How to exercise safely in the heat
Breaking a sweat takes on a whole new meaning when exercising in hot weather. Here’s how to avoid heat-related illnesses without compromising your fitness routine.
From unseasonably hot conditions in the 2023 Sydney Marathon, to elite tennis players calling out extreme playing conditions, changes to our weather patterns mean it’s more important than ever to understand how to exercise safely in the heat.
More than 25 people were taken to hospital after last year’s Sydney marathon — several in critical condition — when the temperature reached about 30C during the September event.
It was baking in Budapest, Hungary, at the 2023 World Athletics Championships in August, with temperatures pushing into the 30s, leading to athletes suffering muscle cramps and dehydration.
The brutal heat and humidity at last year’s US Open in Flushing Meadows, New York City, led world No.3 Daniil Medvedev to exclaim, “One player is gonna die”.
And Dr Elizabeth Hanna, honorary Associate Professor at ANU’s Fenner School of Environment & Society, says it’s only going to get worse.
“The 5th National Climate Assessment out of the US in November found climate change is causing even more extreme heat events, more intense storms and rising sea levels,” Dr Hanna says.
“The rate of warming is catching us all by surprise.
“Everybody is very alarmed — it’s clear we need to prepare for even hotter summers.”
Unpredictable conditions have been rewriting the rules of play for some time, adds Associate Professor Aaron Petersen, senior lecturer in exercise physiology at Victoria University’s College of Sport, Health and Engineering.
“Five years ago, when the worlds (the 2019 world athletics titles) were held in Qatar, the marathons were held at midnight for cooler temperatures, but runners still dropped out,” he says.
“It makes you wonder what we’re going to see in Paris at the Olympics.
“And it’s not just at the elite level. From grassroots sports to recreational activities, everyone is affected.”
The impacts of heat on your body during exercise
“When you exercise in extreme heat, your body has to work harder to maintain its core temperature,” Assoc Prof Petersen says.
“As your body temperature rises, your heart rate increases and blood pressure typically decreases because your body is trying to pump more blood to the surface of your skin to help you cool down.”
Adds Dr Hanna: “This additional load stresses the heart and all of our thermoregulatory (heat response and coping) systems, which can be easily overwhelmed and our core temperature rises.
“If your temperature gets too high, you can experience heat exhaustion, which can cause dizziness, nausea and vomiting or heatstroke, a life-threatening condition that can lead to seizures, coma and even death.”
The heat risk from exercise is affected not just by the temperature but also humidity levels, wind speed and sun exposure, Dr Hanna says.
Other factors contributing to heat risk include exercise intensity and duration, your fitness level and how well you are acclimatised.
“Humans aren’t built to exercise at length in very hot weather and few sports are without risk in the summer heat,” Dr Hanna notes.
“Heat stress can even occur in a hot swimming pool. And endurance sports such as gruelling tennis matches, marathon races and cycling tours are especially hazardous, as are football and cricket.”
How to exercise safely in the heat
Keep hydrated:
“This is critically important,” Assoc Prof Petersen says.
“Current recommendations are that you should drink enough fluid to keep your body mass from decreasing by more than 2 per cent but also make sure you don’t drink so much that your body mass increases.”
Adds Dr Hanna: “To assist you in monitoring how well you’re coping in the heat, you should still be passing urine. And it should be very pale in colour. Dark urine, or passing none at all, is the hallmark of danger.”
Cool threads:
The experts recommend wearing loose-fitting, light-coloured clothing to help your body stay cool.
Shade is your friend:
“Take rests in the shade,” Assoc Prof Petersen says.
“If you start to feel overheated, stop and take a break in a cool place.
Know your temperature:
Monitor your core temperature — 39.5C or higher is probably a sign you need to stop exercising immediately, Assoc Prof Petersen says.
Choose your time:
Avoid exercising in the hottest part of the day.
Choose morning or evening when it is cooler.
More on coping with hot weather:
- Thirsty? This is why you should drink more water
- Best ways to stay cool at home through summer
- How to get a good night’s sleep in the heat
Written by Liz McGrath.
