Skin blood flow and sweating changes following exercise training and heat acclimation

Area of Science:

• Exercise Physiology
• Environmental Physiology
• Thermoregulation

Background:

• Understanding physiological adaptations to exercise and heat is crucial for athletes and military personnel.
• Heat acclimation and exercise training induce significant thermoregulatory changes.
• Previous research indicates altered blood flow and sweating responses post-adaptation.

Purpose of the Study:

• To investigate the effects of exercise training and heat acclimation on thermoregulatory responses.
• To determine how these adaptations influence the relationship between internal temperature and physiological responses like sweating and blood flow.
• To clarify the role of body temperature in mediating changes in forearm blood flow during heat acclimation.

Main Methods:

• Eight subjects participated in a 10-day exercise training program and a separate 10-day heat acclimation program.
• Thermoregulatory responses, including chest sweat rate and forearm blood flow, were measured in relation to internal body temperature.
• Measurements were taken before training, between training and acclimation, and after acclimation at a controlled ambient temperature.

Main Results:

• Both exercise training and heat acclimation significantly lowered the internal temperature thresholds for vasodilation and sweating.
• While not statistically significant, training and acclimation showed a trend towards increasing the slope of the sweating response.
• Changes in the slope of forearm blood flow were minor and inconsistent; however, blood flow was higher at any given internal temperature post-acclimation.

Conclusions:

• Exercise training and heat acclimation effectively shift thermoregulatory thresholds to lower internal temperatures.
• The observed lower forearm blood flow during heat acclimation is likely a consequence of reduced overall body temperature, not a decreased vascular conductance.
• These findings enhance our understanding of human physiological adaptation to thermal stress and exercise.