Can't get off the couch because you're zapped?
You may not need more sleep, just fewer thoughts.
In a new study, British researchers found if your mind is weighed down, so is your body. Researchers say the impact of mental fatigue on physical performance is huge. They found subjects who were mentally drained thought their workout was harder to complete than those who had a clear head.
The full study is published in the March edition of the Journal of Applied Physiology.