Earlier this summer, Glen Kenny spent three days confined to a special chamber inside his University of Ottawa lab where the daytime temperature was set at 40C (104F). 
The purpose was to see how the researcher’s 61-year-old body held up in brutal indoor temperatures observed during a 2021 heat wave that killed hundreds of Canadians. Though he felt fine the first day, by the second, his internal temperature briefly hit nearly 40C — approaching a dangerous level — and by the third he’d lost roughly 10 pounds (4.5 kg).
  
  Glen Kenny beside the Snellen air calorimeter at the Human and Environmental Physiology Research Unit of the University of Ottawa.
 Photographer: Justin Tang/Bloomberg
    Over decades studying the effects of extreme heat on human ...