During a marathon in hot weather, why does an athlete risk exertional heat stroke when sweat evaporation decreases?

💡 Explanation

Exertional heat stroke becomes likely because reduced sweat evaporation inhibits heat dissipation, leading to a rise in core temperature through conduction from the muscles to the core. This is because sweat evaporation is the primary thermoregulation mechanism; therefore, conduction increases body temperature rather than blood pressure, glycogen use, or muscle oxygenation being the primary issues.

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