Key Points: Exercise-induced euphoria is not dependent on endorphins, a new study shows.
Endocannabinoids are more likely the cause of “runner’s high”, and not endorphins as originally suspected. Runner’s high is the euphoria experienced just after intense aerobic activity, such as running.
Aerobic activity, like running, stimulates the body’s endo-cannabinoid system.
In the mid-2000’s, while writing The Athlete’s Way, I was inspired to subtitle it, “Sweat and the biology of bliss”, because of the newly discovered (Spalding et al., 2003, Dietrich & McDaniel, 2004) “bliss molecule”. The production of an endocannabinoid called anandamide, spurred on by aerobic exercise, is also known as manufacturing the “bliss molecule”.
Over the years, I’ve reported on a growing body of evidence-based research related to this topic. (See Motivation to Run (or Not to Run) Is Linked to Cannabinoids” from March 2019). Often, it takes decades for neuroscientific research to trickle into mainstream conversation and become part of public knowledge, as is the case with the link between endocannabinoids and “runner’s high”.
Endo (self produced from within) cannabinoids have been accepted as the key to exercise-induced euphoria by experts in the field, but most of the general population still believes endorphins are the cause of “runner’s high”.
The good news is that, as of 2021, the connection between endocannabinoid and runner’s high is finally getting the attention it deserves. On February 24, 2021, Runners World published a highly informative article (The Reason Behind the Runner’s High Isn’t What You Might Think) based on a peer reviewed paper (Siebers et al., 2021).
The study found “endorphins do not play a significant role in the underlying mechanism of a runner’s high”. Further, “core features of a runner’s high depend on cannabinoid receptors but not opioid receptors”. Basically, stating what has long been suspected, that endocannabinoids are the driving factor behind runner’s high.
Research performed in mice (Fuss et al., 2015) found the benefits of exercise “don’t depend on opioid receptors as assumed; instead, they rely heavily on the endocannabinoid systems receptors,” stated Johannes Fuss of University Medical Center Hamburg-Eppendorf. Since the euphoric feelings of mice can’t be quantified and studied, the experiment had to be repeated with humans.
In a recent double blind study, 63 healthy participants ran on a treadmill at moderate intensity for 45 minutes. During a second treadmill session in an exercise lab, the same participants walked at a casual pace for 45 minutes. On average, study participants “exhibited increased euphoria and decreased anxiety after 45 minutes of running”, as opposed to walking 45 minutes. Runners were randomly given an opioid-receptor blocking medication, Naltrexone (inhibits endorphins), yet participants still experienced exercise-induced euphoria.
“This means endorphins don’t seem to play a major role,” Fuss told Runners World. Based on the new study, researchers have concluded endocannabinoids cause runner’s high, not endorphins, as once suspected.