Tuesday, October 18, 2011

What is "Natural Running?"

CTB Editor's Note: This post is an update, and revision, of the Natural Running post from December, 2010.

This is the magic question. And the problem with magic questions, of course, is that there is no magic answer.

For those with some type of logic function in the brain, this is a big issue. After all, shouldn't it be reasonable that, if we were all to take our shoes off and run, that our form would be relatively the same? But how is that even reasonable? What about those of us with functional or true leg length discrepancies? What about those of us who have shorter Achilles' tendons? What about those of us with chronically tight calves, putting us susceptible to plantar fascii injury?

But, barefoot advocates say, what of the Harvard study that says running barefoot reduces impact force? Running in shoes, the theory goes, allows us to put more impact on the foot than it is designed to withstand, leading to specific injury.

Well, that's not what the study says. From the page linked above, a graph showing the impact when landing with a heel strike in a running shoe:
Figure 1b

Now, for the same study's graph showing impacts when running barefoot with a forefoot strike:
Figure 1c

Notice that the spike goes to the same high point? Running barefoot does NOT reduce actual force.

What the key here, though, is that there is a reduction in the impact transient force. Explained simply, the transient force is that "braking" force that occurs when you excessively heel strike; the foot is absorbing impact while the leg is trying to still come forward (because the foot is extended out in front of you.)

This makes sense: when you run with a forefoot strike, you can't have a heel-toe transition. Of course it will reduce transient force! This isn't telling us anything that, well, anybody should be able to figure out.

To review, what we have talked about so far:
  • Running with a forefoot strike does not reduce actual impact force absorbed, merely the transient force.
  • Running with a heel strike does create a transient force that must be absorbed by the leg.
Now, what of the Hasegawa study?

This 2007 study looked at the footstrike pattern of the elite runners from a half-marathon. The scientists photographed 283 runners at the 15 kilometer mark. The theory posited was that, as most elite athletes were from countries where running barefoot when younger was necessary, that most of the elites would showcase a midfoot or forefoot strike.

The results, meanwhile, were startling: 74.9% of runners photographed exhibited a rear foot strike. Midfoot strike positioning was shown by 23.7%. Forefoot strikes only accounted for 1.4%.

So what makes an elite runner elite? It's not the where that's important; it's how much time the foot spent in contact with the ground. The longer the foot spent in contact with the ground, the slower the runner was. The first 50 runners spent less time on the ground versus the next 50, and that second 50 spent less contact time than the next 50, and so on.

Therefore, it is reasonable to conclude, as the study did, that running economy and efficiency comes from the foot spending less time in contact with the ground, rather than specifically how the foot contacts the ground.


By this point, I'm sure you're now wondering: where are we going with this? We still haven't figured out what natural running is!

Here's the rub: there is no universal answer. We need to separate the core principles of good running form, from the hyperspecifics of a unique foot strike. We must account for the differences in physiology that make humans so different from one another.

Therefore, I would posit that the following elements are key to natural running:
  • The Hasegawa study shows us that running economy is more related to contact time in the ground. Therefore, it would stand to posit that we want to have a faster foot turnover rate.
  • Because of the faster cadence, this will require a shorter stride; it is nearly impossible to overstride if you are trying to keep your footstrikes per minute near the 180 mark.
  • The key of footstrike is to keep it as close under your center of gravity as possible. Whether it lands forefoot or rearfoot or midfoot is, in my opinion, not as important. But landing underneath the knee, keeping the kinetic chain in line from the core downward, is important.
  • We DO want the whole foot to try and contact the ground at as similar a point in time as possible. Our feet are like tripods; we have wide metatarsals and a narrow heel. A tripod is most stable when it is fully in contact with the ground. Therefore, it is reasonable to assume that this is how the foot should engage and absorb impact.
  • Therefore, the core of good, natural running form would include a higher cadence for running economy; a stride that engages the ground under the center of gravity, and attempting to engage the whole foot with the ground at as similar time as possible.


So how on Earth does this all relate to the footwear buzzwords of minimalism and natural running?

Well, let's lead with what might be groundbreaking news: we are not meant for pavement or concrete. The human foot was designed to run on grass or sand, not on the roads. We have built a completely unnatural environment to attempt to perform a natural activity on. That being said, there will be some of us who can run all of our miles in Vibram Five Fingers. However, it is likely that this would be the exception, rather than the rule, considering that running injuries have actually increased as people have tried to run in barefoot-esque shoes.

What to do? I think Jordan Rapp, in this month's LAVA Magazine, states it best:
What I think this reflects is a conscious decision on the part of shoe designers to separate biomechanics...from overall feel, which is influenced by a shoe's cushioning.
Previously, I had discussed the differences between so-called "natural" running shoes from minimal and barefoot styles. Considering that we have talked a fair bit about how there is no truly singular "natural" style, I think using the term "natural running shoe" is misleading. One can run with good form in any type of running shoe, whether it features a large heel-toe offset, or is near flat.

Therefore, when looking at running shoes, it is imperative to first discuss running form. Your running mechanics will dictate the offset that will be best for your running shoes, whether it is the "traditional" 12 millimeter difference between the heel and the toe, or the class of effective zero shoes (6 mm or less), or in between. (As a note, both Saucony and New Balance will be introducing shoes with an 8 millimeter offset in their regular running line, to try and promote a more balanced footstrike. Remember, though, that your feet are dumb: you must tell them where to land.)

After determining the offset appropriate, we may then talk about pronation control and cushioning. As a single example, I run in shoes with a low offset (less than 6 mm), but still feature a midfoot pronation control device. Why? Because even with good running form, my feet still overpronate. And I need a good amount of cushioning, because if I run with a more minimal shoe, I develop a stress fracture in my right foot. This is why I've run in the Saucony Mirage, for example.

Therefore, when shopping, these are the things a retailer needs to know in order to ensure a good fit:
  • Injury history
  • Running goals (training, mileage, speed, etc.)
  • Running history (current mileage, races upcoming, etc.)
  • Running stride or form (if known)
  • Cushioning preferences
So what is natural running? Whatever is natural for you.

No comments: