|The Effects of Warm-Up Stretching in the Golf Swing|
D I S C U S S I O N
In the human body, a kinetic link is composed of physics and physiology. The most efficient way to visualize a complex motion such as a kinetic link is to compare each component to a common movement. The physics component can be represented by the action of snapping a whip. The arm starts the action of the whip but then decelerates and stops, 'passing' momentum and creating enough acceleration and speed at the end of the whip to produce a snap! The physiology component can be represented by the action of a vertical jump. When jumping up from a standing position, the first movement is to 'dip' down. That action preloads muscles for the strongest contraction propelling the body to maximum height.
In the golf swing the kinetic linking process is composed of four 'components' and three 'links.' The components are the hips, shoulders, arms and club shaft. The links are the musculature that connect each component. As the golfer begins the swing with the backswing, components rotate in a clockwise fashion around the orientation of the trunk. This action begins to lengthen muscles and preload (elastic potential energy) the links. Before the club reaches its maximum rotation, the hips begin to rotate in a counter clockwise acceleration toward impact with the ball. The shoulders, arms and club continue in a clockwise direction against the hips, creating muscular preload of the trunk to be used in accelerating the club. The shoulders then follow the lead of the hips in a counter clockwise acceleration while the arms and club continue in a clockwise direction preloading the upper body. The same then occurs between the arms and club preloading the muscles of the forearm and wrist.
Once all of the components are accelerating in a counter clockwise direction, the body uses both physics and physiology to most efficiently create club head speed. The hips are the first component to reach a maximum angular speed. Once a maximum speed is attained, the hip segment then decelerates 'passing' momentum to the shoulder segment. Both the passing of momentum and the action of the muscles between hips and the shoulders (physics and physiology) accelerate the shoulder segment to a maximum speed much higher than that of the hips. The shoulder segment having reached a maximum angular speed now decelerates 'passing' momentum to the arms. Finally, the arms, in the same manner as the hips and shoulders, decelerate passing energy to the club. The club then uncocks or releases and accelerates into impact with the ball with both maximum linear and angular speed creating optimum power.
The results of this study show that there was very little change (either increases or decreases) in the amount of body segment rotation during the backswing for any of the experimental groups. Although it has been theorized and speculated that stretching prior to the golf swing will facilitate a larger range of motion, our data shows that this does not occur. This is significant to understanding the effects of stretching on performance in a complex skill activity. Individual joint range of motion may increase slightly with warm-up stretching as has been shown in previous research, nonetheless, it may not be apparent in a movement like the golf swing in which rotational body segment movement is made up of sequenced combination so joint range of motion. The thought or perception that one may make a 'bigger turn' during the backswing after stretching is not true, however, the movement may feel 'freer' due to the decrease in muscular stiffness as a result of breaking the adhesions and bonds formed during inactivity prior to swinging a golf club.
In spite of the fact that the amount of rotation did not change substantially, our results show that the ability to generate body segment and club head speed did increase when the subjects stretched prior to swinging a club. In fact, angular club head speed increased (club shaft release angular velocity) an average 170% at impact for the MAPS group and 119% for the static stretch group. In comparison to the control group which did not stretch prior to swinging, both stretch groups were able to create considerably more club release velocity at impact. This can be explained in large part to the fact that stretching helps to break adhesions and bonds created during muscle inactivity. Breaking these bonds increases the elastic nature of the muscle. It is the ability to effectively store and use elastic potential energy that increases the amount of muscular work that can be done. This thereby enhances the power production process and facilitates more club head speed.
In addition to enhancing the ability to preload muscles and create power, stretching should also increase the ability to coordinate complex movements. The ability to coordinate body segments effectively augments power production by involving efficient energy transfer. The results of our study show that stretching using a 'machine assisted' passive program may very well be more effective in eliciting increases in coordination. Using the model of the kinetic link, the lower limbs create a force couple at the hip segment. If the action of the hip and shoulder segments is not coordinated properly the speed by the lower body will not benefit the movements of the upper body. The MAPS group increased their ability to transfer speed from the lower body to the upper body when they stretched. In comparison, the static stretching group actually decreased their ability to transfer speed from the lower body to the upper body after stretching.
The reason for the dramatic ability of the MAPS program on the BackSystem3 to increase power production through warm-up effect and coordination skills, may be in part due to the nature of the stretches performed. When stretches are performed on the BackSystem3, the golfer begins the stretch by pushing against the seat and 'rolling' the pelvis. The body is allowed to stretch to a maximum point of resistance and then must reverse the process with the pelvis to return to the starting position. As a result of the controlled and passive nature of the movement bonds are not only broken during warm-up, but movement patterns may be induced. The act of moving the body through coordinated ranges of motion may considerably enhance biomechanics skills during the activity. In addition, it was noted during data collection that the MAPS group performing stretches on the BackSystem3 was in general more effective in isolating muscles and applying force to stretch the muscles. In comparison, the static stretch group had a more difficult time performing the stretches consistently.