Barefoot running, or just a minimalist shoe?
From the Savannah to the Track
Anthropologists such as Daniel Lieberman believe that the human foot developed to run barefoot. His hypothesis is that we were built for endurance running. Prospective studies and randomized controlled trials of barefoot and shod running are difficult to achieve for obvious reasons. Robbins and Gouw argued that plantar sensation induces a plantar surface protective response whereby runners alter their behavior to reduce shock. The less-cushioned shoe permitted increases in plantar discomfort, a phenomenon that they termed "shock setting." Coaches such as Brooks Johnson and Vin Lananna have used barefoot running as part of an overall program to train the body to ran long distances fast. In their opinion, to run properly, the foot needed to grasp and release on a variety of surfaces such as dirt, grass, road, concrete, and gravel.
The Shoe Industry Steps in
Several companies have weighed in with their versions of a running shoe which simulates barefoot running. Adidas' approach was to try and copy the shape of the foot. In theory this will produce smaller lever arms that react faster. The idea for the Nike Free was born out of a visit by a couple of researchers to Stanford where Lananna was having athletes running barefoot as part of their training regimen. Many competitive runners I spoke to use barefoot running or shoes like the Nike Free as part of their training. Nike had students test it for 6 months and those using the Free for 6 months had greater flexibility and strength in the foot.
I interviewed researchers Tobie Hatfield from Nike's innovation Kitchen and Jeff Pisciotta from the Nike Sports Research Lab to find out how the shoe industry has incorporated the concept of barefoot training into their shoe design. They seem to be spearheading the shift back to their spirited roots to the old Bill Bauerman days when they made prototype soles on waffle irons. They studied 20 competitive runners on grass, and kinematics analysis demonstrated a general trend towards full foot contact. If you watch the footage of Abebe Bikila's Rome marathon you will notice the same thing. The perception of some of the runners tested was that they were landing more toward the forefoot than they actually were.
Many believe that racing barefoot is difficult unless you have been running without shoes all your life. Many recreational runners are also starting to try barefoot running in an effort to prevent injuries and improve technique. The problem with this is that some of them will not have the conditioning to handle the transition to barefoot running. Experts in the field agree that any transition to barefoot running be done slowly.
The Cushion Illusion
The running shoe industry has built much of its platform on cushioning. The theory goes that very soft shoes will bottom out when loaded, producing higher impact forces than firmer shoes that do not bottom out. Yet for any of us who have run downhill on concrete, the more cushioned shoes seem to be less jarring. So how do we reconcile this? I interviewed Benno Nigg, one of the foremost biomechanics gurus on running shoes, and he was able to offer a new paradigm.
He started by telling me that there is no article in the literature which supports the notion that peak force transmission will be altered with varied levels of cushioning. In fact peak force transmission does not occur during heel contact as we might intuit, but in midstance, where the internal forces on joints, muscles, and tendons are 4 to 5 times greater than during impact.
There is something else that accounts for the perception that we are more comfortable in a certain level of cushioning. Nigg's vibration model explains that when we impact the ground, our soft tissue compartments (e.g., calf, hamstrings, etc.) start to vibrate. The human body does not like vibrations. Consequently, muscles are activated to dampen these vibrations. The degree of dampening that occurs in various types of shoes is what leads to our perception of comfort in the shoe. So we have an innate sense of what works for our bodies that is probably more accurate than any test could demonstrate for us. We must also consider the fatigue that occurs within the muscles that are working to distribute the vibrations. We know from other studies that fatigue can lead to injuries and this may be part of the answer.
The trend in the shoe industry seems to be toward offering shoes with more minimalist designs. Barefoot training can help train the small muscles that are not trained in stable running shoes. Yet, it is hard to isolate all the force vectors because of the complex arrangement of the joints of the lower extremity. And Robbins' association between injury and wearing shoes may be mitigated by other factors: perhaps in developing countries barefoot runners may be too poor to seek medical attention; also, shod runners may wear shoes because they have problems running barefoot.
Certainly runners that have grown up running barefoot in areas where it is more prevalent, like Kenya, have been conditioned to run more efficiently barefoot than move industrialized countries. Beyond that elite athletes are exceptional in their foot musculature and would have an easier time in general running barefoot than others.
For more information on Dr. Pearl, visit http://docforjocks.blogspot.com.
By Ben Pearl, DPM
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|Publication:||Running & FitNews|
|Date:||Jul 1, 2009|
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