Exercise Euphoria: The runner’s high

Many avid runners will already know what I mean by the “Runner’s High” and the feelings that it provokes, often it is completely unanticipated yet feels as though it’s the most natural feeling in the world. Frequently when on longer training runs that are up to six to ten miles in length, I have slipped into the running high, finding myself in another world for between one and two miles. The run seems effortless, I’m almost gliding with every pace and a sense of fulfilment encapsulates me. One definition from Sach and Berger states the runner’s high is a “euphoric sensation experienced during running, usually unexpected, in which the runner feels a heightened sense of wellbeing, enhanced appreciation of nature and a transcendence of time and space”.

It has been reported that among runners who have previously experienced the high up to 30% of those encounter it on their daily runs, claiming to feel a sense of mental awareness, liberation, exhilaration and pain suppression. Additionally, in an interview of 60 runners it was revealed that the high brought about by running cannot be reliably predicted but can be facilitated by the absence of distraction and cool weather conditions. Runs should be ≥6 miles in length at a comfortable pace and it is also vital there is no concern with regards to timing or pacing.

Several theories exist regarding how the running high is brought about with perhaps the most famous being that of endorphin release, the body’s natural painkiller. However this theory has several problems, fundamentally endorphins are simply too large to pass over the blood-brain barrier. Consequently, although endorphin concentrations do increase within the circulation during exercise, without reaching the brain they cannot be held accountable for the high exercisers experience. Another key hypothesis is that of the opioid system, opioids are psychoactive chemicals that resemble morphine in their pharmaceutical effects. Research has revealed that release of endogenous opioids occurs following prolonged exercise and that this release is closely correlated with perceived euphoria among runners. However, it is also known that the opioid system is accountable for responses such as respiratory depression and other effects that are detrimental to running performance.

Perhaps the most feasible alternative to the endorphin theory is the ‘endocannabinoid hypothesis’’. Cannabinoids, an active ingredient found in marijuana binds with the nervous system to reduce pain and aniexty, producing a profound sense of wellbeing. Our body has the ability to create its own cannabinoids (endocannabinoids), these are composed of lipid molecules small enough to pass over the blood-brain barrier to provoke an affect in the brain. Research findings have shown that exercise increases the concentrations of these endocannabinoids, producing psychological effects closely resembling those associated with the runner’s high. The endocannabinoid systems activation is also thought to elicit a reduction in attentional span, time estimation difficulties, memory impairment and a sense of wellbeing. All of which characteristics are often included in the reported psychological profiles of long distance runners. These findings may be as a consequence of decreased metabolism in the prefrontal regions of the brain with increased endocannabinoid concentrations, whilst also demonstrating disadvantageous affects to cognitive functioning.

As yet there is no reference to a cyclist’s or swimmer’s high, it is likely this is due to endocannabinoid receptors residing in the skin and so as runner’s make contact with ground endocannabinoid release is stimulated. Another key point worth noting is that low level skills such as running are highly controlled by the basal ganglia which are responsible for cognition and habitual behaviours. The net result of this is that they more readily activate the endocannabinoid system than high skilled activities such as hockey or basketball.

Furthermore, endocannabinoids interaction with the neurotransmitter dopamine suggest that they play a role in the brain’s rewarding system, possibly contributing to exercise/running addiction. This many result in detrimental health affects among athletes who continue to train despite a chronic overuse injury. Lastly, it has be observed that the endocannabinoid system also attributes peripheral effects including bronchodilation and vasodilation. Such physiological changes can facilitate endurance performance by allowing for more efficient oxygen transportation, thereby promoting feelings of ease and effortlessness.

This article intended to provide an overview of the “Runner’s High” phenomenon, there is still much room for further research however it is clear that endurance runners frequently encounter many of the mood components mentioned whilst training. The most promising theory is that of endocannabinoids, providing both a physiological and psychological explanation for the exercise high. Although these feelings are subject to great individual variation and it is still unclear how age, sex and exercise intensity can affect the feeling of exercise euphoria.

"I always loved running... it was something you could do by yourself, and under your own power. You could go in any direction, fast or slow as you wanted, fighting the wind if you felt like it, seeking out new sights just on the strength of your feet and the courage of your lungs." - Paula Radcliffe