L5-S1 compression and shear forces

Hi everybody
I have a quick question to ask!
I have developed a model from .c3d files for the study of shoulder muscle activity. As a last step my professor asked me to check the value of the compression and shear forces in the L5-S1 junction, in order to obtain a complete analysis for verification of the NIOSH method, during the simulation, but I'm not sure I have found the correct values.
Could someone help me and tell me where I can find them?

Thanks in advance,
Andrea

Hi @Andrea

Great to hear you are making progress!

The compression and shear force of the L5-S1 joint can be found as part of the InverseDynamicStudy's selected output.

The path will look somethinf like this, depending on your model structure.
...InverseDynamicStudy.Output.BodyModel.SelectedOutput.Trunk.JointReactionForce.L5SacrumMedioLateralForce In the same folder you can find the remaining two directions of the joint reaction force.

Best regards,
Bjørn
AnyBody Technology

Hi Bjørn
Sorry for the delay in my reply but they have been busy days!
Thank you very much for your help!
I have a "theory" question.
For the study of my .c3d file I started from the GRF_prediction model and I was wondering what kind of algorithm for muscle recruitment it uses. Quadratic, polynomial or min / max?

Thank you and have a good day
Andrea

Hi @Andrea

No problem, I'm glad to help!

The GRF prediction tool is made using artificial muscles with very high strengths.
The high difference in strength between these artificial muscles and the Human-Ground residuals that have a very low strength, the models by default use a second order muscle recruitment criteria for more numerical stability.

You can inspect the settings in you model's study under: Main.Studies.InverseDynamicStudy.InverseDynamics.Criterion.Type and Main.Studies.InverseDynamicStudy.InverseDynamics.Criterion.Power

Best regards,
Bjørn
AnyBody Technology