Know what to watch out for when exercising in high heat

With warmer temperatures upon us, using common sense and listening to your body is your best bet to prevent problems such as heat cramps, heat exhaustion and heat stroke.

Age, level of fitness, how accustomed you are to the heat and pre- existing medical conditions are some of the factors that can influence your response to exercise.

Your body is cooled mainly through the evaporation of sweat. When the humidity is high, perspiration stays on your skin and does not evaporate as easily. This can cause your body's core temperature to reach dangerous levels, setting you up for trouble.

Watch out for warning signs
Exercisers should be familiar with the early warning signs of these heat-related illnesses:

  • Heat exhaustion occurs when the body becomes dehydrated. Exerting yourself on hot, humid days means that you are sweating more and losing essential fluids. Without proper amounts of water to replace what has been lost, you slowly begin to suffer the ill effects. Drink water before and after exercise, and take it with you to sip on as you go.

    Some symptoms of heat exhaustion include fatigue, weakness, anxiety, profuse sweating, cold, pale, clammy skin and disorientation.

    Fainting is also a mild form of heat exhaustion that can occur when temperatures are high. This is typically seen when a person is in a standing position for a prolonged period of time, which causes the blood to pool in the lower extremities.

    Although not as dangerous as heat stroke, it should still be taken very seriously. Anyone suffering should be quickly taken to a cool, shaded area and given fluids immediately.

  • Heat stroke is extremely serious and can be fatal. Sometimes referred to as "sunstroke," it is preceded by headache, dizziness, fatigue and hot, flushed, dry skin. If not recognized, the person experiences increased pulse rate and breathing, disorientation and unconsciousness and/or convulsions.

    It is important to immediately move the person to a cool place and seek medical treatment. Wrap wet towels around the victim's body or immerse him in water. If ice packs are available, place them on the wrists, ankles, armpits and neck to cool the larger blood vessels.

  • Heat cramps are the mildest form of heat injury. The individual experiencing heat cramps complains of muscle twitching, cramping and painful spasms of the muscles. Whatever muscles are used most often are the most susceptible.

    Spasms are caused by the failure of the body to replace lost body salts and usually occur after heavy sweating.

  • Heat rash (sometimes referred to as prickly heat) occurs when sweat glands become blocked and inflamed. This painful rash reduces the body's ability to sweat and to tolerate heat.

    Other factors to consider
    Here are some additional tips to help keep you out of danger:

  • Diabetes, high blood pressure, obesity and certain medications can affect your ability to tolerate the heat. This is just one more reason to check with your doctor if you have any type of medical condition or plan on exercising when the weather is hot, especially if you have been sedentary for a long time.

  • Acclimate yourself to the heat if you are unaccustomed to high temperatures and humidity. Hydrate yourself before, during and after the exercise.

  • In the beginning, pace yourself, and exert yourself for shorter periods of time, gradually increasing duration only if there are no difficulties.

  • If possible, exercise during morning or evening hours when it is cooler. Avoid exercising between the hours of 10 a.m. and 3 p.m. If this isn't possible, consider exercising indoors.

  • Wear light-colored, loose-fitting, natural-fiber clothing that absorbs perspiration, like cotton. Avoid fabrics that retain heat, such as nylon, rubberized or plastic suits, sweat shirts or sweat pants.

  • Protect your skin by using a sunscreen, re-applying often.

    Marjie Gilliam is an International Sports Sciences Association and American Council on Exercise master certified personal trainer and fitness consultant. Her Web site is

    (C) 2003 Marjie Gilliam

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