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By Katherine Hobson

Outdoor exercisers dread that first summer heat wave, when what used to be a quick jog turns into a slow, labored slog. But experts say there are strategies you can use to avoid overheating.

When the mercury rises, the body’s ability to maintain a constant temperature diminishes, says Brendon McDermott, an assistant professor of kinesiology at the University of Arkansas. Exercise makes it even harder to keep temperature steady, because “every time a muscle contracts it’s creating heat,” he says.

The body’s most effective method of getting rid of all that heat is by sweating. But sometimes you can’t do that quickly enough to maintain a normal body temperature – particularly when there’s no breeze or if it’s humid, when sweat on your skin can’t evaporate, he says. That leads to discomfort, and either slowing down or stopping altogether, or if you persist, to potentially dangerous heat illness.

There are ways to prepare for shorter exercise sessions in the heat by “precooling,” or bringing down your core temperature ahead of a bout of exercise. A review of precooling research published online earlier this year in the journal Sports Medicine finds that strategies including cooling vests, iced towels and iced slushy drinks all seem to improve performance – at least in a laboratory setting.

More research needs to be done to see how these strategies work in real-life competition, explains Meg Ross, a sports physiologist with the Australian Sports Commission and an author of the review. For the recreational athlete who just wants to be more comfortable during a summertime 5k race or bike ride, there are methods that are cheap and simple, she says. For example, before your run, you could wrap a towel soaked in cold water around your neck, take a very cold shower or sip an ice slushy. (Try mixing crushed ice and cold sports drink in a blender.)

Precooling methods will only have effects for 30 or 45 minutes, says McDermott. So you can also use some of these strategies while you’re working out to stay cool. You could, for example, freeze a bottle of sports drink to sip while on a bike ride or during a tennis match, says Ross.

If you do exercise regularly in the heat, it should get a little easier after about two weeks, as your body acclimates to the new conditions, says Greg Close, a professional triathlete and owner of TriBy3 Performance Coaching. That’s why he advises athletes traveling from a cooler climate to a warm one for a race to simulate warm-weather conditions before they go, say by running on the treadmill with an extra layer on, and to travel a week or more before the event, if possible.

Close also says you’ll acclimate to the heat faster if you don’t spend all day in air-conditioning. So if you really want to get used to the summer conditions quickly, sleep with the window open, if you can stand it.

Whatever strategies you use, it’s key to listen to your body and to not push yourself too hard. If you run 9-minute miles in the crisp October air, don’t expect to maintain that same pace on a muggy July day, says Close. Stay hydrated and ramp up your workouts slowly. And if you’re coming down with a stomach bug or fighting a cold, be particularly cautious, since those conditions can make you more susceptible to heat illness, says McDermott.

He notes that heat stroke often occurs during competition, a tough practice or some other situation where there’s pressure to perform. And it can come on without first getting heat cramps or other more mild symptoms. So if you feel crummy – no matter how many ice slushies you downed before your workout – stop exercising, get to a cool place, hydrate and seek medical help if you don’t feel better.