Hot weather and heart attack

Q: Does exercising in hot weather increase your risk of having a heart attack?

A: Exercising in hot weather can stress your body, because the heart pumps hard to deliver blood and oxygen to your muscles while your body is trying to cool off by sweating. If you sweat too much, you lose more fluid than can be replaced and you become dehydrated. This means your heart pumps even harder to pump the smaller volume of blood through your body. As you become dehydrated, your temperature rises and your nervous system doesn’t work properly, which can lead to brain and heart damage.

To exercise in hot weather, wear light, comfy clothing and work out in the early morning or late evening, when it is cooler. Watch for symptoms of heat exhaustion, including heavy sweating, cold and clammy skin, dizziness, muscle cramps, nausea, and/or a weak and rapid pulse. If any symptoms appear, stop exercising. Cool down by dousing yourself with cool water and drinking fluids. You may need medical attention.

Jennifer H. Mieres, M.D., is director of nuclear cardiology and associate professor of clinical medicine at New York University. She’s also a spokesperson for the American Heart Association.