On a swing and a prayer#

Sun, 11 May 2008 03:12:12 +0000

Having just recently emerged from a long discssion on the LSST forum about armswing, here is my current thought on how/why it works

Possibility 1: Lateral motion is key but fore-aft armswing is taught because it contains about as much lateral motion as is productive - let's hypothesise that more side-to-side causes aerodynamic, upper body torque or shoulder fatigue problems which outweigh the weight shift advantage - but that the fore/aft component as such is irrelevant to overall speed. This is possible (and what I used to believe), but would tend to suggest that a gentle swing is very nearly as effective as a vigorous one, because the lateral range of motion's about the same in either case. Doesn't sound quite right

Possibility 2: That there is an extra ingredient of some kind which means extra force in the fore/aft armswing creates more force in the legs despite the fact they're going in different directions. This is what I now believe based on last week's reading of gait papers and the stuff about CPGs - the exact mechanism may be open to debate, but the possibilities are clearly there for forelimb movement to stimulate neural paths that trigger muscle activity in the hindlimbs.