Heat acclimation and HSP-72 expression in exercising humans.

Area of Science:

• Exercise Physiology
• Molecular Biology
• Environmental Medicine

Background:

• Heat acclimation enhances thermotolerance.
• Heat shock proteins (HSP-72) are cellular markers of stress.
• The relationship between physiological adaptation and HSP-72 expression during heat acclimation is not fully understood.

Purpose of the Study:

• To investigate the effect of a 7-day heat acclimation protocol on HSP-72 expression in human skeletal muscle.
• To examine the relationship between molecular and physiological markers of heat acclimation.

Main Methods:

• Ten recreationally active males underwent a 7-day heat acclimation protocol (cycling at 75% VO2peak in 39.5°C, 27% RH).
• Muscle biopsies were collected on days 1 and 7 (pre-, 6h post-, 24h post-exercise) to measure HSP-72 protein.
• Physiological markers including core temperature, heart rate, oxygen uptake, sweat rate, and plasma cortisol were measured.

Main Results:

• Significant reductions in core temperature, heart rate, and plasma cortisol were observed on day 7 compared to day 1, indicating physiological heat acclimation.
• No significant differences in VO2, intramuscular temperature, skin temperature, or sweat rate were found between days 1 and 7.
• HSP-72 protein expression in skeletal muscle showed no significant changes following the 7-day heat acclimation protocol.

Conclusions:

• The 7-day heat acclimation protocol effectively induced physiological adaptations for heat tolerance.
• Despite physiological improvements, HSP-72 expression in skeletal muscle did not increase, suggesting it may not be a primary molecular indicator of heat acclimation in this context.