It can be hard to exercise or do physical work in very hot or cold environments. Fatigue can set in, making any movement feel sluggish and difficult.<\/p>\n
The mechanics of exactly how this happens inside the body has long been a fascination for Stephen Cheung. In his Environmental Ergonomics Lab, the Brock University Professor of Kinesiology studies how heat, hydration, altitude and cold air and water affect human physiology and performance.<\/p>\n
When the body\u2019s core temperature is lower than normal, for example, the priority is to protect core organs such as the heart, lungs and brain. Blood vessels in other tissues, such as muscle and skin, constrict to conserve warmth, thus reducing the body\u2019s supply of oxygen.<\/p>\n
This decrease in oxygen availability can also impact exercise performance, Cheung has found.<\/p>\n
Cheung and his team conducted an experiment in which research participants rested in a cold chamber until their core temperature dropped by 0.5\u00b0C, and then proceeded to pedal 20 kilometres on a stationary bicycle. Participants took far longer to complete the test when their core temperature dipped below normal levels, Cheung found.<\/p>\n
The process was then repeated, but with participants breathing in higher-than-normal oxygen levels.<\/p>\n
\u201cWe found that there was no difference in their performance level compared to when their core temperature was normal,\u201d says Cheung. He and his team published this finding in their 2018 study \u201cEffects of mild whole body hypothermia on self-paced exercise performance<\/a>.\u201d<\/p>\n In a follow-up study in early 2024<\/a>, the research team found exercise performance could be negatively impacted by up to 30 per cent by simply cooling the skin \u2014 even without a drop in core temperature.<\/p>\n \u201cThis supports the need for athletes and workers to wear proper clothing when working in cold weather,\u201d he says.<\/p>\n Cheung also researches how heat affects the body\u2019s ability to do heavy exercise.<\/p>\n