Loads on Shoulder
When analyzing effects of body position, we assume that BODY WEIGHT acts at the body’s CENTER of GRAVITY.
When analyzing the effect of the position of body segments (eg. shoulder), we assume that the weight of each segment acts at the segmental CENTER of MASS/GRAVITY.
Thus the moment-arm for the entire arm segment with respect to the shoulder, is the perpendicular distance between the Weight Vector (acting at the arm’s CG) and the shoulder. When the elbow is in flexion, the effects of the upper-arm and forearm/hand are analyzed separately. PIC
An important implication in golf is that an extended forearm makes a longer lever and the torque created at shoulder by the arm is greater than when the forearm is flexed at the elbow