How to Prevent Cramps and Illness in the Heat

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Heat cramps are painful muscle spasms that occur in the arms, legs, or abdomen that usually occur after several hours of exertion in the heat. In addition to muscle cramps, other symptoms of heat cramps may include faintness, dizziness, weakness, and excessive sweating. Usually, an athlete suffers from heat cramps after several hours of the exertion and excessive sweating that results in dehydration.

Causes

Muscle cramps are more common during exercise in the heat because sweat contains fluids as well as electrolytes (salt, potassium, ​magnesium, and calcium). When these nutrients, particularly sodium, fall below a certain level due to excessive sweating, the incidence of heat cramps increases.

The exact cause of heat cramps is unknown, but common theories include:

  • Altered neuromuscular control
  • Dehydration
  • Doing a new activity
  • Electrolyte depletion
  • Muscle fatigue
  • Poor conditioning

While all these theories are being studied, there's more evidence that the "altered neuromuscular control" hypothesis is the principal pathophysiological mechanism the leads to exercise-associated muscle cramping (EAMC). Altered neuromuscular control is often related to muscle fatigue and results in a disruption of muscle coordination and control.

Treatment

As soon as you recognize any of the symptoms of heat illness, take the following actions:

  • Stop activity and sit quietly in a cool place.
  • Drink a sports beverage with electrolytes (you can make your own sodium-based solution with 1/4 teaspoon table salt mixed in a quart of water).
  • Gently stretch and massage the cramping muscle.
  • Hold the joint in a stretched position until the cramp stops.
  • Seek medical attention for heat cramps if they do not subside in one hour.

Most muscle cramps are not serious. If your muscle cramps are severe, frequent, constant or otherwise of concern, see your doctor.

Prevent Heat Illness

Remember, it is easier to prevent heat illness than to treat it once symptoms develop. To minimize your risk of developing heat cramps, it's important to hydrate well.

Do not drink alcohol or beverages with caffeine before exercise because they increase the rate of dehydration. Drink plenty of fluids before and during exercise and replace lost electrolytes such as sodium, potassium, and magnesium with food or a sports drink (drink 16 to 20 oz/hour).

Staying hydrated helps, but it's also important to guard against overheating.

  • Avoid exercising during the hottest time of day; train closer to sunrise or sunset.
  • If you are going to exercise in hot weather, acclimatize to the heat for about a week before intense exercise.
  • If you feel your abilities start to diminish, stop the activity and seek out a cool, shaded place.
  • Use sunscreen to prevent sunburn, which can limit the skin's ability to cool itself.
  • Wear a hat with a brim.
  • Wear light, loose clothing, so sweat can evaporate. Better yet, invest in some clothes that wick moisture from your skin to the outer layer of the clothing where it can evaporate more easily. Brands like CoolMax®, Drymax®, Smartwool or polypropylene all have this property.

Prevent Muscle Cramps

Until we learn the exact cause of muscle cramps, it will be difficult to say with any confidence how to prevent them. However, experts and athletes alike recommend fitness fundamentals, such as warming up before exercise, improving fitness, avoiding excessive muscle fatigue, and stretching regularly, paying particular attention to the calves, hamstrings, and quadriceps.

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3 Sources
Verywell Fit uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. Schwellnus MP. Cause of exercise associated muscle cramps (EAMC)--altered neuromuscular control, dehydration or electrolyte depletion? Br J Sports Med. 2009;43(6):401-8. doi:10.1136/bjsm.2008.050401

  2. Jahic D, Begic E. Exercise-associated muscle cramp-Doubts about the causeMater Sociomed. 2018;30(1):67–69. doi:10.5455/msm.2018.30.67-69

  3. Miller KC, Stone MS, Huxel KC, Edwards JE. Exercise-associated muscle cramps: causes, treatment, and preventionSports Health. 2010;2(4):279–283. doi:10.1177/1941738109357299

Additional Reading
  • American Orthopaedic Society for Sports Medicine. Muscle cramps. Updated June 2017.