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As Summer Approaches, Heat Illness Becomes a Concern

As part of our continuing effort to service and educate our membership, each Thursday U.S. Soccer will provide an informative article from one of its departments. Once a week, we will bring you an article/paper/essay that will hopefully enhance your enjoyment and knowledge of the game of soccer - on and off the field.

This month, Dr. Donald T. Kirkendall, who works with U.S. Soccer’s National Teams, writes about heat illness as the hot summer days are just ahead.

As Summer Approaches, Heat Illness Becomes a Concern

By Donald T. Kirkendall

As we approach the summer months, it is always a good time for a refresher on the dangers that high temperatures can bring. Unfortunately, because summer is a very popular time for tournaments and camps, it makes the message of taking proper precautions against heat stroke and other heat-related illnesses and death even more important.

Body heat is produced from ATP, a molecule that contains energy for all the body’s functions. When ATP breaks down, heat is released, and that is where body temperature comes from. If your body breaks it down faster (i.e. while exercising), it needs to eliminate the extra heat to keep the temperature from rising too high.

During exercise, the most important way to lose heat is through evaporation. Sweating is not the process of losing heat, but evaporation of that sweat is. When sweat beads up on the skin, that sweat is being produced faster than it can evaporate.

This process is limited by a combination of heat and humidity – the more humid the air, the slower the rate of evaporation. Some think it has to be 90 degrees Fahrenheit with 90 percent humidity to produce problems. With a temperature of 98 degrees and 60 percent humidity the heat index is 123 degrees, and at 40 percent the index is 107 degrees. This being said, it is important to not rely only on the heat index.

Many think that morning practice sessions are a surefire way to avoid heat illness, but athletes have died in morning sessions. At 9 a.m. it might be 75 degrees, but the humidity can be 95 percent. While the heat index is under 80 degrees, the level of humidity makes it tough for sweat to evaporate.

More important than air temperature is body temperature, which is ideal at 99 degrees. When the body temperature reaches 102 degrees, there is potential for danger. Symptoms of an athlete at this stage include sweating profusely; pale appearance; cramping; a weak and rapid pulse; fast and shallow breathing; and possible fainting. When the body temperature reaches 105 degrees, heat stroke becomes imminent. Sweating may cease, pulse will be rapid, and headache, dizziness, nausea, confusion and seizures may occur. The victim may have dry skin and could lapse into unconsciousness. This is a medical emergency that all teams must be prepared for in both training and matches. This is probably the biggest concern of the medical personnel during a summer tournament or pre-season training camps.

There are many suggestions on how to prevent heat illness, including the following:

    • Pre-hydrate. Avoid caffeine, alcohol and carbonation.
    • Drink two to five times the normal amount of water (non-caffeinated, non-alcoholic, and non-carbonated). Also, replace salts and minerals by drinking fruit juices or sports drinks. Drinking fluids prior to exercise also is very important.
    • Wear clothing that is lightweight, loose, light-colored and breathable
    • Use a sweatproof/waterproof sunscreen of at least 30 SPF
    • Get into shade or air conditioning as often as possible. A cool shower afterward activity lowers body temperature. Mist tents are popular, but while they feel good, I am not convinced they lower body temperature all that much. Mist tents work best with a brisk breeze.
    • Keep a large cooler filled with ice water and drench towels in it to drape over the head and neck during breaks. Cold towels over the head and neck are very effective. Nearly 50 percent of the body’s heat lost is from the head/neck region.
    • Plan training early in the morning (9 a.m.) and late in the evening (after 6 p.m.). Traditional after-school practice time (4 p.m.) is the worst time to train. Not only is the hottest time of the day, the air quality is at its worst, especially if you are in an urban area near traffic. Many colleges in the south do not train in the afternoon during preseason for these reasons.
    • It is critical that players get used to the heat. Individual training prior to formal practice is absolutely essential. It generally takes a person five days to two weeks to acclimatize to the heat.
    • Schedule frequent water breaks (every 15 minutes at least) and allow players time to drink and rest in the shade.
    • A good indicator of a player’s hydration level is their urine color. If it is darker than lemonade, they need to drink more (note that multivitamin use makes the urine a fairly bright yellow due to the B vitamins).
    • Use a buddy system to monitor each other. Cramping and fast shallow breathing is easy to spot. Recognizing these earlier symptoms is key because by the time the buddy is confused or losing consciousness, trouble may be very close. The person most at risk is the overweight, un-acclimatized, poorly conditioned player who might be wearing the wrong clothing or too much clothing (in a misguided attempt to help lose weight).

Preventing heat illness is a very serious matter. Between 1979 and 1996, 2,862 Americans died due to heat-related causes. There was also a rash of heat related deaths in recent years, with Korey Stringer of the Minnesota Vikings being the most publicized. Court cases on Stringer’s death are still pending, but the NFL has since made changes to their guidelines on training in the heat. By educating coaches, players, trainers and parents on the importance of this issue, heat illness and death can be prevented in athletes of all levels.

Questions can be directed to Hughie O'Malley, U.S. Soccer's Manager of Sports Medicine Administration. Hughie can be reached at or at (312) 528-1225.