A snippet from “Mind Wide Open” by Steven Johnson speaks directly to what frequent exercisers know, but what those of us who don’t exercise often, tend to doubt…

“Brain researchers had long suspected that the family of painkilling drugs derived from the opium poppy — heroin, morphine, codeine — targeted a dedicated site in the brain, but it wasn’t until the early 1970’s that a handful of researchers working in separate labs discovered the receptor: a synaptic lock contoured precisely to fit the opiate keys.  This was one of those discoveries whose existence suggests a further discovery.  Though the narcotic allure of the poppy has been part of the human experience since at least the dawn of agriculture, it seemed unlikely that the brain would possess a recepter for a chemical found in a plant that grew in only a few scattered locations around the globe.  The existence of the receptor suggested that the brain produced its own endogenous opiate, and sure enough within a few years scientists had discovered two of them: the enkephalins and endorphins — meaning ‘in the head’ and ‘morphine within,’ respectively.”

He goes on  to the really good part for all of us exercise addicts — or aspiring addicts:

“Newspapers, magazines, and talk radio were flooded with excitement over the brain’s ‘natural high’.  And the surge of interest in fitness and jogging that began twenty-five years ago owes its existence in part to the discovery that these powerful chemicals were released during strenuous activity.  People don’t get in shape simply because it’s in their long-term interests.  They get in shape because working out makes them feel good, and their brains remember the feeling”

Yep, just a little bit of science to throw in there!