Endorphins are “out”; endocannabinoid molecules are “in”.
Ask just about any runner what a “runner’s high” entails and they will probably throw around the word “endorphins”.
However, according to an article posted on The New York Times‘ Health blog, it’s not that simple.
Endorphins are the body’s “home-brewed” opiates and act much like morphine. They are composed of relatively large molecules. Matthew Hill, a postdoctoral fellow at New York’s Rockefeller University states that these molecules are “unable to pass through the blood-brain barrier.”
This means that just because endorphins are found in the bloodstream after exercise does not prove that they are having an effect on the runner’s mind.
So what’s causing the phenomenon?
Researchers are starting to focus on the endocannabinoid system, an altogether-different neurochemical system within the body and brain. A 2003 experiment at the Georgia Institute of Technology found that after 50 minutes of hard running on a treadmill or riding on a stationary bike “significantly increased endocannabinoid molecules in a group of college students.”
For More: The New York Times