The Sequence Of Hip And Selected Upper-Extremity Joint Movements During The Golf Drive (P1)
Purpose of the Study
The purpose of this study was to analyze, using electrogonio-etry and cinematography, the wrist, forearm, elbow, and hip actions of low-handicap golfers while they attempted to accurately drive for maximum distance, The analysis was made at six points in the swing, which were as follows:
- At the top of the backswing.
- At the position in the downswing where the left arm was horizontal.
- At the position in the downswing where the angle formed by the left arm and a vertical line drawn through the acromion process was forty-five degrees.
- At the position in the downswing where the angle formed by the left arm and a vertical line drawn through the acromion process was twenty-two and one-half degrees.
- At the position in the downswing where the long axis of the left arm was vertical.
- At the position in the downswing when the ball was contacted.
It was hypothesized that a common pattern of movemmt of both extremities and the hips of all golfers throughout the downswing could be identified.
Methods and Procedures Ten subjects, five from Western New England and five from Northern New York, participated in the study. Club professionals and golf coaches were asked to identify potential subjects. Those golfers receiving unanimous recommendations were selected as subjects.
Elgons were attached to the upper extremites of the subjects to record the joint action at both elbows, both forearms and both wrists. Two elgons were used at each wrist to record both flexion-extension and abduction-adduction movements. The elgons used to measure elbow action were similar to those used in previous studies by other investigators. The elgons used to measure forearm action and wrist flexion and extension as well as wrist abduction and adduction were especially adapted for this study. A wrist bracelet was developed to hold the wriest portions of the respective elgcns in place. A hip analyzer was also developed in order to ascertain the position and movement of the hips throughout the swing.
Electrical impulses from the elgons were channelled through two electrogoniometer control panels and recordings (goniograms) made on light-sen.ltive paper by using three Honeywell Visicorders. The control panels were used to calibrate the electrical impulses from the elgons by use of a special protractor so that visicorder tracings, could later be converted into the degrees of joint movement.
Two sites were used for testing, one in Northern New York and one in Western Massachusetts. Both sites had a large, flat, grassed area referred to as the “tee area’. Each site also had a target zone that was fifty yards square at a distance of 225 yards from the tee area. There were no obstructions between the tee and the target.
A sixteen millimeter motion picture camera, which was operated at sixty-four frames per second, was mounted on an adjustable tripod sixteen feet in front of the performing subject. The camera was adjusted so that the Center of the exposed frame of film was at the subjects’s shoulder height. Motion pictures taken of each subjects trial were used to determine the six reference points of the left arm movements which were selected for analysis.
The exact moment of ball contact of each trial was recorded on the goniograms by use of an electrical circuit through two contacts between the ball and the tee upon which the ball rested. When the ball was struck the circuit was broken and this was registered on each goniooram. The face of an electric timer, which was started by the tester and automatically stopped at ball contact, was within the framing of the motion oicture.camera and used to synchronize the data from the goniograms and the motion picture film.
Subjects performed repeated tests until each subject had successfully driven six shots into the target zone. This procedure was repeated during a second testing trial so that all subjects performed twelve successful drives.
An enlarger was adaoted to facilitate viewing of single framcs of the motion picture film. This process
allowed the investigator to record the exact readings of the electric timing device and the angular position of the subject’s left arm. By measuring the angle differences and the time differences between adjacent frames, it was possible to assign a given time to each of the selected left arm positions in the swing. This information was used with the time lines on the goniograms to determine the exact moment when the joint angles should be measured to correspond with the reference points selected for analysis. By doing this, it was possible to obtain the angle reading for each joint at each of the selected reference points.
An analysis of the literature on golf revealed a consensus on the sequence of actions necessary for driving a golf ball a long distance. This summation of acts is referred to as a “model swing”. The joint angles and changes in them were used to determine to what extent the subject’s performance agreed with the consensus from the literature. The following information is a resume of the findings.
In determining the left arm positions as the selected reference points, the measurements were made of the angle between the long axis of the left arm and a vertical line passing through the acromion process of the left shoulder. The mean angle of the left arm at the top of the backswing was 137.6 degrees, but there was considerable variability among subject. The standard deviatior. was 28.1 degrees. and the range of the ten scores was from 89.7 degrees to 190.6 degrees.
At ball contact the average angle of the left arm position of all ten subjects was minus 9,1 degrees indicating that it had passed the vertical ;position at this point. All subjects, except one, contacted the ball after the left arm passed the vertical position. The tenth subject made contact at .3 degrees. The values ranged from .3 degrees to minus
23.8 degrees. The standard deviation was 7.5 degrees. The recordings indicated that all subjects followed a similar pattern of movement of the right elbow (see Figure 1). At the top of the backswing, the right elbow was held at a mean position of 112.2 degrees.
The recordings ranged from 96.2 degrees to 121.0 degrees with a standard deviation of 6.61 degrees. At bail contact, the mean position of the right elbow was 149.6 degrees. The standard deviation was 10.35 degrees, and the range of the measurements from tha top of the backswing to ball contact was 37.4 degrees. It was significant that 14.1 degrees of this amplitude was registered between the twenty-two and one-half and the vertical reference positions.
The findings for right forearm rotation revealed an average fluctuation of only 3.5 degrees throughout the downswing (see Figure 2). Again the major portion of this action occurred between the twenty -two and one-half degree and vertical left arm positions. It was also significant to note that there was a large amount of vaAability among the subjects, as indicated by standard deviations ranging from 20.1 degrees to 23.0 degrees at the various reference points.
At the top of the backswing, the right wrist was hyperextended to.a mean angle of 206 degrees (see Figure 3). The average amplitude of the flexion movement of the right wrist during the downswing was 22.3 degrees; 10.2 degrees of this occurred between the twenty-two and one-half degree and vertical positions of the left arm and 12.8 degrees between 5 the vertical position and the moment of ball contact. The mean wrist position at ball contact was 179.7 degrees, a value indicating almost complete extension.
A mean Jue of 200.3 degrees lateral deviation was recorded for the right wrist position at the top of the backswing indicating an abducted position (see Figure 4). There was a rather constant rate of adduction throughout the swing with the mean position for all subjects attained at ball contact reaching 173.3 degrees.
The mean angulation of the left elbow at the top of the backswing was 171.6 degrees (sec Figure 5). At ball contact, it was 176.5 degrees showing a mean amplitude of movement of 4.9 degrees throughout the downswing. One subject registered the greatest amount of flexion, 152 degrees, at the top of the backswing and neared full extension, 179 degrees, at ball contact.
There was very little change of position in left forearm rotation from the top of the backswing, where a mean position of 84.2 d -ees was attained, to the twenty-two and onehalf degree position of the left arm (see Figure 6). From this point on all subjects pronated extensively, one subject registering 31.5 degrees of movement. All subjects continued to pronate the left arm while it moved beyond the vertical position through to ball contact.