JC's Musings

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Can you help explain this?

Athlete A had a left foot navicular stress fracture nearly 4 yrs ago.

Recently Plantiga shoe pods identified a movement compensation where less force (up to 18%) was produced in left foot strike during running i.e. asymmetrical force production.

Strengthening interventions were implemented over six months – but ~11% asymmetry remained.

“Last weekend we used the Lila calf sleeve and placed 400g weight on the posterior of the left calf. We did 2 unweighted trials first to see what her asymmetry was before starting and the result was 14.3 and 12.7% right. Then 3 weighted trials went from 17.6 to 8.3% by the 3rd. After removing the weight the next 2 trials were 9.3 and 6.9% right.  Brilliant! An interesting bonus was that max speed improved as asymmetry reduced.” (Barrie Jennings, Personal Communication)

This is not the first time I have heard this – I have seen this in injured and non-injured athletes where wearable resistance (WR) reduces asymmetry instantaneously, which intuitively makes sense. However, what is perplexing is when the limb is unloaded, the reduced asymmetry is retained or even reduced further. Any thoughts on this?