Runner's high is said to occur when people exercise so strenuously that their bodies reach a certain threshold. It is suggested that β-endorphins are responsible for this state. β-Endorphins are released during long, continuous workouts of moderate to high intensity, corresponding to prolonged physical stress. This also corresponds with the time that the muscles use up their stored glycogen. The presence of β-endorphins would presumably mitigate pain sensation by negatively regulating pain-carrying signals from nociceptive neurons in the spinal cord. Notably, such analgesic effects of β-endorphins could potentially increase the likelihood of injury, as pain sensation could be more easily ignored. Experiencing a runner's high has also been known to cause feelings of euphoria. Although it is called a "runner's" high, the effect can occur anytime that people engage in any strenuous exercise or activity, not just running.
A runner's high has been suggested to have evolutionary roots based on the theory that it helped with the survival of early humans. Current African tribes make use of a runner's high when they are conducting persistence hunting. This is a method in which tribesman hunt an animal and track it for miles, eventually killing it due to its greatly increased vulnerability because it became completely physically exhausted.
In 2008, researchers in Germany reported on the mechanisms that cause a runner's high to occur. Using PET scans, combined with recently available chemicals that reveal β-endorphins in the brain, they were able to compare runners’ brains before and after a run.
Previous research on the role of β-endorphins, in producing a runner's high, included trying to understand the mechanisms at work; that data seemed to demonstrate that the "high" comes from completing a physical challenge rather than as a result of exertion. Studies in the early 1980s cast doubt on the relationship between β-endorphins and the runner's high for several reasons:
- When a μ-opioid receptor antagonist was infused (e.g., naloxone) or ingested (naltrexone), the same changes in mood state occurred as when the person exercised with no blocker.[medical citation needed]
- A 2003 study found that a runner's high might be caused by anandamide, an endocannabinoid. The authors suggest that the body produces anandamide to deal with prolonged stress and pain from strenuous exercise, similar to the original theory involving β-endorphins. However, this study did not report the cognitive effects of a runner's high; which seems to suggest that anandamide release may not be significantly related to runner's high.
- The authors of a 2012 study argued implicitly that endocannabinoids are, most likely, the causative agent in a runner's high, while also arguing this to be a result of the evolutionary advantage endocannabinoids provide to endurance-based cursorial species. This largely refers to quadruped mammals, but also to biped hominids, such as humans. The study shows that both humans and dogs show significantly increased endocannabinoid signaling following high intensity running, but not low-intensity walking. The study does not, however, ever address the potential contribution of β-endorphins to a runner's high. However, in other research that has focused on the blood–brain barrier, it has been shown that β-endorphin molecules are too large to pass freely, very unlikely to be the cause of the runner's high feeling of euphoria.
- It has been suggested that in addition to β-endorphin (a neuropeptide), classical monoamine neurotransmitters (dopamine, norepinephrine, epinephrine, and/or serotonin) might contribute to a runner's high.[medical citation needed]
- Human Mammal, Human Hunter - Attenborough - Life of Mammals - BBC on YouTube
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- P. B. Sparling, A. Giu¡rida, D. Piomelli, L. Rosskopf and A. Dietrich (2003). "Exercise activates the endocannabinoid system". NeuroReport 14 (15). doi:10.1097/01.
- Raichlen, David A.; et al. (April 15, 2012). "Wired to run: exercise-induced endocannabinoid signaling in humans and cursorial mammals with implications for the ‘runner’s high’". Journal of Experimental Biology (215): 1331–1336. doi:10.1242/jeb.063677.
- Burfoot, Amby (June 1, 2004). "Runner’s high". Runner's World.
- Doug Robinson: The Alchemy of Action (2013). Moving over stone.
- Why People Climb Mountains Doug Robinsons lecture at Psychedelic Science 2013 conference.