Sunday, May 16, 2010

If the shoe fits...

The funny thing is that if shoes met the individual needs of the runner in a better fashion, this whole shod versus unshod discussion would become a moot point. However, that is a whole other rant for another day.

Another day has finally arrived. So let me attempt to tackle a very complex issue in the most distilled form of an explantion.

My first training shoes I ever owned for running were purchased in my second year of running for 2 bucks (1969). For the first year, I used my regular sneakers. Those running shoes had a canvas upper, narrow heel, flimsy arch, and no cushioning. Such characteristics are the complete antithesis to running shoes today. Yet somehow, I managed to run injury free for the almost 2 years I ran in that model. The same was true for all of my teammates. There were “luxury” trainers available from Adidas or Pumas. But, most of our pennies were saved to buy the spikes needed to race on the cinder tracks we had in that era. Meanwhile, the road racing groundswell was in the making. Distance Running news became Runner’s World Magazine. Bill Rodgers and Frank Shorter were the pied piper icons to fuel the emerging running boom fire. In the late 70’s RW did their first comprehensive shoe review. A human performance lab did several physical characteristic tests. Based on this data, the shoes were ranked from one to five stars. The idea was innovative and with good intentions. But we all know that many times the road race to hell is paved with good intentions. Sales of 5 star shoes skyrocketed while excellent shoes that didn’t test well were ranked 1 or 2 stars and were suddenly discontinued. For example, one test in the study measured absorption of energy of a weight dropped onto the heel of a shoe. So, here is the classic en vitro versus en vivo scientific principle. Measurements in the test tube in the lab do not reflect what is happening in the real world. This only measures initial impact in the shoe and says nothing about the angular velocities and peak and sustained forces on tendons, muscles, bones and ligaments in the human body. Shoes that were not right for many people flourished and led to the nuclear arms race of which company could produce the biggest attenuation of the initial impact force.

Dr. Daniel Leiberman’s recent studies point out that heel strike causes an initial impact transient, a nearly instantaneous and large increase in force that occurs as the heel comes to a sudden stop upon impacting the ground. The shoe reduces the force by about 10% and slows the rate of loading considerably. This, in addition to distributing the impact force over a larger area of the rearfoot, makes it comfortable to exaggerate heel strike leading to the en vivo stress on the human body.

Shoe reviews do not shoulder all the blame. The consumer who is enthralled with the latest gimmick fuels the diversion away from what is really best for them. Back in the 60’s, Keds had the magic wedge which “make you run faster and jump higher.” It quickly became apparent to shoe companies that you put an untested gimmick (a few weeks use by a wear tester at best) on the market. The Nike “air” is classic example of this. It was sealed gas tubes enclosed in a polyurethane midsole. The Tailwind was a successful selling shoe even though instability injuries were rampant with the shoe. The Columbia attempted to address this instability by added a more stable EVA, but like the spaceship Columbia in its ad, it too, crashed and burned. It took several renditions of the air gizmo before the bugs were worked all. If the consumer wasn't so willing to be the long term ginea pig for an idea they like, gimmicks and gizmos would be an insignificant factor.

Running shoes are supposed to protect the foot. However, running shoes are also a business. They are mostly part of huge publicly traded companies whose concerns are market share, sales, net profits, free cash flow, and everything that goes along with a myopic shareholder quarterly report.

This adds pressure to have shoes on the minimum number of lasts to accommodate the maximum number of people. Many companies copy another company's best selling lasts. This leads to less variation among the brands and even less models to address the subtle genetic diversity in all the feet out there. Not only at the corporate level but also the retail level where stores have only so much capital to stock their shelves. Improper fit leads to abnormal function.

Now add to the fact that Sport Trend magazine did a survey study in the late 80's and found that 80% of the running shoes purchased will never even be used for running.

You can see reasons for wayward goals and distractions of the health quality of running shoes. This is why the barefoot running community knows that unshod feet often outperform the latest couple hundred dollar smart shoe.

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