Specifications

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Having provided torques for the shoulder and elbow it should be possible to run the inverse dynamic
analysis. However, attempting to do so will provide the same depressing error message as before. The
reason is that general muscles share the ability to be unilateral with normal muscles. The direction of action
is controlled by the variable ForceDirection. If the muscle acts in the positive direction of the joint angle,
then it direction should be set = 1, and if it is in the negative joint angle direction it should be -1. In the
present case the external load tends to work in the negative angle direction for the shoulder as well as the
elbow, and hence the muscles should counteract in the positive direction:
AnyGeneralMuscle ShoulderTorque = {
ForceDirection = 1;
AnyKinMeasure &Angle = .Jnts.Shoulder;
AnyMuscleModel &Model = .MusModel;
};
AnyGeneralMuscle ElbowTorque = {
ForceDirection = 1;
AnyKinMeasure &Angle = .Jnts.Elbow;
AnyMuscleModel &Model = .MusModel;
};
Now the InverseDynamicAnalysis can be performed. Having done so, we can open a new Chart View and
look up the two joint torques as the Fm property of the general muscles. We can plot both of them
simultaneously using an asterix as shown below: