Slingshot Form

This week I finished my graduate program in clinical and translational science at UVM and last week presented at the department’s weekly seminar, summarizing my research interests in runner biomechanics, which I explored during my program.  Suffice it to say, at this point I thought I’d have a clear idea of next steps.  Not so!  However, in preparing for the presentation, I leafed through three running books in my library: Running Anatomy by Joe Puleo and Patrick Milroy, Running Form by Owen Anderson, and Anatomy for Runners by Jay Dicharry.  They deliver the same message in different ways: to run fast and avoid injury, you need a strong chassis and you’ve got to be efficient in how you use your energy.  I looked through my blog posts and saw one from June 25th, 2019 drawing from Dicharry’s book that I entitled Gait Keeping.  I’m going to expand on this here, but recommend looking at that prior post too.  

Dicharry suggests thinking about a slingshot, as we probably played with as kids.  You pull it back and there’s tension.  Depending on the thickness of the band and how far you pull it back, the projectile shoots out.  To maximize distance, one shoots neither too high nor low.  Just right.  This principle works for all sports.  In baseball, for example, a sky-high popup is going to stay in the park, as is a line drive.  However, a fly ball stroked with sufficient power and optimal height has a good chance of being a home run.  Dicharry calls his slingshot analogy “elastic recoil” and suggests it is our Invisible Friend, seeing this storing and release of elastic energy as crucial to fast and efficient running.  He illustrates an ideal pendulum and postulates operating beyond this arc is wasted energy.

Running mechanics are obviously much different from baseball, with some 1,500 “fly balls”, or steps, per mile.  If our flight height between landings is too high, we use excess energy going vertical rather than horizontal.  We’re distance runners not high jumpers!  But if the height is too low, it cuts down on flight time, resulting in a shorter horizontal stride length.  We might have to take 1,600 steps instead of 1,500 to cover the same distance.  

This week, I’ve been visualizing what is going on “in the chassis” when I run at different speeds.  My racing cadence is about 180 and training cadence roughly 175.  While this hasn’t changed much, my times have recently slowed more than expected, both racing and training.  Thus, this implicates stride length as the culprit.  Pictures sent by a photographer from different locations at last week’s race confirm this.  My stride extension was clearly shorter than in prior photos, especially toward the end of the race.  So I’ve been focusing on extending a bit further while still landing on my midfoot and maintaining cadence.  This requires a bit more push-off, which is essentially a release of the elastic energy stored during flight.  The result has been noticeable.  Without any increased effort my training pace has dropped about 15 seconds/mile.  That’s significant.  And I’m excited to see how this plays out in my next race!

Our running bodies are pretty awesome!  While they are composed of flesh and bone, they explicitly follow the laws of physics that underlie the field of biomechanics.  It may be useful, at times, to take stock of our stride, measure the components, and adjust cadence or stride length as needed.  It’s not a one-and-done activity.  As we age, various things change in our bodies.  And one can be anal obsessing about all of this.  At the same time it’s good to pay attention and periodically take stock.  To repeat the ending from my May 2nd blog, “As with all things balance.  Goldilocks!”

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