Month: June 2011
The heart of OESH, the midsole, is made in the United States. In downtown Charlottesville, Virginia to be precise, arguably the best place to live (and this from someone who grew up in San Diego, California)! We are a college town (home of the University of Virginia) at the foothills of the Blue Ridge Mountains and the Shenandoah National Park (meaning it’s hilly). Not exactly a typical place for a shoe factory.
The athletic shoe of the past 30 years has been made almost exclusively in Asia. It used to be that shoes were made in Asia because the cost of labor was so much less there. But what’s happened is that because Asia has been making shoes throughout the computer era, Asia, not the U.S., has developed all the sophisticated computerized technologies and equipment to make them. So now it’s not so much the cost of labor as it is that Asia has all the technological know how.
But the OESH midsole is different than any other midsole ever made… anywhere. So we seized the opportunity to research, develop and manufacture the midsole locally here in the U.S. — in our own town. We figured that with all our going to the moon and such, we’d know best how to make a shoe soles. And indeed, from the University of Virginia’s Department of Mechanical and Aerospace Engineering to Noland’s (the local plumbing supply store down the street), we had all we needed right here. Our raw materials and even the equipment that we don’t make in our own factory in Virginia are made in the United States. Toho Tenax America makes our raw carbon fiber filament in their plant in Tennessee. McClean Anderson makes our computerized filament winding machinery in their factory in Wisconsin. Phoenix Equipment makes our automated resin pumping system in its factory in Florida. OMAX Corporation makes our computer controlled water jet saw equipment in Washington. And around the corner, my friend Bill at Specialty Fasteners finds us just about everything else we need.
Now I do still make trips to China to visit the factories that make the rest of OESH – the upper and the outsole. The factories we work with there are the very best in the industry and they take great pride in contributing to the final OESH product. But there’s nothing like working with and supporting our local community to make the core of OESH right here where I have the option of walking two blocks west to see my friends at Martin Hardware store, two blocks south to see my friends at Quality Welding, one block north to Reid Market and one block east to Bodo’s Bagels. I typically go for the Everything Whole Wheat Bagel with herb spread.
The Harvard Indoor Track Revisited (page 4 of 4, the gun lap)
For a shoe midsole to behave like the time tested Harvard Indoor Track, this midsole would has to compress and release in perfect tune with the rise and fall of the peak body weight force. It would have to be a sole that remains stiff at impact but gradually, as the body weight force reaches it peak, compress. Specifically, the slope of the amount of compression and release of the midsole would have to be equal and opposite to the rise and fall of the peak body weight force (when injury causing forces are at their peak).
Designing a shoe sole that effectively gives and gives back would take a comprehensive understanding of how the body weight forces are naturally transferred under the foot and how those forces relate to the position of the rest of the body. It would take combining motion data with body weight force data to understand where and when peak stresses occur. And it would take studying gait in many individuals with varying foot and gait types across a number of conditions to understand natural force and movement patterns and to know which patterns are consistent and which are not. Those comprehensive biomechanical studies were never done 30 years ago. Only recently have we been publishing data that is informing what are these natural and consistent patterns.
I often wonder what Dr. McMahon would have to say about what we now know. He unfortunately passed away in 1999 and I never had a chance to talk to him about the new things we were just beginning to learn then about footwear. He was a brilliant scientist (and a novelist!). But it’s his success with the Harvard Indoor Track that is specifically noted in his obituary – that the track improved efficiency by 3% and reduced injuries by one-half. Powerful. And not forgotten.
The Harvard Indoor Track Revisited (part 3 of 4)
Okay, so the first big difference between cushioning in a shoe and the successful plywood structure of Harvard is that the plywood does not give at impact like a typical cushioned shoe. The second difference, which needs to be emphasized, is that the plywood maximally compresses and releases like a spring when the foot is fully planted. Specifically, the slopes of the rise and fall of the ground reaction force correspond precisely to the equal and opposite slopes of the compression and release of the plywood surface.
While the athletic shoe industry has been designing around trying to cushion impact, any data we may have seen regarding midsole compression relates to what occurs at impact, not what occurs when the body weight force and all the stresses and strains in the body reach their peak. Foam, gel, and air bladders are incapable of providing the same spring like compression and release that Dr. McMahon showed with his plywood structure. Sure, the typical ethlyne vinyl acetate (EVA) sole of the shoe may give underfoot but it doesn’t give back like the plywood spring.
Over these last 30-plus years, nothing has really changed in the design of the typical athletic shoe. It has been mostly about cushioning impact combined with varying amounts of trying to control foot pronation.
So, with all we now know about how the Harvard Indoor Track works, and how the current athletic shoe doesn’t work, how to we go about making a better shoe?
From a biomechanical standpoint we know that attempting to cushion impact reduces feedback to the body, resulting in altered muscle activity and foot position at contact. It has been shown that making impact with a soft surface can actually increase injury. And most recently we showed that a typical cushioned running shoe increases peak knee joint torques associated with knee osteoarthritis.
With all of this in mind, I am hearing that ‘crack’ of the pistol, and tomorrow I’ll take you on our gun lap around Harvard’s Track.
The Harvard Indoor Track Revisited (part 2 of 4)
Dr. McMahon’s results were just as he expected. In the 1977-1978 Harvard indoor track season, injuries were reduced by one-half compared to the prior season. Running efficiency also improved as evidenced by faster race times of approximately 3%, not just by members of the Harvard Track Team, but by runners from visiting schools. These results became well known and his same plywood structure, which is still in existence today, was subsequently built at a number of other indoor tracks. The evidence was clear. A compliant surface that compresses and releases in tune with when body weight forces are at their peak reduces injury and improves efficiency.
This was all in 1978. Could the success of the Harvard Indoor Track (officially known as the Albert H. Gordon Track), now 30+ years time tested, have anything to do with thinking that the same success could be achieved in a running shoe? I don’t know, but it was certainly around that time that the modern day running shoe was developed.
Over the past 30 years, the traditional athletic shoe midsole has comprised all types of foam, gel, and air bladders. To the extent reducing injuries and improving efficiency mattered, I think it may have been assumed that such midsoles would perform like the Harvard Indoor Track. The plywood track compressed and released. Doesn’t foam in a shoe compress and release too? Well yes, but that’s where the similarities end. Analyzed in a sophisticated gait laboratory, current shoe designs don’t measure up to the Harvard Indoor Track.
A typical cushioned shoe, on a person’s foot, behaves nothing like the tried and true Harvard Indoor Track. The first big difference is that the typical traditional shoe cushions “impact”, the very first contact made with the heel of the foot. Plywood on the other hand, does not cushion impact. I’m not sure how this detail was ever missed, but it sure was–and still is. I don’t think anyone ever realized the distinction between what was occurring at impact versus what was occurring later in stance. And we now know just how important that first contact with the ground is for providing feedback to the foot and body.
I’m not exactly sure where the basis for cushioning impact ever came from—but it wasn’t from any scientific study that I know of. The idea of cushioning impact (or at least trying to) has been one of the cornerstones of athletic shoe design for the past 30+ years. But I can’t find any evidence to support that it’s actually impact that causes injury. In fact, there is biomechanical evidence to support the opposite — that impact has nothing to do with injury, as discussed in my recent post. It was clear from McMahon’s data that the plywood surface did not compress at initial contact. Rather the plywood compressed and released much later in the stance phase, in tune with when the foot is fully planted and the body weight forces are at their peak.
But there’s more to the distinction between this heel cushioning we still encounter in running shoes and a firm plywood interface. And being integral to the most dramatic result of the Harvard Track, we’ll discuss it at length during our third lap around the oval tomorrow.
The Harvard Indoor Track Revisited
I live in Charlottesville, Virginia, home of the University of Virginia (UVa), where I recently retired as professor and chair of the department of physical medicine and rehabilitation to launch OESH Shoes. Though I love UVa, I must admit a lot of good things come from dear ol’ Harvard. The inspiration for OESH came from my years at Harvard Medical School (where I also received my M.D.), studying gait and footwear. While a lot of the concept for OESH came from my own biomechanical studies on gait and footwear, some of it also came from the work of a fellow Harvard researcher, Thomas McMahon, a biomechanical scientist who I overlapped with slightly. I haven’t heard his work much mentioned lately but think it deserves re-visiting. Any legitimate discussion attempting to determine whether or not an athletic shoe midsole could ever reduce injury north of the foot has to consider his work.
Dr. McMahon studied the effects of imposing a compliant surface between the foot and an otherwise hard ground surface. By compliant, he meant a surface that compressed and released in tune with the rise and fall of the body’s center of mass during running (and jumping). To do this, he first built a workable compliant ground interface that would consistently compress and release in a laboratory environment. After considering a number of different compliant-like surfaces, the one he studied extensively was a simple sheet of plywood draped across 2X wood supports on either side. He had subjects run up and down the middle of the plywood and measured the deflection of the plywood in relationship to the rise and fall of the subjects’ center of mass (measured with markers placed over the subjects’ trunks). He experimented with changing the compliance of the plywood by changing the distance between the wood supports. And he found a perfect window of compliance (the Goldilocks structure – not too compliant and not too stiff) that increased stiffness in the lower extremity while simultaneously reducing foot contact time.
All that was just the groundwork (so to speak) for his next experiment–which may be the best controlled scientific experiment regarding the effect of human ground interface on injury rate ever done. What he did was incorporate his plywood structure into the Harvard Indoor Track. This was completed, along with help from Dr. Peter Greene, in 1977. Dr. McMahon’s plywood structure was placed on top of the existing hard surfaced indoor track. Essentially, the track comprised plywood draped across wood supports that ran between the lanes (covered by a thin polyurethane layer). This matched the surface from his laboratory work meant to reduce stresses and strains throughout the body. McMahon hypothesized that the compliant surface should not only reduce injury, but also improve running efficiency.
I’ll discuss what this Goldilocks surface revealed in my next post. Until then, I’m off to have some porridge before today’s run.
A student working with me this summer asked me, “It all seems so obvious when you look at the graphs. Why haven’t any of the big athletic shoe companies ever noticed this before?”
Here’s the answer… The graphs are the result of comprehensive human biomechanics research. And meaningful, comprehensive biomechanics research requires you to combine force plate data with motion data. Otherwise, it’s kind of like salt without pepper, bacon without eggs, or Lennon without McCartney… only far worse, if you can imagine. But to my knowledge, no athletic shoe company had ever done this type of research. Or if they did, they certainly never published it or incorporated it into their marketing formulas. For me, it took not just building two fancy gait laboratories (first and second) and spitting out dazzling graphic images, but actually digging into all the data, for many years, while being simultaneously equipped with a medical understanding of the meaning of it all.
Then after discovering how a shoe really needs to work, there’s the not so small matter of a big athletic shoe company being able to admit, “oops, we’ve been completely wrong about how to make a shoe.”
But even the athletic shoe company giants can’t run from the fact that most injury causing forces–not just joint torques–peak when the foot is fully planted. It’s becoming increasingly recognized that cushioning impact is the wrong time to protect the body — unless you are in a car accident and happen to have your shoes duct taped around your head.
So what does this mean with respect to footwear? Simply, in order to reduce stresses and strains in the body, the midsole of a shoe must provide compliance (compress and release) when the foot is fully planted. A simple concept but one that requires true innovation and a whole new way of making shoes. Far easier for big shoe companies to respond with a new marketing spin of “less of our flawed technology is more.”
In the graphs from the study below, compare the dotted line (representing a standard neutral running shoe) with the solid line (a barefoot control). There is an approximate 50% increase in the knee varus torque, which is a well known variable for knee osteoarthritis between the femur and the tibia. For brevity, we included data on a neutral running shoe but observed the same effect across just about every non-OESH shoe.
I say this again because the above graphs are the basis of the design of OESH Shoes: peak stresses and strains associated with injury do not occur at impact but rather, much later when the foot is fully planted.
And now you know the rest of the story.
Last time I discussed the common misperception that impact causes injuries.
Today, I’m going to show you the critical link in the chain describing the real instant of vulnerability. It’s actually pretty obvious when you think about it (kind of like you always find your car keys in the last place you look)…vulnerability occurs when your entire body weight is supported by a planted foot.
As you can see above, the knee joint torques and forces reach the top long after the impact arrows. Rather, at around 10-20% of the gait cycle, the foot becomes fully planted. Here is where the knee joint torques and forces reach their maximum. And indeed, it is these peak torques and forces, not the small ones at impact, that relate to knee osteoarthritis.
Although impact sounds dramatic and is certainly what causes injuries in falls (and motor vehicle accidents), impact is not what causes repetitive type injuries during normal walking and running. Any biomechanics research that combines force plate data with motion data demonstrates that most forces related to injury peak when the foot is fully planted. Importantly, this is the case for just about every injury prone area, not just the knee. For example, we get stress fractures in very specific anatomic sites. The peak forces through these sites occur when the foot is fully planted — not at impact.
I cannot say this enough, as it goes against the marketing spin of billions: peak stresses and strains associated with injury occur when the foot is fully planted.
So what does this mean with respect to footwear? This is where the rubber meets the road, and I will describe the science of it all in my next post.
Paul Harvey did a “the rest of the story” segment on one of my first research studies on shoes. He was a nice guy and I was in awe of his digging in beyond the typical headline news. In that same vein, I now give the rest of the story on another of my studies published about a year ago–this one on traditional running shoes.
The study received a lot of attention by the press and is often cited in barefoot-versus-shoe running forums and discussions. Reporters were all over one main point…that traditional (non-OESH) athletic shoes increase the peak knee and hip joint torques linked to the development of osteoarthritis. But what has not been well covered is when these injury-relevant torques occur in the running cycle.
Frequently, the study is described by an eye-catcher such as: “Recent research shows that running shoes increase impact forces at the knee and hip.” Perhaps because ‘impact’ sounds so awful it’s been blamed for just about every walking and running related injury, including the most significant, knee osteoarthritis (which we all get to some degree if we’re lucky to live long enough). But our research broke through a glass ceiling of assumptions and showed that these increased forces or torques were not occurring at impact.
In fact, the joint torques and forces at impact are very small.
Rather, the increases in the injury-related torques occur when the foot is fully planted.
Below are some of the graphs that were published in the article. You can see that when the body’s impact force is at its maximum (shown with arrows), the knee joint torques are very small.