A marathon runner is nearing exhaustion in hot weather. Why does core body temperature continue to rise even as the athlete's sweat rate plateaus?

💡 Explanation

The runner's core temperature rises because the rate of heat generation from muscle activity matches, or even exceeds, the maximum rate of heat loss through evaporation. Therefore, heat accumulates, rather than being dissipated, and the body overheats; this happens rather than vasodilation or shivering affecting core temperature, or the hypothalamus resetting the setpoint.

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