Flexion forces on specific vertebra

[faa198501 (Faris Almalki)]

Dear AnyBody support team,

1-I am trying to measure the forces on the L3 vertebra and also on the L3L4 joint in the spinefixationwithforcedependantkinematics during flexion, I just want to make sure that the details of the anyscript I am using are correct?:

AnyForceMomentMeasure2 ForceMeasure2 = {

  RefPoint = &Main.Model.EnvironmentModel.GlobalRef;
  IncludeSegments = {&Main.HumanModel.BodyModel.Trunk.SegmentsLumbar.L3Seg};
  
  IncludeForces = {&Main.HumanModel.BodyModel.Trunk.MusclesSpineRight.Multifidi.MFdL1L3, &Main.HumanModel.BodyModel.Trunk.MusclesSpineRight.Multifidi.MFdL3L5, &Main.HumanModel.BodyModel.Trunk.MusclesSpineRight.Multifidi.MFmL3S1, &Main.HumanModel.BodyModel.Trunk.MusclesSpineRight.Multifidi.MFtsL3Ligament, &Main.HumanModel.BodyModel.Trunk.MusclesSpineLeft.Multifidi.MFdL1L3, &Main.HumanModel.BodyModel.Trunk.MusclesSpineLeft.Multifidi.MFdL3L5, &Main.HumanModel.BodyModel.Trunk.MusclesSpineLeft.Multifidi.MFmL3S1, &Main.HumanModel.BodyModel.Trunk.MusclesSpineLeft.Multifidi.MFtsL3Ligament};
            
  IncludeGravity = On;

2-Also when using this script I get three lines in the chart, blue, orange and green. what does each one resembles?

3-The force I get is constant value of -20 N...please let me know why do I get this specific value and why it doesn't change with the motion?

4- How can I measure the forces and moments on the L3L4 joint. When I tried using AnyForceMomentMeasure, I got the following errors:

1. when adding L3L4Jnt as segment:
   ERROR(OBJ8) : SpineFixationWithForceDependentKinematics.main.any(161) : ForceMeasure2.IncludeSegments : Type restricted object-pointer has been linked with object L3L4Jnt of unacceptable class AnySphericalJoint
   Allowed classes are: AnySeg

b) when adding L3L4Jnt as RefPoint:
ERROR(OBJ8) : SpineFixationWithForceDependentKinematics.main.any(160) : ForceMeasure2.RefPoint : Type restricted object-pointer has been linked with object L3L4Jnt of unacceptable class AnySphericalJoint
Allowed classes are: AnyRefFrame

...or should I use the reaction forces for joints forces, for example: (Main.Study.Output.Model.BodyModel.SelectedOutput.Trunk.JointReactionForce.L3L4ProximoDistalForce). For the moment I only see moment for cervical joints not lumbar, how can I measure moments on lumbar joints?

Thank you very much

[toerholm (Søren Tørholm)]

Sorry about the slow reply, here are some answers.

1: In the code you have listed i do not understand why you would want to use GlobalRef, as the refpoint. In the example on the wiki All about Kinetics · AnyBody/support Wiki · GitHub global ref is being used but this is because the model is a one segment model connected in a joint with global ref so in this case the example code can be used to find the torque the muscles generate around this node. In your case i assume you may want to use nodes related to L3L4 joint or L2L3 joint.

2: if you in the chart click icon #3 "Data View" you can see the colors and corresponding names.

3: that could be simply the mass of L3 (around 2 kg) times gravity, the multifidi muscles do not connect to globalref

4: I think you will need to change the RefPoint to be a node in the L3L4 joint. so e.g. the L3L4 joint node on the L4 segment.

Best regards
Søren