NEW YORK (Reuters Health) – Athletes who get extra shut-eye over an extended period of time could see significant improvement in their athletic performance, mood, and alertness, research shows.

“Our results begin to elucidate the importance of sleep on athletic performance and more specifically, how sleep is a significant factor to peak athletic performance,” Cheri Mah of the Stanford Sleep Disorders Clinic and Research Laboratory told Reuters Health.

In an ongoing study, Mah and colleagues are testing the impact of extra sleep on five healthy students on the Stanford University men’s and women’s swimming teams. For the first two weeks of the study, the swimmers maintained their usual sleep-wake pattern. The athletes then extended their sleep to 10 hours per day for 6 to 7 weeks.

Athletic performance, assessed after each regularly scheduled swim practice, showed marked improvement with the extra sleep, Mah reported Monday at SLEEP 2008, the annual meeting of the Associated Professional Sleep Societies.

“Various drills including reaction time off the block, 15-meter sprint, and turn time improved while kick strokes increased with extra sleep,” she said.

Specifically, after obtaining extra sleep, athletes swam a 15-meter sprint 0.51 seconds faster, reacted 0.15 second quicker off the blocks, improved turn time by 0.10 seconds and increased kick strokes by 5 kicks.

“Athletes also experienced decreased fatigue and increased energy as well as decreased daytime sleepiness,” according to Mah.

While this study focuses specifically on collegiate swimmers, it supports data from Mah’s other studies in different sports. For example, in a study involving six players on the Stanford men’s basketball team, sprint times and free-throw shooting improved with extra sleep, as did ratings of mood and alertness.

Taken together, these data suggest “that athletes across all sports can greatly benefit from extra sleep and gain an additional competitive edge to perform at their highest level,” Mah said.

“It is interesting to note,” Mah added, “that many of the athletes in various sports I have worked with, including the swimmers in this study, have set multiple new personal records and season best times, as well as broken long-standing Stanford and American records while participating in this study.”