Figure 1. . Black arrows indicate the segment coordinate system (X, Y, Z) with i=0, the racket/hand segment; i=2, the forearm segment; i=3, the upper arm segment, and i=4, the thorax. The axes X and Y, as well as a floating axis Z define the joint coordinate system and the movement orientations of the shoulder. The pivoting axis to measure the swingweight and twistweight was fixed at 10 cm from the handle extremity (*).