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Running In The Heat

Overheating Is Risky Business

Published July 21, 1997, in The Post-Standard.

By Dr Kamal Jabbour, Contributing Writer

Running In The Heat Can Be Hazardous To Your Health

As the temperature and humidity rise, the medical community reminds us of the dangers of exercising in the heat. In particular, all-season runners, those who run and race all year, should take added precautions. To state the matter simply: heat kills.

When you run, your body burns glycogen and fat, and converts them into energy. This conversion is very inefficient. About ten percent of the converted energy generates motion. The remainder is wasted as heat. The blood carries the heat to the skin to dissipate it through evaporation and perspiration.

Heat and humidity limit your body's ability to dissipate the extra energy. High ambient temperature slows down heat dissipation, while high humidity prevents evaporation. As a result, the internal body temperature rises dangerously, leading to serious injury or death. Children have a lower tolerance to heat than adults, given their lower ratio of skin surface to body weight.

Signs of heat injury include thirst, dizziness, nausea, chills, and dry skin due to the absence of sweat. Stop running immediately, and drink water. Get help if you do not feel better.

To run and race safely in the heat, you must enable your body to dissipate the extra heat. First and foremost, avoid dehydration. When you run, you lose 3 to 5 cups of fluids per hour. This results in a smaller blood volume, with a lower capacity to carry heat to the skin. Thirst is a poor indicator of the body's need for water. Runners should drink water all the time, at least one gallon every day. A colorless urine is a good sign of adequate hydration.

When running, drink a cup of water every 15 to 20 minutes. Road races should have at least one water station every 2 miles. At every station, grab two cups. Drink one cup, and pour the second cup on your head, since the scalp has a rich supply of blood vessels. Beware those races that offer sports drinks. In that case, skip the second cup.

Carry water on long runs, or plan to pass by public parks and schools that have water fountains. It also pays to know your neighbors. Many friendly neighbors leave water hoses outside for runners use. You may also place water bottles on the course before the run, as long as you pick them up afterwards. Do not act suspicious when you drop the bottles in the bushes, lest you get a mayoral lecture.

On hot and humid days, run early in the morning. Run in the shade when possible. Avoid direct sun light and blacktop surfaces. Wooded trails serve both purposes, and offer a change of scenery and relief from the pounding on the roads.

Wear loose-fitting and lightly colored clothes. The loose fit allows air to circulate and cool your skin. The light color reflects the sun. Never wear plastic or nylon sweat suits; they are dangerous. A hat, a sunscreen and sunglasses provide added protection from the sun's harmful rays.

Maintain a healthy diet. Avoid fat, salt, alcohol, sweetened drinks, and coffee. They act as diuretics. Increase your consumption of fruits and vegetables to replace lost minerals.

Do not run if you have a fever. The body is already at a thermal disadvantage. Running will only increase your temperature and endanger your life.

The summer need not be an off-season. You can train your body to run safely in the heat. You can achieve heat acclimatization by gradually increasing the time spent running in the heat. In 7 to 10 days, a runner develops a richer supply of blood vessels to the skin, and increases the secretory capacity of the sweat glands. These changes result in a decrease in heart rate, body temperature, sweat salt content, metabolic rate, muscle lactate accumulation and muscle glycogen utilization, resulting in more efficient heat dissipation.

Despite their best intentions, many runners live in a state of dehydration. Race performance suffers, and the risk of heat injury increases. To make matters worse, studies indicate that long distance runners are six times more likely to develop kidney stones than the overall population. So, please drink more water, and run smart.

Kamal Jabbour runs on the trails of Highland Forest in the summer. His RUNNING Column appears in The Post-Standard on Mondays. He maintains The Syracuse Running Page and receives email at jabbour@syr.edu.


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