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Exercising safely in hot weather
Tips for exercising safely in hot weather with emphasis on avoiding heat exhaustion, dehydration, and other dangers.



It's July and a heat wave is on. You are used to exercising and enjoy your daily run, but the paper says that the heat index will be up today and to stay indoors during the elevated temperatures. What do you do?

First, let's discuss what happens when you exercise in the heat. When you are exercising, your body's muscles burn glucose as its fuel. This fuel burning will cause your body temperature to rise while you are exercising. Your body will also increase the blood flow to the skin, and begin sweating in response to this increased internal temperature.

The sweat cooling by evaporation is how your body tries to cool itself off. But if the amount of heat produced is MORE than the evaporation of sweat can handle, or the weather is humid, which means that the sweat evaporates more slowly, the body's internal (core) temperature will rise and thermal, or heat injury, can occur. This is more likely in hot weather, and extra caution is needed. Normally, a person who exercises and is in good condition can handle temperature ranges of 65 to 85 degrees, but as the temperature rises, special precautions need to be taken. Also, the more strenuous the activity, the greater the risk of heat related problems. With hot, humid weather thermal injury can begin to occur in 12 to 15 minutes after starting strenuous exercise (such as competitive sports, running, or biking up a hill).

How do you help your body stay cool enough when you are exercising in a hot climate or during the summer? The following ideas will help.

1.Work up gradually:

It is important to acclimate your body gradually to higher temperatures. This means take it easier and exercise for a shorter period of time when the weather is hot and humid. Cut back your normal routine as the thermometer rises, and then gradually work back up to a longer workout over the next few weeks. Warm up in the shade, doing your stretches there, if possible. Over time the body's core (internal) temperature will drop during exercise and the metabolic rate at rest will decrease as it acclimates to the heat. Your body will also learn to sweat more in response to exercise, helping to cool itself off. Try to exercise in the shade as much as possible by choosing shady tree lined streets for walking and jogging.

2. Time of day counts:

Do NOT exercise when the temperature and humidity are both high, since this increases the risk of hyperthermia. This means that when the outdoor temperature is above 90 degrees F. and the humidity is above 75 % you should exercise inside, such as at a mall or health club, or only during the coolest parts of the day, such as early morning or late evening. Avoid the hours of 10:00 a.m. to 2:30 p.m., when temperatures tend to soar. Listen to the heat indexes on the radio since they will also be a guide to how hot it feels to your body. A special caution: as a person ages, their ability to regulate body temperature decreases, and this precaution becomes doubly important.

3. Dress for the heat:

Minimal, loose fitting clothing that is comfortable will help promote heat loss and evaporation. Light colors and clothing made of cotton or sweat wicking fabrics are best. Avoid open-mesh jerseys and tank tops, since they will cause overexposure to the sun. A brimmed hat can help shade your face. And always use a good sunscreen product with a SPF of at least 15 (waterproof is best since you will be sweating) to prevent sunburn.

A wet bandana or ice pack scarf around the neck can also help with staying cool.

4. Drink up:

One of the biggest risks of exercise in hot weather is dehydration. For this reason it is important to drink plenty of WATER while exercising. In hot weather, it is a good idea to drink plenty of water (two eight ounce cups) an hour or two before starting to exercise. Follow this with another cup every 20 minutes during exercise and an additional cup or two within a half hour after exercising. The body can lose up to a quart of water an hour while exercising, so drink up, even if you don't feel thirsty. Your body needs the extra fluid.

If you are competing strenuously, or are exercising outdoors for more than 90 minutes, a fluid with 5% to 8% carbohydrate, and minimal electrolytes, such as Gatorade or Powerade is okay. Avoid sodas, since they will tend to dehydrate you more (caffeine is a diuretic) and the fluid replacement is inadequate.

A hot weather hint: carrying a bottle of frozen water in a fanny pack is a good idea. It will supply you with cold water and will help keep you cool.

You will probably not need salt tablets or replacement unless you are on diuretics. In this case, consult with your medical doctor and follow his or her recommendations.

5. Know when to stop:

It is important to know the signs of heat exhaustion and heat stroke. These can occur when your body can no longer cool itself and your internal body temperature begins rising. Listen to your body carefully when exercising in warmer weather. This is NOT the time to push on if the following symptoms occur:

Weakness

Dizziness

Tiredness

Nausea

headache

Sweating stops

Body temperature goes up

If you become nauseated or dizzy, rest immediately in the shade and drink plenty of fluids until you begin to feel better. If symptoms persist or worsen, get medical help immediately.

6. Watch out for heated pools:

Heated pools can cause a person to become dehydrated and overheated during the summer. The water temperature should ideally be 75 to 78 degrees F. (and no more than 80 degrees) for vigorous workouts. You will still be sweating on hot days, and it is important to drink plenty of fluids as advised above, and listen carefully to your body.

8. Cool down afterwards:

Be sure to stretch in the shade or a cool area afterwards, and drink fluids to help replace water loss during the exercise. Do NOT take a hot bath or shower right after exercising, or go into a sauna, since the risk of fainting and heart attack are increased by the heat causing a suddenly lowered blood pressure.

Special precautions:

If you are very underweight, overweight, pregnant, or an older adult, consult with your doctor on his recommendations. You should not go above a moderate intensity level (60 to 70 % of predicted maximum heart rate) when exercising in the heat. Rest frequently and drink plenty of water before, during, and after exercise.

By following these recommendations, you can make your exercise sessions during the summer a safe and fun experience. With proper preparation and precautions, you can stay in shape even during the hot months without sacrificing your health and keep your fitness level up.