Analysis Of Elite Golfers’ Kinematic Sequence In Full And Partial Shots (P4)
This study showed a clear proximal-to-distal temporal relationship of movement onset and maximum angular speed at the pelvis, upper torso and hand segments in the golf swing. The same temporal structure was evident at all test conditions, among different gender and level of expertise. Further, results revealed a summation effect of angular velocity from proximal-todistal, with each succeeding segment generating a larger rotational speed than the proximal segment. However, the increment in speed from proximal-to-distal was different among gender and level of expertise.
In this study, steps were taken to limit possible sources of error for the kinematic measurements. To minimize metal interference the capture volume for the EM system was distanced from any structural metals, but due to the participants’ golf shafts, steel was used within the field. A pilot study, however, displayed similar results for kinematic data collected using the electromagnetic system setup compared to those of an optoelectronic system lacking the issue of metal interference. Other notable sources of error for both systems in vivo are sensor (marker) displacement with respect to the underlying bone and inaccurate and inconsistent placement of sensors (markers). To limit inaccurate and inconsistent placement of sensors, the same investigator performed the sensor attachment procedures for all participants. To minimize displacement with respect to the underlying bone, sensors were placed at sites where the thickness of underlying tissue was minimal for the participants.
Motion sequences for full-swing shots have previously been investigated in the literature. Studies have either demonstrated that the pelvis segment moves into the downswing ahead of the upper torso, or that the shoulder joint attain maximum angular velocity prior to the wrist joint. Findings based on data where motions of pelvis and upper torso have been estimated by determining transverse plane rotations, whereas motions of the upper limb and golf club have been modeled as a planar movement in a single inclined plane. In the present study, the magnitude of the spatial angular velocity vector for each of three body segments was utilized to examine the sequence of motion. Consistent with previous observations of full-swing shots, results revealed that pelvis moved into the downswing ahead of the upper torso .24,25,26 The proximal-to-distal order in which upper torso and hand segments reached maximum angular speed has not been reported earlier, but is in line with earlier observations in which the shoulder joint attain maximum angular speed prior to the wrist joint. 27,28 Although the role of PDS cannot be explained by kinematic data alone, the temporal relation between segments with a period where distal segments accelerated while the more proximal was decelerating indicates that participants could utilize interaction torques effectively to generate high club speed.
The current study extends findings from previous studies by adding support for a universal kinematic sequence in partial and full-swing shots of skilled golf players. The temporal parameters tested were not significantly affected by group. Thus, timing did not change significantly with gender or level of expertise among participants. The temporal relationship of movement onset and maximum angular speed at the pelvis, upper torso and hand segments showed a clear PDS organization for all shot conditions (Fig. 4). While there exists a solid body of evidence in support for that PDS provides mechanical merits when the largest possible ball speed is required, merits of PDS in partial golf shots are less evident. However, Hamilton et al. reported that a given torque or force can be more accurately generated by a stronger muscle than a weaker muscle. A potential role of PDS, therefore, can be to improve accuracy and minimize the speed-accuracy tradeoff.
A common kinematic characteristic of PDS is a summing effect of segmental speed.31 Participants’ maximum segment angular speeds increased in a PDS pattern for all test conditions (Fig. 5). This is in line with earlier findings in full-swing shots regarding the increase in maximum angular speed from pelvis to upper torso and from upper torso to left wrist and club shaft. However, this summing effect of segmental speed has previously not been reported for partial shots. The significantly larger increments of maximum angular velocity from upper torso to hand for the male players compared to the female amateurs in full-swing shots (Fig. 6) are consistent with results reported by Zheng et al. where the major differences between male and female professionals were significantly lower wrist and elbow joint angular velocity for the females. These results can help explain differences in hand speed and performance factors such as driving distances in full-swing shots. Interestingly though the significantly larger increments of maximum angular velocity from upper torso to hand for the male pros compared to the female amateurs in full-swing shots were also present in partial shots, where participants were required to hit the same distances. This indicates that the observed differences between gender may exist due to disparities in anthropometrics, flexibility and strength characteristics. Another interpretation may be that the different increments of maximum angular velocity from upper torso to hand in partial shots reflect a difference in level of expertise, where the male pros with long-term training should have developed a more efficient way to produce the preferred performance goal.
An interesting future direction to investigate is how instruction affects segment interaction and ultimately performance. Southard reported that in a task of striking a ball on a tee using the hand, subjects who were instructed to perform the task as fast as possible acquired the PDS organization of segmental motions by the end of five days practice. However, those who emphasized accuracy of the ball placement did not acquire the PDS segmental motion. There were no significant differences in accuracy by conditions or day of practice even though there were significant differences in velocities by condition and practice. In what way initial conditions/instructions influence the progress of segment interactions in golf, has not been reported.
In conclusion, the temporal relation of segment kinematics suggests a common PDS organization in partial and full-swing shots for skilled golfers. The temporal relation and speed-summation effect of segmental angular speed indicates that participants did utilize interaction torques in a proximal-to-distal manner. A role of the observed PDS organization and speed-summation effect in full and partial shots might be to improve accuracy and, potentially, golfers should concentrate on speed initially in learning the golf swing in order to enhance a change in movement organization.