Exercising in the Heat · prepare, protect, cool

高温下运动 · 准备、防护与急救

Place · Level 3

运动产热靠汗蒸发散掉, 湿度一高就失灵 · 热射病是急症 · 热适应是最强防护 · 补水别过量 · 降温先于转运

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cofactor · 1

Water & Electrolytes
In the heat, cooling runs mainly on sweat evaporation, and sweating takes both water and sodium with it. Both ends of fluid replacement are dangerous: losing more than 2% of body mass degrades performance and raises heat strain, while drinking plain water beyond sweat losses dilutes blood sodium.

How the body dumps heat

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身体怎么把热甩出去

During exercise, muscle works like an engine: most of the energy doesn't become movement — it becomes heat (roughly 80%). That heat has to be shed fast, or core temperature climbs.

The body sheds it two ways: skin blood flow carries heat to the surface, and sweat evaporation carries it away (evaporating 1 liter of sweat removes about 580 kcal). The key point — evaporation is the workhorse, and when humidity is high, sweat can't evaporate, so cooling collapses. A humid 30°C is far more dangerous than a dry 30°C.

There's a second problem: skin and muscle compete for blood flow. Skin needs blood at the surface to dump heat; muscle needs blood to do the work; the heart has to supply both, and it copes by driving heart rate up (González-Alonso 2008). That's why on a hot day the same pace feels much harder.

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Educational content, not medical advice — consult a clinician.

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