Many nonrunners simply cannot fathom the idea of spending an hour — or multiple hours — running. For fun.
Runners, on the other hand, have a hard time letting a day go by without running. Part of the love of the sport can be credited to the “runner’s high” phenomenon.
So what is a runner’s high?
During a prolonged period of running, generally at least a half-hour, many runners experience an increased feeling of euphoria, decreased anxiety and a decreased feeling of pain. Researchers once attributed this “high,” a happy, floaty, I-can-go-all-day sensation, to an exercise-induced release of endorphins, the natural painkillers released during periods of intense exercise, pain or stress — as well as while eating and during orgasm. The high likely is more related to endocannabinoids, but we’ll loop back to that point.
Runners are not the only ones who can experience a runner’s high, of course. It’s common in endurance athletes or after an intense exercise session, like a high-intensity interval training workout.
According to Dr. Doug Hiller, an orthopedic surgeon and clinical professor at the Elson S. Floyd College of Medicine at Washington State University, any endurance athlete can reach this high, as long as the exercise lasts long enough and the maximum heart rate effort ranges between 70 and 85%.
“It does happen in many other sports, but most of the studies are on running and cycling, partially because they are easy to study in the lab,” he said. “One research group tested subjects who were in a choir. They found that the endocannabinoids [indicating a “high”] were elevated after singing.”
Unlocking the runner’s high is not universal among all runners. Hiller said about two-thirds to three-quarters of athletes report having had the experience. Some reach it on every run or very frequently, while others may have never felt, or rarely feel, a runner’s high. Part of the explanation behind the range could be that the feeling is subjective, so while someone may chemically experience a runner’s high, they may not notice anything significant happening.
There do seem to be a few common themes about how to increase the chance of feeling that euphoric high.
Kati Leigh, event director for MerGeo, a Seattle-based company that puts on trail races and other events in the area, believes there are many different ways to unlock the runner’s high. “Some people only achieve a high while trail running. Some people only achieve a high when they run with others. Some people only achieve a high when they have a high-intensity workout,” she said.
For some, the harder the run, the higher the high.
“Oftentimes, the most rewarding runs are the most difficult,” said Abram Dickerson, course director for Aspire Adventure Running. “Sometimes that struggle arises from a hard day or general mental or physical lethargy that has to be overcome. Sometimes the challenge lies in the nature of the distance or elevation gain specific to a run. There is definitely a relationship between the struggles and rewards connected to running.”
A correlation between effort and the runner’s high would also explain why endurance athletes tend to remain happy, even after putting in hours of effort during an especially tough race.
Hiller has worked in the Ironman medical tent at the major Hawaii race since 1985 (and is a three-time finisher himself) and has seen his fair share of exhausted athletes. “I’ve seen incredibly exhausted people who are as happy as people can be, and a few who are not. It seems very individual and depends a lot on their race experience and expectations versus performance on race day.”
Leigh agrees that a harder effort generally results in a high. “I am most likely to experience a runner’s high when I am pushing beyond my baseline fitness,” she said. At the races she directs, she sees this firsthand in participants.
“On race day, most runners are happy before the event. Yet when they finish, their enthusiasm is dialed up all the way,” she said. “It’s thrilling as a race director to see how runners are transformed when they cross the finish line.”
Running in nature seems to foster higher instances of runner’s high for some, too.
“Natural settings invite a sense of flow and quiet that is harder to access when we’re surrounded by screens and pavement,” Dickerson said. “As we move our bodies in nature, we become more awake to the rhythms of the terrain, the seasons, the light, the weather, the forest — and there is an ease in which we simply slip into a state of flow.”
Leigh finds that her daily worries slip away when she runs on dirt. “Trail running requires a higher focus on foot placement than road running,” she said. “It’s easier to find a flow in the forest because the mind is more focused on the body’s movement.”
While personal preference and effort seem to play a role in reaching that runner’s high, there is plenty of hard science on the subject.
After observing that the molecular structure of endorphins does not allow them to cross the blood-brain barrier, German researchers looked to the endocannabinoid system, which is the system affected by tetrahydrocannabinol, best known as the compound found in cannabis that gets you “high.”
In 2015, a research team led by Dr. Johannes Fuss at the University Medical Center Hamburg-Eppendorf in Germany tested the relationship between cannabinoid receptors and running with exercise-conditioned mice. The mice were split into two groups: one would run for five hours on an exercise wheel while the other would remain sedentary.
The team saw that the exercise group displayed significantly less anxious behavior and a higher tolerance for pain than the sedentary group.
The researchers performed the same experiments on mice given antagonists that blocked endocannabinoids and endorphins in the brain. The mice with endorphin blockers showed minimal change in the results, while the mice with endocannabinoid blockers continued to display signs of anxiety and pain sensitivity, despite having run for five hours.
In 2021, the same research team replicated the experiment with humans. They recruited 63 experienced runners and administered similar tests. (A key difference: The drug used to block endocannabinoids in mice is not legal for human use.)
The volunteers ran for 45 minutes one day, then walked for 45 minutes another. After each workout, the scientists drew blood and performed psychological tests on the subjects.
The researchers found that while most participants said they felt a high during the run, none did during the walk. There was no difference between the placebo group and the one that took the blockers.
More importantly, all participants showed an increase of endocannabinoids in their blood after running and similar changes in their emotional state, even if their endorphin system had been deactivated. Essentially, the findings indicated that endocannabinoids are more likely responsible for runner’s high and reaching that state requires high heart rate activities, like running.
While research shows conclusively that exercise, generally, is good for us mentally and physically, perhaps the individual experience of the runner’s high — why some feel it when others don’t, and how to unlock the feeling — is a mystery that will never truly be understood.
“I don’t think there is a single path towards a runner’s high or an easy way to quantify the experience,” Dickerson said. “I experience a sense of satisfaction and accomplishment for every run I’ve ever done, regardless of how small or big. I have never regretted going for a run. Ever. So, really the answer is to run.”