Hot Tips

Q: I live in Tucson, where summer temperatures are often over 100 degrees. Even when I go cycling in the early morning, the temperature is often in the low 90s.

Regardless of how much liquid I drink, the heat is wearing me out. Do you have any information about training in very hot weather?

S.S.

A: You must do all you can to help your body cool itself through sweat evaporation. It's very important to be well hydrated before you exercise in 90-degree plus heat. If you aren't well hydrated, you won't produce enough sweat to cool yourself off.

Don't use thirst as a standard to judge your hydration level. By the time you feel thirsty, you may be more than a quart low on fluids. The best signs of being well hydrated are clear urine and a full bladder every two to three hours. Drink plenty of water the night before your workout. Avoid caffeine and alcohol, which act as diuretics.

To assess your level of dehydration, weigh yourself during and after the workout. Any weight loss is due to fluid loss and should be replaced before your next workout. Drink as much water as you can before your ride and try to drink five to 10 ounces of cool water every 15 minutes during your ride. Allow sweat to accumulate and cool you. Don't wipe it off.

Avoid retaining heat by wearing light-colored clothing made of natural fiber or one of the new synthetic cooling fabrics, such as CoolMax. Wear a helmet that allows airflow to cool the large vascular supply to the scalp.

Acclimatize to the heat gradually. Once you've had heat illness you're more prone to develop it again. Adjust to the heat by exercising at 65 to 75 percent of your usual intensity over the first two weeks, then gradually build up to full effort.

Try breaking your workout into two shorter ones instead of one long one. If possible, ride on a surface that doesn't reflect heat back up, such as a shady path. Even lighter colored concrete is better than black pavement.

If the heat overwhelms your body's cooling mechanism, you're sure to get hyperthermia (heat illness). The first sign is usually mild fatigue and headache from dehydration. It's soon followed by cramping, dizziness, nausea, irrationality and loss of muscle control. Heatstroke is the final stage when the body's cooling mechanism is completely out of whack. It can result in unconsciousness and death.

Any sign of lightheadedness, headache or cramping is a sign of impending heat illness and danger. Stop exercising, get out of the sun, drink something cool, put cool compresses on your armpits and groin, loosen your clothing and get close to a breeze or fan.

See this article on Hyperthermia for a more in depth discussion about heat illness. Good Luck!

About the authors: Carol L. Otis, M.D., is Chief Medical Advisor to the Sanex WTA and a UCLA student health physician. Roger Goldingay is a former professional soccer player. They are married and the co-authors of The Athletic Woman's Survival Guide.

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