Irene Davis is a professor of physical therapy and head of the Running Injury Clinic at the University of Delaware. She is one of the world’s leading experts on running biomechanics and injury. She is also a barefoot running advocate, and perhaps the most credible barefoot running advocate on the planet.
I’ve consulted Dr. Davis as an expert source in my writing for many years and I have the greatest respect for her work. Recently she emailed me to contest a statement critical of barefoot running that I made in an article that was referenced in a piece by Ross Tucker on the Science of Sport blog. This exchange led to the following interview.
Matt Fitzgerald: Explain the kind of research you do.
Irene Davis: The focus of our research has been the relationship between lower extremity mechanics and injury. In the first part of my career I was really trying to establish and identify these mechanisms, and then in the past 10 years or so we’ve been working on developing protocols to alter people’s gait patterns so we can reduce those mechanics that we’ve found to be associated with injury. And most recently we’ve been studying the effect of strike patterns and minimal footwear on loading in runners.
You did not start off as any kind of barefoot running advocate. How did you become one?
I started out doing work in orthotics and footwear and motion control shoes and cushioning shoes. When I think about it now, it really wasn’t in sync with my philosophy of treatment, which is to try and get people to their optimal level of function with a minimum amount of support. So, for example, when I was starting out as a young PT I was working at a rehab center with spinal cord patients and working to try to minimize the amount of equipment people needed (low backs on their wheelchairs and so forth). It was just my philosophy. If I was going to give someone a lower extremity orthosis, I was going to try and give them the least support so that they had to really utilize their neuromuscular control.
But that philosophy sort of went out the window when I went down the road of providing foot orthotics to people who had foot-related problems. I think it’s just part of your training: If people have plantar fasciitis you need to put something in there to support the arch.
And then came the Nike Free. It was Chris McDougall back in 2005 who came to me and said, “Hey, Dr. Davis, what do you think of this?” I really hadn’t thought much about minimal footwear. I can remember when the Robbins paper came out because I was at Penn State at the time doing my PhD and I didn’t think a lot of it. It was barefoot running and it was kind of interesting but it never really impacted the way I thought. So when [Chris] asked me that question I started to think maybe less really is more. I asked, why do we treat our foot any different than any other part of our body? I mean, if you have a shoulder problem, Matt, I’m not going to put you in a sling for the rest of your life. I might put you in a sling to support the structure until it heals but then I’m going to wean you off of it. It’s like that for every other part of the body. If you have a back injury we might put you in a back brace. But if I keep you in a back brace, yes, I’m going to support those muscles so they don’t have to do the work, but those muscles are going to get weaker, so you’re probably going to be more susceptible to injury.
So that’s really what gave me pause about how we approach treating injury to the foot. That was part of it. The other part was that, starting around 2000, we started down this path of looking at the relationship between impacts and injury. What we found was that the folks who had a history of stress fractures had higher impacts when they landed. You know what the vertical ground reaction force looks like, right? You get that impact peak and then you have the second peak, which is higher. It kind of looks like a mitten, with the thumb being the first part. That peak force, which is about three times your body weight, did not distinguish between who got injured and who did not. But the impact peak—that impact force that happens early on—did. The characteristics of that impact were the magnitude of that peak, the rate of loading of that force (or how the steep the slope of rise to that peak was), and peak tibial shock, which happens at just about the same time. So we found that both retrospectively and prospectively—and prospectively is obviously a lot more compelling—that this impact was related to injury.
And then Born to Run comes out, and it just makes you think. I’m not one who thinks the running shoe industry is an evil empire. But they are just making shoes beefier and beefier and injury rates are not reducing. That’s pretty clear. Whether they were increased as a result of shoes—we don’t have that data, and we’ll never be able to get that data from back then, because we weren’t collecting it. But it really started me thinking, wow, maybe shoes are causing a problem. And then if you look at barefooters, they don’t land on their heel. And you don’t land on your heel because it hurts. And if it hurts, it’s very clear to me that Mother Nature, evolution—whoever you want to have responsible for that—didn’t intend for us to land on our heels when we run. Because if it did, we would do it barefoot. That’s how we came into the world. We spent much more of our time [as a species] on earth barefoot. And I do believe that we evolved to run. I believe that hypothesis, and I know it’s just a hypothesis.
I now believe—and we have some very strong prospective data that we’re going to be publishing soon—that suggests that the high impact force associated with heel striking relates to the development of an injury later on. And we’ve grouped all injuries. It has strengthened my conviction that we invented the heel strike in running and that it’s one major contributing factor to the development of running injuries.
What will it take to settle the question of what runners should do with respect to footwear?
Obviously, we need a lot more evidence. We need evidence that running barefoot results in less injuries than running barefoot, and I don’t think we have that. We have a lot of anecdotal evidence. On the other side of it we need evidence that shoes don’t prevent injuries. We need prospective studies comparing injury rates in barefoot and shod runners. My hypothesis is we’ll see some plantar fasciitis and some posterior calf injuries and maybe even some stress fractures [in barefoot runners] resulting from the training, because people do too much too soon. We may find that people cut their foot more. I never cut my feet. I have blistered my foot on the hot pavement. So we might see different kinds of injuries.
What about performance?
We need studies to see whether running without shoes influences performance. I can tell you that when you take shoes off, it decreases the mass and that’s been shown to reduce the energy cost of running. So I think that can have a beneficial effect.
I have runners who have run personal bests in bare feet. I have a kid who went through four years of compartment syndrome in high school. He had compartment syndrome in all four compartments of both legs. Eight fasciotomies. Three pair of orthotics. Motion control shoes. Cushioning shoes. He had so much pressure in the anterior compartment that it cut off the nerve so the nerve couldn’t transmit the signal and the dorsiflexors couldn’t keep the foot up, so he was running with foot drop. He was recruited by Delaware, but he couldn’t get through the season. Last November he was completely despondent. Someone suggested he try the Vibrams. That was in November. In April he won the Delaware Marathon [Editor’s Note: Mike Wardian won the 2010 Delaware Marathon. Mike is not the runner Dr. Davis refers to. Thanks to Mike Monagle of the Delaware Running Company for this correction]. And he just did a distance medley relay—he ran the last leg, the 1600, in 4:32, his personal best, completely barefoot.
I know it’s a testimonial, but what it tells me is that it’s possible to compete [barefoot] as well or better than you did in shoes.[sgi:MattFitzgerald]
Check out Matt’s new book: RUN: The Mind-Body Method of Running by Feel.