The Scientific Case Against Vibram's FiveFinger Running Shoe

Last week's class-action settlement by Vibram, an Italian footwear manufacturer known for making silly-looking lightweight running shoes, recalls the recent case against Sketchers, a company that agreed to pay out $40 million after falsely claiming that walking in its product would give you Kim Kardashian's bootie. The difference between the two cases, as much as there is one, appears to be the readiness with which we, the public, consume the scienceish PR from running shoe companies. So let's take a look at the actual science that was on trial.

To recap, the suit against Vibram's FiveFinger line of minimalist running shoe was filed by Valerie Bezdek in March of 2012. She claimed the company deceived customers by advertising that its shoe could reduce foot injuries and strengthen foot muscles, without basing those assertions on any scientific evidence. After some legal haggling, Vibram decided to settle with Bezdek and others from California and Illinois who joined in the class-action suit. As part of the settlement, the company agreed to refund up to $94 per pair of shoes and to deposit $3.75 million into an escrow account to be distributed among those who purchased a pair of Vibram FiveFingers between March 21, 2009 and the settlement.1

This seems like a victory for the little guy—for all of those who were duped into believing that a ridiculous toe shoe could reduce running injuries—but in truth, Vibram only settled to minimize the public relations damage and to avoid any additional legal expenses, and has given the standard denial of wrongdoing that goes along with most of these settlements.

So what's the deal? Was the company lying about its product? Or was there some evidence to suggest that the FiveFinger could really prevent injury? As it turns out, there are just a handful of peer-reviewed studies examining the company's claims, and the results paint a mixed picture.

Barefoot running has been around for centuries, but it has enjoyed a renewed popularity the past few years. Part of that has to do with Born to Run, Christopher McDougall's book about Tarahumara Indians who figured out how to run hundreds of miles without rest or injury within Mexico's Copper Canyons. (Spoiler: They don't wear Asics). A number of scientific papers support the claim that going barefoot is healthy and natural and that running shoes are not only unnecessary but also potentially dangerous. For most of us, running barefoot isn't practical—I see plenty of glass, nails, and needles on the ground when I jog in Manhattan—so a company called Vibram created an extremely lightweight shoe called FiveFingers that was supposed to mimic the barefoot experience while providing a thin layer of protection.2 Seems reasonable, right?

The first small study to formally examine the claims made by Vibram was released in 2009, and looked at how the shoe affected eight experienced barefoot runners. Each participant was given a pair of the Vibram FiveFingers and instructed to run for six minutes at 12km/hr on a specially calibrated treadmill that could measure stride length and frequency, foot pressure distribution, and a host of other variables relating to the foot-ground interface. The runners then performed the same experiment barefoot and then again with a conventional running shoe.

The researchers concluded that the FiveFingers model was effective in imitating the barefoot conditions while providing a small amount of protection. The study was tiny—just eight participants—and only examined experienced barefoot runners, but it reaffirmed conventional wisdom about the shoe: It was like running barefoot, but safer.

Two years later, another study using the same type of calibrated treadmill compared the FiveFinger to a conventional running shoe in fourteen experienced male runners. The study found that compared to the Vibram product, cushioned running shoes impair something called ankle proprioception which, generally speaking, is how the body senses the position of the ankle joint. (This is obviously important for runners.) Again, the study was small and not particularly generalizable to the average consumer because it just looked at experienced runners, but it suggested that FiveFingers might be superior to that old pair of Reeboks in your closet and there was no indication that Vibram was intentionally misleading customers.

Things took a turn, however, when more researchers began to investigate whether the FiveFinger could actually prevent or limit injury as the company claimed. In a 2013 study, 36 experienced recreational runners underwent magnetic resonance imaging (MRI) before and after a 10-week trial of running. Seventeen subjects were in the control group (they ran in their traditional shoes), while the other 19 were in the experimental group (gradually transitioning to the Vibram FiveFinger). Using MRI, the severity of bone marrow edema—fluid that accumulates after inflammation or injury—was scored on a range of 0–4 for all of the runners (0 = no bone marrow edema, 4 = edema in more than 50% of the length of the bone, which represented a stress fracture).

MRI scores revealed that subjects in the Vibram group had more bone marrow edema (a proxy for injury) after 10 weeks of running than those in the control group. Researchers ultimately concluded that runners transitioning to the Vibram FiveFingers needed to do so very slowly to avoid potential stress injury in the foot. It wasn't a devastating result, just an indication that the FiveFinger wasn't a panacea for all runners.

But things got worse from there. A few months later, in December 2013, a larger study of 99 recreational joggers preparing for a 10k found running in the Vibram FiveFinger shoe increased the likelihood of experiencing an injury, specifically increasing pain at the shin and calf when compared to a neutral shoe like the Nike Pegasus 28 or the partially minimalist Nike Free 3.0 V2. Clinicians like me were instructed to exercise great caution when recommending minimalist footwear to runners who were otherwise new to it.

It appears that study—which contradicted everything about Vibram's marketing campaign—made winning the class-action lawsuit difficult for the company. While there's no doubt that many have enjoyed great success with the FiveFinger running shoe, the company could no longer claim that it's product reliably reduced running injuries. They could've commissioned more studies to continue the fight in court, but clearly the costs of doing so were outweighed by the benefits of settling. So people who like the shoe will continue to use it; those who don't can get their money back.

As for the utility of other minimalist running shoes, it appears that the jury is still out. A study published last month shows that barefoot inspired footwear may reduce the incidence of knee injuries, but the shoes do so by putting more stress on the Achilles tendon. Other studies muddy the picture even further, presenting some evidence of the benefits for certain types of runners. So while it might be satisfying to say that Vibram and other minimalist shoe companies lied to consumers, it's probably not that simple. There are studies that show the benefits of running barefoot as well as studies that show the pitfalls and the truth — whether the shoe is actually good for you — will vary from person to person.

We'd like to know: Have you tried a minimalist running shoe? Or barefoot running? If you own a pair of FiveFingers, do you plan to return them? Tell us about your experiences.

Matt McCarthy is board-certified in internal medicine. You can follow him on Twitter here.

Image by Jim Cooke


1 Most claimants can expect to get between $20 and $50 per pair.

2The shoe was originally marketed to yacht racers to maintain grip on slippery decks without compromising the barefoot experience