NEW YORK -
Finding the energy and will to exercise is all in our heads.
That's the latest from the University of Copenhagen.
When we work out, the brain releases serotonin, which tells our muscles to keep going.
The university's newest research found when a certain amount of serotonin builds up, the brain tells the body to stop because it's exhausted.
Doctors say this could lead to better treatments for people who suffer from chronic fatigue.
