What Really Causes Runner's High?

For decades, the state known as “runner’s high” -- a sense of euphoria that follows exercise -- has been attributed to endorphins.  Endorphins are chemicals your body makes which have receptors and actions much like those of pain-relieving morphine.

Endorphins, however, are composed of large molecules which are unable to pass the blood-brain barrier.  This means that they cannot have an effect on the mind.  Researchers have been looking for other candidates to explain runner’s high, and research suggests that your endocannabinoid system may actually be more responsible for that feeling.

The New York Times reports:

“In a groundbreaking 2003 experiment, scientists ... found that 50 minutes of hard running on a treadmill or riding a stationary bicycle significantly increased blood levels of endocannabinoid molecules in a group of college students ... Other researchers have found that endocannabinoids may be what nudge us to tolerate or enjoy exercise in the first place.”

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