Credit 10 hours a sleep a night for these mad dunking skills.

Over the course of a basketball season, college players usually grow more fatigued and performance wanes. But 11 Stanford University players’ performance improved as the weeks went on, according to controlled skill tests. Not only were their reaction times and mood better, but their sprint times and shooting accuracy also improved, Stanford researchers found.

Their secret? More sleep.

Researchers asked the players to aim for 10 hours of sleep a night—a significant boost from their usual 6 to 9 hours. The athletes wore watch-like monitors that recorded movement, giving researchers an accurate account of how long each one slept.

In addition to their performance gains, the players also reported being less and less sleepy during the day as the season went on. (No surprise there.)

Scientists are still trying to figure out what sleep is doing to affect athletic performance, says Charles Samuels, M.D., medical director for the Centre for Sleep and Human Performance in Calgary and a researcher who studies the importance of sleep for members of the military, law enforcement, and the Canadian Olympic Team.

Though researchers know that sleep has powerful effects on the brain, metabolism, immune system, and tissue repair, it’s still a mystery how these effects work together to improve athletic performance. “All we can say at this point is that we definitely see impairments across the board when you restrict sleep, and when you get sleep back, those impairments improve,” Samuels says.

Should You Sleep In On Weekends?

Though these athletes probably believed they were at the top of their game at the start of the season, they were actually chronically sleep-deprived, says the study’s lead researcher Cheri Mah, M.S., of Stanford. “You can look at sleep extension as improving performance, or you can look at the flip side, that these athletes started out already not at their full potential,” Mah says. “Maybe they were just coming back up to what would have been their baseline.”

Mah’s best performance-improving tip? Chip away at that sleep debt over time, even if it’s just 30 more minutes a night—but it has to be for the long haul. “You have to be patient. You can’t just sleep more for one night or one week,” she says. “You’ll see the best improvements over a long period.”