Extra sleep helps athletes perform better

Although many studies have been done on the negative effects that sleep deprivation has on the performance of athletes, not much has been done on how extra sleep affects athletic performance. But recently a small study was done by taking 6 basketball players from the Stanford University team and measuring how stats like sprint times and free-throw percentages were affected by extra sleep. For the first two weeks the players kept with their normal sleeping habits, and for the second two weeks they were asked to get as much sleep as possible. When their individual athletic statistics were compared they all did better in the second two week period compared to the first.

My only question is this: How do the researchers know the athletes were getting enough sleep in the first place? I don't know many college kids that regularly get enough sleep every night, so maybe this was just another test of sleep deprivation (the first two weeks) versus getting enough sleep (the second two weeks) -- not necessarily getting extra sleep.