LITTLE ROCK — Proponents of barefoot running have argued that modern athletic shoes compromise natural running form. But now a first-of-its-kind study suggests that in the right circumstances, shoes make running physiologically easier than going barefoot.
The study, published online in the journal Medicine & Science in Sports & Exercise, began by recruiting 12 well-trained men with extensive experience running barefoot.
“A novice barefoot runner moves very differently than someone who’s used to running barefoot,” said Rodger Kram, a professor of integrative physiology at the University of Colorado, who oversaw the study.
“We wanted to look at runners who knew what they were doing, whether they were wearing shoes or not.”
Specifically, Kram and his colleagues hoped to determine whether wearing shoes was metabolically more costly than running unshod.
In other words, does wearing shoes require more energy than going barefoot?
A few earlier studies have suggested that in terms of physiological effort, it’s easier to go barefoot.
After all, shoes have mass; they add weight to your feet, and pushing weight through space, as you do with every step while running, demands energy.
These earlier studies generally concluded that every additional 100 grams (or about 3.5 ounces) added to your feet should increase the energy cost of running by about 1 percent. Over many miles, that 1 percent becomes magnified if you wear heavy running shoes, which can easily weigh 400 grams (four fifths of a pound) or more.
But for the new study, Kram and his colleagues wanted to use a relatively lightweight, cushioned shoe. They chose the Nike Mayfly, a model that, as the name intimates,is a flyweight, barely reaching 150 grams (three-tenths of a pound).
The runners were asked to run repeatedly on treadmills, either wearing the shoes or not. The runners were never completely barefoot; when unshod, they wore thin yoga socks to protect them from developing blisters and for purposes of hygiene.
Next, the researchers taped 150 grams’ worth of thin lead strips to the tops of the runners’ stockinged feet. By adding an equal amount of weight to the bare foot, they could learn whether barefoot running really was physiologically more efficient than wearing shoes.
It wasn’t. When barefoot runners and shod runners carried the same weight on their feet, running barefoot used almost 4 percent more energy in each step than running in shoes.
Of course, most barefoot runners don’t go jogging wearing leaded Band-Aids. But notably, even when unweighted barefoot running was compared foot-to-foot with running in the Mayflys, the shoes won out.
For eight of the 12 runners, wearing shoes remained slightly more efficient than being barefoot, even though the shoes added weight.
It’s important to note that the study looked only at the metabolic efficiency of wearing shoes, compared with going barefoot. The scientists didn’t evaluate the common claim that running barefoot lowers injury risk.
“What we found was that there seem to be adaptations that occur during the running stride that can make wearing shoes metabolically less costly,” said Jason R. Franz, a doctoral candidate at the University of Colorado who led the study. Shoes, he said, “provide some degree of cushioning.” If you eschew shoes, “something else has to provide the cushioning.”
That something, he and his colleagues believe, is your legs. If you are barefoot, the job of absorbing some of the forces generated when your foot strikes the ground shifts to your leg muscles, a process that Kram calls the “cushioning effect.”
The difference in metabolic cost between going barefoot or wearing lightweight shoes is of interest mostly to competitive runners.
For the rest of runners, the question could be whether to invest in a slimmed-down trainer. “There is a metabolic cost to wearing really heavy running shoes,” Franz said. Lightweight models that provide cushioning to spare leg muscles, without mass to slow movement, may be the physiologically smartest alternative to being bare, he said.
ActiveStyle, Pages 23 on 04/02/2012