For many recreational runners, going for a run is a fun way to stay fit and burn calories. But it turns out that an individual has a tendency to adapt to the same comfortable pace in short and long races, and that pace is the one that minimizes the energy use of his body in a given distance.
“I was very surprised,” says Jessica Selinger, a biomechanist at Queen’s University in Kingston, Canada. “Intuitively, I would have thought that people run faster over shorter distances and slow down over longer distances.”
Selinger and colleagues combined data from over 4,600 brokers, who ran 37,201 runs while wearing a fitness device called Lumo Run, with physiological data from the lab. The analysis, described April 28 in current biologyit also shows that it takes more energy for someone to run a given distance if they run faster or slower than their optimal speed.
“There is a speed that will make you feel better,” says Selinger. “That speed is the speed where you’re actually burning the fewest calories.”
The runners were between 16 and 83 years old and had body mass indexes ranging from 14.3 to 45.4. But regardless of the participants’ age, weight or gender, or whether they ran only a narrow range of distances or races of different lengths, the same pattern appeared in the data repeatedly.
The researchers thought running was performance-driven, says Melissa Thompson, a biomechanist at Fort Lewis College in Durango, Colo., who was not involved in the new study. This new research, she says, is “talking about preference, not performance.”
Most of the related research, says Selinger, has been done in university labs, with study subjects who are generally younger and healthier than the general population. By using wearable devices, the researchers were able to track far more runs, under more real-life conditions, than is possible in a laboratory. That allowed scientists to look at a “much broader cross-section of humanity,” she says. Treadmill tests that measure energy use at different rates were used with people representative of those included in the fitness tracker data to determine optimal energy-efficient speeds.
Because the study includes a wide range of conditions and doesn’t control for things like fasting before running, it’s more confusing than data collected in labs. Still, the sheer volume of real-world running recorded by wearable devices supports a compelling rule of thumb about how humans run, says Rodger Kram, a physiologist at the University of Colorado Boulder who was not involved in the study. “I think the rule is correct.”
The results do not apply to very long runs when fatigue begins to set in, or to the running performance of elite athletes or others who consciously train for speed. And a runner’s optimal pace can change over time, for example with training or age.
There are quick tricks for those who want to speed up and burn a little more calories to temporarily overcome their body’s natural inclinations: Listen to upbeat music or jog alongside someone with a faster pace, says Selinger. “But it seems your preference is to sink back into that optimum.”
The results are consistent with observations of optimal pacing for animals such as horses and wildebeest, and also correspond to the way humans tend to walk at a rate that minimizes your individual energy use (Serial number: 09/10/15).
It makes sense that humans are adapted to run at an optimal speed to minimize energy use, says co-author Scott Delp, a biomechanist at Stanford University. He imagines himself to be a primitive human ancestor who goes out to hunt difficult prey. “It can be days before I get my next meal,” he says. “So I want to expend the least amount of energy on the way to get that food.”