Here’s How to Get Used to Running in the Heat

Slogging through hot summer K’s? You’re not alone—but here’s what you can do to make it easier.

With the heat and humidity of summer come sweaty runs, early morning or late evening K’s to avoid overheating, and carrying water. Being hot on a run is expected as temps rise, but this type of weather bothers some runners way more than others. You might even know someone who can take the heat and humidity in stride better than you can.

To find out why, we tapped Kimberly Carter, D.O., an avid runner and physician with UCHealth in Firestone, Colorado, Heather Milton, M.S., C.S.C.S., an exercise physiologist at NYU Langone’s Sports Performance Center, and Geoffrey Dreher, D.O., assistant professor in the Department of Orthopaedics at Johns Hopkins University School of Medicine, to explain why some runners are more affected by rising temps than others, and what you can to make those hot, humid runs less miserable.

Why does the heat bother some runners more than others?

One of the biggest—and perhaps most obvious—factors is whether or not you’re used to exercising in this type of weather.

“Those who live at higher heat environments are less affected because our bodies adapt and acclimate to the environments we are in, for instance by increasing sweat rate for cooling,” says Milton.

Duration of activity, hydration status, exercise intensity, and fitness level also play a role, Milton adds. But, the most likely cause of heat intolerance in some individuals is simply not being used to it, according to Carter.

How well your body adapts to heat is typically related to your prior exposures and current fitness level. That means the more you have gradually increased your run duration and heat exposure—a.k.a. heat acclimation—the more well-equipped your body is to maintain its core temperature, which will limit discomfort, according to Dreher.

When it comes to humidity—which is essentially how much water content is in the air, Milton explains—it’s harder for our bodies to cool ourselves off through sweating in this type of weather, because our sweat is not evaporated in wet air as easily as it is in dry air.

However, there are some people who have a condition called heat intolerance. This means the body isn’t able to undergo the physical adaptations that need to occur in order to become heat tolerant. Some medical conditions, medications, and supplements may cause heat intolerance, such as multiple sclerosis, hyperthyroidism, blood pressure medications, and caffeine. Sometimes, certain supplements used by athletes to enhance performance can also cause heat intolerance, Carter says.

“It is usually the combination of humidity and heat that causes the intolerance,” Milton says.

Is there any way to get used to the heat faster?

Getting acclimated to working out in heat and humidity typically takes 10 to 14 days of exposure in exercise sessions that last 60 to 90 minutes. So, when beginning to exercise in heat, you should do so in a gradual manner over a two week period so your body’s thermoregulation—the process that allows your body to maintain its core internal temperature—can adjust and you can remain safe, explains Dreher.

But, in order to keep up the adaptations that occur, you must have continued exposure. It’s worth noting that these adaptations can be lost in as little as one week of discontinued exposure to the heat, Milton says. So, if you want to be able to comfortably run in the heat all summer, that also means you can’t let up on your training, otherwise you’ll be back to feeling just as hot as you did when you first started running in the heat.

“When building your exercise, I would recommend increasing duration first, then intensity,” Dreher says. “It is also very important to be well hydrated—before and during exercise—as this helps optimize your body’s thermoregulation processing in heat.”

Wearing clothes that are lightweight, light colored, and sweat-wicking will help as well. But be sure not to exercise in heat when you are sick or taking new medications that may affect your body’s thermoregulation (such as antihistamines, diuretics, vasodilators, and stimulants to name a few), adds Dreher.

And, rather than overexerting yourself, you can try to maintain moderate intensity. In heat, this may mean dialing down the activity you are used to doing on normal temps, explains Milton. And, being hydrated is important. Try to get at least 2-3 L of water per day, especially if you plan to run, Milton says.

“Start slowly and allow yourself to acclimate. By building slowly over at least two weeks, you have a better chance of tolerating the activity without it beating you up,” Milton says.

However, if you feel too hot or lethargic to exercise, your body is telling you that you are not prepared to safely continue, Dreher says, and you should stop or slow down immediately.

Are there any temperatures when runners shouldn’t log K’s outside?

When exercising outdoors in the heat, it is important to take into account the actual temperature as well as the humidity level to get the “real feel.” While there isn’t an official “danger zone” temperature that people should avoid working out in, there is general consensus that if the heat index is 32 degrees or above there is higher risk of sustaining heat-related illness, explains Carter.

What are signs of heat illness?

If you do decide to run in hot temperatures, you should be sure to look out for signs of heat illness. Some of the common signs of heat illness are dizziness, nausea, unsteadiness, confusion, overwhelming fatigue, cramping, and a persistently accelerated heart rate. If you develop these warning signs, it is important to get out of the heat and cool down your body, Carter says.

This can also turn into exertional heat illness, which is a very serious and potentially deadly condition that can develop if the warning signs of heat illness are ignored, Milton explains.

How can you recover after a hot run?

Be sure that both before and after exercise, you’re properly hydrated. Additionally, after you’re done running, take time to cool down by walking a bit to lower your heart rate and start the recovery process. Monitoring closely for heat illness symptoms is also important.

Carter suggests some effective cooling methods are seeking shade, consuming cool drinks, removal of clothing and pouring cool water on the body or taking a cool shower.

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