An increasing number of runners use minimalist shoes like Vibram Fivefingers, or go barefoot, swayed by claims that it will help them run more naturally and quickly. But what does the scientific evidence say?

Going unshod or slightly shod is supposed to force a runner to start landing on the front of the foot, rather than striking the ground heel-first. Heel striking, barefoot proponents say, tends to be worse on your feet than favoring the forefoot, which is more physiologically efficient. Forefoot landings allow a runner to go longer and faster with less effort, proponents claim. A recent study published in the Journal of Applied Physiology now casts a bit of doubt on this.

In the study, researchers from the University of Massachusetts, Amherst observed 19 heel-strikers and 18 runners that typically landed on the ball of the foot. Both groups ran at three different speeds on a treadmill, and their metabolic economy was calculated by measuring the runners’ exhalations and oxygen consumption. The groups were also asked to run at slow, middling, and fast speeds while using the opposite of their preferred technique.

Heel-striking, the data showed, required less oxygen to achieve the same pace when striking with the forefoot. Heel-striking also resulted in less burning of carbohydrates for energy and more burning of fat.

“The results suggest that the [forefoot-favoring] pattern is not more economical than the [rearfoot] pattern,” the authors wrote.

Other research has also pointed towards injury risk associated with minimal running shoes. In February, a Brigham Young University team found that transitioning to Vibrams was hard on a runner’s feet. In their study, 10 out of 19 runners that switched to Vibrams had increases in bone marrow edema – excess fluid in the bone that can lead to inflammation – and two suffered foot stress fractures. Just one of the 17 runners in the control group had increased bone marrow edema.

However, that BYU study was criticized by Mark Cucuzzella, a professor of family medicine at the West Virginia University School of Medicine who's also a competitive runner and the owner of a store specializing in minimalist shoes. Seven of the 36 subjects did not fully document their training, Cucuzzella pointed out. He also said the transition program used by the researchers was too hasty (though it was what was recommended by Vibram at the time of the study).

“In my opinion, no coach or advocate of minimalism would ever suggest a runner completely transition to FiveFingers in 10 weeks if coming out of a traditional shoe,” Cucuzzella said in an email back in March. “For most who have years [of experience running only] in traditional shoes, it takes months, even years, to be able to do the majority of running in FiveFingers.”

Many runners are primarily interested in barefoot running because they think it will help them avoid injuries, but few people turn to physical therapists or coaches to help make the transition, according to research published in the Journal of Strength and Conditioning Research last July. Learning proper running form isn’t just a matter of strapping on a pair of Vibrams.

"Just because you put on a minimalist shoe doesn't necessarily mean you're automatically going to adopt a forefoot strike," University of Central Florida researcher Carey Rothschild said back in July.