Induced Acceleration Analysis - Interpretation

[Pia Stefanek]

Hi,
I am currently working on my master Thesis thereby using the OpenSim Software. I weakened m. rectus femoris by modifying the contraints file (activation deficit simulation). Then, I implemented a path spring parallel to m. rectus femoris with different stiffness values and observed the effects on different muscles during walking. I also performed IAA for the femur. It can be observed that the accelerations for all muscles increase (negative or positive), compared to healthy m. rectus femoris. The overall femur acceleration stays constant both cases. Does anybody know what could be the reason?

I thought that Maybe the spring is not considered in the OpenSim IAA calculation and therefore the spring contribution to Femur acceleration has to be 'overtaken' by other muscles in the Simulation. Is this a possible explanation?

Another interesting fact is that the weakened m. rectus femoris without spring implementation produces the same force curve as the weakened m. rectus femoris with spring implementation. But the acceleration curves in both cases differ. The Femur acceleration of m. rectus femoris with spring implementation shows higher values. Does this mean that m. rectus femoris has to use more of its produced force for Femur acceleration because of the implemented spring?


Thank you very much in Advance.

Pia