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If you are a runner, you know exactly what runner's high is. If you're not a runner, you have probably heard of it, and you're probably skeptical. It's supposed to be the intense happy and uplifting feeling that kicks in after about 45 minutes of running (this varies depending on your speed and fitness level) and often lingers on after you've finished your run.
The runner's high is a myth. It is a myth in the sense that it is not one thing. So there is no such thing as the runner's high. There are at least four very different mechanisms at work here, so there are at least four very different runner's highs.
1. Endorphins: This has been the standard explanation of runner's high. Endorphins are nature's painkillers; they work a bit like morphine. The general idea is that running for a long time gets painful, and the body produces natural painkillers to alleviate this pain. We have pretty solid evidence that this actually happens, especially in long-distance runners. But this can't be the whole story as research about endorphin blockers show. Runner's high kick in even if the athlete takes endorphin blockers (opioid antagonists).
2. Endocannabinoids: The other chemical substance that the body produces while running is endocannabinoids. As the name suggests, endocannabinoids are similar substances as cannabis. So the body produces a marijuana-like substance, which gives you a quite literal runner's high. Again, the evidence that endocannabinoids are produced during running is convincing, but is this the whole story?
3. Defocused attention: Vision scientists routinely make a distinction between focused and defocused (or distributed) attention. Attention is, as a default, focused on the task you are performing. You need to attend to the road when you are driving, you need to attend to your boss when she is telling you off, and so on. But on those rare occasions when there is not much to attend to (maybe during meditation or during long aesthetic experiences), your attention gets defocused, and this can lead to an immensely pleasurable feeling, as both meditators and friends of long black-and-white films where nothing happens can attest. And given that during running, the body goes on autopilot after a while, the same defocusing also happens while running.
4. Top-down influences: You probably ran a lot in gym class, sometimes even for a full hour. I know I did. No recollection of anything like runner's high, though. Why not? Probably because you had no idea it was a thing. Now you do, and you are probably looking out for its smallest signs. And when they appear, you're just leaning into it. We know from literally thousands of studies that your beliefs and desires can alter your experiences, and something like this is bound to happen in the case of runner's high as well. This is not to say that runner's high is just a matter of self-suggestion, but knowing about this effect of running can surely make you notice it more (or notice it at all).
There is no single phenomenon of runner's high. There are at least four different runner's highs, with different time-scales and slightly different feels. They are often intertwined, but each one can happen without any of the others. That's mainly good news. We don't have to chase the Holy Grail of the runner's high. You can just enjoy whatever high running gives you.
