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Intermittent exercise-heat exposures and intense physical activity sustain heat acclimation adaptations
J Luke Pryor1, Riana R Pryor1, Lesley W Vandermark2
1Central California Sports Sciences Institute, Department of Kinesiology, California State University, United States; Korey Stringer Institute, Department of Kinesiology, University of Connecticut, United States.
Journal of Science and Medicine in Sport
|December 18, 2018
Summary
Intermittent exercise-heat exposures every fifth day effectively sustain heat acclimation (HA) adaptations for approximately one month. This strategy maintained physiological and perceptual benefits, reducing strain during exercise in heat.
Area of Science:
- Environmental Physiology
- Exercise Science
- Heat Acclimation Research
Background:
- Heat acclimation (HA) confers significant physiological and perceptual benefits for exercise in hot environments.
- The duration of these HA adaptations after cessation of heat exposure is a critical factor for practical application.
- Maintaining HA adaptations is crucial for individuals regularly exposed to heat, such as athletes and military personnel.
Purpose of the Study:
- To investigate whether intermittent exercise-heat exposures (IHE) every fifth day can sustain heat acclimation (HA) adaptations.
- To assess the retention of HA benefits 25 days after initial heat acclimation.
- To compare physiological and perceptual responses between a control group and an IHE group at 25 days post-HA.
Main Methods:
- A randomized controlled trial involving 16 non-heat-acclimatized men.
- Initial HA achieved through 10-11 days of exercise in a hot environment (40°C, 40% RH).
- Participants were randomized into a control group (CON) exercising in temperate conditions or an IHE group exercising in hot conditions every fifth day for 25 days post-HA.
Main Results:
- Both groups demonstrated successful heat acclimation, with significant reductions in heart rate (HR), thermoregulatory, physiological, and perceptual responses post-HA.
- At 25 days post-HA, the IHE group exhibited lower post-exercise HR and physiological strain index compared to the CON group.
- The IHE group maintained significantly lower post-exercise core body temperature (Tre) and improved perceptual responses compared to pre-HA levels, indicating sustained adaptations.
Conclusions:
- Intermittent exercise-heat exposures every fifth day for 25 days effectively sustain key heat acclimation adaptations.
- This strategy maintained heart rate and core body temperature adaptations, alongside reduced perceptual and physiological strain during exercise-heat stress.
- IHE represents a viable method for prolonging the benefits of heat acclimation for approximately one month.
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