Have you ever seen a bare- foot runner win a race? No, you probably haven’t. A study reported in Medicine & Science in Sports & Exercise may explain why. Researchers at the University of Colorado found that, despite the claims of barefoot enthusiasts, running with cushioning is actually more economical than running shoeless on a hard surface.
Unlike past studies comparing the energy cost of shod and unshod running, this one controlled for important factors that may have biased earlier results.
These factors included barefoot running experience, foot strike pattern, shoe weight and running speed.
Twelve male runners participated in the experiment. All were experienced barefoot runners and mid- foot strikers. The subjects ran at a fixed pace of roughly eight minutes per mile on a treadmill under several conditions: barefoot (actually, wearing very thin socks for hygienic reasons), wearing super-light (150g) Nike Mayfly racing flats, and with various amounts of weight attached to their bare feet or to their shoes. Oxygen consumption was measured to determine the energy cost of each condition.
Interestingly, the energy cost of running with and with- out shoes was roughly the same. But when an amount of weight equal to that of the racing flats was attached to their bare feet, the runners used three to four per cent more energy than they did in their Nikes. In other words, when weight was controlled for, running barefoot was less economical than running in lightweight shoes.
“These results got us thinking,” says Rodger Kram, the study’s lead author. “If lightweight shoes have the same energy cost as running barefoot, then there must be something good about shoes that’s counteracting the negative effect of their mass. We suspected that it was probably cushioning.”
To test his hunch that a cushioned landing surface saves energy otherwised used to soften foot strike when barefoot, Kram and his colleagues designed a follow-up experiment in which subjects ran barefoot on a cushioned treadmill. Sure enough, the runners used 1.7 per cent less energy on a treadmill whose belt was cushioned with 10mm of the same kind of foam that is contained in running shoes than they did on the non- cushioned belt.
According to Kram, who recently presented his findings at a meeting of the American Society of Biomechanics, the take-home lesson is that, for maximum running performance, not only are shoes better than no shoes, but shoes with a little cushioning are better than minimal shoes, despite a bit of extra weight.
“If you’re really trying to save seconds,” he says, “lighter isn’t always better.”