July 8, 2010

Custom Shoes May Not Help Prevent Injuries

A new study suggests that wearing sneakers tailored to your foot shape might not help protect you against injuries.

New Balance, which was the shoe company used in the study, helps runners choose the best shoe for them by determining their foot shape 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 depending on how their feet roll and distribute their weight when they hit the ground.

Overpronators have feet that roll too far inward on each stride, while the feet of underpronators do not roll enough.  Shoes are marketed under the assumption that by making some adjustments, runners can improve their mechanics and thus prevent injury.

Taking a flat footprint and examining how much of the foot is in contact with the ground when the runner is standing still is how pronation is measured.  Marine Corps who were recruited to wear the sneakers 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 who led the study, had the 1,400 Marine Corps feet analyzed and randomly assigned to one of two groups.

One group got a running shoe that was marketed for their type of pronation.  The 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 that were in the other group got assigned stability shoes, regardless of their foot shape and pronation.  The recruits then trained for 12 weeks, wearing their assigned shoes and altering them with combat boots.

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

The study team measured injuries and found that there was little difference in how often members of the two groups got injured.  This was true for both men and women.

About 42 percent of men assigned custom fitted shoes and 41 percent of men in the stability shoe group got injured over the 12-weeks training period.  About 37 percent of women in custom fitted shoes and about 45 percent in stability shoes were injured regardless of their foot type.

The study was reported in The American Journal of Sports Medicine.

The findings are aligned with similar studies that the investigators have done with Army and Air Force recruits.  There still was no significant difference in injury rates based on shoe assignments when the researchers combined data from the three studies.

Dr. Joseph Hamill, an exercise scientist at the University of Massachusetts at Amherst, told Reuters that one explanation of the findings is that the footprint technique for assigning running shoes does not 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.

Runners would need to be monitored on a treadmill in order to do a more thorough analysis.  However, that is not always feasible and Jones said it is not clear that technique would be more helpful.

"There's no evidence that dynamic measurements make a difference either," he told Reuters. He also said that this could be because people with different foot shapes actually get injured at similar rates to begin with.

Jones said that the message to runners is not to focus too much on motion control, cushion and labels. 

"What it means," he said, "is that you can choose the shoe you like most and that feels the best."

The Naval Health Research Center supported the study.  The investigators reported that they had no conflicts of interest during the study.


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