Muscle modelling


Is there anyway that I can vary muscle mass/volume? I have tried changes in segment mass but from the model view it shows a change in bone mass which is not what I am after.


Hi Ammar,

I don’t fully understand, what is your goal with that?

Hi Amir

I want to vary the mass/volume of the muscle on the hip (preferably the abductor region) to simulate potential affects following surgery as some muscle can be removed; or to put it another way, how do I increase/decrease the number of muscle attachements. I have been trying to do this by going to Bodypartsetup 2 and selecting Right Leg TD and seeing if I can increase/decrease the number of muscles. If this is not possible, would it be possible for me to vary the strength of the muscles present at the hip?

Hi Ammar,

I suggest that you change the strength of the muscle, that is used by others to simulate effects of surgeries. If you set the strength to 0 it will be equal to removing it completely.
There is in the model tree a section for Muscle Parameters (MusPar). This is also handled in the tutorials in section Muscle Modeling, Muscles Models.
Please be aware that if you change something in the Body Section, you will have these changes in all models!

Thank you Amir I will let you know if I have any problems

Hi Amir

So what I have done is set the F0=0 for some of the muscles around the hip. I have selected Right_Leg_TD and Left_Leg_TD and simple muscles for the leg. However, I keep on getting kinematic analysis failed at time zero. I have tried using different combinations of initial conditions but still no luck. Is this perhaps due to there being too many unknowns and how would I correct this? I have attache my model


I took the model you uploaded, put it into a clean AMMR1.3.1, includede the CreateMarker Classes again and it runs smooth.

Which muscles did you change? Did it run before?

Hello Amir

Thank you for your swift response. I have now got it to run after making some changes to the kinematic tolerances. I changed the gluteus maximus and gluteus minimus muscles and set their F0=0. However, by entering the values for one leg this affect occurs in the opposite leg too i.e gluteus maximus and minimus =0 in both the right and left leg. I only want this reduction in strength to occur in one leg, how would I do this?



Hi Ammar,

Actually, there is a way to distinguish left and right leg.

Main.Studies.HumanModel.BodyModel.Left.Leg.Sign = -1
Main.Studies.HumanModel.BodyModel.Right.Leg.Sign = 1

So you can put some code in ‘MusParSimple.any’ file like this:

[b]AnyVar SignVar = .Sign;
AnyVar Left_Mus_Effect = 0.0;
AnyVar Right_Mus_Effect = 1.0;
AnyVar Mus_EffectFactor   = iffun(eqfun(SignVar, -1), Left_Mus_Effect, Right_Mus_Effect );[/b]
AnyMuscleModel GluteusMaximusSuperior1Par = 
   AnyFolder &MuscleParameters = .CadaverMusPar.GluteusMaximusSuperior;
   AnyInt MuscleElemNo = 1; 
   AnyVar PCSA = MuscleParameters.VolumeMuscleBelly/(6*MuscleParameters.OptimalFiberlength);   
   F0 = .StrengthScaleShank*.PCSAfactor*PCSA*[b].Mus_EffectFactor[/b];

Then you can set different effect factors for left and right leg muscles.

I hope this may help you.

Best regards,