Get enough zzz's and you'll…
Avoid the aches.
A full night's rest can end those I'm-too-sore gripes that make you skip Spin class. "Sleep is the most important part of physical recovery," says Peter Walters, Ph.D., professor of applied health science at Wheaton College, who has studied sleep patterns in athletes. One reason: While you snooze, your body releases 80 percent of its total production of human growth hormone, the fuel created in your brain's pituitary gland that repairs and strengthens muscles. Fewer aches mean you'll enjoy exercise more and want to do it more often.
If you're sleep-deprived, a 30-minute power nap in the afternoon can help you sprint faster during a subsequent workout, researchers at Liverpool John Moores University say. (Woo-hoo, higher calorie burn!) For optimal results, shake off any siesta grogginess by leaving a one-hour window between waking and exercising, the study's authors recommend.
Sharpen your focus.
Clocking two extra hours a night for six weeks helped basketball players up their shooting percentage by 9 percent, the Stanford Sleep Disorders Clinic and Research Laboratory reports. "No time!" you say? Even 30 minutes more each night may improve skills during activities that take focus and determination, scientists say. That translates to better performance, in a boot camp class or at the office.
Not a morning person?
Try a P.M. workout. If you are done two hours before bed, it may not disturb your sleep, a Finnish study suggests.