Varying muscle strength

I have been trying to vary muscle strength but have had thus far no luck. I have tried to simulate gait with some muscles having zero strength to see what would happen. When I do it however I get the same result for the normal gait (no change in muscle strength) to the modified gait (some muscles given a force output of zero). I have added a sample of what I am doing below where I have multiplied PCSA by zero. I am not sure what I am doing wrong, any suggestions?

AnyMuscleModel GemellusSuperior1Par = {
AnyFolder &MuscleParameters = .CadaverMusPar.GemellusSuperior;
AnyInt MuscleElemNo = 1; // The element number for the muscle
AnyVar PCSA = MuscleParameters.VolumeMuscleBelly/(1MuscleParameters.OptimalFiberlength);// Muscle volume is devided between muscle branches, and devided by fiber length to calculate PCSA
F0 = .StrengthScaleShank
.PCSAfactorPCSA0; // Maximum force output at optimum fiber length

Dear Asif,

just to make sure:

  • What model are you using?
  • What Leg type are you using?
  • What Muscle type are you using?
  • What file did you change?

Hi Amir,

Sorry for being too brief previously.

  • In terms of model I am using AMMR V1.5 Anygait and I am using the .C3D files which are given as default
  • I am using the LeftLeg_TD and RightLeg_TD
  • For muscle type I am using Simplemuslces
    -I changed the Muscle Parameters (MusPar) section

I have also seen a previous thread from a colleague of mine on this forum
I have tried to use the code by Moonki but am still having issues as I do not think I understand what the code means.

Dear Asif,

there is a MusPar file that describes the muscle parameter for the 3element muscles and there is a MusParSimple for the simple muscles.

So in your case, if you are using simple muscles you should edit the MusParSimple.any

Dear Amir,

I have carried out what you said by multiplying the F0 for certain muscles with zero to simulate no muscle. I do now get differences in the output of muscle strength when comparisons are made. However the motion in the f/e, a/a and i/e rotation planes is the exact same and that is what I am really looking it. Is it possible to change the muscle strength and therefore have a change in the motions produced in each plane.


please have a look at sections 3-5 at:
AnyBody uses InverseDynamics so Motion is always input and not output.