A new study was published in the British Journal of Sports Medicine looking at injury risk in runners using minimalist footwear. I saw one podiatrist exclaim online that this study represented the “end of the minimalist shoe fad”. I find it hard to understand why there is such a push from healthcare professionals to label light, flexible shoes a fad. A very sound argument can be made for why minimalist shoes are better than traditional running shoes. It may take some time for this to be shown in research, for reasons I will touch on later in this post, but first let us look at the somewhat misleading abstract of this present study:
Examining injury risk and pain perception in runners using minimalist footwear
Br J Sports Med; Published Online First 19 December 2013
Background: This study examines the effect of progressive increases in footwear minimalism on injury incidence and pain perception in recreational runners.
Methods: One hundred and three runners with neutral or mild pronation were randomly assigned a neutral (Nike Pegasus 28), partial minimalist (Nike Free 3.0 V2) or full minimalist shoe (Vibram 5-Finger Bikila). Runners underwent baseline testing to record training and injury history, as well as selected anthropometric measurements, before starting a 12-week training programme in preparation for a 10 km event. Outcome measures included number of injury events, Foot and Ankle Disability (FADI) scores and visual analogue scale pain rating scales for regional and overall pain with running.
Results: 99 runners were included in final analysis with 23 injuries reported; the neutral shoe reporting the fewest injuries (4) and the partial minimalist shoe (12) the most. The partial minimalist shoe reported a significantly higher rate of injury incidence throughout the 12-week period. Runners in the full minimalist group reported greater shin and calf pain.
Conclusions: Running in minimalist footwear appears to increase the likelihood of experiencing an injury, with full minimalist designs specifically increasing pain at the shin and calf. Clinicians should exercise caution when recommending minimalist footwear to runners otherwise new to this footwear category who are preparing for a 10 km event.
The conclusion states that “minimalist footwear appears to increase the likelihood of experiencing an injury”. Looking a little closer we see this is not the case. The study actually had two minimalist shoe groups that they labeled partial and full. The partial minimalist group ran in the Nike Free 3.0. The full minimalist group ran in Vibram 5-Finger Bikilas.
It was the partial minimalist group (Nike Free 3.0) that had the significantly higher rate of injury. There was not a significant difference in the rate of injury between the neutral shoe group and the full minimalist group. So the conclusion should more accurately state that “running in partial minimalist footwear increased the rate of injury, but running in full minimalist shoes did not increase the rate of injury”.
To be even more accurate, the study should say that runners using the Nike Free 3.0 had a higher rate of injury than runners in the Nike Pegasus. You can not declare that partial minimalist shoes (plural) increase the risk of injury when only studying one model. That would be like saying driving luxury cars increases the risk of your engine catching on fire, but then only studying people driving Jaguars XF’s.
The Nike Free has some minimalist features, like a 4mm drop and a flexible sole. But it also has cushioning and some arch support similar to traditional neutral shoes. If minimalist shoes really caused injuries, wouldn’t it make sense that the most minimalist shoe in the study would cause the most injuries? That’s not what the researchers found.
The runners using the Vibrams, which are more of a true minimalist shoe than the Nike Frees, did not have significantly more injuries. The authors could have just as likely concluded that running in minimalist shoes does not increase the likelihood of injury, but they didn’t. The reason they didn’t may have something to do with the Vibram group reporting significantly greater calf and shin pain after the 12 weeks.
Anyone who has transitioned from bulky traditional running shoes to minimalist shoes knows that it takes time to build up calf strength and flexibility. Less supportive, zero-drop shoes require you to use your calf muscles to a greater extent than traditional raised-heel shoes. The study did not find any difference between the groups for pain level in other areas of the body they looked at (foot/ankle, low back, pelvis/groin, knee).
There is certainly some calf soreness that comes a long with transitioning to less cushioned and supportive shoes, just as there is soreness anytime you exercise a muscle group that hasn’t been used in a while. I consider this one of the benefits of running in minimalist shoes, the transfer of stress from the knee to the calf muscles and Achilles tendon.
The abstract didn’t report what types of shoes the runners were using prior to taking part in the study, but my guess is that most were in traditional running shoes. Cushioned, raised-heel shoes with support features make up the overwhelming majority of the running shoe market. It has been shown before that wearing traditional shoes changes the way people run. Runners who are adapted to using traditional shoes need time, often several months or longer, to condition themselves to run without the cushioned heels and support. Sometimes gait training is necessary to undo the motor patterns learned from wearing traditional shoes. The study only allowed the runners one week to adjust to the shoes they were given. I am willing to bet the outcome of this study would have looked very different with a group of runners already running in minimalist shoes.
To use another car analogy, imagine a study was done where researchers switched the positions of the gas and brake pedal and then studied who had more accidents, the drivers in the traditional cars or drivers in cars with the pedals switched. The study would probably find that driving with the gas pedal on the left caused more accidents. But it would be wrong to conclude that having the gas pedal on the left is dangerous. It is only dangerous because people are accustomed to having the accelerator on the right.
Same goes for shoes. If people didn’t start running in raised-heel, cushioned shoes then running in minimalist shoes would never be an issue. Remember, there is no scientific reason why traditional shoes are designed the way that they are. Only tradition. But because traditional shoes are so widely used, the effects caused from running in them over time need to be taken into account when conducting a study like this. To examine what the true difference in injury rates is, we would need to compare runners who have grown up using traditional shoes to runners who have grown up wearing minimalist shoes. Since minimalist shoes have only gained popularity in the last several years (and still only make up only a small fraction of the shoes on the market) it may be a while before large studies like this are possible.