On the left is the average number of muskuloskeletal injuries per runner. The asterisk indicates that there’s statistically significant difference between the two groups, with the shod group suffering more injuries. That’s the headline result – but there’s an extremely important caveat. On the right, the number of injuries per 1,000 miles is shown, and in this case there’s no statistically significant difference between the two (though the barefoot group has a higher average).
That’s because the shod group ran nearly twice as much (40 kilometres per week) as the barefoot group (23 kilometres per week) throughout the study. To be fair, the authors make this point clear in their paper. But given this enormous difference, it’s puzzling to me that they even bother to list the first “main finding” of their paper as “Significantly fewer muskoskeletal injuries were reported in barefoot runners than in shod runners.” To me, this is an utterly meaningless comparison given the huge difference in weekly mileage.
The only way the comparison has any relevance is if they’re arguing that barefoot running reduces injuries by preventing you from running as much as you’d like. That’s not a completely crazy point. When they looked at non-muskuloskeletal injuries on the plantar side of the foot (i.e. the sole), such as blisters, cuts, bruises, and stubbed toes, they found a total of eight such injuries in the shod group and 57 in the barefoot group. It’s not surprising, but it’s worth acknowledging.
In terms of the usual running injuries, there were a few apparent differences between the two groups: the shod group had more plantar fasciitis, while the barefoot group had more Achilles tendinitis, for example. But given the small numbers, it’s hard to read too much into these subcategories.
I’m surprised at the results, to be honest. They recruited their subjects from “online forums and running groups” around the world (they don’t specify which ones, but mention in the intro that there are 93 chapters of the Barefoot Runners Society in 23 countries). Given that barefoot runners tend to be more enthusiastic and evangelical about their footwear choices, I’d have guessed there would be a risk that you’d end up with a committed barefoot group who might be tempted to downplay their injury self-reports. On the other hand, maybe I’m underestimating the enthusiasm of the shoe-wearers of the world!
In the end, it’s a useful data set, and hopefully a starting point for future studies. The bottom line: the idea that switching to barefoot (or minimalist: the barefoot group ran about 25 percent of their miles in “true minimalist shoes”) will automatically reduce your risk of injury remains unproven for now.