Buying running shoes? A new study suggests that wearing sneakers tailored to your foot shape might not protect you against injuries.

New Balance, the maker of shoes used in the study, helps runners choose the best shoe for them by determining their foot shape, among other factors, in the company’s online “Find your Total Fit” feature.

But “simply measuring the foot morphology with (this type of) technique is not sufficient for prescribing footwear if your objective is to prevent injuries,” Dr. Bruce Jones, an investigator on the study who manages the injury prevention program at the U.S. Army Public Health Command in Aberdeen Proving Ground, Maryland, told Reuters Health.

Shoe companies market different sneaker models to runners based on how their feet roll and distribute their weight when they hit the ground - a term referred to as pronation.

Overpronators have feet that roll too far inward on each stride, while the feet of underpronators don’t roll enough. Shoes are marketed under the assumption that by adjusting for some of these differences, runners can improve their mechanics and thus prevent injury.

Pronation is generally measured by taking a flat footprint and examining how much of the foot is in contact with the ground when the runner is standing still, a method used by many running specialty stores. But Marine Corps recruits who were fitted for sneakers this way got injured just as frequently as those who were all given a basic shoe made for runners who pronate normally.

Dr. Joseph Knapik, an epidemiologist at Aberdeen, led the study of about 1,400 Marine Corps recruits. The recruits - both men and women - all had their foot shape analyzed and were randomly assigned to one of two groups.

One group got a running shoe that was marketed for their type of pronation: runners whose footprints indicated they were overpronators got a motion control shoe, underpronators got a cushion shoe, and those with normal pronation got a stability shoe.

Members of the other group were all assigned stability shoes, regardless of their foot shape and pronation. Then the recruits wore their assigned shoes, alternating with combat boots, for 12 weeks of training.

During the study, Knapik and his colleagues kept track of different kinds of injuries in the recruits, including overuse injuries and injuries to tendons and ligaments as well as bones and muscles.

In every way the study team measured injuries, there was little difference in how often members of the two groups got injured. This was true for both men and women.

In all, about 42 percent of men assigned custom fitted shoes and 41 percent of men in the stability shoe group got injured over the 12-week training period. For women, approximately 37 percent in custom fitted shoes and about 45 percent in stability shoes regardless of their foot type were injured - a difference that was not statistically significant.

The results are published in The American Journal of Sports Medicine.

The findings agree with similar studies the investigators have done with Army and Air Force recruits. When they combined data from the three studies, there still wasn’t a significant difference in injury rates based on shoe assignment.

New Balance representatives could not be reached for comment.

One explanation of the findings, said Dr. Joseph Hamill, an exercise scientist at the University of Massachusetts at Amherst, is that the footprint technique for assigning running shoes doesn’t work.

“It’s not going to prevent injuries by assigning shoes based on a static measurement,” Hamill, who was not involved with the study, told Reuters Health.

To do a more thorough analysis, runners need to be monitored on a treadmill, or with more specialized equipment. But that’s often not feasible - for Marine Corps recruits or for recreational runners. And Jones said it’s not clear that technique would be more helpful.

“There’s no evidence that dynamic measurements make a difference either,” he said. This could be, he added, because people with different foot shapes actually get injured at similar rates to begin with.

The message to runners is not to focus too much on motion control, cushion, and stability labels, Jones said. “What it means,” he said, “is that you can choose the shoe you like most and that feels the best.”

The study was supported by the Naval Health Research Center. The investigators report that they had no conflicts of interest in this study.

SOURCE: The American Journal of Sports Medicine, published online June 24, 2010.