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Determining stiffness during hopping

  1. Feb 25, 2007 #1
    Hello everyone,

    I'm a biomechanist attempting to determine stiffness (K) during a hopping task. Basically we instruct a subject to hop at 2.2Hz on a force plate and determine stiffness of the lower body based on force and time values.

    As you can imagine this is a pretty "loose" transferrance from engineering to biomechanics, and the oscillations are not perfect. :uhh:

    The equation that is then used to determine stiffness is:

    K = Peak Force / Change in Length

    Where Peak force is in the Z axis and the change in length is from 0 (standing still) until peak hopping displacement.

    My question to everyone is:

    Should I use an integration of the force value to determine displacement, which has been recommended by some of the previous literature
    Should I use a projectile motion equation to determine vertical displacement during the hops

    Either way seems like it has some flaws, however I'd like to receive the opinions of others before I make up my mind.

  2. jcsd
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