Heat and exercise: Keeping cool in hot weather

Stay safe during hot-weather exercise by drinking enough fluids, wearing proper clothing and timing your workout to avoid extreme heat.

By Mayo Clinic Staff

Whether you're running, playing a pickup game of basketball or going for a power walk, take care when the temperatures rise. If you exercise outdoors in hot weather, use these common-sense precautions to prevent heat-related illnesses.

How heat affects your body

Exercising in hot weather puts extra stress on your body. If you don't take care when exercising in the heat, you risk serious illness. Both the exercise itself and the air temperature increase your core body temperature.

To help cool itself, your body sends more blood to circulate through your skin. This leaves less blood for your muscles, which in turn increases your heart rate. If the humidity also is high, your body faces added stress because sweat doesn't readily evaporate from your skin. That pushes your body temperature even higher.

Heat-related illness

Under normal conditions, your skin, blood vessels and perspiration level adjust to the heat. But these natural cooling systems may fail if you're exposed to high temperatures and humidity for too long, you sweat heavily, and you don't drink enough fluids.

The result may be a heat-related illness. Heat-related illnesses occur along a spectrum, starting out mild but worsening if left untreated. Heat illnesses include:

  • Heat cramps. Heat cramps are painful muscle contractions. Affected muscles may feel firm to the touch. Your body temperature may be normal.
  • Heat syncope and exercise-associated collapse. Heat syncope is a feeling of lightheadedness or fainting caused by high temperatures, often occurring after standing for a long period of time, or standing quickly after sitting for a long period of time. Exercise-associated collapse is feeling lightheaded or fainting immediately after exercising, such as after a race.
  • Heat exhaustion. With heat exhaustion, your body temperature rises as high as 104 F (40 C), and you may experience signs and symptoms including nausea, vomiting, headache, weakness, and cold, clammy skin. If left untreated, this can lead to heatstroke.
  • Heatstroke. Heatstroke is a life-threatening emergency condition that occurs when your body temperature is greater than 104 F (40 C). Your skin may be hot, but your body may stop sweating to help cool itself. If your heatstroke occurs during exercise in hot, humid weather, you may continue to sweat for a short time after exercising.

    You may develop signs and symptoms including confusion, irritability, heart rhythm problems, dizziness, nausea, visual problems and fatigue. You need immediate medical attention to prevent brain damage, organ failure or even death.

May. 16, 2014 See more In-depth