03 May 2010

Barefoot running: Part 2

Part two of Dr Ross Tucker's five-part series on the science behind barefoot running.

Part two of Dr Ross Tucker's five-part series on the science behind barefoot running. This is a topic that always inspires passionate responses from both sides of the aisle, so to speak, and generally, both sides of the debate dismiss the other argument out of hand. 

Q: The claims of barefoot ambassadors is that 'barefoot' running forces you to land more midfoot/forefoot, simply because it hurts to land on the heel.  This makes your step automatically shorter and keeps your knee bent when landing. Natural running proponents claim this way of running makes the runner less prone for injury. Would you agree that midfoot/forefoot landing, bended knees and shorter steps benefits the runners body? 

A: The changes in landing and kinematics (knee angle, ankle angle) when you shift from shod to barefoot running are pretty well established.

So the most noticeable change when you run barefoot is that you land further forward, your knee is bent, and also your ankle is more in what is called plantar-flexion – your foot and toes are pointed away from the body.

One of the consequences of these adjustments is that your stride is shortened, but this is at least partly made up for by an increase in stride rate.

This is easy to test for yourself – you can run 100m in shoes and without, and count the strides, feel the landing of your foot, and you’ll have confirmed the running science within 30 seconds!

There’s also evidence that the pattern of muscle activation – when different muscles are active during the stride – changes in the final few hundred milliseconds before your foot strikes the ground, and that’s because the brain, anticipating that there is no longer an air cushion or gel pad inside a soft heel, is going to do the job of ‘softening the landing’ for you. 

The body is remarkable this way, and this "natural" response to being barefoot is, I believe, one of the most compelling arguments for barefoot running.  The best study showing this cushioning response is
Lieberman et al's recent study in Nature, which we posted on previously, and is also summarized on their excellent website.

As for the second part of the question, whether it’s better to run this way, the full body of evidence does not exist, yet. 

What has been shown is that a shift in running technique can change the loading patterns, so that the eccentric loading on the knee is reduced when the forefoot/midfoot landing is used. 

In contrast, the ankle loading rises compared to heel striking.  This has important consequences, which we'll definitely discuss later on. 

Changing the loading pattern and the eccentric loads in particular will affect injury risk.

However, nobody has yet done the study that changes a runner's technique and then tracks them over many months, or years even, to see how their injury rates change. 

This would be a mighty difficult study to do – it would have to be very long-term, and control for a number of other factors (weight, running speed, training volume, training history, skeletal dimensions because there would be considerable individual variation between people, and so on – too many factors contribute to injury for there to be a keyhole study to find the answer). But the key is that nobody has really provided the evidence.

And in theory, the verdict could go either way.

Either you are an advocate for barefoot running, and you believe that the bent knee and forefoot landing is protective, and you cite studies that have found reduced impact forces when running barefoot, such as the recent work by Lieberman et al, which is really provocative and breaks through this argument for the first time.

Even here, the practical application of the research is not so simple – just because the impact force, particularly that initial impact, is reduced, does not mean that a habitually shod runner switching to barefoot running will reduce injury risk.

Or, on the other hand, you might choose to adopt the position that being barefoot simply changes the loading patterns, not the load, and that the extra work being done on the calf and tendons is worse for you.

You therefore decided that you need the stability provided by the shoes and that barefoot running will never work.

Note here that you don’t exactly have a lot of evidence to support this position either!  30 years of shoe research has not shown that shoes protect runners against injury. 

Neither side has this study.

But apart from all the scientific debate, and the discussion around whose evidence is stronger, what it means, there is a practical problem with making the change from shoes to barefoot running, and that’s what the marketers have overlooked.

This is my biggest word of caution in this whole debate. When you run barefoot, you are changing loading patterns and muscle activity considerably.

Your calf muscles and ankle joint, in particular, do  more work running barefoot than in shoes.

The same is true for newly-trained Pose runners incidentally – the loading on the ankle goes up while the loading on the knee decreases.

The problem is that the calf, Achilles tendon and ankle are not used to this and you pretty much guarantee injury.

This is why the scientists who are arguing the merits for barefoot running (Lieberman et al) are being so careful to encourage a prudent approach to barefoot (or Vibram) running.

Unfortunately, that prudent approach has not been shared by media or marketers, which is why they had to
issue a statement on the front page of their website after their paper in Nature. 

That statement is testament to the challenge faced by runners who switch to barefoot and it should be cold water on the hostility they often show towards anyone who dares to suggest that they are at risk.

This situation is much worse if you force the forefoot landing, which is what many people do when they read the marketing hype – they go out and force themselves to land on the forefoot, which is a recipe for disaster, because the only way they can achieve this is to point their toe down, by actively contracting the calf.

Suddenly, four times your body weight is being thrown onto a contracted calf muscle, and the only outcome is a very hurt soleus muscle, or worse.

So the short answer to your question is that if you’re not careful about how you run barefoot (or mid/forefoot, in the case of Pose), and how you teach your body to do it, you basically guarantee yourself an injury, which makes you worse off than running in shoes.

I think that people will under-appreciate how difficult the switch can be, and a lot of people will injure themselves because of misinterpreted science.

Out of 100 people to attempt barefoot running, I’d be surprised if 30 pull it off without some ‘trauma’, and I’d be willing to be that at least 30 pick up an injury that forces a long lay-off, maybe a return to shoes. 

Of course, 30 will succeed and be much better off, which may power the movement even more. 

You are far more likely to hear about the success stories than about the guy who damages his Achilles tendons in a week and abandons the plan. 

And well done to those who succeed - they've found a solution.  But to suggest that this solution will work for everyone may be making the same error that others have made before.  Quite what determines who succeeds, I don't know.

Q:  What about the act of shifting the pelvis as chi running proposes and the relationship to mid/forefoot landing?

A: This is the correct way to change the body position during running, and you see it in a number of athletes who run efficiently (and who have never heard of Pose or Chi, incidentally).

You simply cannot run when you are leaning backwards, with your weight behind you. So by getting your pelvis forward, you bring your body more into an effective running position, and one of the consequences is that your footstrike will move forward slightly, since your feet will be moving under your body, rather than reaching out for the landing on the heel.

But the key, again, is that you can’t control the landing cognitively, it is the consequence of otherwise good form.

And crucially, you can have this good form and still land on the heel! You cannot judge a runner’s efficiency by looking solely at their footstrike, and this is a problem I have with how the whole debate has been positioned.

The contact point of the foot is a consequence of numerous other factors, pelvis position being one of them. It’s not the diagnostic, or the fingerprint that identifies good vs. bad technique, and a lot of runners would be better off not worrying about the foot.

Q: The above is a health perspective on the advantages of running with a shorter stride and lending on the mid/forefoot. What do you think about the claim that the runner is faster in this way of running, due to the fact that it is a less energy consuming way of running (obviously speed over longer distances, we’re not talking sprint here)?

A: Same as for the injury aspect – there’s no evidence for this. The theoretical argument once again works both ways – there are some studies that suggest that landing on the heel produces the most efficient energy return and produces the lowest oxygen consumption for a given speed (which immediately contradicts the basis for the question). However, other studies have shown the opposite, which means your question is valid after all! So the jury is well and truly out on this one.

Its interesting Haile Gebrselassie is very
clearly a heel striker during marathons, though he was a famously reported forefoot striker when on the track, often being pointed to as the unwitting endorser of forefoot landings.

There is also the practical issue that someone who is a heel-striker, and who suddenly decides to switch to a mid-foot or forefoot landing because they think it might be more efficient is highly unlikely to be able to run very well, and risks injury anyway (see Q4)

And finally, a
study on Pose found that months of supervised Pose training succeeded in shifting the landing point to a more forefoot one, but the runners were less efficient than before, by a considerable margin.

So the possible benefits of forcing yourself to land on the mid-foot may be small (or non-existent), whereas the downside includes serious injury to calf, Achilles or ankle, and overall, I wouldn’t force it in a runner until evidence is absolutely convincing.

That’s not to say you cannot introduce training methods that very gradually, and unconsciously, help to improve running by (among other things) changing running form.

Form drills, uphill running, sprinting are all training methods that will have natural effects on form. I see these as distinct from cognitively changing technique, which is what this debate leads to.

Q: There seems to be lot of debate between researchers at the moment on the subject. Which of the two parties (barefoot vs. modern running shoe) do you see as having the most valid research outcomes at this moment?

A: At the moment, the barefoot position is in the ascendancy. I realize that in this interview, I’ve said that evidence is lacking, but I still believe they have merit.

The problem is that neither extreme is likely correct.

The extreme view that shoes protect against injury and are necessary and should be prescribed according to specific tests like foot shape is very much in doubt.

That’s why the barefoot group occupies the stronger position – their ability to cast doubt on conventional wisdom is better than that of the shoe advocates to criticise the position that being barefoot is better.

I think the conventional wisdom about shoes is changing, more and more people are recognising that all the gadgets sold as injury prevention devices are not effective, and so the minimal movement gains momentum.

Having said that, the extreme view that we should be barefoot or in minimal shoes is just as likely incorrect.

There will be a middle ground where the best scenario for the most people exists. I believe that shoes are crucial for some runners, who would be unable to run without the level of cushioning and support they offer.

In theory, maybe barefoot works for everyone. But years of deconditioning and wearing shoes, along with biomechanical factors, may make it absolutely impossible for some people to make the transition. So now you have a choice - run in shoes and keep going 10km a day, no problem.

Or shift to barefoot and run a few hundred metres a day and break down injured. It's just too difficult, practically, for some people to shift.

For others, perhaps a majority, smart training and gradual progression can see them running successfully and injury-free in lightweight shoes.

And “smart training” includes some barefoot running, even if it is once or twice a week, for reduced distances. I’ve no doubt that it helps and may protect against injury, and I think it is a matter of time before there is some evidence for this.

ut neither side is going to convince me that they’re 100% correct in the extreme, and shoes are not endangered species just yet!

Part 3: So far, I've looked at the issue from the side of the barefoot. Next, we'll look more at shoes, and why this perception exists that shoes prevent injury, how marketing messages have shaped those beliefs, and what scientific exists (or is lacking, as the case may be) supporting shoes.


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