What are the components that make up an efficient and effective golf swing, through a biomechanics perspective?

The Answer

Why is it important to understand the components of a golf swing?

The understanding of the golf swing has implications, not only for coaches and players of the game, but for physical educators alike. Smith et al. (p. 225, 2012) explains that for "coaches to improve sports skills, they have a well developed internal model of a technically correct performance". The understanding of biomechanical principles within golf has the ability to interpret the  interplay of movements within other sports or physical activities, and therefore allow a scaffold for learners who have varied experience in other sports. The analysis includes movement and muscle patterns, as well as the internal and external forces that have an influence on the outcome of the swing. The golf swings that will be reviewed are from right-handed players, who are using iron-clubs for their swing. The club choice within golf is important, because the loft and degree of club-face are varied, and directly impact the distance and desired outcome. 

What type of movement is a golf swing?

Due to the sequential movements of body parts in order for the entire movement to generate force, the swing can be described as a throw-like movement (Blazevich, 2007). This occurs where the shoulders, elbows, wrists, and fingers work in segments to allow the club to reach its peak during the back swing, then to the torso and hip rotation to begin the down swing section of the movement, which begins with the shoulders, then the elbow and wrist movements allowing the club to make impact the ball. Within a throw-like movement, the summation of the forces is generated from the club-head onto the ball at high speeds, in contrast to a push-like movement, where the force generated is applied very slowly (Blazevich, 2007). 

What are the phases that need to be completed in order to perform a golf swing?

Golf Digest (2005) Swing Sequeces: Ernie Els

As described by Maddalozzo (1987), the golf swing can be broken down into 3 phases. These include the Preparation phase (grip, posture, stance, and ball position), the Execution phase (back swing, down swing, and impact), and finally the Recovery phase (follow through after impact). The breakdown of movements within phases will allow particular patterns to be seen, and therefore easier to understand through a biomechanical lens.

PREPARATION PHASE

Tiger woods super slow-motion (2011)
[screenshot]

As aforementioned, the preparation phase is broken down into the grip, posture, stance, and ball position. Hume et. al. (2005) explains the different types of grips used on a golf club, including strong, neutral, and weak. The different variations of tightness of grip can influence the displacement of the ball as well as force production. A player might slide the grip up and down the shaft of the club, depending on the distance they would like the ball to travel. This is an example of increasing or reducing the moment of inertia, which can be larger with an increase in particles further away from the pivot point, or decreased with particles closer to the pivot point (Blazevich, 2007). From a golf perspective, the moment of inertia can be altered when the centre of rotation (the hands) are either closer to the main mass of the club head to decrease desired distance or further away to increase the distance the ball will travel. 
Due to the observation that the golf swing is a throw-like movement, it is important that the player has a stable base while performing the swing to reduce the amount of imbalance. Furthermore, the width of the stance can either restrict turning freely during the swing, or can cause a lack of stability during the swing. A stance that is too wide can cause a lack of hip rotation, while a stance that is too narrow can cause balance and stability to be lost (Madalozzo, 1986). The theory of stability, where stability is directly proportional to the area of the base at which the body rests (Reddy, 1993) suggests that the players are to have their head slightly over the ball, but not enough to lose balance. This means that knees should be shoulder width apart and slightly flexed, similar to the Tiger Woods diagram, allowing the centre of gravity to be distributed lower over the base of support, while still allowing the player to be over the ball. This also allows equilibrium to exist, where the centre of gravity of a body falls within its base (Reddy, 1993).

MOMENT OF IMPACT - COMPARISON BETWEEN ADAM SCOTT AND TIGER WOODS

The comparison between two elite players of golf gives the ability to see the contrast in styles, while both still performing the shot with a successful outcome. The still photos above display both Tiger Woods (left) and Adam Scott (right) at the end of their execution phase; just as they are about to make impact with the ball. In these screenshots, the angle of depletion of both player's knees are compared. As you can see, Woods' angle is very minimal, almost having a straight leg, with a slight bow, in contrast to Scott's, who has a more severe angle in approaching to hit the ball.  The more severe angle of Scott and the more bowed shape of Woods have potential to cause implications on the outcome of their golf swing. Scott's knee is facing inward, illustrating force on the ground from the right foot. Due to Newtons 3rd law (every action has an equal and opposite reaction) (Blazevich, 2007), the force that is exerted from the foot to the ground is equal and opposite in its direction, meaning the force is being applied in the direction to where the trajectory is intended, and therefore has the ability to add to the summation of forces as described earlier. As well as the added force, the dropping of the knee also allows the centre of gravity to be distributed efficiently from the two feet in the preparation phase, to the left foot when in the final stages of the execution phase. According to Keogh & Hume (2012), within an alteration in ground reaction force (weight transfer), the golf ball displacement has the potential to be maximised while in the execution phase.This movement is in contrast to Woods, who uses a thrust of his hips and pelvis to generate the force and altar the distribution of weight between right and left feet, which allows the force to move in the direction of the intended projection. 

How much energy is put into a golf swing?

Nesbit & Serano (2005), describes the fundamental purpose of a golf swing is to "do work to generate club head kinetic energy, which is ultimately transferred to the ball through impact". Blazevich (2007), describes kinetic energy as the energy associated with motion, as shown in the video above (USPGA, 2013). As a coach, it would be beneficial to know the energy expenditure of a golf swing in order to altar the equipment, or undertake physiological training to better use the energy. To answer this question, the test subject is going to be Adam Scott and his average club speed (120mph or 53.79ms-1), and the average weight of a golf club (330g). From the these values, the amount of kinetic energy will be seen from the golf swing on the golf club when put into the kinetic energy formula as shown.  

The mathematics displays the values when put into the equation and, from this, it can be shown that Adam Scott's average kinetic energy on the club head is 477J. In addition, the kinetic energy was reduced when the club mass was reduced, as well as when the club speed was reduced. When combined with Adam Scott's heart rate reserve, a percentage can be produced that shows how much of the heart rate reserve (HRR%) is used per golf swing. It is then able to be seen whether the kinetic energy should be increased with either physiological training or equipment change, dependent on how much HRR% is left to be used. The largest benefit of identifying energy expenditure is being able to identify that the effects of forces that are applied over a distance are determinable which provides an introduction into factors such as range of motion, timing, and the sustainability of those forces (Nesbit, 2005).

Are there any influences on the golf ball that affects the trajectory?

The Golf Ball Principles diagram (2014) illustrates the effect of drag and lift on a golf ball during flight. Penner (2002) describes that golf ball spinning backwards travelling through the air will have, in addition to drag, a force perpendicular to the ball’s velocity; this is commonly referred to as lift. As a golfer who wants to maximise distance, it is important to try and generate as much lift in order to increase distance of the ball travel. The lift, as described by Penner (2002), and the video on the left (USPGA, 2014), is directly affected by the amount of backspin put on the ball, as it changes the direction of pressure and allows the ball to lift upwards. Although backspin is favourable for increase in distance, too much backspin has the ability to generate too much lift, and therefore reduce to distance of the shot. According to Bearman and Harvey (1976), the maximum range can be obtained through a 58ms-1 launch speed, as well as a backspin of approximately 60rps. Furthermore, depending on the shape of the green, or to prevent a hazard such as a bunker, it would be useful to be able to curve or shape the ball in a certain direction to favour the outcome against the particular challenge. When hitting a golf ball and it either fading or drawing out of a straight line, a pressure differential occurs and the ball begins to swerve; this is called the Magnus effect. the force that is created by the unequal pressure is the Magnus force (Blazevich, 2007). As a golfer, it is important to be able to manipulate the golf swing to suit the desired outcome; ultimately having control on the spin of the ball and therefore the pressures and forces surrounded the ball, controlling the shot more efficiently. 

How else can we use this information?

As described earlier, the biomechanical principles allow for an easier transfer of knowledge of body patterns, for example, between different games and sports. The biomechanical principles that have been discussed can be used by physical educators, coaches, sport participants and students, in order to assist in the understanding of how to perform movements efficiently, as well as to provide a justification toward an outcome of a movement. For example, the understanding of which movement is being performed for a particular skill can allow for a breakdown of components within the movement, to maximise force production, including the direction of force as explained in Newtons 3rd Law, such as in a high-jump exercise. In addition, the grasping of the concepts such as energy expenditure within a baseball pitch can allow for a change in action or specific training programs to positively influence the preferred outcome, as well as understand how different grips and spins on the ball can influence the direction and displacement of the baseball. Lastly, applying knowledge of how centre of gravity can influence activities such as gymnasts performing a floor routine will allow for more balance, and could also generate a greater amount of force while preparing for a large aerial manoeuvre with an understanding on how to increase the moment of inertia. From a different perspective, the analysis of biomechanical principles can allow for modifications in an effort to prevent or aid the treatment of injury (Meister et. al., 2011).

References

Blazevich, A. (2007). Sports Biomechanics: The basics: optimising human performance. London:A.& C. Black, 41-183

Golf Digest (2005) [IMAGE], accessed from http://www.golfdigest.com/golf-instruction/swing-sequences/2007-09/ernieels

Golf Principles Diagram (2014) [IMAGE], accessed from http://fitting.2ndswing.com/technology-golf-ball-fitting/

Hume, P., Keogh, J. & Reid, D. (2005) The role of biomechanics in maximizing distance and accuracy of golf shots. Sports Medicine, 35 (5), 429-249

Keogh, J. W., & Hume, P. A. (2012). Evidence for biomechanics and motor learning research improving golf performance. Sports Biomechanics, 11(2), 288-309.

Maddalozzo, G. J. (1987). Sports Perforemacne Series: An anatomical and biomechanical analysis of the full golf swing. Strength & Conditioning Journal, 9(4), 6-9.

Meister, D. W., Ladd, A. L., Butler, E. E., Zhao, B., Rogers, A. P., Ray, C. J., & Rose, J. (2011). Rotational biomechanics of the elite golf swing: benchmarks for amateurs. J Appl Biomech, 27(3), 242-51.

Nesbit, S. M. (2005). A three dimensional kinematic and kinetic study of the golf swing. Journal of sports science & medicine, 4(4), 499.

Nesbit, S. M., & Serrano, M. (2005). Work and power analysis of the golf swing. Journal of sports science & medicine, 4(4), 520.

Penner, A. R. (2003). The physics of golf. Reports on Progress in Physics,66(2), 131.

Reddy, P. C. (1993) Principles of Scientific Coaching in Chapter 2: Meaning of Equilibrium, Motion, and Force, 3-13

Smith, A., Roberts, J., Wallace, E., & Forrester, S. (2012). Professional golf coaches’ perceptions of the key technical parameters in the golf swing. Procedia Engineering, 34, 224-229.

United States Golf Association (2013) Science of Golf: Work, energy, and power [VIDEO] accessed from https://www.youtube.com/watch?v=dB36sW-iYBY&index=16&list=PLnU5qUEfww3fxzPIJzmeYcUOQvLJfIhIe

United States Golf Association (2014). Science of Golf: Why do golfballs have dimples?[VIDEO] accessed from https://www.youtube.com/watch?v=XkaLsVOrBk0&list=PLnU5qUEfww3fxzPIJzmeYcUOQvLJfIhIe&index=9