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Extension exercises are commonly used to strengthen and stretch the back, triceps and legs. But for weekend warriors and elite athletes alike, there's one extension that is often forgotten -- sleep extension.

A newly-released sleep study reveals elite athletes who extended nightly sleep and reduced accumulated sleep debt improved significantly on various drills measured after every practice. Can you actually make up for lost sleep? Hope so, because when it comes to sleep debt, likely 99.9 percent of adults are in the red.

Five Stanford Women tennis players took part in the study. After aiming for 10 hours of sleep a night for five to six weeks, and comparing drill results to a two to three week baseline of typical sleep/wake patterns, the athletes sprinted significantly faster, and hit/served more accurately. Good news for a tennis player, first-serve accuracy is critical in a match.

Bottom line on this study -- sleep is critical for optimal performance. You may spend hours training in the gym for that extra edge, but strengthening your sleep schedule may be just what the performance doctor orders.