Intense exercise leads to intense endorphins

Researchers in Finland have found that when you’re working out, the level of endoprhins released in the brain directly correlates to the intensity of exercise you’re doing. That’s a good thing for people doing high intensity interval training, or HIIT, because HIIT is miserable.

Scientists believe exercise-induced endorphin release may in part be the body’s way of motivating a person to power through activities that are no fun, but good for you. The new study, conducted at the University of Turku, shows that the popular (but miserable) high-intensity interval training leads to a burst of endorphin released into the brain, which the researchers speculate alleviates some of the physical and emotional stress caused by the awful, high-intensity exercise. A lower-tempo, less demanding, traditional and entirely reasonable one-hour aerobic routine, sadly, has no similar effect.

In the study, HIIT significantly increased the release of endorphins and other opioid peptides in the brain areas controlling pain and emotions. HIIT also induced negative feelings in the exercisers. Although one-hour aerobic exercise did not induce significant release of endorphins, it increased pleasurable feelings and euphoria. Said researcher Tiina Saanijoki: “Our results highlight that exercise intensity affects endorphin release and that the brain opioid system is involved in both positive and negative feelings caused by physical exercise performed at different intensities.”

“Exercise-induced endorphin release may be an important mechanism which supports exercise motivation and maintenance of regular exercise. At moderate training intensities, the pleasurable sensations caused by the possible release of endorphins may promote habitual exercise. At very high exercise intensities the release of endorphins appears to be linked to increased negative feelings and pain, and may be needed to manage the emotionally and physically demanding challenge. However, such negative feelings may discourage further exercise.”

Exercise intensity should be taken into account when starting new exercise routines, she said. The results were published in Neuropsychopharmacology.

(Editor’s note: It bears repeating that HIIT is miserable.)

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