

How Extreme Heat Affects the Body
Aug 26, 2025
Dhruv Khullar, a New Yorker contributor and health policy professor, shares his harrowing experience at the Korey Stringer Institute, where he underwent a brutal heat test to understand extreme heat's effects on the body. He describes intense symptoms like cramps and dizziness while discussing the dangers of heatstroke with expert Douglas Casa. The podcast emphasizes how climate change is making cases of heat-related illness more common, affecting everyday individuals, not just athletes or laborers, and highlights the urgent need for better preventive measures.
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Personal Heat-Chamber Test
- Dhruv Khullar walked on a treadmill for ninety minutes in 104°F with 40% humidity and felt puffy, cramping, dizzy, and had a headache.
- He lost over 1 kilogram (≈2.2 lbs) of sweat and required time to feel rehydrated and clear-headed.
A Near-Fatal Race Collapse
- Douglas Casa described his exertional heat-stroke collapse as a 16-year-old during a 10K race and nearly died.
- Prompt emergency care saved his life and set him on a career studying heat-related illness.
Blood Flow Is A Three-Way Tradeoff
- During exertion in heat the body's finite blood volume must supply skin, heart, and muscles simultaneously, creating an impossible demand when dehydrated.
- Dehydration shrinks the circulating volume and worsens the competition, so performance and cooling both fail.