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 is physiologically tuned to the rise and fall of the body’s center of mass 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 by putting a bunch of foam inside the midsole of 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, air bladders, and plastic. 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 in no way 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 midsole cushions “impact”, the very first contact made with 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. We have shown that cushioning in a shoe reduces reflex muscle activity around impact and alters foot and ankle position (both of which are detrimental). On the other hand, striking a hard object, like a board, has a very good biomechanical effect, up-regulating feedback from the sole of the foot upward.
I’m not exactly sure where the basis for cushioning impact ever came from—but it wasn’t from a legitimate scientific study. 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 a single shred of biomechanical 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 poofy 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.