By GINA KOLATA
Published: March 27, 2008

THE runner’s high: Every athlete has heard of it, most seem to believe in it and many say they have experienced it. But for years scientists have reserved judgment because no rigorous test confirmed its existence.

Yes, some people reported that they felt so good when they exercised that it was as if they had taken mood-altering drugs. But was that feeling real or just a delusion? And even if it was real, what was the feeling supposed to be, and what caused it?

Some who said they had experienced a runner’s high said it was uncommon. They might feel relaxed or at peace after exercising, but only occasionally did they feel euphoric. Was the calmness itself a runner’s high?

Often, those who said they experienced an intense euphoria reported that it came after an endurance event.

My friend Marian Westley said her runner’s high came at the end of a marathon, and it was paired with such volatile emotions that the sight of a puppy had the power to make her weep.

Others said they experienced a high when pushing themselves almost to the point of collapse in a short, intense effort, such as running a five-kilometer race.

But then there are those like my friend Annie Hiniker, who says that when she finishes a 5-k race, the last thing she feels is euphoric. “I feel like I want to throw up,” she said.

The runner’s-high hypothesis proposed that there were real biochemical effects of exercise on the brain. Chemicals were released that could change an athlete’s mood, and those chemicals were endorphins, the brain’s naturally occurring opiates. Running was not the only way to get the feeling; it could also occur with most intense or endurance exercise.

The problem with the hypothesis was that it was not feasible to do a spinal tap before and after someone exercised to look for a flood of endorphins in the brain. Researchers could detect endorphins in people’s blood after a run, but those endorphins were part of the body’s stress response and could not travel from the blood to the brain. They were not responsible for elevating one’s mood. So for more than 30 years, the runner’s high remained an unproved hypothesis.

But now medical technology has caught up with exercise lore. Researchers in Germany, using advances in neuroscience, report in the current issue of the journal Cerebral Cortex that the folk belief is true: Running does elicit a flood of endorphins in the brain. The endorphins are associated with mood changes, and the more endorphins a runner’s body pumps out, the greater the effect.

Leading endorphin researchers not associated with the study said they accepted its findings.

“Impressive,” said Dr. Solomon Snyder, a neuroscience professor at Johns Hopkins and a discoverer of endorphins in the 1970’s.

“I like it,” said Huda Akil, a professor of neurosciences at the University of Michigan. “This is the first time someone took this head on. It wasn’t that the idea was not the right idea. It was that the evidence was not there.”

For athletes, the study offers a sort of vindication that runner’s high is not just a New Agey excuse for their claims of feeling good after a hard workout.

For athletes and nonathletes alike, the results are opening a new chapter in exercise science. They show that it is possible to define and measure the runner’s high and that it should be possible to figure out what brings it on. They even offer hope for those who do not enjoy exercise but do it anyway. These exercisers might learn techniques to elicit a feeling that makes working out positively addictive.

The lead researcher for the new study, Dr. Henning Boecker of the University of Bonn, said he got the idea of testing the endorphin hypothesis when he realized that methods he and others were using to study pain were directly applicable.

The idea was to use PET scans combined with recently available chemicals that reveal endorphins in the brain, to compare runners’ brains before and after a long run. If the scans showed that endorphins were being produced and were attaching themselves to areas of the brain involved with mood, that would be direct evidence for the endorphin hypothesis. And if the runners, who were not told what the study was looking for, also reported mood changes whose intensity correlated with the amount of endorphins produced, that would be another clincher for the argument.

Dr. Boecker and colleagues recruited 10 distance runners and told them they were studying opioid receptors in the brain. But the runners did not realize that the investigators were studying the release of endorphins and the runner’s high. The athletes had a PET scan before and after a two-hour run. They also took a standard psychological test that indicated their mood before and after running.

The data showed that, indeed, endorphins were produced during running and were attaching themselves to areas of the brain associated with emotions, in particular the limbic and prefrontal areas.

The limbic and prefrontal areas, Dr. Boecker said, are activated when people are involved in romantic love affairs or, he said, “when you hear music that gives you a chill of euphoria, like Rachmaninoff’s Piano Concerto No. 3.” The greater the euphoria the runners reported, the more endorphins in their brain.

“Some people have these really extreme experiences with very long or intensive training,” said Dr. Boecker, a casual runner and cyclist, who said he feels completely relaxed and his head is clearer after a run.

That was also what happened to the study subjects, he said: “You could really see the difference after two hours of running. You could see it in their faces.”

In a follow-up study, Dr. Boecker is investigating if running affects pain perception. “There are studies that showed enhanced pain tolerance in runners,” he said. “You have to give higher pain stimuli before they say, ‘O.K., this hurts.’ ”

And, he said, there are stories of runners who had stress fractures, even heart attacks, and kept on running.

Dr. Boecker and his colleagues have recruited 20 marathon runners and a similar number of nonathletes and are studying the perception of pain after a run, and whether there are related changes in brain scans. He is also having the subjects walk to see whether the effects, if any, are because of the intensity of the exercise.

The nonathletes can help investigators assess whether untrained people experience the same effects. Maybe one reason some people love intense exercise and others do not is that some respond with a runner’s high or changed pain perception.

Annie might question that. She loves to run, but wonders why. But her husband tells her that the look on her face when she is running is just blissful. So maybe even she gets a runner’s high.

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