The ‘Runners High‘ is the sense of euphoria that runners experience that temporarily helps them feel relaxed and calm during a run. It is also often associated with reduced anxiety and a lessened ability to feel pain. It is not specifically due to running and can occur with any aerobic activity. There is quite a bit of variability between runners in their experience of this and not all experience it. It is more often experienced by runners who have been at it for a while and during the longer duration runs. This is probably related to the longer-term mental health benefits of regular aerobic exercise.
Evolutionary theory would suggest that our bodies release chemicals to take the edge off the discomfort of physical activity when it was essential for finding food and fleeing predators to increase a person’s chances of survival. The modern-day ‘runners high’ that makes running gratifying might have evolved to serve as a reward that kept early humans hunting and gathering for their survival.
Running does increase the production of a number of chemicals that could account for this. There are several possible mechanisms for the ‘runners high’:
The ‘runners high’ was widely thought to be due to endorphins which are released in greater amounts when running and doing other aerobic exercises. Endorphins act centrally in similar ways to opioids like morphine. With a longer duration of exercise, the increased levels of endorphins are thought to have a morphine-like effect on the body and may account for the sensation of well-being. However, support for this hypothesis is not as much as in the past as endorphins do not pass the blood-brain barrier, so any effect that they do have would be on the muscles to modulate pain sensations.
More recent research have suggested the mechanism could be via the increased release of endocannabinoids which are the same chemicals that are mimicked by cannabis or marijuana. Endocannabinoids can alleviate pain and improve mood. When humans run there are increased levels of endocannabinoid that as neurotransmitters activate cannabinoid receptors giving the equivalent of a ‘marijuana high’. Unlike the endorphins, they do pass the blood-brain barrier.
Other neurotransmitters might play a role. Norepinephrine, dopamine and serotonin are produced in greater amounts during exercise and have all been shown to help to reduce depression and play a role in mood regulation.
Another theory suggests that the prolonged increased body temperature during longer duration aerobic activities may affect the hypothalamus, which is involved in temperature regulation mechanisms. The increased temperature may indirectly affect mood.
Leptin is a hormone that regulates the feeling of hunger and some recent research suggests that it may play a role in the ‘runners high’. The research showed that mice with less leptin would run substantially further than mice with normal levels. The authors suggested that this could be because mice with less leptin were more likely to experience the sensation of the ‘runners high’. Linking it to the evolutionary theory they hypothesized that a fall in leptin levels increases motivation for physical activity via the reward of the ‘runners high’ as a means to increase the motivation for the pursuit of food to survive. Leptin also plays a role the pathophysiology of obesity and Type 2 diabetes.
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