For decades, endorphins have hogged the credit for producing “runner’s high,” that fleeting sense of euphoria and calm that many people report experiencing after prolonged exercise.

Endorphins, for those who know the word but not the molecules’ actual function, are the body’s home-brewed opiates, with receptors and actions much like those of pain-relieving morphine. Endorphins, however, are composed of relatively large molecules, “which are unable to pass the blood-brain barrier,” said Matthew Hill, a postdoctoral fellow at Rockefeller University in New York.

Now an emerging field of neuroscience indicates that an altogether-different neurochemical system within the body and brain, the endocannabinoid system, may be more responsible for that feeling.

Any pot users “feeling” this argument?

The endocannabinoid system was first mapped when scientists (American ones) set out to determine just how cannabis, a k a marijuana, acts upon the body. They found that a widespread group of receptors, clustered in the brain but also found elsewhere in the body, allow the active ingredient in marijuana to bind to the nervous system and set off reactions that reduce pain and anxiety and produce a floaty, free-form sense of well-being. Even more intriguing, the researchers found that with the right stimuli, the body creates its own cannabinoids (the endocannabinoids). These cannabinoids are composed of molecules known as lipids, which are small enough to cross the blood-brain barrier, so cannabinoids found in the blood after EXERCISE could be affecting the brain.

Since 2003, a flurry of research has been teasing out the role that endocannabinoids play in the body’s reaction to exercise. Other researchers have found that endocannabinoids may be what nudge us to tolerate or enjoy exercise in the first place.

Whether this accumulating new science establishes, or ever can establish, definitively, that endocannabinoids are behind runner’s high, is uncertain. Still, endocannabinoids are a more persuasive candidate, especially given the overlap between the high associated with marijuana use and descriptions of the euphoria associated with strenuous exercise.

“Pure happiness, elation, a feeling of unity with one’s self and/or nature, endless peacefulness” and “inner harmony.” Ahhhh.

You can read the whole article if you wish at the following address

http://well.blogs.nytimes.com/2011/02/16/phys-ed-what-really-causes-runners-high/