in VO2max, time-trial performance, lactate threshold, or any physiological parameters. These data demonstrate that heat acclimation improves aerobic exercise performance in temperate-cool conditions and provide the scientific basis for employing heat acclimation to augment physical training programs.
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Acute and adaptive responses in humans to exercise in a warm, humid environment
Article
  • Apr 1997
 Acute and repeated exposure for 8–13 consecutive days to exercise in humid heat was studied. Twelve fit subjects exercised at 150 W [45% of maximum O2 uptake (V.O2,max)] in ambient conditions of 35°C and 87% relative humidity which resulted in exhaustion after 45 min. Average core temperature reached 39.9 ± 0.1°C, mean skin temperature (T– sk) was 37.9 ± 0.1°C and heart rate (HR) 152 ± 6 beats min–1 at this stage. No effect of the increasing core temperature was seen on cardiac output and leg blood flow (LBF) during acute heat stress. LBF was 5.2 ± 0.3 l min–1 at 10 min and 5.3 ± 0.4 l min–1 at exhaustion (n = 6). After acclimation the subjects reached exhaustion after 52 min with a core temperature of 39.9 ± 0.1°C, T– sk 37.7 ± 0.2°C, HR 146 ± 4 beats min–1. Acclimation induced physiological adaptations, as shown by an increased resting plasma volume (3918 ± 168 to 4256 ± 270 ml), the lower exercise heart rate at exhaustion, a 26% increase in sweating rate, lower sweat sodium concentration and a 6% reduction in exercise V.O2. Neither in acute exposure nor after acclimation did the rise of core temperature to near 40°C affect metabolism and substrate utilization. The physiological adaptations were similar to those induced by dry heat acclimation. However, in humid heat the effect of acclimation on performance was small due to physical limitations for evaporative heat loss.
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Heat acclimation, aerobic fitness, and hydration effects on tolerance during uncompensable heat stress
Article
  • May 1998
The purpose of the present study was to determine the separate and combined effects of aerobic fitness, short-term heat acclimation, and hypohydration on tolerance during light exercise while wearing nuclear, biological, and chemical protective clothing in the heat (40 degrees C, 30% relative humidity). Men who were moderately fit [(MF); <50 ml . kg-1 . min-1 maximal O2 consumption; n = 7] and highly fit [(HF); >55 ml . kg-1 . min-1 maximal O2 consumption; n = 8] were tested while they were euhydrated or hypohydrated by approximately 2.5% of body mass through exercise and fluid restriction the day preceding the trials. Tests were conducted before and after 2 wk of daily heat acclimation (1-h treadmill exercise at 40 degrees C, 30% relative humidity, while wearing the nuclear, biological, and chemical protective clothing). Heat acclimation increased sweat rate and decreased skin temperature and rectal temperature (Tre) in HF subjects but had no effect on tolerance time (TT). MF subjects increased sweat rate but did not alter heart rate, Tre, or TT. In both MF and HF groups, hypohydration significantly increased Tre and heart rate and decreased the respiratory exchange ratio and the TT regardless of acclimation state. Overall, the rate of rise of skin temperature was less, while DeltaTre, the rate of rise of Tre, and the TT were greater in HF than in MF subjects. It was concluded that exercise-heat tolerance in this uncompensable heat-stress environment is not influenced by short-term heat acclimation but is significantly improved by long-term aerobic fitness.
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Responses to the thermal environment
Article
  • May 1977
  • Fed Proc
Human responses to the thermal environment and to internal heat production serve to maintain a narrow range of internal body temperatures of 36-38 C. There are two categories of responses: voluntary or behavioral responses, and involuntary or physiological autonomic responses. Voluntary or behavioral responses consist generally of avoidance or reduction of thermal stress by modification of the body's immediate environment by modification of clothing insulation or by comfort conditioning of his microenvironment. Physiological responses consist of peripheral vasoconstriction to reduce the body's thermal conductance and increased heat production by involuntary shivering in the cold, and peripheral vasodilation to increase thermal conductance and secretion of sweat for evaporative cooling in hot environments. Autonomic responses are proportional to changes in internal and mean skin temperatures. Repeated exposures to heat, humidity, and exercise will modify the physiological response mechanisms by acclimation to produce more effective responses. Physiological responses also depend on the point in a diurnal cycle, on physical fitness, and on the sex of the individual. Behavioral responses rely on thermal sensations and thermal discomfort. Thermal discomfort appears to be closely related to the level of autonomic responses so that warm discomfort is closely correlated with skin wettedness, and cold discomfort similarly relates to cold extremities and shivering activity.
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