Sweating is part of any exercise program, whether you are working out during the dog days of August or in January.
“The typical sedentary individual living in a temperate climate will lose about 2 liters of fluid each day due to sweating, respiration and urination,” said Mitch Kanter, director of the Gatorade Sports Science Laboratory in Barrington. “On hot days, the same person could lose 4 to 6 liters.
“Add exercise on top of that and the fluid loss is even greater. An athlete in training could easily lose 5 to 10 liters daily–more during hot weather.”
Several nutrients are lost through sweating, but replacing the fluid is the highest priority for keeping the body from overheating or breaking down.
The key nutrients lost in perspiration are sodium and potassium, both integral to the workings of cells. You will lose about 8 to 10 times more sodium than potassium.
But in most cases people can afford the lopsided loss. The typical American diet provides 5,000 to 7,000 milligrams of sodium or salt, although the federal Recommended Daily Allowance is 500 milligrams (and the body uses even less, about one-twentieth of a teaspoon, every day).
Salt tablets, once a staple for youth football practices during late summer, now are known to be a bad idea. A bit of sodium after exercise (about the amount found in a cup of sports drink or handful of pretzels) is plenty for helping the body retain fluids. But too much salt not only discourages urination, it also forces more fluids to leave individual cells to dilute sodium levels in the bloodstream. That makes cells less efficient at producing energy.
“There is an optimal sodium level in the bloodstream,” Kanter said. “The body’s fluids will respond accordingly to keep it in balance.”
Potassium is perhaps more of a concern for some exercisers who don’t eat foods rich in the mineral, such as bananas, oranges and orange juice, potatoes, peas, beans and yogurt.
“Even so, we don’t lose as much as people think,” Kanter said. “Potassium is blamed for muscle cramping, but frequently it is the overall loss of fluids–dehydration–that causes the problem.”
To prevent muscle cramping or fatigue during a workout, nutritionists recommend drinking 16 to 20 ounces of water two hours before exercise, then another 8 ounces 15 to 30 minutes before you begin. During physical activity, try to drink 4 ounces every 15 minutes. Afterward, the guideline is to drink a pint for each pound lost during the activity. (You can weigh yourself before and after exercise on occasion to get an estimate; otherwise, 1 to 2 pints is a good minimum to keep in mind.)
The beverage of choice still is water, though research shows that some sports drinks (with no more than 6 percent to 8 percent sugar to ease rapid absorption) can help the body retain energy during workouts or events lasting more than one hour.
Another good idea: After an especially sweaty workout, eat some foods that are watery, such as melon, oranges or vegetable soup, to get some additional fluids with your carbohydrate reload.
Perspiring a lot is not always the sign of a good workout. It might mean you are working too hard too quickly during an exercise session, or perhaps you are wearing too much clothing (such as long pants on a hot day or a sweatshirt when a T-shirt is enough after the body warms up). The body has overheated and your workout will be cut short.
Some athletes, notably wrestlers, will cut weight for an event by sweating profusely. But this is merely a removal of fluids from the body that will subsequently return (along with the pounds) when the normal physiological functions are allowed to resume.
