It's been a rather frantic week, and I know there is a series on weight hanging in between Part 3 and Part 4. I'm hoping to get to that next week, when hopefully I'll have a little more time!
But today, I have to comment on this latest study, which I know will become bigger in the coming days - it is a new study that will reignite the barefoot vs. shoe debate, one of the more controversial issues in running.
I am actually planning a whole series on this topic, because I was recently interviewed by a Dutch Running magazine, Run2Day, and I'm going to post that entire interview (with additions) on the site at some point in February.
The scientists took five group of runners and had them run both barefoot and in shoes. The groups were: Habitually shod adults in the USA, Recently shod adults in Kenya, Habitually barefoot adults in the USA, Barefoot adolescents in Kenya, and Shod adolescents in Kenya.
Each group ran in shoes and barefoot and they measured foot-strike pattern (whether the runner lands on the heel, midfoot or forefoot) and kinematic and kinetic variables like impact force, loading rate, and joint angles.
The findings - a shift in landing, a reduction in force
It turns out that people who run barefoot, even when shifting from shoes to the barefoot condition (the habitually shod groups), shift the landing point to the forefoot. There's nothing new there - it's been known for many years that running barefoot changes the footstrike. Hundreds of studies exist to show this. The next difference is the ankle angle - the barefoot runner has a more plantarflexed ankle when they land - what this means is that the toe is pointed away from the body more (compared to dorsiflexion, when you pull it back towards you at the ankle). Again, hundreds of studies have shown this.
Next are the impact forces. Here's where there is some disagreement. Previous studies have occasionally disagreed on how barefoot running affects impact forces - some say it actually increases them, with high variability between individuals. Most suggest a reduction, particularly early on during impact (first impact). The Nature study has found that being barefoot AND landing on the forefoot reduces both the loading rate and the peak impact force. In fact, it's three times lower in barefoot runners who forefoot strike (which is most of them) than in heel strikers wearing shoes. In theory (though this too is disputed), higher impact forces and loading rates equals greater injury risk, and so the study is suggesting that perhaps people who are barefoot or minimally shod have a better chance of avoiding injury.
And here is where it gets tricky. I must point out that the title of the paper is Foot strike patterns and collision forces in habitually barefoot versus shod runners. I highlight the word "habitually", because it's quite important to appreciate the impact that this word may have on how you apply this finding.
I guarantee that the media are going to be all over this and they are going to tell you that you should be running barefoot or in Vibrams. You will hear how science has proven that being barefoot will prevent injuries, and that those of you who are injured should blame your shoes as you lob them into the garbage bin.
None of these suggestions is true, yet. And Dan Lieberman who headed up this latest study would not even be suggesting this himself. The final sentence in the paper in fact reads "controlled prospective studies are needed to test the hypothesis that individuals who do not predominantly RFS either barefoot or in minimal footwear, as the foot apparently evolved to do, have reduced injury rates" (good science always recognizes what it DOESN'T say, and Lieberman and co fit this category).
What the Nature study hasn't measured is the long term (or even the short term) effects of the change on loading rates on different joints. If you wish to guarantee yourself an injury, then go out for a 2km run barefoot on a hard surface, and you will be asking your calf muscles and Achilles tendons to do work that for perhaps 30 years, they haven't had to do.
And I will illustrate this with our own insight into footstrike and injury. When the Pose research was done in Cape Town, athletes basically had their footstrike patterns changed through 2 weeks of training in the new method. The biomechanical analysis found lower impact forces (sound familiar? Same as the Nature paper), and even less work on the knee joint. This was hailed as a breakthrough against running injuries, because lower impact plus lower work on the knee meant less chance of injury. Jump ahead 2 weeks, and 19 out of 20 runners had broken down injured. Why? Because their calves and ankles were murdered by the sudden change. And the science showed this - the work on the ANKLE was significantly INCREASED during the forefoot landing.
The point is, changing how you run, whether by technique training or a change in shoes (like running barefoot) will load muscles that may be very weak, and joints and tendons well beyond their means. If however, you are a habitually barefoot runner, then you can do this, because your body has been prepared for it. For everyone else, I think we may be underestimating the time it will take to transition successfully to barefoot running (or forefoot striking, if you're going to force that change 'unnaturally').
And there is my point - taking this kind of interesting study, and dispensing advice, is a risky business. As a friend pointed out yesterday - the media's interpretation of this study will be a "stimulus plan for physical therapists and podiatrists". Going from years of shoes into minimal shoes or barefoot will injure you if you are not careful.
The Nature study provides a good discussion point. It's intriguing, and certainly does suggest advantages to barefoot running. It is not the last word, but rather the latest word in this debate. Nor is it revolutionary, because for many years, we've known that being barefoot changes ankle angle on impact, footstrike and loading rates (though quite how they change is not agreed upon).
I'm sure a lot more will be written - I'll even cover some of it when I do that interview series on this topic in the coming weeks. For now, that's the last I'll say on this particular issue, but debate is always welcome!
P.S. Daniel Lieberman has launched a website on this topic, and it's well worth a look. It is obviously based on his research (this study forms the bulk of it), but it's a good, clear explanation of the concepts. Again, the same word of caution applies - don't jump from one to the other. If there is one section of that website that you should read over and over, it is the Training tips section. Most will not, and they'll become the statistics (and the stimulus for physical therapy), but if you manage it right, then the site will be a great help to you!