After a few quick stretches, the tennis player goes out on the tennis court for the first match of the summer. He volleys with his opponent and decides to practice his serve. After a good shot, he rushes the net. Suddenly, his leg freezes in a cramp, and he falls down in pain—a victim of the heat.
"Most heat-related illnesses can be prevented with a little knowledge and preparation," says Eugene L. Kastelberg, M.D., a sports medicine specialist in Richmond, Va. "What most people don't understand is that these illnesses are not only common, they can be fatal during peak summer months."
The elderly and athletes are at greatest risk for injury. When weather forecasters talk about a heat index of 90 degrees or above—that's the temperature in the shade—everyone should take extra precautions.
The four most common heat-related emergencies are cramps, fainting, exhaustion, and heat strokes. These illnesses occur when the body can no longer cool itself properly.
"When it's humid, the air is already saturated with water, so it's harder for the body to dissipate heat through sweating," explains Dr. Kastelberg.
Evaporation of sweat keeps the body cool. Every gram of sweat that evaporates removes 540 calories from the surface of the skin. When you can no longer sweat or your sweat cannot evaporate because of high humidity, you can no longer dissipate heat and your body temperature may rise. When the body temperature increases too much, most people experience headache, dizziness, muscle weakness, cramps, or nausea. This is called hyperthermia. If body temperature goes too high or hyperthermia persists too long, collapse and death may follow.
Dr. Kastelberg says that many summertime athletes miss the chance to prevent heat-related injuries when they don't take the time to acclimate themselves. "If you're playing football in August, you should have started working out in July," he says.
He suggests that exercisers begin with sessions at 50 percent of their performance level in the month before beginning competition or regular exercise.
According to Dr. Kastelberg, there are several rules of thumb for exercising and drinking fluids. If you exercise in the heat for an hour, you should drink water at least 15 minutes before exercising and every 15 minutes during exercise. For exercise lasting longer than 60 to 90 minutes, athletes should drink a commercial carbohydrate and salt replacement fluid. They also can drink a homemade glucose solution, mixing one cup of sugar-sweetened fruit juice, 1/3 teaspoon salt, and one quart of water. Dr. Kastelberg says that athletes should only try new types of replacement fluids during training sessions and not on the day of competition.
If you lose more than 3 percent of your body weight during exercise, you need to replace that weight with both foods and liquids before exercising again. You can judge your weight loss by weighing before and after heavy exercise.
"The biggest mistake people make is that they think thirst is a sign of dehydration. In actuality, thirst is a late sign. You shouldn't wait until you are thirsty to begin drinking fluids. Instead, go for prevention," says Dr. Kastelberg.
This is a form of muscle spasm and tightening that occurs as a result of intense exercise in the heat. It could be caused by lack of sodium and fluids. Treatment: Rest, cool down, stretch, and drink rehydrating solutions.
This is caused by dehydration and sudden cessation of exercise. Treatment: Drink fluids and lie down in a cool place with your feet elevated. To avoid heat syncope, gradually end your workout with a cool-down activity like slowly walking or pedaling a bicycle.
Symptoms of heat exhaustion are exhaustion; weakness; feeling faint; excessive sweating; hot, red skin; slightly elevated temperature (less than 104 degrees F); decreased urine; and disorientation. Other symptoms include heat cramps, headache, rapid heartbeat, fainting, muscle aches, vomiting, and diarrhea. Treatment: Rest, cool down rapidly with fans and ice packs, and drink fluids. IV fluids may be needed. Seek further medical attention if necessary.
Heat stroke is a medical emergency. Heat stroke occurs when the body loses its ability to regulate its temperature through sweating. The most telling signs of heat stroke are an elevated temperature (greater than 104 degrees F), rapid heartbeat, shallow breathing, lack of sweating, and hot, flushed dry skin. This may progress to mental impairment ranging from confusion and hysteria to coma. Treatment: Hospital emergency treatment, including removal of excess clothing and cooling the body with ice or fans. CPR, oxygen, and IV fluids may also be needed.
When outside, wear a hat and stay in the shade as much as possible. Avoid asphalt and pavement, if possible. They are normally hotter than dirt or grass, and they radiate infra-red heat.
Drink plenty of water before any activity. For strenuous exercise, drink water or a salt replacement fluid about every 15 minutes. If you have pale clear urine, you are drinking enough fluids.
Schedule strenuous outdoor activity for the cooler parts of the day. Normally, this is before 10 a.m. and after 6 p.m.
At the beginning of the warm weather season, spend several days acclimatizing yourself to the heat by gradually increasing your activities outside.
If you are on any medications, consult with your doctor before undertaking any strenuous activity in the heat. Some drugs can cause dehydration.
Wear light-colored, loose-fitting clothes. Natural fibers like cotton help the body release heat better.
Eat light foods, as well as plenty of fruits and vegetables, because they contain water.
Take cool or tepid baths and showers to cool down.
Avoid alcohol and caffeine, which can interfere with sweating and fluid loss.
Simplify meal preparation to cut down on cooking time. Use a microwave if possible.
If your home does not have air conditioning, use fans to circulate the air. Spend as much time as possible in air conditioned buildings such as libraries or shopping malls.
© 2013 Main Line Health