Wednesday, August 29, 2012

Reducing the Peak

For a baseline measurement of loading rate, the runners ran at their normal pace with their normal gait while wearing conventional motion-control shoes (a French model, the Kalenji Kiprun 2000). Then the researchers measured loading rate under four other scenarios: having the runners switch to a racing shoe that's 5 ounces lighter than the training shoe (the Kalenji Insipid Comp); having the runners increase their turnover by 10%; having the runners switch to a midfoot strike; and doing all three of the preceding changes at once (what the researchers called "combi").
When the runners switched to a midfoot strike, or when they ran in "combi" mode, they no longer produced an impact peak (a spike of impact concentrated in a fraction of a second), and they reduced their overall loading rate by about 50%. Only increasing turnover, or only switching to the racing shoes, didn't produce these changes. (It should be noted that the racing shoe used in this study has a heel-to-toe drop of 10 millimeters, which is 2 millimeters higher than that of the training shoe used. A larger heel-to-toe drop is often associated with a higher impact peak.)
The takeaway is that a midfoot strike by itself is as effective as midfoot striking with higher turnover in racing shoes in reducing impact loading rate; theoretically, this finding should be of most interest to runners who have a history of shin stress fractures.

This is not the most well written article ever, but still reinforces a point that Dr. Romanov and others have discovered and documented over the years; there's a natural shock absorbing system built into the body, and big, so called shock absorbing shoes, work against the way we were built to run.

Some of this is "too easy" (as my Army trainers used to say with a grin).

Landing on the ball of the foot allows many springy, well muscled parts of the leg to absorb impact and produce force; further, most running animals have legs that work in a similar way.  The idea of landing on the heels - and sending the impact through the solid bones of the heel, to the knee, to the hip - seems almost ridiculous in comparison.

Turnover is not the key to good running - it is a correlate.  Turnover is a function of keeping the legs close to the body's center line - one could move the feet too slowly or too quickly.  Thus, it also makes sense that the study didn't find it to be an independent variable for reduction of impact peak. 

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