Hi guys,
I'm looking at some joint kinematics in rock climbing and comparing them to fiber length and seeing some oddities. Specifically, I'm looking at knee angle and vastus intermedius fiber length, which ought to have approximately a 1:1 relationship since the knee is 1 DOF in the model used(Gait2354) and the vastus spans directly across the knee. However, this does not appear to be the case, as one subject reaches and maintains greater knee flexion yet has a smaller maximum fiber length. Activation is overridden to 1.0, and these data are from the same (unscaled) generic model.
Why/how is this occurring? Is this possibly related to musculotendon dynamics, since the vastus intermedius has such a long tendon, or maybe velocity since the climber with greater peak knee flexion achieves a faster contraction velocity?
Here's the relevant data plot:
http://people.virginia.edu/~caz3b/Knee.png
