Most long distance runners have experienced the “runner’s high” — a feeling of enhanced mood and relaxation following a strenuous run. Its presence is unmistakable, but also hard to explain, and even harder to scientifically prove. Recently, researchers used high-tech brain imaging to demonstrate changes in brain activity that correlate with this phenomenon. Perhaps more importantly, this runner’s high is also linked to decreased pain perception, providing a potential therapeutic mechanism for sufferers of chronic pain.

German researchers used positron emission tomography (PET) to detect brain activity before and after a 2 hour run. Endorphins are the proposed molecules that increase after a long run, and their actions are primarily on the opiate receptors within the brain. In the study, radioactive opiate receptor agonist were injected and imaged with PET. After a long run, participants brains’ showed decreased binding of the radioactive molecule, demonstrating that their opiate receptors were occupied by an endogenous substance. The level of radioactivity within the brain was markedly decreased from that imaged before running.

The brain regions involved in this running-induced endorphin binding included the limbic and prefrontal regions, both involved in emotional processing. Participants reported increased euphoria and happiness, with euphoria levels correlating directly with the activity in these brain regions following exercise.

Opioid receptors in the brain are targets of potent painkillers and elicit drugs, such as morphine, codeine and heroine. These drugs markedly reduce the perception of pain, and increased doses produce euphoria. Because this same effect, albeit to a lesser degree, has now been detected with strenuous exercise, researchers may be able to apply exercise as a harmless and non-addictive painkiller.

Many patients with chronic pain become resistant to the effects of prescription pain medicine, and they also run the risk of addiction and dependence. By triggering the release of natural endorphins, long distance running may allow chronic pain patients to find some relief without the attendant risks of addictive medications.

Reference

Boecker, H., Sprenger, T., Spilker, M.E., Henriksen, G., Koppenhoefer, M., Wagner, K.J., Valet, M., Berthele, A., Tolle, T.R. (2008). The Runner’s High: Opioidergic Mechanisms in the Human Brain. Cerebral Cortex. DOI: 10.1093/cercor/bhn013