Stay hydrated. A surprising number of tennis players are de-hydrated even before they toss their first serve. In hot conditions, even a 1-percent dehydration level can affect performance, says Michael Bergeron, Ph.D., an assistant professor at the Medical College of Georgia and a member of the USTA Sports Science Committee. “When your body is even slightly dehydrated it has to make adjustments, which can have negative effects,” Bergeron says. “Play or training will feel more difficult and you’ll fatigue earlier.” Drink plenty of fluids before, during, and after play. Weigh yourself before and after playing; for every pound you’ve lost, drink 20–24 ounces of fluids to make it up.
