How to Stay Cool When You're Exercising in the Heat

Too hot to run? Try one of these pre-cooling methods before you head out the door. (Photo: Antonio Guillem/Shutterstock)

Remember that promise you made in the dead of winter a few months ago? When it was bitter cold and snowing, snowing, snowing and you swore on your frozen fingertips that you would never complain about the heat again?

Well fast-forward to this past week, with record-breaking high temps around the country and I've seen more than a few social media posts begging for relief from the heat and humidity. For as much as I complained about running in the snow, sleet and below-freezing temperatures this winter, I'm determined not to complain about the summer weather. But that doesn't mean I'm not looking for ways to cool things down when the mercury rises. And a new study may just have some answers when it comes to the best ways for runners to stay cool when they're exercising in the heat.

The trend of pre-cooling — or finding ways to lower your body temperature before exercising — has become popular with runners looking to improve their speed and intensity in higher temperatures. Some runners have tried downing icy beverages before a run in an attempt to lower the body's core temperature, while others have donned vests filled with ice packs to cool skin temps. But which one is better at keeping runners cool throughout the workout? That's the question researchers at the Environmental Extremes Laboratory at the University of Brighton in the United Kingdom decided to answer.

How they tested pre-cooling

For the study, which was published in the Scandinavian Journal of Medicine and Science in Sports, researchers tested the effects of different pre-cooling methods on 12 experienced male runners. The runners were asked to sit in a hot, humid room on three separate occasions for 90 minutes before running strenuously on a treadmill for 30 minutes while researchers tested their core and skin temperatures, heart rates and blood lactate levels. The runners also completed self-evaluations about the difficulty of the workout.

Before the first workout, the runners drank a room-temperature, sweetened beverage. For the next workout, they drank about 16 ounces of a sweetened slushy drink. And for the last workout, the researchers used several methods to cool the runners' skin temperatures, including draping cold towels around their necks, immersing their arms in cold water, and even asking the runners to wear ice-pack filled undies.

Researchers noted that when the men drank the sweetened slushy (sweetened because previous research has shown that sugary, iced beverages lower the body temperature more than shaved ice alone,) their core body temperatures dropped significantly and quickly. And when they donned the ice packs and cold towels, their skin temperatures plummeted considerably.

So which method had the most long-lasting effect for the workout? The researchers found that compared to the workout in which the men did not pre-cool at all, they performed significantly better with both the slushy and the frozen underwear methods. And by the end of both pre-cooled workouts, their core and skin temperatures were about the same, indicating that the benefits they reaped from either method had leveled off by the end of the workout.

Interestingly, the study found that the skin temperatures of the men climbed slowly during the workout after they pre-cooled with ice-filled vests and cold towels. But when they drank the slushies, their core temperatures increased just as quickly as they had decreased. In other words, the effects of the core cooling wore off much more quickly than those of the skin cooling.

So what does this mean for you and your next 90-degree run? It means that it's worth it to take about 30 minutes before you exercise to bring down your body temperature so that you can feel cooler during your workout. Your best bet is to wrap a cold towel around your neck, or — if you're very brave — stick an ice pack down your pants. But if slushies are your thing, feel free to give that a try, too. The effects may not last for your entire workout, but they may cool you off enough to get you off and running. And sometimes that's all it takes to get out the door.