Maximum Torque Values

[Pia Stefanek]

Hi,

I used the MoBL-Arms model to simulate a handbike movement and a wheelchair movement of the upper extremity. I used the following OpenSim tools: Scaling, Inverse Kinematics and Inverse Dynamics. Now I want to compare the computed joint Torque values to maximum joint torque values. I want to know the joint torque values that the model can produce maximally.
I started with the shoulder joint. I used the plot tool and displayed the shoulder moments (Elevation angle, Shoulder elevation and shoulder rotation) in relation to the joint angle (Elevation angle, Shoulder elevation and shoulder rotation).
I only selected the muscles that contribute to the shoulder movement.
Unfortunately, the peak values of the torque curves are sometimes lower than the maximum torque value during movement.

Is it correct to compute the model's maximum torque values as I described above?
Thank you for any input.

Regards,
Pia

[Dimitar Stanev]

Note that you can select the range of motion for calculating the maximum moment induced by the muscles when you vary the abscissa. Typically, you have to group the muscles into those that induce a positive or negative moment. If you sum the contribution of every muscle spanning the joint, then the total moment will be smaller since some may induce a negative moment. In the Advance Options you have to check Activation override = 1 so that the acting muscles are fully actuated.

[Pia Stefanek]

Thank you very much for your reply!

As you said I grouped the muscles into those who produce a positive and a negative moment for example for the shoulder elevation moment.

My wheelchair movement simulation yielded the following result for the shoulder elevation moment:
Maximum negative moment: -90 Nm (Curve1)

Curve1

Shoulder_elevation_moment_WC.PNG (27.75 KiB) Viewed 246 times

Then I checked which muscles produce the highest negative shoulder elevation moment:
PECM2, PECM3, TRIlong, BICshort, LAT3 and CORB (Curve2)

Curve2

SelectionofMuscles.PNG (52.91 KiB) Viewed 246 times

I added these muscles up to check for the maximum negative shoulder elevation moment: -57Nm (Curve3)

Curve3

Shoulder_elevation_MAXmoment.PNG (28.48 KiB) Viewed 246 times

Where is my mistake?

Thank you!