ABOVE: A runner on the Race Across the USA in 2015
BRYCE CARLSON
We all have limits, and a new study suggests those limits are pretty similar among individual humans—at least at the metabolic level. Researchers tracked runners’ energy expenditure before and after they completed the equivalent of a marathon six days a week for nearly five months straight, then compared their results with studies of other high-intensity activities, and found that the longer the event, the lower the metabolic rate participants were able to sustain.
The maximum metabolic rate for longer-term activities, they report today (June 5) in Science Advances, is about two and a half times an individual’s resting energy use—likely a reflection of a limit on the number of calories the human digestive system is able to absorb.
“Conceptually, people had been looking for one number—they were looking for some level of energy expenditure that is sustainable indefinitely. ...
