The Importance Of Wrist Torque In Driving The Golfball (P4)
Under virtually static conditions at the initiation of the downswing, the muscular torque generated by the torso reached a value of approximately 75 Nm before decreasing as a result of the force-velocity properties of the torque generator as the torso picked up rotational speed (Figure 3). A similar pattern was observed for the early phase of the torque generator at the shoulder, where it reached a value of 83 Nm before momentarily decreasing as a result of the force-velocity properties of the generator that were attenuated by the arm’s increasing angular velocity relative to the torso. As impact neared, the muscular torques generated by both the torso and shoulder increased again as a result of the torque generator at the wrist joint being activated. The reason for this behavior was that the activation of the wrist torque generator increased the angular velocity of the club segment, which in turn decreased the angular velocities of the arm and torso segments. This reduction of the relative angular velocities of the torso and arm segments, via segment interactions, enabled the output of their torque generators to increase as impact neared. The final brief reduction in torque output at the shoulder joint is attributed to a brief increase in the arin’s relative angular velocity that coincides with a slight decrease in angular velocity of the wrist joint just before impact.
The optimized simulation, SIM-1 (Figure 4A), revealed that the active wrist torque commenced shortly after the natural uncocking of the wrist joint had begun. Thus the wrist torque was not responsible for initiating the uncocking of the wrist joint but was employed to augment the naturally occurring wrist action induced by the centrifugal pull of the club. This active uncocking of the wrist joint using muscular torque was delayed until the arm segment was approximately 30° below a horizontal line through the shoulder joint.
The sensitivity of the simulation to the timing of the wrist torque was examined by advancing and delaying the onset of wrist torque by 50 ms from that found to be optimal. The results revealed that activating wrist torque 50 ms late reduced the clubhead speed at impact by 4.6%, as compared to a reduction of 2.0% when the wrist torque was activated 50 ms early.
A visual comparison between the image sequence of SIM-1 (Figure 4A) and that of a real life elite professional golfer, Nick Faldo (Figure 4B), revealed a marked similarity in the starting and end positions. The only apparent difference between the two sequences appears in the greater delay of the wrist uncocking during the downswing for the elite golfer. This can be attributed to the greater rotational speed of the torso exhibited by the professional golfer as he completed the downward swing in less time.