Increasing humidity affects thermoregulation during low-intensity exercise in women

Area of Science:

• Environmental Physiology
• Occupational Health
• Thermoregulation Research

Background:

• Growing number of women in manual labor roles.
• Limited research on women's thermoregulation in hot-humid environments.
• Need to understand physiological responses to heat stress in female manual laborers.

Purpose of the Study:

• Assess the impact of increasing relative humidity (RH) on women's thermoregulation.
• Investigate physiological responses during low-intensity exercise mimicking manual labor.
• Determine safe exposure limits for women in hot-humid conditions.

Main Methods:

• 10 women completed 90-min walks at 35% VO2max in 35°C at 55%, 70%, and 85% RH.
• Measured rectal temperature (Tre), mean skin temperature (Tsk), heart rate, and respiratory parameters.
• Controlled environmental conditions to isolate the effect of relative humidity.

Main Results:

• Increasing RH significantly decreased evaporative heat loss (E) while increasing heart rate and sweat rate.
• Most physiological changes occurred after 70% RH.
• Rectal temperature exceeded 38°C only at 85% RH after ~80 minutes.

Conclusions:

• Heat storage increased with rising RH due to reduced evaporative heat loss.
• Women exercising at low intensity in 35°C maintained safe rectal temperatures up to 70% RH.
• Findings provide critical data for occupational safety guidelines for women in hot environments.