Imagine for a moment, the wind blowing through your hair, your skin glistening with the slightest sheen of moisture, a steady breath in and out, and your feet softly caressing the pavement as you place one foot in front of the other with the grace of a cheetah while the moon shines down.
Unfortunately, my running form does not embody the description above. Nevertheless, I still attempt to get my body moving, reminding myself of all the wonderful benefits of exercise – cardiovascular health, endorphins, stress relief, flexibility, and better sleep, and the list goes on.
Despite the many positive benefits of exercise, many people fail to take the time to prioritize it. According to the US Department of Health and Human Services, less than 5% of adults in the US participate in 30 min of physical activity a day. Around the world, obesity is prevalent, with 39% of the world’s adults and 20% of school-aged children meeting the criteria for being overweight.
The Merry-Go-Round
Why don’t people take the time to exercise? When there is a choice between sleeping another 45 minutes or watching your favorite episode of ‘insert the name your favorite Netflix series,’ or exercising, the first two options seem much more appealing. Humans are creatures of habit, and it takes discipline to break one routine for another. And most species (us included!) avoid adverse experiences. Who wants to get hot, sweaty, out of breath, or be sore for a day or two?
Unlike many of us couch potatoes, rats seek out running opportunities. In fact, rats find running so reinforcing they will do it instead of eating even if hungry!
Researchers have taken advantage of these rodent preferences and have used running wheel paradigms to investigate everything from addiction to exercise. In a recent publication in the Psychonomic Society journal Learning & Behavior, Robert Boakes (pictured below) and Jiahao Wu attempted to better understand the role of timing in wheel running in rats.
As nocturnal creatures, rats run mostly at night. Boakes and Wu queried if rats could be entrained to run if given consistent access to the wheel at specific times of the night rather than at random times at night. After all, humans quickly become conditioned, or entrained, to feel sleepy when given consistent cues, such as the setting of the sun or the mid-afternoon siesta following lunch.
Boakes and Wu tested older, group-housed rats and younger, individually housed rats in different experimental groups that varied whether they had a fixed or varied time of night and the three-hour period during which wheel access was given (early, mid, or late). Control rats experienced the same conditions, except they did not have access to the wheel. The running apparatus and setup used for the experiment are pictured in the images below.
Across two studies, a fixed time of night was associated with more wheel turns or faster running (white and black squares lines in the two figures below). Moreover, this effect appeared the strongest for the rats that had access to the wheel in the middle of the night (the white squares line in both figures below).
These patterns of wheel running suggest that a fixed schedule of access was associated with entrainment and resulted in more running. Perhaps having a little time to become active or wake up seemed to have facilitated the mid-phase group as rats in this group ran the most on average for both the older and the younger groups. Moreover, the rats in the fixed groups weighed less, which was ultimately associated with eating less food overall as determined by Experiment 2.
According to Boakes, the findings
… bear on the claims that 1) exercise can become addictive and 2) the increase in running by rats in an activity wheel may reflect the development of such an addiction. The data reported in the paper do not support 2.
One Small Step for “a” Man (or rat), One Giant Leap for Mankind (or ratkind)
If one was willing to take the leap and generalize these results to the human circadian rhythm, one might conclude that we should set that alarm to rise with the sun and hit the treadmill or the pavement about three hours after we wake up to benefit the most from our version of the running wheel. Whether human or rat, creating consistent exercise habits is associated with positive benefits, and we should all be taking some time to do so these days.
Psychonomic Society article focus of this post:
Boakes, R. A., & Wu, J. (2020). Time-of-day affects the amount rats run during daily sessions in activity wheels. Learning & Behavior, 1-8. https://doi.org/10.3758/s13420-020-00436-3
