Newswise — Summer's here and you're ready to get outside and exercise. Before you do, you might want to check out the heat index. Whether a competitor or a weekend runner, cycler or hiker, when the heat index is high it will have an effect on the body. When you get into extremely high temperatures or high humidity, "It's wise to check the heat index before working out to avoid heat exhaustion or heat stroke," said Gary Sforzo, professor of exercise and sport sciences at Ithaca College.
The heat index (http://is.gd/1yIKV) combines the ambient temperature and humidity and shows when you should use caution with, or in some cases cancel, your exercise plans. For example if you plan to exercise in 100 degree heat in Texas where the humidity is about 50 percent, you should use about the same level of caution as exercising on the East Coast in 90 degree heat when the humidity may be close to 90 percent.
Sforzo lays out rules to avoid heat stress: 1. Wear lighter clothing. 2. Adapt your workout on caution days. 3. Remain hydrated.
"It is always important to hydrate any time you exercise on hot and humid days; it is important not only to take in enough fluid but to take in electrolytes as well. Sodium in particular is important and most of the commercial brands of performance drinks out there have adequate electrolyte and mineral composition so you have no fear. So, while water is good, if you are going to be out for more than an hour or two, it is also necessary to add a performance supplement formulated with a low concentration of fluid and electrolytes, which is a 6% solution."
For competitors who travel to other parts of the country, he adds a fourth rule: Get acclimatized.
"It's best to get there at least a week ahead of time to become acclimatized to the new conditions. You are not fully adapted in 7 days but substantially enough to avoid heat problems," said Sforzo.
Some warning signs to look for are heat cramps, which generally go away shortly after you stop exercising. "More serious is heat exhaustion. You may experience dizziness, weak, rapid pulse, low blood pressure and possibly a headache," said Sforzo. But again, he emphasizes this can be avoided by following the four rules.
"With heat stroke you will feel confusion, you may become disoriented and may actually stop sweating because you are so dehydrated that fluid left in the body is being used by the muscles and cannot go to the skin."
Do not rely on your thirst mechanism, warns Sforzo. "You have to drink more than you think you need. Under challenging conditions you must drink something with electrolytes.
"Another danger is hyponatremia (low sodium). Sodium is critical to muscle function and heart muscle, so you don't want to go low on sodium. There have been many cases of hyponatremia in long distance races because athletes tend to take in a lot more water and that actually hurts the sodium concentration because it dilutes the ions. When the sodium becomes too low the muscles cannot function properly. But the solution is simple — take a beverage that has electrolytes," said Sforzo.
To avoid heat issues, Sforzo suggests checking a heat index chart. "Don't become obsessed about it, but if in doubt, if climatic conditions are changing, or if you are competing and you know you are going to ratchet it up, you want to be on the safe side and that might just mean taking in a little more fluid if it gets extreme. You have to start questioning the wisdom of competing; cancelling is better than getting sick. If you are not acclimatized or ready for this situation, it can be a real danger."
Dr. Gary Sforzo studies enhancing exercise performance in humans across the lifespan. Topics he has studied include: exercise physiology and exercise program design; performance aids; benefits of regular exercise; physiological mechanisms underlying exercise performance; enhancing athletic performance; credentialing and advanced study in exercise physiology; older adults exercising; children exercising; alternative forms of resistance; cognitive impact of exercise; graded exercise testing and prescription; exercise for disease intervention; and aging and exercise. Research: Improving techniques for resistance or cardiovascular exercise to improve fitness; effects of exercise in older adults; a new technique using elastic bands during weight lifting; problems associated with measuring heart rate during exercise; alternative forms of resistance exercise; culture differences in fitness, the order of cardiovascular and resistance exercise in an exercise session; the cognitive impact of exercise.
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