Okay Athletes and Warriors! The weather is warming up in most parts of the globe, and even though that's a great time to amp up your workouts, be sure to take all safety into consideration before you do.
Experts Warn: Ease Into Hot Weather Workouts
WASHINGTON (AP)--For couch potatoes who begin an exercise program when it's hot, even working up a sweat takes practice.
The practice is called acclimatization. It's the process of getting your body used to the special demands of hot weather. "You don't sweat as much until you are acclimated," said Dr. Janice Zimmerman, director of the medical emergency center at Ben Taub General Hospital and an associate professor of medicine at Baylor College of Medicine in Houston.
Beginners should not feel alone in this. Even trained athletes who plunge into working out in hot weather could benefit from time to adjust, Zimmerman said. "A period of acclimatization is necessary from a safety standpoint for just about everybody," she said. The risk in not easing into exercise is in overexerting before your body has learned how to shed heat efficiently. The outcomes could range from having a less rewarding workout to, in the worst cases, triggering an underlying heart problem or fatal heat stroke.
The body has two main ways of doing controlling heat, Zimmerman said. One is to dilate blood vessels near the skin. Blood that's heated in the body core by exercise can be cooled by radiating the heat through the skin into the air. Dilated blood vessels bring more blood to the skin. "It operates kind of like a car radiator does," Zimmerman said. The other method is by sweat production, which acts more like the car's air conditioner. Evaporation has a cooling effect. And when sweat evaporates, it gives up heat, which cools the skin. "The more you sweat, the more heat you lose," Zimmerman said. "As people get acclimated, they sweat more and lose heat better."
How long it takes to become acclimated varies from person to person, Zimmerman said. Trained athletes, who already sweat efficiently, take less time than do untrained people to get used to heat. However, the technique of acclimatization is the same for the trained and untrained - starting at a comfortable level and increasing it gradually.
Sweat output requires liquid input to keep the body's water level up. And people can lose water more easily than they realize. "The best way to say it is, if you just go by thirst alone, you'll probably underdrink by a third," said Mike Sawka, chief of the Thermal and Mountain Medicine Division, U.S. Army Research Institute of Environmental Medicine, Natick, Mass.
That's because the brain doesn't sense thirst until the fluid levels are already drawn down. The body then has to play catchup, drinking until the feeling of being thirsty goes away. As hot weather wears on and people become used to it, they become better at matching their liquid needs to their liquid output, Sawka said. But a person can lose 3 percent of body weight before feeling thirsty, Zimmerman said. And people may go through the summer in a continuous state of slight dehydration. This can account for the pounds that many people lose each summer, thinking they've been burning more calories by being more active, she said. "People are proud of that fact, but the reality is they are losing water, not fat," she said.
People also can see their exercise performance drop without realizing it, Sawka said. "If I ride a bike and I'm not competing, I'll just notice I rode a little slower - or I might not notice," he said. An athlete keeping track of time or distance might feel thirsty but not care, focusing instead on the event, Sawka noted. And an older person might not notice thirst quickly, he said - age dulls the ability to sense thirst. This is especially a risk for older people because dehydration, which makes the heart beat faster, can trigger underlying problems such as heart disease, he said.
For all exercisers, the way to head off trouble is to drink even when they are not thirsty, and water is the best drink, the experts said. Sports drinks that replace sweated-off carbohydrates and electrolytes are valuable only for people who exercise an hour or more, Sawka said. Some drinks should be avoided, Zimmerman said. Alcohol is among these, she said - it is a diuretic, so it makes you excrete water. Caffeine is a mild diuretic, so drinks with caffeine are "better than nothing," she said.
However, a noted researcher sees value in some flavored drinks. The use of salt and carbohydrates, as found in sports drinks, stimulates thirst, said Dr. Oded Bar-Or of McMaster University in Hamilton, Ontario. His research looked at children, but the results probably hold for adults as well, the Canadian scientist said.
In Bar-Or's experiments, children who got a lab-prepared flavored drink with salt and carbohydrates drank enough to keep themselves fully hydrated. Flavored water alone left his test subjects slightly dehydrated, and plain chilled water did even less good, he said.