If people go running by your home accompanied by their cats, geckos, ferrets, parrots, or rats, then you live in a very different neighborhood, perhaps even a different world, than I do. It's just not part of our relationship with those species, however close we may be to them. Yet running is something that many of us share with our dogs. Dogs typically like running, which is yet another commonality between dogs and humans.
OK, perhaps not ALL humans. In recent years, people have become more sedentary than at any time in our history, and many of our dogs have joined us on the couch. As a result, that rush of good feelings we get from running -- the runner's high -- is no longer as widespread. Yet, the potential to activate the chemical reactions that cause the runner's high still exists in both dogs and people.
The runner's high is caused by neurotransmitters called endocannabinoids that signal the reward centers of our brains. They lessen pain and anxiety as well as create feelings of pleasure and well-being. Running results in higher levels of endocannabinoids.
Researchers at the University of Arizona investigated the production of endocannabinoids in multiple species as a result of running. These scientists wanted to know whether species that do a lot of long-distance running evolved to like running via the pathway of reward centers in the brain. The researchers predicted that running would result in chemical changes that are associated with pleasure in species with a history of endurance running, but not in species whose natural history does not include such running.
They compared the effects of running on endocannabinoid levels in three species. Two of the species -- dogs and humans -- come from long lines of endurance runners. The other species, the ferret, is not an endurance running species, though they can run quickly over short distances.
The researchers trained dogs, people, and ferrets to run and walk on a treadmill and took blood samples from them before and after each session. Blood taken from dogs and people after running contained highly elevated levels of one endocannabinoid called anandamide. Blood from ferrets after running did not have elevated levels of any endocannabinoids. None of the species had elevated levels of any endocannabinoid after walking.
Dogs and humans receive a pleasurable chemical reward for running, but this quirk of brain chemistry that makes both dogs and humans love running is not universal among mammals. Ferrets, for example, derive no such benefit. The scientists who conducted the study concluded that chemical changes from running and subsequent effects on the brain help endurance-running species enjoy running. The brains of dogs and humans are primed to like endurance running, which may have provided the evolutionary mechanism necessary for us to develop such skill at it.
This study shows that dogs and humans, unlike ferrets, achieve the runner's high. A friend of mine who hates running believes the study also suggests that she is part ferret, but scientific evidence to support this claim remains elusive.
Karen B. London, Ph.D. is a Certified Applied Animal Behaviorist, Certified Professional Dog Trainer and the coordinating editor for this paper's weekly running column, "High Country Running." She runs and trains for races with dogs and people. Her favorite training partners are her husband Rich and her old dog Bugsy, who was half Black Lab and half Handsome Stranger.