Fall in forearm skin temperature during grade walking on a treadmill

Area of Science:

• Exercise physiology
• Human thermoregulation
• Environmental physiology

Background:

• Understanding core temperature regulation during exercise is crucial for performance and safety.
• Previous research indicated cutaneous vasoconstriction during exercise, but its role in core temperature rise was unclear.

Purpose of the Study:

• To investigate the relationship between heat production, heat loss, and core temperature changes during walking.
• To differentiate the effects of metabolic heat production versus total heat production on thermoregulatory responses.

Main Methods:

• Seven male subjects performed graded walking on an incline at varying speeds (0.5-9 km/hr).
• Measurements included rectal temperature, sweat rate, and forearm skin temperature under controlled environmental conditions (20°C, 40% RH and 28°C, 40% RH).
• Calculated heat production included metabolic heat production (M) and external work (W).

Main Results:

• Rectal temperature increased with metabolic heat production (M), independent of total heat production (H).
• Sweat rate was proportional to total heat production (H), not metabolic heat production (M).
• Forearm skin temperature fall correlated with metabolic heat production (M), not total heat production (H), indicating reduced dry heat loss.

Conclusions:

• The rise in core body temperature during exercise is primarily due to decreased dry heat loss.
• Reduced dry heat loss is linked to a fall in skin temperature, which is dependent on metabolic heat production.
• Cutaneous vasoconstriction likely contributes to the observed decrease in dry heat loss during exercise.