HIIT Triggers The Release of Endorphins

You've probably heard the term runner’s high. It's usually associated with long distance running. The release of endorphins in the brain is behind this effect. A new study conducted at the University of Turku shows that endorphins are also released during High Intensity Interval Training (HIIT).
 
Using positron emission tomography, researchers determined that HIIT significantly increased the release of endorphins compared to a steady state moderate intensity 1-hour run. Scientists theorized this might help your body compensate for the physical and emotional stress of intense exercise.