In a hot dry environment, which thermoregulatory mechanism accounts for virtually all body heat loss during vigorous exercise?

• A Evaporation ✓
• B Convection
• C Radiation
• D Conduction

Explanation

During vigorous exercise in a hot environment, evaporation of sweat becomes the dominant and eventually the only effective avenue of heat loss, responsible for over 80 percent of heat dissipation. Radiation and convection require a thermal gradient from skin to environment, which disappears or reverses when ambient temperature exceeds skin temperature. Conduction is negligible except in water immersion. In hot dry air, sweat evaporates readily, making this mechanism essential for preventing dangerous hyperthermia.

Reference: Ganong's Review of Medical Physiology, 26th ed.

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