If your performance at the gym has been second-rate lately, it may be due to the lack of shut-eye you've been getting at night.

Researchers from Stanford University found that getting a proper night's sleep can improve physical performance, in addition to increasing alertness and improving mood. Citing this study, Muscle & Body magazine reports that university swimmers participated in this study, with researchers finding that those who slept enough every night for several weeks noted faster 15-meter sprint times, faster starts off the blocks, improved turn times, and increased kick strokes.

Previous studies on athletes playing football, tennis, and basketball yielded similar results. It would appear, then, that if you want to improve your game a bit or just bang out a few more reps at the gym, you'd be wise to get to bed early at night.