A decent point about comparison that’s often missed: comparing like-to-like means that interventions must be executed at the same level of proficiency as controls:

For the past few years, 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, running shoes make running physiologically easier than going barefoot.

The study, conducted by researchers at the University of Colorado in Boulder, began by recruiting 12 well-trained male runners with extensive barefoot running experience. “It was important to find people who are used to running barefoot,” says Rodger Kram, a professor of integrative physiology, who oversaw the study, which was published online in the journal Medicine & Science in Sports & Exercise.

“A novice barefoot runner moves very differently than someone who’s used to running barefoot,” Dr. Kram says. “We wanted to look at runners who knew what they were doing, whether they were wearing shoes or not.”

Specifically, he and his colleagues hoped to determine whether wearing shoes was metabolically more costly than going unshod. In other words, does wearing shoes require more energy than going barefoot?

You see this a lot in educational research — the teachers involved are either more trained in the intervention or the control, which can foul the results quite a bit, even in a cross-over design.

There’s actually lots more great stuff in this article — what the researchers found was that the lack of the weight of shoes was actually a confounding variable in judging the efficiency of other aspects of barefoot running — basically the like-to-like comparison they designed compared ultralight running shoes to barefoot + small weighted band-aids, and once the variable of shoe weight was controlled for in this way the efficiency association was reversed…another reminder that it’s usually more about the definitions than the stats.

I should add that this study probably addresses the concerns of only a small amount of barefoot runners — not everybody cares about efficiency.