Unless you’ve been living under a rock the past few years, you’ve probably caught wind of the barefoot running movement.

Spearheaded mostly by Christopher McDougal’s best seller Born to Run (affiliate link), and aided by an army of internet evangelists, the barefoot running movement holds, broadly speaking, that running without shoes will strengthen your feet, encourage proper running form, reduce running injuries, and improve performance.

These are fairly bold and extensive claims, and to address all of them at once would require a lengthy article. So, this week’s article will be focused on the question of arch and foot strength: is there any evidence that barefoot running strengthens the feet? And if so, will this prevent injury?

The research on barefoot running and foot strength

Despite the popularity of the barefoot running movement, there have been relatively few studies on most of the claims made by its proponents. It’s been well established that running without shoes encourages a flatter foot strike at the ground, and that people who run barefoot are more likely to be forefoot strikers. But beyond that, the data is scarce.

Foot strength in minimal shoes

While there are no studies on whether barefoot activity increases foot strength, there is one study on just that subject using a type of minimal shoe—the Nike Free (affiliate link).

As you may know, the Free is an odd shoe with deep grooves running the length and width of the shoe to make the midsole very flexible. So, while the shoe itself is a solid half or three-quarters of an inch thick, it’s quite easy to fold and twist the sole of the shoe, the idea being that this is supposed to be similar to not wearing any shoes at all.

In a surprisingly well-designed study presented at a 2005 scientific conference, 50 athletes were split into two groups for a five month training program, one which received a Nike Free shoe, while the other was given a traditional training shoe. Both groups used these shoes only for their warm-ups before their main workouts, not full-time. Strength measurements of the various muscles in and around the foot were taken before and after the five-month training period.

The group which received the minimal shoes demonstrated significant gains in strength both in the “intrinsic” muscles underneath the arch, and the “extrinsic” muscles along the lower leg which control the foot and ankle.

Since only some muscles were strengthened relative to the control group, the authors hypothesized that the gains in strength were related to the minimal footwear, which increased the demands on the tendons and muscles in specific areas of the lower leg and foot which had more mobility due to the flexible sole.

Now, this study didn’t examine barefoot running at all. But it isn’t too much of a stretch to hypothesize that barefoot activity would result in the same types of gains in muscular strength, given that the most salient difference between the Free and a traditional shoe is its flexibility. But even if we grant ourselves this stretch of reasoning, we still have to figure out whether these gains in muscular strength would be beneficial.

The importance of intrinsic foot muscles

Again, the experimental evidence is sparse. But I did uncover a pair of very interesting studies which appear to demonstrate the importance of the intrinsic foot muscles.

The first, published in 2008 by Donella Headlee and colleagues at the University of Virginia, connected fatigued intrinsic foot muscles with an increase in pronation.

Using 21 healthy adults, the researchers measured the navicular drop—a proxy measurement for how much your foot pronates during weight-bearing—in the feet of the volunteers before and after a demanding set of exercises for the toe flexor muscles on a custom weight machine. Using high-tech equipment to measure the signal sent to the foot muscles, they demonstrated that the exercises did indeed tire out the intrinsic foot muscles. When their navicular drop was measured again, the researchers found that it increased by about 2 millimeters: a small but statistically significant result. What this demonstrates is that the arch is not a static structure: it’s supported by the intrinsic foot muscles, especially while weight-bearing.

This finding is bolstered by another study, published this January by a group of researchers led by Luke Kelly in Doha, Qatar. Kelly et al. investigated the extent to which the body relies on the intrinsic foot muscles for balance and stability when standing on one leg.5 Using electromyography, a technique that measures the electrical activity in muscles, the researchers demonstrated that transitioning from standing on two legs to one brings about a large jump in muscle activity in the foot. These muscles contract even harder to bring the body back into balance when its center of gravity drifts to one side of another.

Final thoughts and recommendations based on the research

While these three studies are helpful, and do seem to indicate that the intrinsic foot muscles play a role in arch integrity and stability, it’s still a stretch to apply these universally to barefoot running, as there are plenty of holes in our understanding and possible problems with these studies.

The first study, for example, despite being quite well-designed, was funded by Nike, which might cast some doubt in the impartiality of the results. And the second two studies look at fairly mundane tasks, not long or fast running.

It is likely that running barefoot, or in any minimal shoe, will increase the strength of your intrinsic foot muscles. But it’s uncertain as to whether this increase in strength will translate to any performance or injury-avoidance gains.

Are the intrinsic foot muscles in a normal runner strong enough to maintain balance and arch integrity while training? Does strengthening these muscles with barefoot or minimalist training reduce injury risk? If so, what amount of training is needed, and how much is too much? These are all big questions that remain unanswered.

In the meantime, however, if you want to try out barefoot running or want to start using a minimalist shoe, I recommend two protocols:

Start with a specific series of lower leg, hip, and foot strengthening exercises. These exercises will help develop a strong foundation and increase your flexibility and proprioception. If you’ve been accustomed to wearing traditional shoes, with lots of support, cushioning, and a higher heel you’re entire life, the reeducation and strengthening process is essential to transitioning to a minimal shoe without getting injured.

Introduce minimalist or barefoot running like the athletes in the Nike Free study: Go barefoot or minimalist for your warm-up or cool-down for your workouts, or tack on 10-15min at the end of a run a few times a week. Doing this should lead to the same types of strength gains as the subjects in Brüggemann et al., without some of the troubling injuries and tissue strains endured by people who jump into wearing minimalist or no shoes full-time. That’s how 2:39 marathoner Jason Fitzgerald incorporates barefoot running into his training. Learn more about why and how Jason does this in the podcast he did with us.

Listen to our in-depth podcast with minimalist running expert Dr. Mark Cucuzella. We talk about the benefits of minimalist running as well as how it helped Dr. Cucuzella go from being told he couldn’t run anymore to running under 2:40 for a marathon 24 of the last 25 years!

If you are convinced, check out this fantastic barefoot running shoes resource.