For those looking to stay fit and get fresh air, exercising outdoors is the best option. But it can be dangerous to do so if your city is experiencing extreme heat, an increasingly common weather in Canada.
Our bodies generate a lot of heat when we exercise, says Stephen Cheung, a professor and senior research fellow in the department of kinesiology at Brock University who studies the impact of extreme conditions on human physiology.
When heat builds as we exercise, how effectively we can cool down depends on a lot of environmental factors: about 90 per cent of heat loss happens through our skin as it exchanges heat with the surrounding air. But it’s more difficult when the environment’s temperature is 37 degrees C (or, body temperature) or higher (on the flip side, heat transfers out of our bodies very quickly when it’s cold).
Humidity also makes it harder for our bodies to cool down. “We get rid of heat through sweating and using our body heat to evaporate that film of sweat out to the environment,” Cheung says.
In a dry climate, where there’s not much water in the air, water evaporates easily. In a hot, humid environment (like southern Ontario, for example), the air is already saturated with water, so it can’t take any more. “You can get away with exercising pretty hard in a hot and dry environment. But it becomes really challenging in a hot and humid environment.”
When we’re exposed to extreme heat for a long time it may lead to heat stroke, resulting in a core body temperature greater than 40 degrees Celsius. Dr. Samantha Green, a family doctor at Unity Health in Toronto, says that you should always be on the lookout for signs like dizziness, disorientation and loss of consciousness, which are symptoms of heat stroke.
“Heat stroke really is a medical emergency, and the longer they experience increased body temperature, the worse the outcome,” Green says. “So call 911, and get that person cooled down immediately.”
Heat exhaustion, which is a milder form of heat illness, is also dangerous but harder to notice: Green says that people experiencing heat exhaustion may just generally feel unwell, be nauseous and fatigued.
However, it’s important to stay vigilant and cool down whenever you start to feel unwell. Elderly people in particular are more vulnerable to heat stroke and heat exhaustion because their temperature perception is worse. People with chronic heart disease, lung disease, diabetes or who take medication that might contribute to poor temperature regulation (such as beta-blockers, allergy medications and some antidepressants) should also be extra careful when exercising outdoors in the heat.
How to stay cool while working out during extreme heat
Hydrate before: “Stay hydrated” is some of the most basic wellness advice out there, but there is truth to it: Cheung says that ensuring you are “normally hydrated” before exercising, meaning that you’re at your regular hydration levels, will “give your cardiovascular system the best chance of helping you thermoregulate.”
While normal hydration levels vary from person to person, Cheung says that drinking a couple of glasses of water the hour before exercising in the heat will keep you adequately hydrated (as well as drinking water while you work out).
Protect yourself from the sun: Sunscreen won’t just protect your skin from cancer but also help with thermoregulation. “If you get a sunburn that damages your skin, it damages the blood vessels and their ability to deliver blood to your skin, which harms your sweating response,” Cheung explains.
Wear loose clothes: Football players are some of the most at-risk athletes because of all the equipment they wear that contributes to overheating, Green says. When working out in extreme heat, make sure you wear breathable clothes made out of materials such as cotton and hats with ventilation.
Avoid the afternoon: Don’t go outdoors to exercise in the afternoon, when the sun is at its highest and hottest. Instead, Cheung says to work out early in the morning or in the evening when it’s cooler.
Exercise in nature: Concrete can create “heat islands,” where the temperature around paved areas is elevated. Try exercising on grass or in the shade of trees to stay cooler and avoid hot spots from the built environment.
Cool down after: Green recommends misting yourself with water. “You can also apply cold, wet clothes or even ice packs to the back of the neck, armpits and groin – those are areas with a lot of blood vessels and blood supply, so it’s a fast way to quickly cool the body,” she explains. Cheung adds that finding shade, heading into an air-conditioned space and drinking cold water will also help regulate your body temperature after working out in extreme heat.