08 Mar Biomechanical Analysis of the Modern Golf Swing
The introduction of diagnostic tools in the past decade such as 3 Dimensional Motion Analysis, Force Plate testing, and Movement assessments strategies have allowed for a very precise analysis of the modern day golf swing. In this day and age subjective reviews of the golf swing and what transpires in the execution of the golf swing are no longer prevalent. Science has certainly advanced the game in every aspect. These advances include the biomechanical and physicals components of the game. Provided below is a review of the golf swing from a biomechanical perspective.
Phases of the Golf Swing
Through biomechanical studies by the American Sports Medicine Institute (ASMI), located in Birmingham, Alabama, a sequential model of the golf swing has been developed. Through the utilization of this model in conjunction with the kinematic sequence we can review the golf swing and determine the necessary physical requirements of the body for the execution of a biomechanically efficient golf swing in which the kinematic sequence remains intact. ASMI has broken down the golf swing into the following, “series of biomechanical movements”:
In order to better understand the connection between the golf swing, the kinetic chain, anatomy, and the interaction of these three entities we will look at each phase of the golf swing from a biomechanical perspective.
The set-up position often referred to as the “address” position, is the position in which the golfer places the body to begin the golf swing. According to Glenn Fleisig, M.D., the set-up position is a functional body position, that includes the proper grip. A balanced, “athletic” address position, which is consistent swing to swing, will provide the golfer with the correct starting position for the swing. According to Leadbetter and Huggan, a slight variation in weight distribution should be present when using different length clubs. The hips should be aligned in the direction of the target, while the right shoulder (right handed golfer) should be dropped slightly. The knees and hips should be comfortably flexed, resulting in the right shoulder being approximately directly above the right foot. Inconsistency in either how the body is set up or with the grip leads to inconsistency from shot to shot.
The body, in terms of muscle activity, is fairly low at address. The muscles of the body are supporting the body in a specific anatomical position and preparing to swing the club. Even though muscle activity is low at address, certain levels of joint mobility, muscular flexibility, and stability are required of the kinetic chain in order to position itself in the correct set-up position. Improper placement of the body prior to execution of the golf swing will directly lead to re-routing of the club, poor sequencing, and the development of numerous compensations in the golf swing. Typically, the cause for an improper address position will be from either poor mobility in specific joints or a lack of stability in certain body segments.
The backswing is when the body begins to move the club. The backswing is the portion of the swing that places the body in the correct position to begin the downswing. During the entire backswing the body begins the recruitment of energy that will be transitioned at the top of the backswing towards the ball. Key points from a biomechanical analysis of the backswing are: as the club moves backwards shear force is applied to the anterior portion of the right foot while at the same time a posterior shear force is applied to the left foot. (Fleisig, Biomechanics of Golf) This is the beginning of torque development in the body that will be transitioned into the clubhead at impact. Rotation of the knees, hips, spine, and shoulders continues during the backswing. The order of this rotation is the knees, hips, and torso occurring around an approximate vertical axis through the center of the body. This creates additional torque to be translated into the clubhead in later stages of the swing. The important point to remember in the backswing is that the entire rotation of these body parts occurs around an imaginary axis of the body. The body during this portion of the swing is creating/storing energy to be released during the downswing phase of the golf swing.
The biomechanical analysis of the backswing indicates this is the stage of the swing at which speed development begins. The process by which this occurs is through the creation of torque and the development of torque by the body requires rotation. Rotation in the lower body, torso, and shoulders is contingent upon a number of physical parameters such as joint range of motion, muscular extensibility, stretch reflex, and segmental strength in the lower body, hips, core, and upper back. If any of these physical entities are lacking, the ability to execute the backswing and develop torque will be diminished.
The completion of the backswing is termed the “transition” stage of the swing. The transition point of the swing is where the body completes its backward movement and begins the forward movement. The best reference point to when the transition stage of the swing begins is when weight shift onto the inside of the right foot is completed (right-handed golfers) and movement back towards the left foot begins. Research indicates the transition of the swing is where additional elastic energy is stored within the body. This is a result of the lower body moving forward as the upper body continues to “coil” backward (i.e. “X-factor). Studies show at the completion of the transition (top of the backswing) the hips are closed approximately 45 degrees and the shoulders are closed to about 100 degrees. (Fleisig, Biomechanics of Golf)
The transition phase of the golf swing as with every other phase of the golf swing requires specified levels of joint mobility and segmental stability. Limitations in thoracic spine or hip mobility will typically result in compensations or inefficient movement patterns to occur at this stage of the golf swing. In addition, an inability to stabilize the lumbo/pelvic/hip complex will negate the ability to maintain the correct postural position required in the initiation of the downswing phase.
After completion of the transition, the downswing begins. Weight shift continues during the downswing. The generation of torque is created in the lower body and then is transitioned up through the body into the club. The majority of torque in this phase of the swing is generated by the glutes, hamstrings, quadrcieps, and core musculature of the body. (Fleisig, Biomechanics of Golf) The torque created in the lower body creates acceleration in the upper body as energy is transferred onto the clubhead. Studies indicate there is moderate muscular activity in the pectoralis major (chest), latissimus dorsi (upper back), and rotator cuff muscles during the downswing. (Geisler, Kinesiology of the Full Golf Swing) The downswing is complete at the point in which impact occurs with the golf ball.
A model commonly used to demonstrate the biomechanics of the downswing is referred to as a double pendulum. This pendulum consists of an upper and lower pendulum. The upper pendulum represents a link between the two wrists on the club and either the left shoulder or a point between the two shoulders. (Fleisig, Analysis of a Mechanical Model of the Golf Swing) The lower pendulum represents the represents the club from the wrists to clubhead. (Milburn, PD, Summation of segmental velocities of the golf swing)
Downswing – Upper Pendulum Acceleration
After completion of the transition stage and commencement of the downswing, the golfer will continue the weight shift onto the left foot through movement of the pelvis toward the intended target line. During this movement of the kinetic chain force is applied onto the anterior portion of the right foot and posterior side of the left foot, which in turn generates a counterclockwise torque (right handed golfer). (Carlsoo, S, A kinetic analysis of the golf swing) The torque generated by the lower body is transferred to the torso with an additional amount of energy supplied by the musculature of the lumbo/pelvic/hip complex. (McCarrol, JR, Sports Injuries: Mechanisms, Prevention, and Treatment) This additional torque provided by the lumbo/pelvic/hip complex creates a counterclockwise acceleration of the upper pendulum. In addition, muscular of the upper pendulum concentrically active during the downswing were eccentrically loaded during the backswing.
Final notes of the upper pendulum is muscular of the right and left shoulder are contributing to speed generation. In addition, a negative torque by the wrists remaining radially deviated during the early stages prevents the lower pendulum from opening and maximum dorsiflexion of the right wrist (right handed golfer) occurs when the club is approximately horizontal to the ground. (Milburn, Summation of segmental velocities in the golf swing)
Downswing – Lower Pendulum Acceleration
The lower pendulum of the downswing is initiated once the club has reached a parallel position to the ground. At this position ulnar deviation of the wrists occur sequentially allowing the left forearm to supinate and right forearm to pronate, commonly referred to as a “knuckles down” move. (Hay, JG, The Biomechanics of Sports Technique) At this stage the release of the wrists begins the acceleration of the lower pendulum and sequential deceleration of the upper pendulum. (Hay, JG, The Biomechanics of Sports Technique)
The mechanics of the lower pendulum is directed by the pectoralis major, subscapularis, latisimus dorsi, and the arms. (Milburn, PD, Summation of segemental velocities in the golf swing) Motion analysis of the golf swing indicates maintaining club shaft-to-left arm angle into the latter stages of the downswing allows a great summation of forces by the upper pendulum due to low moment of interia. (Leadbetter D, and Huggan, J, The Golf Swing) The less skilled golfer will not maintain this clubshaft-arm angle typically referred to as casting and as a result loose a substantial amount of speed.
Keeping the kinematic sequence in place during the downswing allows for the generation and transfer of speed into the golf ball. In order for this to occur, high levels of neuromuscular efficiency, strength, mobility, and power are required in the lower body, core, and upper body. In addition, the transfer of energy via the kinetic chain to the club requires efficiency within the process of accelerating and decelerating kinetic chain segments. This component requires a foundation of inter-muscular and intra-muscular coordination to exist within the kinetic chain. This allows for power to be generated by each of these segments, transferred efficiently to the next segment of the kinetic chain and also allows for each of these segments to decelerate once energy has been transferred to next.
Impact is the point at which the potential energy/speed generated by the body during the backswing, transition, and downswing is transferred into the golf ball. Impact with the ball occurs for approximately half a milli-second. (Fleisig, Biomechanics of Golf) The purpose of impact is to hit the ball in the correct direction with the chosen amount of force. At impact, weight transfer is complete and shear forces from both feet are towards the intended target. The clubhead and ball at impact are in contact for approximately half a millisecond (0.0005 seconds). Any error in timing, positioning of the kinetic chain, sequencing of the swing, or positioning of the clubface will directly affect the impact position, ball flight, speed, and direction.
Biomechanically at the impact position the counterclockwise rotation of the feet is complete. Research indicates at impact the left foot (right-handed golfer) is supporting 80% to 95% of the golfer’s weight. (Fleisig, Biomechanics of Golf) In addition to the percentage of weight shift, research has found the lower handicap golfer had their weight supported toward the heel of the left foot, whereas the higher handicapper supported the weight in the middle of the foot. (Richards, J, Weight transfer patterns during the golf swing) The hypothesis behind this differentiation at impact between the lower and higher handicapper was the skilled golfer obtains more counterclockwise rotation during the swing.
Maximum clubhead speed is intended to occur at the impact position. Higher handicap players due to biomechanical inefficiencies and or physical dysfunctions loose speed prior to impact resulting in a loss of distance and potential ball flight direction.
Execution of the impact position requires the release of the hands with correct timing for the transfer of speed to the club head. In order to perform the wrist release, weight shift correctly, sequence the transfer of energy through the body, and release speed into the golf ball, all phases of the golf swing leading up to this point must be executed correctly. Errors in the kinematic sequence or phases of the golf swing caused by physical limitations, poor mechanics, or improper equipment will affect impact. Physical dysfunctions in terms of mobility, flexibility, stability, strength and/or power development will “show up” at impact relative to ball flight, distance, and direction.
After contact, the impact stage of the swing is complete and the follow through stage begins. The follow through is essentially the deceleration of the body after contact with the ball has been made. This is completed with the body rotating to a completion point where the clubhead is behind the golfer. The follow through is where the kinematic sequence of the swing ends, energy not transferred into the golf ball is dissipated, and the body slows itself back down. It is the deceleration phase of the golf swing.
Biomechanically after impact with the golf ball is complete the left forearm continues to supinate, the right forearm continues to pronate, pelvis and thoracic spine rotations concludes. Deceleration of the kinetic chain requires activation of the subscapularis, latissimus dorsi, and pectoralis major. In addition, both legs rotate as the right knee flexes and left ankle suppinates. (McCarroll, JR and Gioe, TJ, Professional golfers and the price they pay) The right heel will lifted off the ground during the follow through positioning the majority of the vertical load on the left foot (right handed golfer). (McCarroll, JR, Sports Injuries: Mechanisms, Prevention, and Treatment)
Deceleration of the kinetic chain during the follow phase of the golf swing requires a high level of eccentric and stabilization strength of the muscular system. This allows for dissipation of energy not translated into the club head and a slowing down of the body. Poor conditioning of the neuromuscular system or limited joint ranges of motion may limit the ability of the golfer to execute this phase of the golf swing efficiently.
The above synopsis provides a review of the modern day golf swing. The review provides both a biomechanical and physiological review of the athletic actions occurring in the execution of the swing. Invariably the modern day golf swing requires a physical foundation to execute proficiently, mechanical efficiency in the execution of golf swing, and equipment correctly matched to the characteristics of the both the golfer and golf swing.
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