C3D file muscle activation adjustment

[hansir1 (chenping)]

Enfleur

Dear AnyBody Team.
I am working with a C3D file and then trying to debug the muscle activation in an inverse dynamics analysis, and the muscle activation rises very abruptly at 14 fps and 45 fps respectively, how should I debug it to significantly reduce the activation? How can I debug this to significantly reduce the activation? I have tried body poses, limb lengths, heights and weights, and even measuring the position of points in space.

With best regards

Hans

[dschander (Divyaksh S. Chander)]

Hi Hans,

Welcome to the AnyScript forum!

Do you mean the muscle activation rises abruptly at frame number 14 and 45? It could be due to the recording of the c3d file (maybe there are some artefacts in the recording and the raw data needs to be looked into?), it could be related to the transition between contact of the foot with ground and not.

Can you describe a little bit more about the experimental setup and the model you are using for this work?

Best regards,
Dave

[hansir1 (chenping)]

Dear Divyaksh S.Chander

Good afternoon and thank you,
I took your advice last week and re-collected the data and the activation is now down to 0.03%. However, the problem today is the inverse dynamics KKT matrix issue, which prevents the analysis from being run, and the dynamics can only be run up to two thirds of the way.

With best regards

Hans

[dschander (Divyaksh S. Chander)]

Hi Hans,

Sorry for the delayed reply, it has been a busy week.

The error that you see is normally a case when the solver is not able to balance all the forces and find a solution and there can be many reasons for it. Unfortunately, it's not so easy to figure out what's going on. I have tried to put together some points for you:

Have you run the parameter identification and optimization study? Does the motion look ok when the simulation throws an error?

Can you describe a little bit more about the model? It looks like a box lifting model but around the time that you see the error, is there something particular that is happening (like the subject is grabbing or releasing the box?).

Is the subject always on the force plate? It looks like you have single force plate in your model, have you set settings correctly in your model: there is a setting ALLOW_MULTI_LIMB_CONTACT in the ForcePlates.any file to allow multi limb contact with the single force plate.

I hope this helps.

Best regards,
Dave