If you're having a less-than-perfect day, you'll likely feel better if you get moving. Michael Bracko, an exercise physiologist and fellow of the American College of Sports Medicine, explains why.
How does exercise improve your mental outlook?
The simplest way it can help is that exercising temporarily takes your mind off the problem, thus reducing mental stress. It can also give you time to think through problems, or provide an escape and time to think about nothing.
What about "runner's high"?
During exercise, endorphins -- which are opiate-like substances -- are secreted by the brain. They have the same painkilling mechanism as morphine, [so they can] cause a sense of euphoria when the endorphins bind with the brain's receptor sites.
What's the best way to benefit?
Any vigorous, repetitive activity -- such as cycling, hiking, swimming, or walking -- done for 30 to 90 minutes can induce this state. But to simply clear your mind, as little as 15 minutes of activity can help.