A comparison of heat acclimation by post-exercise hot water immersion and exercise in the heat

Aims This meta-analysis aims to evaluate the effectiveness of heat acclimation (HA) via hot water immersion protocols and their effect on time trial (TT) performance, heart rate (HRE, HRM and HRTT), rectal temperature (Tre), Rate of perceived exertion (RPE), psychological stress index (PhSI), thermal comfort (Tcomf), thermal sensation (Tsen) and maximum oxygen uptake (Vo2max). Methods Pubmed, Scopus, Sportdiscus and Web of Science databases were used alongside the grey matter sites Google Scholar and Researchgate. The databases were then searched for randomised control trials and mixed-method design studies. Two RTCs, six repeated measure design studies and one randomised crossover design study were included after screening a total of 50 titles and 28 full-text articles. Sample sizes range from 1 - 13 with all participants having not participated in any form of heat training 6 months before their inclusion in the study. Results The mean difference (MD) for Heart rate (HR) was -9.1125 BPM (95% CI p = 0.026) and was considered to be statistically significant. The MD for Rectal temperature (Tre) effect size was -0.3814 Tre (°C) (95% CI; p = 0.05). The MD for sweat rate was 0.085; (96% CI; p = 0.0179) The changes in RPE, PhSI, Tcomf and Tsen were too small to be considered statistically significant. There was no significant difference between pre and post HA for Vo2max and PV. This meta-analysis implies that HA via HWI may improve tolerance to discomfort during heat exposure and thus subsequently improve physical performance during exercise in hot conditions. Conclusion The primary finding of this meta-analysis is that athletic performance is improved with post-exercise hot water immersion heat acclimation training. HWI HA protocols should focus on the following guidelines: 40-50 minutes of submaximal exercise (>65% of Vo2max) should be followed directly (within 10 minutes) by 40 minutes of hot water immersion at 40°C with the individual immersed up to their neck. The HA protocol should last between 6-9 days with a single bout of HWI every day for this period.

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Post-exercise Hot Water Immersion Elicits Heat Acclimation Adaptations That Are Retained for at Least Two Weeks

Frontiers in Physiology ◽

10.3389/fphys.2019.01080 ◽

2019 ◽

Vol 10 ◽

Cited By ~ 2

Author(s):

Michael J. Zurawlew ◽

Jessica A. Mee ◽

Neil P. Walsh

Keyword(s):

Water Immersion ◽

Heat Acclimation ◽

Hot Water ◽

Post Exercise ◽

Hot Water Immersion

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Post-exercise hot water immersion elicites heat acclimation responses in endurance and recreational athletes. A systematic review and meta-analysis

10.31236/osf.io/peuc7 ◽

2020 ◽

Author(s):

Jack Martin

Keyword(s):

Heart Rate ◽

Rectal Temperature ◽

Meta Analysis ◽

Water Immersion ◽

Heat Acclimation ◽

Hot Water ◽

Design Studies ◽

Post Exercise ◽

Study Results ◽

Hot Water Immersion

AIms This meta-analysis aims to evaluate the effectiveness of heat acclimation (HA) via hot water immersion protocols and their effect on time trial (TT) performance, heart rate (HRE, HRM and HRTT), rectal temperature (Tre), Rate of perceived exertion (RPE), psychological stress index (PhSI), thermal comfort (Tcomf), thermal sensation (Tsen) and maximum oxygen uptake (Vo2max). Methods Pubmed, Scopus, Sportdiscus and Web of Science databases were used alongside the grey matter sites Google Scholar and Researchgate. The databases were then searched for randomised control trials and mixed-method design studies. Two RTCs, six repeated measure design studies and one randomised crossover design study were included after screening a total of 50 titles and 28 full-text articles. Sample sizes range from 1 - 13 with all participants having not participated in any form of heat training 6 months before their inclusion in the study. Results The mean difference (MD) for Heart rate (HR) was -9.1125 BPM (95% CI p = 0.026) and was considered to be statistically significant. The MD for Rectal temperature (Tre) effect size was -0.3814 Tre (°C) (95% CI; p = 0.05). The MD for sweat rate was 0.085; (96% CI; p = 0.0179)The changes in RPE, PhSI, Tcomf and Tsen were too small to be considered statistically significant. There was no significant difference between pre and post HA for Vo2max and PV. This meta-analysis implies that HA via HWI may improve tolerance to discomfort during heat exposure and thus subsequently improve physical performance during exercise in hot conditions.Conclusion The primary finding of this meta-analysis is that athletic performance is improved with post-exercise hot water immersion heat acclimation training. HWI HA protocols should focus on the following guidelines: 40-50 minutes of submaximal exercise (>65% of Vo2max) should be followed directly (within 10 minutes) by 40 minutes of hot water immersion at 40°C with the individual immersed up to their neck. The HA protocol should last between 6-9 days with a single bout of HWI every day for this period.

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Exercise heat acclimation and post-exercise hot water immersion improve resting and exercise responses to heat stress in the elderly

Journal of Science and Medicine in Sport ◽

10.1016/j.jsams.2021.05.017 ◽

2021 ◽

Author(s):

Kirsty A.M. Waldock ◽

Oliver R. Gibson ◽

Rebecca L. Relf ◽

Gregor Eichhorn ◽

Mark Hayes ◽

...

Keyword(s):

Heat Stress ◽

Water Immersion ◽

Heat Acclimation ◽

The Elderly ◽

Hot Water ◽

Post Exercise ◽

Hot Water Immersion

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Heat Acclimation by Postexercise Hot-Water Immersion: Reduction of Thermal Strain During Morning and Afternoon Exercise-Heat Stress After Morning Hot-Water Immersion

International Journal of Sports Physiology and Performance ◽

10.1123/ijspp.2017-0620 ◽

2018 ◽

Vol 13 (10) ◽

pp. 1281-1286 ◽

Cited By ~ 9

Author(s):

Michael J. Zurawlew ◽

Jessica A. Mee ◽

Neil P. Walsh

Keyword(s):

Heat Stress ◽

Oxygen Uptake ◽

Maximal Oxygen Uptake ◽

Perceived Exertion ◽

Water Immersion ◽

Heat Acclimation ◽

Time Of Day ◽

Hot Water ◽

Rating Of Perceived Exertion ◽

Hot Water Immersion

Purpose: Recommendations state that to acquire the greatest benefit from heat-acclimation, the clock time of heat-acclimation sessions should match that of expected exercise-heat stress. It remains unknown if adaptations by postexercise hot-water immersion (HWI) demonstrate time-of-day-dependent adaptations. Thus, the authors examined whether adaptations following postexercise HWI completed in the morning were present during morning and afternoon exercise-heat stress. Methods: Ten males completed an exercise-heat stress test commencing in the morning (9:45 AM) and afternoon (2:45 PM; 40 min; 65% of maximal oxygen uptake treadmill run) before and after heat-acclimation. The 6-d heat-acclimation intervention involved a daily 40-min treadmill run (65% of maximal oxygen uptake) in temperate conditions followed by ≤40-min HWI (40°C; 6:30–11:00 AM). Results: Adaptations by 6-d postexercise HWI in the morning were similar in the morning and afternoon. Reductions in resting rectal temperature (Tre) (AM −0.34°C [0.24°C], PM −0.27°C [0.23°C]; P = .002), Tre at sweating onset (AM −0.34°C [0.24°C], PM −0.31°C [0.25°C]; P = .001), and end-exercise Tre (AM −0.47°C [0.33°C], PM −0.43°C [0.29°C]; P = .001), heart rate (AM −14 [7] beats·min−1, PM −13 [6] beats·min−1; P < .01), rating of perceived exertion (P = .01), and thermal sensation (P = .005) were not different in the morning compared with the afternoon. Conclusion: Morning heat acclimation by postexercise HWI induced adaptations at rest and during exercise-heat stress in the morning and midafternoon.

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Hemodynamics of post-exercise vs. post hot water immersion recovery

Journal of Applied Physiology ◽

10.1152/japplphysiol.00260.2020 ◽

2021 ◽

Author(s):

Michael A. Francisco ◽

Cameron Colbert ◽

Emily A. Larson ◽

Dylan C. Sieck ◽

John R. Halliwill ◽

...

Keyword(s):

Cardiac Output ◽

Mean Arterial Pressure ◽

Arterial Pressure ◽

Femoral Artery ◽

Superficial Femoral Artery ◽

Water Immersion ◽

Recovery Period ◽

Hot Water ◽

Post Exercise ◽

Hot Water Immersion

This study sought to compare the hemodynamics of the recovery periods following exercise versus hot water immersion. Twelve subjects (6 F, 22.7 ± 0.8 y; BMI: 21.8 ± 2.1 kg·m-2) exercised for 60 minutes at 60% VO2peak or were immersed in 40.5oC water for 60 minutes on separate days, in random order. Measurements were made before, during, and for 60-minutes post-intervention (i.e., recovery) and included heart rate, arterial pressure, core temperature, and subjective measures. Brachial and superficial femoral artery blood flows were assessed using Doppler ultrasonography and cardiac output was measured using the acetylene wash-in method. Internal temperature increased to a similar extent during exercise and hot water immersion. Cardiac output and mean arterial pressure were greater during exercise than during hot water immersion (both p<0.01). Sustained reductions in mean arterial pressure compared to baseline were observed in both conditions during recovery (p<0.001 vs before each intervention). Cardiac output was similar during recovery between the interventions. Stroke volume was reduced throughout recovery following exercise, but not following hot water immersion (p<0.01). Brachial artery retrograde shear was reduced following hot water immersion, but not following exercise (Interaction; p=0.035). Antegrade shear in the superficial femoral artery was elevated compared to baseline (p=0.027) for 60 minutes following exercise, whereas it returned near baseline values (p=0.564) by 40 minutes following hot water immersion. Many of the changes observed during the post-exercise recovery period that are thought to contribute to long-term beneficial cardiovascular adaptations were also observed during the post-hot water immersion recovery period.

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