simtk.org

Hello,

Opencap gives me the rotation of the pelvis and lumbar spine, I would like to calculate the rotation of the shoulder girdle and I would like to know how the pre-defined rotations are calculated.

I have tried different ways of estimating this rotation during walking, but the data does not coincide with the automatic ones, and so I am unable to determine whether the rotation of the shoulder girdle is correct.

Thanks in advance for your attention

Since the entire trunk is modeled as a rigid body, the rotation of the shoulder relative to the pelvis is entirely defined by the lumbar joint. You can check out the euler sequence of the lumbar joint in the .osim file to see where lumbar_rotation falls in the sequence. Since it is an euler angle, it is expected to differ from a physical angle (e.g. the angle between the line connecting the shoulder markers and the line connecting the ASIS).

Perfect, thank you very much for your help