A marathon runner collapses mid-race on a hot day, exhibiting disorientation and cessation of sweating. Why does cessation of sweat contribute to this athlete's hyperthermia?

💡 Explanation

The athlete's thermoregulation fails as sweat glands stop functioning; therefore, the evaporative cooling mechanism is lost, because sweat evaporation absorbs heat from the skin. This lack of evaporative heat loss exacerbates hyperthermia, rather than muscle shivering, altered blood viscosity or vasodilation directly causing it.

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