Neuroscience Psychology

Why does exercise make a person happy?
Answered by Susan Sherwood and Discovery Fit & Health
  • Susan Sherwood

    Susan Sherwood

  • Discovery Fit & Health

    Discovery Fit & Health

  1. Unless you've chosen a form of exercise you loathe, by the end of the session your mood will probably improve. You may have positive feelings because you're anticipating health benefits; or because it can be fun to socialize during team sports or partner workouts; or you may just be happy to have some time alone riding your bike. But what about that pinnacle of exercise elation?

    The "runner's high," that feeling of bliss, can occur during any long, intense cardiovascular exercise. It's been attributed to endorphins, which act like opiates in the body. Endorphins are secreted when the body is under stress or in pain. Sensations of joy can occur during a powerful workout, but it turns out that endorphins aren't the cause: Endorphin molecules are too big to cross the blood-brain barrier.

    Research suggests the real culprits may be endocannabinoids (literally, cannabinoids within the body). Unlike endorphins, these chemicals are indeed tiny enough to traverse that blood-brain blockade. Scientists have known for a long time that a cannabinoid (THC) found in marijuana can connect to the nervous system, leading to heightened feelings of happiness and serenity. In 2003, scientists from the Georgia Institute of Technology found a particular endocannabinoid -- anandamide -- in the blood of cyclists and runners after they'd experienced sustained exercise.

    Endocannabinoids can reduce feelings of pain, dilate blood vessels and bronchial tubes and induce tranquility. The Georgia Tech researchers believe that the ednocannabinoid system reacts to stress and pain experienced by the body during prolonged exercise. This could have been an evolutionary development, a method of keeping the body going when injured or overworked.

    Two studies done with mice have advanced our knowledge of endocannabinoids in compelling ways. Italian scientists studied mice during favorite pursuits: running on wheels and drinking sweet liquids. During both activities the endocannabinoid system was activated, displaying an interesting commonality between sweets and exercise.

    A French study involved breeding mice whose brains were not able to process endocannabinoids.  Compared to standard mice, the modified mice ran on their wheels (a beloved activity, remember) only half as much. It appears that when their bodies were not able to access the benefits of the endocannabinoids, the mice had less incentive to run.

    This research into the "runner's high" may benefit others; it's possible that, in the future, medical marijuana may be supplanted by exercise as therapy for glaucoma and chronic pain.

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  2. What is it about exercise that lifts a person's mood? It's not just having more energy, feeling fit, getting in great shape and reaching goals, although these are certainly important effects and are part of the happiness equation. There's a physical reason for the happiness you feel from exercising, and it comes from the release of endorphins, the "feel-good" hormones. The Karolinska Institute found that when rats exercised, the results were similar to when they were given antidepressants; exercise also helped form new brain cells.

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