We've all heard of — and many of us actually experience — runner's high. A state where, after or during intense exercise like running, your body pumps out endorphins and you just feel, well, fantastic and like you have all of the energy in the world. For those who get runner's high, it's addicting and prompts them to keep up with their regular sweat sessions. Turns out, that may be exactly why Mother Nature created it. According to a new study published in The Journal of Experimental Biology, humans may have evolved to get runner's high to encourage high-endurance performance, as our hunter-gatherer predecessors had to basically be long-distance endurance athletes to survive.
To test this theory, researchers looked at humans, dogs and ferrets. (Yes, ferrets.) Runner's high is caused by endocanabinoid signaling in the reward centers of the brain, so researchers set out to examine endocanabinoid levels in the blood before and after exercise. While dogs and humans are high-activity mammals, ferrets are generally not, so the researchers hypothesized that increased endocanabinoid levels would not be present after exercise for the ferrets.
The results? The researchers found that endocanabinoid rocketed in the blood of the dogs and humans after a brisk run. Additionally, the human runners were also much happier after the exercise. However, when the team looked at the ferrets' blood, the animal's endocanabinoid levels did not, as they suspected, increase during exercise. (The ferrets were also none too happy to give blood samples, the researchers noted.)
So what does all this mean? According to the study, natural selection used the feeling of runner's high to motivate endurance exercise in humans and other animals that walk and run over long distances. Also, natural selection may have been motivating higher rather than low-intensity activities in groups of mammals that evolved to engage in these types of aerobic activities, researchers note.
Despite the new information on why we evolved to get runner's high, researchers don't think it'll help reverse the obesity epidemic, as it takes working out at a very high level to get your endocanabinoid levels up. However, for those who are fit and able to really push themselves? It's a bonus, and one that keeps us rewarded for hitting the gym.
Jennipher Walters is the CEO and co-founder of the healthy living websites FitBottomedGirls.com and FitBottomedMamas.com. A certified personal trainer, lifestyle and weight management coach and group exercise instructor, she also holds an MA in health journalism and regularly writes about all things fitness and wellness for various online publications.