Low muscle force

Hi,

I was previously working with the GaitLowerExtremity Model (v 5.3 AMMRv 1.5.1) and now adapted the MoCap Model to my needs (v 6.0 AMMRv 1.6.2).
I am looking at graded walking and for several of my trials I get pretty low quadriceps forces (added up all parts of vastii and rectus femoris in Matlab). I have checked the force, which is alright, also the trial itself looks good. Low muscle forces occured in both versions. A quadriceps force of aprrox 200N just doesn’t seem to be right. Do you have any advice for me, regading which mistake I might have made, what I could check, etc.?

I have attached my Model (v 6.0 AMMRv 1.6.2) and one trial were such a low quadriceps force occurs. I have adapted the “\Body\AAUHuman\ToolBox\Mocap\ForcePlateType2AutoDetection” file which is now named ForcePlateType2AutoDetectionCorner and I copied it into the the Model folder to zip-&upload it together.

I would appreciate your help!
Thanks,
Nathalie

Hi Nathalie,

I just recalled that I had helped you with a similar problem before.

I tried to run your model and could find an issue.

In your modified force plate class template, it will use the ‘ContactDetection.any’ file to detect which limb (left or right foot) is in touch with the force plate.

And there are some important variables to check whether a limb is in contact with that force plate:
P1WithinQuad , P1WithinHeight , P1WithinBox,
P2WithinQuad , P2WithinHeight , P2WithinBox,
WithinBox, WithinBoxAndVelBelowThreshold

The role of this file is to check whether some points(HeelContactNodeLow and ToeLateralContactNode in the foot) are in the force plate area and it will also check the height tolerance and the velocity tolerance.

Because your force plate is inclined, so it seems that the height tolerance check is not working for your model.
If you check the P1WithinHeight and P2WithinHeigh values, these values should be 1 if the force from the force plate should be transferred to the human foot.

So now there are several ways to solve your problems.

  1. Simply you can try to use different values for ‘HeightTolerance’ and ‘VelThreshold’ for you force plate class template instances in the ‘Input\ForcePlate.any’ file.

  2. Create your own ‘ContactDetection_InclinedForcePlate.any’ file which also considers the inclination of the force plate

  3. If you know which limb will touch a certain force plate in advance, then you can just create your new ‘ForcePlateType2Corner.any’ file from the original ‘ForcePlateType2.any’ file.
    After that you can use this ForcePlateType2Corner class template instead of using the current ForcePlateType2AutoDetectionCorner class template.

I would recommend you to try the last method because now we know that the left foot will touch the left force plate and the right foot will touch the right force plate in your model. :slight_smile:

I hope this may help you.

Best regards,
Moonki

1 Like

Thanks Moonki, it works :slight_smile:
(did option #3)