I am performing an inverse dynamics analysis using ground reaction forces and kinematics measured on skiers. Ground reaction forces were collected from a force plate mounted between the ski and the ski binding. So the coordinate system of the GRFs is always the same as the calcaneous. I know the distance of the origin of the force plate, relative to the calcaneous, and am using those coordinates [px,py,pz] as the point of application in my GRF.mot file. So essentially, the point of application of the GRFs never changes for my application, and I am specifying that the force and torque components are expressed in the coordinate system of the calcaneus, not the ground (global).

Lateral View.PNG COM_Foot.jpg

However, in a few other posts on the OpenSim Forum, I have seen people using Center of Pressure for the location of the applied GRFs. Can someone verify for me that it is correct (or not) to use the xyz position of the force plate, relative to the body (calc) that I am applied the loads to?

It is somewhat confusing because if I use the File -> Preview Experimental data, it forces the user to view the data in the ground coordinate system, so I am having a difficult time visually verifying that I am applying the GRFs to the location I think I am.

Thank you for your help.