Cloud Nine

by Josh D. Fitzwater

Hundreds of miles of biochemical insight are pounded into the soles of Chris Gillen's running shoes. That's because Gillen the runner, who has cultivated a taste for ultra-marathons, is also Gillen the Kenyon professor of biology, who teaches a course on the physiology of exercise. Running-every stride, every breath-makes the science that much more real.

And this applies to the feeling of elation known as the runner's high. Gillen brings intense personal experience to his scientific understanding of the biochemistry at work here.

"For me, the half marathon distance maximizes the runner's high, and I don't get it when I go easy," Gillen says. "I have a propensity to shed tears at finish lines, which are undoubtedly connected to runner's high. It's embarrassing to have race volunteers rush to my aid when I'm really just having a nice happy cry."

Over the past sixteen years, Gillen has run twenty-four marathons and ten ultra-marathons-1,828.8 miles in all-to gain a deeper knowledge of exercise through physical experience. He spent his sabbatical in 2011-12 writing a book on how the body reacts to exercise and devoted a chapter to the euphoric state that runners experience.

In the forthcoming book, called Molecules that Move Us: The Hidden Mechanics of Exercise, Gillen notes that scientists don't agree on an explanation for the phenomenon. "The common notion is that a runner's high is the result of endorphins in the brain," he says. "However, there is an emerging notion that it's also endocannabinoids-natural molecules that your brain makes that have similar mechanisms to cannabinoids, the active ingredients of marijuana."

With a half-smile, he adds, "Compelling research has been done to suggest that these endocannabinoids are involved in the good feeling people experience after running or hard exercise."

He elaborates. "At the core of our brain's circuits are 'pleasure neurons' that release a chemical called dopamine. High dopamine levels in certain parts of our brain make us feel marvelous. Our pleasure neurons are held in check by nearby neurons that secrete inhibitory chemicals.

"Endocannabinoids and endorphins bind to these inhibitory neurons and block their action. In other words, endocannabinoids and endorphins knock out the normal brake that curbs pleasure neurons, freeing them to secrete dopamine and thereby inducing nice feelings."

The mechanism may not be entirely understood, but the healthful body-mind connection is real. "What is very clear," Gillen says, "is that exercise definitely affects the brain in demonstrable ways, both acutely-right after exercise people feel good-and also chronically by improving connections in the brain, more synapses. So exercise does seem to make you smarter."

He smiles. "Quite the opposite of the notion of a dumb jock."

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