Dear Researchers,

I am using The Vicon Motion Tracking system for capturing human gait. I have
come across one serious question. I am using my own model to put the markers
on the subject's body. For each segment (for example upper arm), I use 3
non-collinear markers to define a coordinate system. What I get as the
output of the Vicon is a CSV file containing Rx, Ry, Rz of each segment
either in terms of Euler angles YXZ or Helical axis .

My question is how can I calculate flexition/ extension (in sagittal plane)
of each joint i.e knee joint given Rx, Ry, Rz in terms of either YXZ Euler
angles or Helical angles?

I really appreciate your comments and help,


Babak Hejrati

PhD student

University of Utah