A few weeks ago I addressed the role that personality plays in making us runners. As a follow-up, I recently spotted this great article in the New York Times which presents the results from a scientific article entitled “Wheel Running in the Wild.” In the investigation, authors sought to answer the question of what drives wheel-running in captive rats and mice. Is it a neurotic behavior that arises from captivity OR is it a true desire to engage in physical activity? This question is suprisingly important (and previously unanswered). For example, many studies seek to determine whether physical activity has genetic determinants, but it’s hard to use the model of captive rodents exercising on wheels if we don’t know whether this is innate, learned or adaptive/maladative behavior. Similarly, studies looking at the effect of exercise training on major cardiovascular, psychological and metabolic outcomes (e.g., Does exercise prevent brain tissue loss in Alzheimers Disease? Does exercise improve insulin sensitivity?) in animal models could be confounded if it turns out that the very act of exercising on a wheel in a cage is a stressful and forced activity.
So, back to the research study. The authors, Johanna Meijer and Yuri Robbers, did a very simple experiment: they placed exercise wheels outside (in a yard garden and dunes), and monitored them with motion sensors and automatic video cameras. And guess what! Animals (largely mice, about 88% of the time, as seen from the graph on the right) hopped on the wheels and ran with wild abandon. Frogs, shrews and slugs also showed up, although the slugs caused “haphazard rather than directional movement of the wheel and were therefore excluded from the analysis.” Researchers also observed that “some animals seem[ed] to use the wheel unintentionally, but mice and some shrews, rats and frogs were seen to leave the wheel and then enter it again within minutes in order to continue wheel running…indicat[ing] that wheel running may well be intentional rather than unintentional for these animals. Mice ran for more than 1 min in 20% of the cases, with a maximum duration of 18 min… similar to what [laboratory] mice do. The mice only ran in our wheels and never walked slowly.” Overall, both running speed and distance covered were comparable between mice in the wild on the wheels and laboratory mice. In other words, the wild mice ran because they wanted to. They just liked it.
Somehow, reading this article made me very happy…that wild mice might encounter a wheel and run out of curiousity, exhileration, enjoyment and/or fulfillment. And while we can seek to understand the genetic, psychosocial or cultural determinants of physical activity, we shouldn’t ignore that the thrill of movement and simple pleasure of being active may be the most important reasons for why we do what we do each day for exercise.