"Exercising in hot weather can put extra stress on a person's heart and lungs," explained Family Practice physician Walter Dombroski, M.D. "Both the exercise itself and the surrounding air temperature can work together to increase a person's overall body temperature.
"The body is always working to keep a balance between how much heat it makes and how much it loses. People suffer heat-related illness when the body's temperature control system is overloaded. A person normally cools down by sweating. However, under some conditions, a person's body temperature rises very rapidly and may damage the brain or other vital organs.
"Several factors affect our body's ability to cool itself during extremely hot weather," Dr. Dombroski said. "When the humidity is high, sweat does not evaporate as rapidly, which prevents the body from releasing heat efficiently. Other conditions that can limit the ability to regulate body temperature include being very young or old, obesity, fever, dehydration, poor circulation, sunburn, prescription drug use or alcohol use.
"Under normal conditions, your skin, blood vessels and perspiration level adjust to the heat. But these natural cooling systems may fail if a person is exposed to high temperatures and humidity for too long. The result may be a heat-related illness, such as heat cramps, heat exhaustion or heatstroke."
Avoiding Heat-related Illnesses
Take it slow: "If you're used to exercising indoors or in cooler weather, take it easy at first," Dr. Dombroski cautioned. "As your body adapts to the heat, gradually increase the length and intensity of your workouts. If you have a chronic medical condition or take medication, ask your doctor if you need to take additional precautions."
Drink plenty of fluids: "Our bodies are nearly 70 percent water," he advised. "We use water to regulate body temperature, protect our joints and organs, and to help transport oxygen to cells. People need to make sure that these water levels are replenished, because their ability to sweat and cool down depends on adequate hydration."
During hot weather, people need to drink more liquid than their thirst indicates. "Increase your fluid intake, regardless of your activity level during extremely warm conditions," Dr. Dombroski added. "This is especially true during periods of heavy exercise in a hot environment, in which a person should drink 16-32 ounces of cool fluids each hour. Overall, it takes an average of 64 to 80 ounces to replace the water the body loses in 24 hours. Avoid drinks containing caffeine or alcohol, as they make a person lose more fluids."
If you're planning on exercising intensely or for longer than one hour, consider hydrating with sports drinks, which can replace the sodium, chloride and potassium lost through sweating. However, if you are on a low-salt diet, talk with your doctor before drinking a sports beverage. Also, avoid very cold drinks, because they can cause stomach cramps.
Dress appropriately: Lightweight, loose-fitting clothing promotes sweat evaporation and cooling by letting more air pass over the body. Avoid dark colors, which can absorb the heat. A light-colored hat can also limit your exposure to the sun.
Avoid midday sun: Exercise in the morning or evening, when it's likely to be cooler outdoors rather than the middle of the day. If possible, exercise in the shade or in a pool.
Wear sunscreen: A sunburn decreases your body's ability to cool itself.
Have a backup plan: If you're concerned about the heat or humidity, stay indoors. Work out at the gym, walk laps inside the mall or climb stairs inside an air-conditioned building. If your home does not have air conditioning, go to the shopping mall or public libraryeven a few hours spent in air conditioning can help your body stay cooler when you go back into the heat.
If you do decide to go out into the hot weather to exercise, be on the lookout for heat-related illnesses. Signs and symptoms may include:
Nausea or vomiting
"If you suspect a heat-related illness, stop exercising and get out of the heat as soon as possible," Dr. Dombroski concluded. "Drink plenty of water, and wet and fan your skin to cool down. If you don't feel better within 60 minutes, contact your doctor. If you develop a fever higher than 102 F or become faint or confused, seek immediate medical help."
Walter Dombroski, M.D., is a board certified Family Practice physician affiliated with Salem Community Hospital's active medical staff and Firestone Healthcare. His office is located at 2364 Southeast Boulevard in Salem, 330-332-4833.