In the gait model, there was no change in muscle force with increased load

In the example of the static model of the ShoulderBag, when the weight of the shoulder load is changed, the muscle forces are changed. But in the gait analysis model (GaitVaughan), after the shoulder load is increased, the muscle force is unchanged, why is this?

Addendum: In the gait model, only the load is changed, and the drive (Marker data) of the gait remains unchanged.

Hi @jiang

The GaitVaughan model is only set up to investigate lower limb muscles and compare them to EMG measurement. It has a reaction force between the pelvis and global coordinate system which is probably what is recruited when you add a load above the pelvis. Try and see if that reaction force is used more when adding the bag.

This concept if often used in some variety in mocap model to act as residual forces and often refered to as the hand of god. You can read more about it here.

Best regards,
Bjørn
AnyBody Technology

Thank you for your reply.
Now I want to study the trends of muscle and joint forces under the same gait with different loads.
How can I modify the model?

Hi @jiang

You should probably use one of the real mocap model which handles the hand of god in a different way. There you should be able to apply the bag load as you did now.

Best regards,
Bjørn

I didn't find mocap model. Is it the same example as ShoulderBag and GaitVaughan?

Hi Bjorn,
How can I get an application example for Motion Capture and Gait Analysis?
There is no example of this in the Anybody software I installed.
Is there a link to download it?
Thanks

Hi @jiang

The Mocap examples are located under AMMR/Application/MocapExamples there you can find models that uses both c3d and bvh input.

Best regards,
Bjørn
AnyBody Technology

Hi Bjorn,
I'm using an old version. AnyBody is V4.0 and AMMR is V1.0. I don't have this exercise in my Application. I want to study the trends of muscle and joint forces under the same gait with different loads.How can I modify the model?
I want to modify this problem based on GaitVaughan's model.
I think should be changed JointsAndDriversOldMethod. Any file.

AnyReacForce PelvisGroundReaction = {
AnyKinLinear Lin = {
AnyFixedRefFrame & ref1 =.. GlobalRef;
AnySeg & ref2. = the Main Model. HumanModel. Trunk. SegmentsLumbar. PelvisSeg;
};

AnyKinRotational rots = {
AnyFixedRefFrame & ref1 =.. GlobalRef;
AnySeg & ref2. = the Main Model. HumanModel. Trunk. SegmentsLumbar. PelvisSeg;
Type = RotVector;
};
};

But I don't know how to rewrite it. Please help me.

Hi @jiang

Your version of both AMS and AMMR is very outdated. You should consider having your license upgraded to benefit from all the improvement that the system has undertaken.

We can only provide limited support for such old version.
You can download the newest version of the AMMR here and try a model from that.
There is also code to show how you can model the residual forces differently.

You are very welcome to send me a private message with your affiliation and license details - then we can discuss a possible upgrade.

Best regards,
Bjørn

Hi Bjorn,
My AMS cannot run the latest AMMR. How should I modify this option on the basis of AMSV4 and AMMRV1? How do you get rid of ground reaction? I would like to modify the connection between the Pelvis and the ground. But I don't know where I should connect the Pelvis.

Hi @jiang

As mentioned i think you best chance is to look at the implementation in the new ammr mocap models.
That should give you an idea of what is needed.

Best regards,
Bjørn