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Sweat rate and sweat composition following active or passive heat re-acclimation: A pilot study
Lisa Klous1, Cornelis de Ruiter1, Puck Alkemade1
1Department of Human Movement Sciences, Faculty of Behavioural and Movement Sciences, Vrije Universiteit Amsterdam, Amsterdam Movement Sciences, Amsterdam, The Netherlands.
Temperature (Austin, Tex.)
|February 8, 2021
Summary
Active heat re-acclimation (HRA) increases local sweat rate (LSR) and improves sweat electrolyte balance more than passive HRA. This study compared controlled hyperthermia (CH) with hot water immersion for HRA effectiveness.
Area of Science:
- Human physiology
- Thermoregulation
- Exercise science
Background:
- Heat acclimation (HA) improves thermoregulation.
- Heat re-acclimation (HRA) may restore heat tolerance.
- Active and passive HRA methods exist, but their comparative efficacy is unclear.
Purpose of the Study:
- To investigate the effects of active (controlled hyperthermia; CH-CH) versus passive (hot water immersion; CH-HWI) heat re-acclimation (HRA) on local sweat rate (LSR) and sweat composition.
- To compare HRA methods against a control group (CH-CON) following initial heat acclimation (HA).
Main Methods:
- Fifteen participants underwent four heat stress tests (HST): pre- and post-HA, and pre- and post-HRA.
- HRA interventions included CH-CH (n=6), CH-HWI (n=5), and CH-CON (n=4).
- LSR and sweat electrolyte concentrations (sodium, chloride, lactate, potassium) were measured on the arm and back.
Main Results:
- Both HA and HRA significantly increased LSR and decreased sweat sodium, chloride, and lactate concentrations.
- Active HRA (CH-CH and CH-HWI) induced greater LSR increases than the control (CH-CON).
- CH-CH resulted in superior sweat sodium and chloride conservation compared to CH-HWI and CH-CON.
Conclusions:
- Active HRA, particularly using controlled hyperthermia, enhances local sweat rate and electrolyte conservation more effectively than passive HRA.
- Both active and passive HRA methods contribute to restoring heat tolerance after an initial acclimation period.
- Findings suggest that active HRA protocols may be more beneficial for optimizing physiological adaptations to heat.
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