Dr. Daniel Lieberman of Harvard is well-known for his studies of barefoot running, and I’ve discussed that before. He and his colleagues have a new study out, Foot Strike and Injury Rates in Endurance Runners: a retrospective study, in Medicine and Science in Sports and Exercise. (The lead author is Adam Daoud.)
It is not a barefoot running study, but does address some of the issues related to barefoot running.
What the study did was look at injury rates for runners who run with a rear-foot strike (RFS) versus a front-foot strike (FFS). These were competitive runners on the Harvard Cross Country team. None of them ran barefoot; the study only looked at the effect of how they regularly landed when running. However, we all know that barefoot runners almost exclusively use a front-foot landing (they don’t strike, because they feel what is going on), so this is relevant to barefoot running.
These runners have to be considered elite runners. They push their bodies way farther than most of us, most likely training both longer and harder (particularly harder). In this study, 74% of the 52 runners were injured at one point or another. The study had 36 rear-foot strikers and 16 front-foot strikers.
What the study found out was that rear-foot strikers had approximately twice the injury rate for repetitive stress injuries as front-foot strikers. The study also looked at what they called “traumatic injuries” and found no difference in the injury rates.
There were a lot of injuries: 67 traumatic injuries and 181 repetitive stress injuries. It wasn’t really clear to me just what they considered “traumatic injuries” (or quite how strike pattern wouldn’t matter). Traumatic injuries are defined as injuries that come from outside one’s body, rather than from inside. That is, it is injury coming from an external blow of some sort.
Here’s the list of what they considered traumatic injuries: Traumatic muscle strain, Traumatic joint sprain. That’s it. I get what a typical traumatic joint sprain might be: a sprained ankle. For traumatic muscle strain: pulling a muscle? Anyways, how you land does not seem to affect these injury rates.
The list of repetitive stress injuries is long and detailed. Here it is (scary, isn’t it?): Tibial stress injury – MTSS, Knee pain, Repetitive muscle strain, Iliotibial band syndrome, Tendinopathy – Achilles, Plantar fasciitis, Stress fracture – metatarsal, Foot Pain, Hip pain, Lower back pain, Stress fracture – femur, Stress fracture – tibia, Thigh pain, Tendinopathy – peroneal, Repetitive joint sprain, Tendinopathy – tibialis anterior, Stress fracture – sacrum, Cartilage damage – labrum, Stress fracture – fibula, Tibial stress injury – stress reaction, Tendinopathy – tibialis posterior.
On that list, the main injuries were the following: medial tibial stress syndrome (shin splints), iliotibial band syndrome (the pain on the outside of the knee), patellofemoral pain syndrome (the pain on the front of the knee), and Achilles tendinopathies (pain at the Achilles tendon).
Another interesting finding of the study was that they expected to find certain injuries specific to a front-foot strike. These included things like metatarsal fractures, Achilles tendonitis, and general foot pain. They did not find that—injury rates for those were about the same for both RFS and FFS runners (though, as I look at the numbers, we’re getting into pretty low statistics at this point).
How does this apply to barefoot running? First of all, it does seem to show that the fore-foot landing that you have to use when barefoot really does have an advantage (yea evolution!). However, it does not address some of the other advantages that barefoot runners tout. For instance, one of the most important part of barefoot running (and here I really do mean real barefoot running) is the importance of feedback from the soles. Again, this study did not look at that at all. Barefoot running is about more than just good form.
The authors of the study do present a number of caveats to the study that I want to highlight.
This study, like most injury studies, has limitations and we caution against extrapolating the above results to assuming that all runners are necessarily less likely to be injured if they FFS. For one, the population of subjects studied here, collegiate runners, are not representative of many amateur runners, but instead are highly competitive and motivated, frequently train at high intensity in terms of distance and speed, and are perhaps more likely to ignore injuries in their early stages––factors that may help account for the high rate of injury. These differences, however, may be useful for studying the causes of injury because the training intensity of the subjects studied likely amplifies injury rates. If RFS runners on a college cross country team who run approximately 40 miles a week at speeds of approximately 3.0 to 4.5 m/s for women and 3.5 to 5.0 m/s for men are roughly twice as likely to get a moderate or severe injury than FFS runners, then it is possible that runners who train less intensely have lower rates of injury but with similar differences in relative injury rates between FFS and RFS runners. This speculative hypothesis merits testing in other populations.
Another thing to keep in mind is that this was a retrospective study, not a randomized one. In a truly randomized study, two cohorts would have been identified and each person would have been assigned a strike pattern in advance. Then the data would have been collected. That is a better way to do studies, but I also suspect it would be well-nigh impossible to do for this sort of data. As the authors put it:
A final limitation of the study is that it is retrospective and not randomized. We do not know how and why subjects in this study became either RFS or FFS runners, and whether other factors related to injury predisposed them to adopt different running forms. Such explanations seem unlikely, but should be explored.
The authors also address the issue of transitioning from RFS to FFS. Here is what they say:
Another point to consider is that this study did not test for the effect of transitioning from RFS to FFS running, and it is unclear and unknown if runners who switch from RFS to FFS strikes will have lower injury rates. FFS running requires stronger calf muscles because eccentric or isometric contractions of the triceps surae are necessary to control ankle dorsiflexion at the beginning of stance, and shod FFS runners also generate higher joint moments in the ankle. Runners who transition to FFS running may be more likely to suffer from Achilles tendinopathies and calf muscle strains. FFS running also requires stronger foot muscles, so even though impact forces generated by FFS landings are low, runners who transition are perhaps more likely to experience forefoot pain or stress fractures. They may also experience plantar fasciitis if their foot muscles are weak. However, these injuries are treatable, and they may be preventable if runners transition, slowly, gradually, and with good overall form.
Many new barefoot (and minimalist) runners will be familiar with some of those symptoms. That is why it is so important to actually do it barefoot so that the sole quickly tells you when you are doing too much too soon (and even then Barefoot Running Exuberance Syndrome can take hold).
Finally, other folks (including Christopher McDougall) have also written about this study. You might be interesting in what they have to say. From Chris McDougall: Why is running form “controversial”? Because your pain is worth a lot of money. From Men’s Fitness: The First Scientific Support for Minimalist Running. From the New York Times Health blog: Does Foot Form Explain Running Injuries?
One thing is clear: Dr. Lieberman and his colleagues are continuing to do a good job of examining just what is going on in barefoot and minimalist running.