Abstract
INTRODUCTION:
Adaptations to short-term (<7 exposures) heat-acclimation (HA) decay rapidly and are lost within 2 weeks, likely compromising pre-competition/deployment training [1]. 6-days of post-exercise hot water immersion (HWI) has been suggested to retain heat adaptations for 2 weeks [2]. However, the effects of this method on overall fatigue (e.g. neuromuscular, cognitive and perceived) remains unknown and may compromise training. This study aimed to 1) investigate the effect of 6-days post-exercise HWI on neuromuscular, cognitive and perceived fatigue pre and post exercise in a hot environment; 2) examine the effect of one maintenance session of post-exercise HWI per week on overall fatigue during 20 days of HA decay.
METHODS:
10 healthy males (22±3 yrs, 78±18 kg) completed HA: 6-days of post-exercise (running at 65% VO2max for 40min, 22°C) HWI (40min, 40°C). A Heat Tolerance Test (HTT = running 30min at 9km.h-1 2% slope at 40°C, 40% humidity) [3] was performed pre and post HA. Every 6 days post HA, a maintenance post-exercise HWI session was performed and a HTT was completed post10 and 20 days. Maximum voluntary contraction of the quadriceps (MVC), central [voluntary activation (VA)] and peripheral alterations [high-frequency doublet (Db100), twitch (Pt)] were evaluated pre and post each HTT. Cognitive performances (accuracy, reaction time, omission) to response inhibition (Stroop) and working memory (3back-letter) were performed pre and post each HTT. Perceived fatigue (ROF scale) was evaluated each day. Two-way repeated measure ANOVAs and Holm correction for post-hoc tests were performed.
RESULTS:
Increase in rectal temperature and heart rate at rest and during the HTT were lower post HA compared to pre and sustained post20 (all p<0.001). Expansion in plasma volume and sweat rate, observed post HA, were not sustained post10 (respectively, p=0.02 and p=0.04). VA pre-post HTT was better preserved post HA and sustained post20 (p=0.002). Decrease in MVC, Db100 and Pt due to HTT was not different pre and post HA (respectively, p=0.3, p=0.3 and p=0.2). Accuracy to cognitive tasks was not impacted by HTT (p=0.7) but reaction time was faster post HTT compared to pre (p=0.002). All cognitive performances were improved after HA and post20. Perceived fatigue was stable during HA to post20 (p=0.4).
CONCLUSION:
HA of 6 days post exercise HWI induced beneficial HA related adaptations (lower rectal temperature and heart rate, higher plasma volume and sweat rate); re-trained once a week, some of these adaptations were sustained for 20 days. HTT alterations on central component were limited by HA, and it was preserved for 20 days, while peripheral alterations were not. This simple, practical and effective HA strategy does not induce additional fatigue, and may preserve central function, during an exercise in a hot environment.
REFERENCES:
1.Garette et al., Eur. J. Appl. Physiol, 2009
2.Zurawlew et al., Frontiers in Physiology, 2019
3.Mee et al., Journal of Thermal Biology, 2015
Adaptations to short-term (<7 exposures) heat-acclimation (HA) decay rapidly and are lost within 2 weeks, likely compromising pre-competition/deployment training [1]. 6-days of post-exercise hot water immersion (HWI) has been suggested to retain heat adaptations for 2 weeks [2]. However, the effects of this method on overall fatigue (e.g. neuromuscular, cognitive and perceived) remains unknown and may compromise training. This study aimed to 1) investigate the effect of 6-days post-exercise HWI on neuromuscular, cognitive and perceived fatigue pre and post exercise in a hot environment; 2) examine the effect of one maintenance session of post-exercise HWI per week on overall fatigue during 20 days of HA decay.
METHODS:
10 healthy males (22±3 yrs, 78±18 kg) completed HA: 6-days of post-exercise (running at 65% VO2max for 40min, 22°C) HWI (40min, 40°C). A Heat Tolerance Test (HTT = running 30min at 9km.h-1 2% slope at 40°C, 40% humidity) [3] was performed pre and post HA. Every 6 days post HA, a maintenance post-exercise HWI session was performed and a HTT was completed post10 and 20 days. Maximum voluntary contraction of the quadriceps (MVC), central [voluntary activation (VA)] and peripheral alterations [high-frequency doublet (Db100), twitch (Pt)] were evaluated pre and post each HTT. Cognitive performances (accuracy, reaction time, omission) to response inhibition (Stroop) and working memory (3back-letter) were performed pre and post each HTT. Perceived fatigue (ROF scale) was evaluated each day. Two-way repeated measure ANOVAs and Holm correction for post-hoc tests were performed.
RESULTS:
Increase in rectal temperature and heart rate at rest and during the HTT were lower post HA compared to pre and sustained post20 (all p<0.001). Expansion in plasma volume and sweat rate, observed post HA, were not sustained post10 (respectively, p=0.02 and p=0.04). VA pre-post HTT was better preserved post HA and sustained post20 (p=0.002). Decrease in MVC, Db100 and Pt due to HTT was not different pre and post HA (respectively, p=0.3, p=0.3 and p=0.2). Accuracy to cognitive tasks was not impacted by HTT (p=0.7) but reaction time was faster post HTT compared to pre (p=0.002). All cognitive performances were improved after HA and post20. Perceived fatigue was stable during HA to post20 (p=0.4).
CONCLUSION:
HA of 6 days post exercise HWI induced beneficial HA related adaptations (lower rectal temperature and heart rate, higher plasma volume and sweat rate); re-trained once a week, some of these adaptations were sustained for 20 days. HTT alterations on central component were limited by HA, and it was preserved for 20 days, while peripheral alterations were not. This simple, practical and effective HA strategy does not induce additional fatigue, and may preserve central function, during an exercise in a hot environment.
REFERENCES:
1.Garette et al., Eur. J. Appl. Physiol, 2009
2.Zurawlew et al., Frontiers in Physiology, 2019
3.Mee et al., Journal of Thermal Biology, 2015
| Original language | English |
|---|---|
| Publication status | Published - Jul 2023 |
| Event | European College of Sport Science Annual Congress - Paris, France Duration: 4 Jul 2023 → 7 Jul 2023 https://sport-science.org/index.php/component/content/article/2-uncategorised/130-welcome-to-ecss-paris-2023 |
Conference
| Conference | European College of Sport Science Annual Congress |
|---|---|
| Abbreviated title | ECSS Paris 2023 |
| Country/Territory | France |
| City | Paris |
| Period | 4/07/23 → 7/07/23 |
| Internet address |