The reference coordinate system, established when the subject addresses the ball, places the X-axis (alpha) perpendicular to the club shaft and aligned with the bottom edge of the club face as viewed down the club shaft, the Z-axis (gamma) pointing down the club shaft, and the Y- axis (beta) completing a right-handed coordinate system. The alpha component coincides with the swing angular motion, the beta component is a measure of the pitch motion of the club relative to the swing, and the gamma component is the roll angular motion about the long axis of the shaft. ...
Figures 10, 11, and 12 illustrate the beta component of the angular velocity, angular acceleration, and torque respectively for the selected subjects. The beta angular components indicate the pitch motion of the club. While the beta motion is the smallest of the angular motions, Figures 10 and 11 show that it is still significant. Since the path of the grip and club head define different planes (Figure 3), pitch motion of the club must take place. As the speed of the club increases, so must the beta motion as is indicated in Figure 10. The large variations in beta velocity curves among subjects further emphasize the relative difference in hand and club head paths taken to impact. The scratch golfer had the least pitch motion up to impact and the lowest beta angular velocity at impact. All four subject exhibited a stabilization of the pitch motion as indicated by the low beta angular accelerations at impact (Figure 11).
The beta torque curves exhibit large subject- to-subject variations. In general, the torques increased towards impact which coincides with the rapid pitching of the club, then tend toward zero near impact as the pitch accelerations approach zero. The large negative torques after impact result mainly from the mechanical rolling over of the wrists which attempts to pitch down the club. All beta actions exhibited large ranges (Table 3). These motions and torques reflected characteristics of individual swing style, and were not related to skill level or club head velocity.