These painful muscle spasms are often caused by exercising in hot weather.

By Leah Groth
June 17, 2020
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As temperatures rise during the summer, so do instances of heat-related illnesses. While they are often on a spectrum of severity—with heat stroke as the most severe and heat rash labeled as less severe—it's still important to know about any ailment you might fall victim to due to high temperatures this season and what you can do about it.

What are heat cramps?

Heat cramps are one of the less severe heat-related illnesses, or medical issues that result from the body's inability to adjust to hot temperatures, but they're still not something you should ignore. "Heat cramps are painful, involuntary spasms of the muscle that tend to occur during intense exercise in hot environments," Elizabeth Gardner, MD, a sports medicine doctor, orthopedic surgeon, and assistant professor of orthopedics and rehabilitation at Yale School of Medicine, tells Health.

Because of their close association with exercise, heat cramps are often termed "exercise-associated muscle cramps," says Dana Nuetze, MD, PhD, an associate professor of family medicine at University of North Carolina School of Medicine. That's because "they don't always occur when an athlete is performing in warmer tempratures," she adds. Heat cramps are also common in workers and laborers who sweat a lot during strenuous activity outside in the heat, per the National Institute of Occupational Health and Safety (NIOSH).

What are the symptoms of heat cramps, and what do they feel like?

According to the NIOSH, the symptoms of heat cramps are mainly muscle cramps, pain, or spasms in the abdomen, arms, or legs. David Della-Giustina, MD, an emergency medicine doctor and professor of emergency medicine at Yale School of Medicine, says those heat cramps feel like a muscle spasm, or what's known as a charley horse. 

Dr. Gardner notes heat cramps should only involve only the skeletal muscles. “If there is involvement of any other system in the body [like your chest], then medical care should be sought immediately,” she explains.  

Before the onset of full-on heat cramps, there are often some momentary spasms of tightness, called fasciculations. “If you do feel these, it is important to briefly rest and rehydrate, which can prevent the progression to full cramps,” she points out. When heat cramps occur, the muscles feel like they have “locked up” and can’t be relaxed.

What causes heat cramps?  

Dr. Della-Giustina explains that heat cramps usually occur when someone is performing strenuous activity in the heat, after the individual has been active for some period of time—about 30-45 minutes, depending on their activity level. "It occurs in people who are just hiking as well as those in more strenuous activities," he adds.

The NIOSH says heat cramps are caused by a depletion of the body's salt and moisture levels, and low salt levels in muscles can cause painful muscle cramps. Dr. Gardner also points out that heat cramps are most common during pre-season workouts in athletes when the body hasn't yet adjusted to the intensity of an activity or hot temperatures. In addition to profuse sweating and inadequate replacement of fluids and electrolytes, wearing extra layers of clothing or protective equipment, which prevents efficient sweat evaporation and body cooling, can also put an athlete at risk for heat cramps.

There are also medications, supplements, and other substances that increase your risk of heat cramps, according to Todd Sontag, DO, a family medicine physician at Orlando Health. These include certain blood pressure medications, caffeine, alcohol, some anti-depressants, some allergy medications, and many illicit drugs.

How can you prevent and treat heat cramps? 

Thankfully, it's relatively easy to prevent heat cramps—it can be as simple as maintaining balanced electrolyte and hydration levels before, during, and after exercise. "Athletes must be educated about the importance of this, and should be given time during training for hydration breaks,” says Dr. Gardner. “Acclimatizing athletes to hot weather, and undergoing exercise periodization, where the intensity and duration of activity is gradually increased over days, both allow the body to better adjust to the environment.”

Dr. Della-Giustina adds, "if you are going to be active outdoors, eat food with salt as well as drinking electrolyte solutions such as the sports drinks,” One pro-tip: You can dilute your sports drinks with water for better results. "It is actually better to be this way as it enhances absorption," says Dr. Della-Giustina. 

And if you do start to experience heat cramps, Dr. Della-Giustina recommends stopping whatever you're doing and taking a rest. Then, do a little stretching and drink a solution that has some electrolytes in it such as the sports drinks. That said, if the cramps do not improve within an hour, you should seek medical care ASAP.

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