Two and three decades ago, I used to get this rush whenever I got about a third of the way back down a mountain I'd just run up. I assumed it was endorphins. It felt like cocaine. Occasionally, I'd boost the high by tucking a cigar into my waistband with a waterproof match taped to it. The combination of my natural high and the cigar smoke produced the equivalent of a huge bong.
The thrill is gone. I quit the cigars, and the runner's high doesn't come anymore.
So I asked the Time Barrier researcher, Lee Michaelides, whether the runner's high disappears after a certain age. His answers surprised me. I'm holding a Google Hangout with him this afternoon, and as usual the interview will post on YouTube.
Meanwhile, here's what Lee wrote:
The majority of athletes never experience a runner's high. And of those that do, it may not be as frequent as popular anecdotes suggest. Your friend Amby Burfoot calculated his personal ratio of one runner’s high for 21,600 workouts. As for the age thing, there have been studies comparing guys in their early 20s with guys in the 80+ bracket. Age doesn’t seem to be a factor in endorphin production.
However, you may be asking the wrong question.
The latest research suggests that beta endorphins may have nothing to do with a runner’s high. In the 1970s it was a popular idea that exercise triggered an endorphin release that made you feel euphoric. And indeed exercise does trigger a release of beta-endorphins, a chemical known to decrease pain. But according to recent research it probably doesn’t make the athlete feel euphoric; the molecule is too large to pass the cellular barrier between blood and brain.
So what accounts for the euphoria? A couple theories offer different answers. Endorphins called endogenous opioids, produced in the brain, don’t have to cross the cellular barrier. They might be responsible for the runner’s high. Studies, to date, have been unable to prove this theory. Until recently the only way to test the theory would be with a spinal tap. That didn’t happen for ethical reasons. Today brain scans prove that exercise does indeed produce endogenous opioids. But scans alone can’t tell if any of these is the one that triggers euphoria.
Other researchers are working on a new theory: Exercise triggers a release of endocannabinoids. As in, cannabis. The body produces the same chemical that makes a marijuana smoker high. These molecules are small enough to move throughout the body and brain. Research shows that humans and other endurance-running mammals, such as humans and dogs, release this chemical after long, intense running. This release doesn’t happen when people and animals walk. And fast-twitch mammals, such as ferrets, don’t get high from running.
David Raichlin says it's all about evolution. “A neurobiological reward for endurance exercise may explain why humans and other cursorial mammals habitually engage in aerobic exercise despite the higher associated energy costs and injury risks, and why non-cursorial mammals avoid such locomotor behaviors. The fact that running, and endurance exercise in general, remains an enjoyable and psychologically beneficial recreational activity for tens of millions of humans today suggests that we still may respond to a neurobiological trait that evolved early in our lineage.”