Mascle activity during sit-to-stand

[masahiro yokota]

Hello, everyone.
I use OpenSim to examine muscle activity during sit-to-stand movement.
I’ve made some STS motion, but result of SO data is too large than I expected. This picture is result of the muscle activity of soleus_r and ercspn_r. I think these values are too large.

soleus_r erecspn_r.PNG (35.4 KiB) Viewed 280 times

I created some models and carried out simulation in the following procedures.

1. I made a motion file from motion capture data. I used Kinect and marker as the motion capture device. To analyze STS motion patterns, I focused on 7 joint angles(ankle_r, ankle_l, knee_r, knee_l, hip_r, hip_l, lumbar_extension) because I acquired these joint angles on sagittal plane in motion capture experiment.

2. I use “gait2392_simbody” as a model. I fixed calcn to the ground using “WeldConstraint” .

3. To examine muscle activity, I did SO from these models.

Do you think there is any problem of my procedures? If I have some mistakes, please tell me where I should change my procedures.

[Dimitar Stanev]

Hi,

It is possible that the muscles are operating in a bad region, e.g. too stretched. You can calculate the muscle's fiber length to check this. If the muscle is stretched then these forces are due to the passive component of the muscle.

It is also possible the constraint is not properly satisfied. You can check the activations and the residual forces.

Best

[masahiro yokota]

Hi, Dimitar
Thank you for your reply.
I checked muscle's fiber length, but I don't know which data I should compare with.(I can't confirm these are too large,small or OK)
If these are not exactry, do I need to change the mot file?

[Josh Baxter]

If you are using the default muscle and slack length parameters, this 'jerky' muscle loading may come from noisy kinematics. were these kinematics adequately filtered?