Scientists used to believe that a runner’s high was due to the release of endorphins into the system, but it was never proved conclusively. It appears that while there is an uptick of endorphins in the blood after exercise, there is a barrier to these endorphins being absorbed into the brain. It might turn out that this state of mind is actually caused by the release of chemicals similar to those released into the body when smoking marijuana! Nothing has been proved conclusively yet, but if humans were more like mice….
http://www.popsci.com/runners-high-looks-lot-like-smoking-weed-in-brain
Far out man!
Splattered Brains 