KINGSTON, Ontario – A new study lead by a Queen’s researcher has found that when recreational runners are left to their own devices and outfitted with a wearable fitness tracker, they prefer to run at the same calorie-saving pace, regardless of the distance ran – contrary to the explicit goals of competitive racing.
Previously, scientists theorized that runners burn the same amount of calories for a given distance no matter how fast they run because the energetic cost depends mostly on the weight of runner and time run. But a new study, published in Current Biology, helps upend this thinking in favour of a more economical one. With data from more than 4,600 runners totaling more than 28,000 hours of running, researchers compared energy-saving running speeds measured in a lab setting to the preferred, real-world speeds measured by wearable trackers and found the two to be indistinguishable.
For this investigation, the researchers gathered data from 26 runners on treadmills and identified the energetically optimal speeds based on their oxygen consumption. They compared this to data collected from thousands of recreational runners outfitted with a waistband tracker from Lumo Run.
Although the data from lab studies may be more consistent and manageable, Jessica Selinger, the study's lead author who was formerly a postdoctoral scholar at Stanford and is now an assistant professor with the School of Kinesiology and Health Studies at Queen's University, said that the sheer volume of information made available through wearables is unobtainable in the lab. “Wearables can also reveal the choices we make in the real-world without the oversight of a researcher or constraints of the lab environment, she added. By fusing the two, a new window has opened up into runners' behaviour” says Dr. Selinger.
From an evolutionary point of view, energy minimization is considered optimal, to the point that it’s done across the animal kingdom.
"Minimizing energy expenditure has evolutionary advantages – it allows us to move farther on fewer calories. We share this trait with other animals, be it flying birds, swimming fish, or galloping horses – there's evidence that we all move in calorie conserving ways out in the wild," said Dr. Selinger.
Even if runners are not food-deprived, they still act like their evolutionary history constrains them. Running requires more energy than swimming, flying or walking, and for humans, running requires twice the energy than that found in other comparably-sized mammals.
Regardless of speed, running and other physical activities have numerous benefits such as building muscular strength and bone density or improving mental health, and the study's researchers emphasize that runners can achieve these benefits at a range of speeds—optimal, slow or fast.
“Our findings show that the preference for energy efficient movement is strong—even when we go for a jog, perhaps with the goal of burning calories, we move at a speed to minimize them. This means that if we want to run at a faster pace, we may need to consciously focus on doing so. Or, use other tricks like running with a faster partner or listening to fast paced music” says Dr. Selinger. “It is important to understand what objectives shape our locomotion, and what influences how we move if we are looking to train athletes, develop assistive devices, or even understand our evolutionary history."
By applying useable data from wearables, and perhaps improving wearables by adjusting algorithms according to research results, the researchers envision expansive ways to enable fitness based on natural, “free-living” human behaviour.
The study is now available in Current Biology.
Additional co-authors of this work are from Seattle Pacific University and Lumo Bodytech, and the Stanford Bio-X, Maternal & Child Health Research Institute (MCHRI), and the Wu Tsai Neurosciences Institute and the Wu Tsai Huan Performance Alliance at Stanford University.
This work was funded by the Natural Sciences and Engineering Research Council of Canada, the National Institutes of Health, the Wu Tsai Human Performance Alliance, and the Joe and Clara Tsai Foundation.