View Full Version : Spherical / polar coordinate systems to model shoulderbiomechanics

07-28-2010, 06:35 AM
Greetings, biomechanics community.

I am currently working on a project to model the biomechanics of
baseball batters during swings. As per a recent suggestion, I am
considering using a polar/spherical coordinate system to measure
glenohumeral movement for both shoulders. For simplicity sake, let's
say I only have two markers, effectively a shoulder joint center and an
elbow joint center, and I know their x, y, and z coordinates in the
global Cartesian coordinate system. Are there any suggestions on how to
calculate the two polar angles, especially given the fact that the body
rotates about 90 degrees during the swing, effectively swapping the X
and Y axes? Any thoughts on this matter are appreciated. Thank you.

Dave Fortenbaugh, M.S.


American Sports Medicine Institute

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