Hydration essential during workouts: Water, sports drinks aid in rehydration Published March 2, 2007 By Tyler Hemstreet 62nd Airlift Wing Public Affairs MCCHORD AIR FORCE BASE, Wash., -- Since about 70 percent of an adult's body is made up of water, staying properly hydrated during a workout is crucial. Just a small percent change in body weight, due to a loss of fluid from sweat, can place a big strain on a body during exercise, according to the Gatorade Sports Science Institute, a research and educational facility established in 1988 to share current information and expand knowledge on sports nutrition and exercise science that enhances the performance and well-being of athletes. After a long workout, people may lose a pound or two of weight, said Patrick Conway, 62nd Medical Operations Squadron exercise physiologist. "That weight is not fat loss, that's just water you're losing," Mr. Conway said. "It can be misleading." The water that people lose during the workout needs to be replaced, he said. The equation to find out how much water needs to be put back in the system is as simple as taking the amount of weight (in ounces) lost during exercise and adding it to the amount of fluid (in ounces) consumed during the workout. Adding the two will let people know how much liquid (in ounces) they should drink to replace the sweat they lost, according to the GSSI. The GSSI also recommends drinking 17-20 ounces two to three hours before athletic activity and drinking an additional seven to 10 ounces of fluid 10 to 20 minutes before working out. People should also drink between seven and 10 ounces every 15 minutes while working out, according to the GSSI. After a workout, make sure the hydration continues, Mr. Conway said. The body may take a while to rehydrate, sometimes even up to 36 hours, he said. "There's a lot of work the body has to do to get that water back," he said. When it comes to what to drink, Mr. Conway said sports drinks work well to replace energy and lost sodium through sweat during the workout. Sports drinks also contain carbohydrates that fuel working muscles and fight fatigue, Mr. Conway said. A sports drink with a carbohydrate level of about six percent has been demonstrated by research to help fuel the active body quickly and supply enough energy to working muscles, according to the GSSI. But it is best to save the sports drinks for working out and while the body is burning energy, Mr. Conway said. "You don't need all that extra sodium if you're not doing the work," he said.