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(1/11/12)

Barefooting

Were we born to run Ö barefoot?

 

The book Born To Run, by Christopher McDougall, has had an immense impact on the running world and beyond. The hardcover was on the best seller list for most of 2010, the paperback for much of 2011, and thereís a movie in the works. It is largely responsible for the boom in barefoot running and minimal shoes. It has spawned great interest in ultra running, especially the Leadville 100 (the 2011 race sold out months earlier than ever before).

 

While I highly recommend the book - itís entertaining, informative, and inspiring Ė Iím skeptical about barefoot running. I think itís good that this has gotten runners to think about their form (Iíve been teaching running form since 2003, using the same principles found in Chi, Pose and almost every other running form system and minimalist). Despite the evangelical zeal of barefoot runners, itís not the magical cure for all running injuries and running shoes are not evil; the science doesnít show either.

 

In part 1 Iím going to briefly review the book and critically evaluate barefoot running. In the part 2, Iíll look at ways to strengthen your feet and improve your form. This should be valuable to you whether or not you are thinking of going barefoot or minimal (I will use these terms almost interchangeably throughout), and absolutely essential if you do.

 

Born To Run: At its core, the book is a wonderful tale of adventure travel. Beyond the adventure, McDougall weaves in everything from the evolution of ultra running, Tarahumara history and culture, an analysis of the running shoe industry, to cultural anthropology (i.e., were we born to run?). Thatís where the book hits its mark.

 

The adventure took place in 2006, when a group of Americans travelled down to Copper Canyon, in Mexico, for a 50 mile race with the Tarahumara. The Americans were a cast of characters including 6-time Western States 100 winner Scott Jurek, a guy named Barefoot Ted, a 20-something party animal who would stay up all night drinking and then win a race the next day (subsequently, she has gotten serious and has run sub-15 for 100miles), and the author. They were travelling down to meet up with Caballo Blanco (his true name and background are revealed at the end of the book), perhaps the biggest character of them all, an American who had been living with the Tarahumara. The story of how the race came about, traveling to Copper Canyon, and the race itself is quite entertaining.

 

The book has one of the best histories of ultra-running, and the most detailed account Iíve read of the much heralded 1994 Leadville 100mi run battle between Ann Trason and the Tarahumara. In that race, Tarahumara runner Juan Herrera held back early on, while Ann Trason led for much of the race. When he finally let go, he flew by Ann, averaging 2 min/mi faster, to shatter the course record and win by 34 minutes. His winning time of 17:30 stood as the record for 8 years (who knows how much faster he wouldíve run if he hadnít held back). Ann Trasonís 2nd place finishing time of 18:06 is still the womenís record, over 1.5 hours faster than any other woman has run at Leadville.

 

Were we born to run Ö barefoot?

The part that created all the buzz in the running community (and beyond), and made the barefoot movement take off is the claim that we, humans, were born to run, and run barefoot. The argument combines both bio-mechanics (the heel is important for balance when standing and walking, but not necessary for running) and evolutionary biology.

 

The evolutionary biology theory of barefoot running (i.e., born to run) is that our ability to run long gave us an advantage over our prey. Even the fastest humans are a lot slower than four-legged animals (and we didnít have the weapons to kill them from afar), but we could run them to death (almost literally) over time. Humans keep cool through sweating. Other animals donít sweat. They dissipate heat through breathing. So, while they can easily out sprint us, they quickly begin to overheat, have to switch much of their breathing from energy to cooling. Quickly they slow, and if forced to continue, they overheat, and stumble and collapse, making them easy to kill.

 

There are several problems with the claim that since our ancestors ran barefoot successfully, we should too.

 

1) Itís unlikely that all of our ancestors were good runners and hunters. Itís likely that only the few good runners were the ones who hunted. In other words, we werenít all born to run.

 

2) Ancient humans grew up without shoes and developed strong and tough feet. They also were physically active Ė climbing trees, building shelters, etc., - developing strong core and stabilizing muscles. In contrast, we sit behind a desk, in front of a TV, drive cars, etc.

 

3) While some of us may have been born to run, I donít know that we were born to race, and to do so for 26 miles on pavement.

 

Are shoes to blame?

McDougallís book includes a near indictment of the running shoe industry claiming that cushioned shoes enable heel striking (which leads to injury). Barefoot advocates state that injury rates havenít changed since the introduction of cushioned and motion control running shoes Ė 70% in the 70s, and 70% today Ė and that if shoes were better, they would have declined. However, there are several problems with this argument. And, thereís no scientific evidence that shoes either hurt or help runners.

 

Before the first running boom, when shoes were strips of thin rubber attached to a leather upper, most runners were built like me (I did my first race in 1971) Ė wispy, thin, efficient (i.e., born to run). As the number of runners has grown immensely, so has the variety of body types. On average, runners today or slower (and probably heavier) than before the modern running shoe - median marathon times in 1980 were 3:32 for men and 4:03 for women; in 2008 they were 4:16 & 4:43. A lot of newer runners may not have been born to run. In fact, cushioned and control shoes may be preventing them from getting more injured, and may have been necessary to enable them to get into and continue running.

 

Even with efficient runners, it could be that modern shoes have allowed runners to train more and harder before they become injured. In other words, injury rates may remain a constant regardless of whether or what kind or shoes runners wear, because runners will tend to push themselves in training to the point they get injured.

 

Rather, the problem with shoes may be that it restricts your foot from functioning naturally. Your foot is supposed to pronate, the arch collapse, toes splay out, flex at the mid-foot. This is all part of dissipating some of the impact, and gathering energy in a spring-like fashion to return to your push off. If you wear shoes that restrict those motions, you donít allow the muscles to strengthen and learn to operate efficiently.

 

Even for those who have an efficient stride in shorter runs/races, itís not clear thatís sustainable over a longer race (i.e., Ĺ-marathon and longer). High speed video analysis of runners towards the latter half of longer races show that even the majority of elite runners land on their heels (although, Iím not sure whether such analysis is really able to distinguish between where it appears the foot strikes and where the major impact is). So, as your foot fatigues, you may need some heel cushioning. And, cushioning may forestall the fatigue that, among other things, makes you more susceptible to injury.

 

I donít have much to say about zero and low heel drop shoes because they are so new onto the market, and there hasnít been time to study them. I read one report that implied that the amount of heel cushioning didnít matter, but whether there was cushioning or not did. However, that was a very small and not very scientific study.

 

Is forefoot better?

The science does not show that barefoot running or forefoot (for purposes here, I use forefoot and midfoot interchangeably) striking reduces injury. Harvard evolutionary biologists Daniel E. Lieberman, whoís work is widely cited in the book and by barefoot advocates, states on his website, ďPlease note that we present no data on how people should run, whether shoes cause some injuries, or whether barefoot running causes other kinds of injuries. We believe there is a strong need for controlled, prospective studies on these issues.Ē

 

Dr. Liebermanís most widely cited study shows how loading rates are significantly higher with heel strikers vs. forefoot strikers. There are several problems with this analysis. Force exerted down onto a strike plate doesnít equate to force transferred up through a cushioned shoe. More loading doesnít necessarily mean excessive; no one has showed how much is too much. Loading rates, rather than indicating excessive stress on the body, may simply indicate inefficiency. In fact, thereís a theory that the higher loading stresses the bones, making them stronger. Also, itís not been shown that such measures in a lab represent whatís happening in the real world.

 

Another theory says that your body adapts to the stresses it encounters and automatically adjusts your stride (you automatically adjust your stride when you change from concrete, to dirt, to mud or sand). In other words, if heel striking hurt, you wouldnít.

 

Itís not clear that forefoot striking reduces injuries. For one, landing off your heels means your muscles absorb more of the impact. Those who donít take the time to properly adapt to fore/midfoot striking are prone to more soft tissue injuries. Even after properly adapting, on longer runs and races, muscles fatigue (bones donít), becoming less efficient, less able to stabilize and support, which can lead to greater injury. Other studies have shown that higher frequency (hertz) forces, associated with heel striking, travel through bones, while lower frequency forces, associated with forefoot striking, travel through the muscles. So, changing to mid/forefoot striking may be trading off one set of injuries for another.

 

More than forefoot

Forefoot striking alone is not sufficient, and may not even be necessary for an efficient stride. For example, the University of Virginiaís Center For Endurance Sport has done analyses that indicate that where your foot lands relative to your body Ė your foot should land under the center of gravity (COG) - is more important. While they say that most people who land under their COG do strike forefoot, they can show you heel strikers who land under their COG and forefoot strikers who land in front. Regardless of what part of the foot you land on or what kind of shoe you are wearing, landing under your COG produces less impact than landing in front. Itís also more efficient.

 

Letís add two more important characteristics of an efficient foot strike - the direction your foot is moving, and your stride rate.

 

When your foot hits the ground, it should be pulling back. This ďpaw backĒ motion (like a cat scratching) means that you are using the existing inertia of your bodyís forward motion over the ground (or the groundís/treadmillís backwards motion under you) to help propel you forward. When you land flat, or with your feet moving forward relative to the ground (sounds like sandpaper), not only is the impact greater, but you stop your forward momentum (actually slowing yourself down), and require that much more energy to generate the forward momentum. Another way of thinking of this is when you have to move a heavy object (e.g., a large box), itís easier to move it if you get a running start. Combine the paw back with landing under your COG, and it takes less energy to produce a more powerful stride than how a lot of runners land. Itís easier to push something away from your body than pull it towards you.

 

A faster stride (most non-elite runners can benefit from a faster stride) is more efficient, has less impact, and leads to faster running. Stride rate is much more a factor of how much time your foot is on the ground, than how much time itís in the air. When you land, the muscles and tendons in your foot and leg collect energy and then return it, like a spring. That return of energy can happen very quickly. The longer your foot is on the ground, the more energy is absorbed, and the less is returned to propelling you forward. A faster stride means you donít have to propel yourself as far in the air meaning less energy and less impact.

 

And thatís just foot strike. Other factors to consider include pelvic tilt, arm swing, shoulders and head tilt.

 

Can we adapt?

Even if it turns out that barefoot and/or forefoot running is better for runners, itís not clear how easily, or even whether we can adapt to it after a lifetime of wearing shoes. Analysis of runners at barefoot/minimalist races (done after the start when runners have settled into their stride) has shown that the majority of runners still land on their heels.

 

Anecdotally, having watched a lot of runners, and through my own experience, itís not clear that itís the cushioning that causes people to run on their heels. Rather, it may be that people have different, natural running styles, perhaps altered by lack of ankle flexion from years of little or misuse (e.g., high heeled shoes). I know runners whose heels never seem to touch the ground regardless of what kind of shoe theyíre wearing, and others who canít get off their heels. Personally, Iím able to consciously alter my foot strike in whatever kind of shoe Iím wearing. For me, at least, itís not the shoe that dictates my foot strike, but how my muscles are conditioned to fire.

 

Bottom line

Before you rush out and buy a pair of barefoot shoes (contradictory terms), consider whether you need to change. If you have recurring injuries - not just in your foot, but radiating up to your hips and lower back Ė then you might benefit from a change. However, the irony is that those who can benefit from it the most can afford it the least. Iíve always had a fairly efficient stride and good feet, and have never worn supportive shoes. I can, and have run a few miles barefoot with no build-up. However, for those who donít have good feet and have been wearing supportive shoes, you may only be able to run a few seconds barefoot without risking injury, and it may take months of build up before you can do any substantial barefoot running.

 

There is a lot of benefit in working on your running form, even for efficient and injury free runners. Athletes in every other endurance sport Ė e.g., cycling, swimming, x-c skiing Ė work on their form. Whatever the reasons, most non-elite runners donít; they just run.  Becoming more efficient will make you faster, less likely to get injured, and less tired. You will be able to wear lighter (which should also make you faster), less supportive shoes, and thus less expensive shoes, that will last longer.

 

In the next part I will talk about how to strengthen your feet, how to transition to less supportive shoes, and more about who should consider going barefoot.

 

References:

NY Times article 6/8/11 - http://well.blogs.nytimes.com/2011/06/08/are-we-built-to-run-barefoot/

Barefoot lab at Harvard - http://www.barefootrunning.fas.harvard.edu/

RW interview with biomechanics expert Benno Nigg, 1/9/11 - http://peakperformance.runnersworld.com/2011/01/jan-9-veteran-biomechanics-expert-benno-nigg-doubts-that-barefootin-forefootin-or-pronation-control-will-change-injury-rates.html

Science of Sports blog on barefoot running, 6/6/11 - http://www.sportsscientists.com/2011/06/barefoot-running-shoes-and-born-to-run.html

UVA Center for Endurance Sports - http://uvaendurosport.wordpress.com/

          http://uvaendurosport.com/