If you think that "runner's high" is all in your head, you're right and German researchers are thrilled that they can see it on a brain scan. Until now, the rush of a runners' high has been hard to document but researchers in Germany used PET scans to study the brains of 10 distance runners before and after they ran. They found that running caused the body to produce endorphins, the chemicals associated with mood changes.
The endorphins actually flooded parts of the brain linked to love and euphoria. In fact, the researchers could actually see how much of a rush the runners were describing because the more euphoria the runners reported, the more endorphins researchers detected in their brain scan.