Differences in dry-bulb temperature do not influence moderate-duration exercise performance in warm environments when...

Area of Science:

• Exercise physiology
• Environmental heat stress
• Human thermoregulation

Background:

• Ambient humidity significantly impacts aerobic performance in warm environments.
• Previous research has not isolated the effect of temperature by keeping humidity constant.
• Understanding the independent effect of temperature is crucial for optimizing exercise in heat.

Purpose of the Study:

• To investigate the independent contribution of dry-bulb temperature on thermoregulatory, perceptual, and performance responses during cycling.
• To control for vapor pressure while manipulating ambient temperature in a warm environment.
• To assess the impact of varying dry-bulb temperatures on physiological and subjective outcomes during a fixed-duration cycling trial.

Main Methods:

• Fourteen trained male cyclists completed a 30-minute cycling trial under two conditions: moderate heat (MOD) and mild heat (MILD).
• Environmental conditions were matched for vapor pressure but differed in dry-bulb temperature (MOD: 34.9°C, MILD: 29.2°C).
• Measurements included core and skin temperatures, sweat rate, cutaneous blood flow, power output, and perceptual responses.

Main Results:

• No significant differences were observed in rectal temperature, local sweat rate, cutaneous blood flow, mean power output, or total work completed between the MOD and MILD conditions.
• Despite similar physiological strain and performance, all perceptual measures, including perceived exertion and thermal discomfort, were significantly higher in the MOD condition.
• Weighted mean skin temperature was higher in the moderate heat condition.

Conclusions:

• Dry-bulb temperature does not independently affect high-intensity cycling performance in warm, compensable environments when vapor pressure is controlled.
• Perceptual responses, such as perceived exertion and thermal discomfort, are negatively impacted by higher dry-bulb temperatures even when physiological strain is matched.
• These findings highlight the importance of both temperature and humidity in exercise performance and comfort, suggesting that perceptual factors may be more sensitive to temperature changes than physiological ones.