Edward McInnes 2127448 & Anthony Azzopardi 2135664
Introduction
The origin of the modern game of golf has been traced back to Scotland in the 15th century (International Golf Federation – IGF, 2016). Since the origin of the sport, golf has become a worldwide activity with a range of leagues played at amateur, professional, global and Olympic levels. Unlike many sports, golf is played without umpires or referees for the majority of the game, thus the integrity of the players to abide by the rules is essential for the game itself (The R&A, 2016). Golf is a ball and club sport with the aim of hitting a ball in a hole with the least amount of hits or ‘strokes’ possible. This is traditionally in a series of 18 holes, a typical golf course composition. In competition play, the player with the least amount of strokes is deemed the winner.
In reference to the rules of the game, a player must strike the ball with a club from the ground where it lies (The R&A, 2016). On most holes, the first hit takes place from a ‘tee’ with the typical aim of hitting the ball so that it lands as close to the hole as possible, to minimise the amount of strokes. This skill is called the ‘drive’. In order to play a successful drive there are certain biomechanical principles involved, for both the player and the equipment.
Golf Legend Bubba Watson demonstrating a successful golf drive (YouTube, 2014)
…
Major Question – Within golf, what are the biomechanical principles behind driving for optimal distance?
The Answer:
Movement phases of the golf drive:
- Set up
- Backswing
- Downswing
- Follow through
(reference)
Biomechanical principles discussed within this blog:
This blog aims to look at the biomechanical principles required in performing a golf drive for optimal distance. The blog will be based around the movement phases of the drive and the equipment involved, integrating the biomechanical principles in these phases. The following biomechanical concepts will be covered:
- Levers
- Coefficient of Restitution
- The Magnus Effect & Air Resistance
- Impulse-momentum
- Kinetic chain
- Torque
- Balance
- Drag
- Centre of mass
- Inertia
- Angular momentum
- Angular velocity
- Newton’s Three Laws of Motion
- Throw-like movement patterns
- Velocity
- Acceleration
- Projectile motion (Angle of Trajectory)
Biomechanics of Equipment
When we look at the biomechanics involved with the equipment such as the club and the ball itself, three principles which affect optimal distance on the drive are; Levers, Coefficient of Restitution and the Magnus Effect & Air Resistance.
Levers
Lever length, the length of the arm-club lever, plays a vital role when driving for optimal distance. Blazevich (2010) highlights that at the end of a longer lever the velocity is greater, hence faster in comparison to the velocity and speed achieved at the end of a shorter lever. With this understanding and in terms of golf, we focus upon angular velocity which is the function of the angular velocity of the club head and the length of the arm-club lever, thus, to achieve optimal ball displacement (optimal driving distance), the main focus for the golfer is to maximise angular velocity at the point of impact (Hume, Keogh, & Reid, 2005).
Image identifying the arm-club lever
Coefficient of Restitution
Coefficient of Restitution (COR) is simply describes the proportion of total energy which is lost or retained (passed on) when two objects collide and is expressed as a figure between 0 and 1; where ‘0’ meaning all energy is lost in the collision and ‘1’ all energy is retained (Blazevich, 2010). When COR is 1 and all energy is retained, this is called elastic collision. In regards to the golf drive, it is impossible to achieve an elastic collision between the ball and the driver head due to different materials and weights of the driver head and ball which are colliding (“Driver Head Coefficient of Restitution and/or Characteristic Time”, 2016).
In relation to the United States Golf Association (USGA), the COR of titanium spring-faced drivers clubhead cannot be higher than 0.830, thus no more than 83% of energy can be transferred from clubhead to ball (“Driver Head Coefficient of Restitution and/or Characteristic Time”, 2016). With saying this, how do drivers impact COR. In today’s game of golf and the use of titanium spring-faced drivers in comparison to the old stainless steel drivers allows the face to flex inward more thus, the ball is not compressed as much against the face (Wishon, 2012). Hence, the approximate COR when using the stainless steel drivers tests at 0.822 in comparison to the current titanium spring-faced drivers of 0.830, resulting in a 4.2 yard gain for every increase of COR (“Driver Head Coefficient of Restitution and/or Characteristic Time”, 2016).
Magnus Effect & Air Resistance
When spin is placed on a ball the pressure around the ball is altered, this is called the magnus effect (Burglund & Street, 2011). The spinning ball grabs the air which flows past it due to friction between the air and the ball, thus, this causes air on one side of the ball to slow down (Blazevich, 2010). This can be seen in Figure 16.1.
How does the magnus effect alter optimal distance when driving in golf? “Golf drivers are designed with a backwards-angled clubface, to impart a backward spin on the ball to increase hitting distance” (Blazevich, 2010, pg. 194). The added backspin on a golf ball allows for added loft thus resulting in a longer flight due to directing air upwards in front and downward behind it, creating a pressure difference (Burglund & Street, 2011).
In conjunction with backspin, the golf ball itself plays a roll when driving for optimal distance. Golf balls are typically dimpled, thus affects air flow by causing the boundary layer of air around the ball to become turbulent. This is ideal as “the turbulent flow is able to stay very close to the surface of the ball for a longer period of time unlike laminar flow, thus, allows for a smaller separation of air flow around the ball creating a smaller area of low pressure behind the ball, causing deceleration at a slower rate than the smooth ball” (Burglund & Street, 2011, pg. 10). This is similar to reducing fluid drag (Blazevich, 2007). Hence, with less deceleration, this enables the ball to travel at its highest level for longer resulting in greater distance covered.
The “Set-Up” or Starting Position
The set-up or starting position for the execution for a golf drive involves certain techniques. The golfer should have an effective grip of the club with suitable ball position, be in correct biomechanical position (golf posture) coordinated with the golfers target goal and have established a stable balance (Hume, Keogh, & Reid, 2005).
Ball Position and Grip
The ideal position for the ball position when performing the drive is to position the golf ball at the lowest point of the full swing. The ball should be near the inside heel of the leading foot, but with saying that towards the center so the golfer does not need to out stretch their body. This can be seen in the corresponding video.
(YouTube, 2012)
Ben Hogan states that “golf begins with a good grip” with the major function of the hands is to firmly hold onto the golf club while the club is swung through the impact zone (“Perfect Golf Swing”, 2016). There are three grips typically used by golfers and are termed as; strong, weak or neutral.
Deciding if you naturally hold the club in either a weak or string way is dependent on the thumb and index finger of each hand (Vs) (“Golf Grip – Strong, Weak or Neutral”, 2015).
As seen in the above photo:
“A strong grip, the Vs are right of the center of the shaft; you can see the knuckles of your left hand, a neutral grip; the Vs are down the center line of the shaft and you can see three knuckles on each hand and a weak grip, the Vs are left of center and you can see the knuckles of your right had. (The above description is for a right-handed player; the opposite is true for a left-handed player)” (“Golf Grip – Strong, Weak or Neutral”, 2015)
Golf posture & Stance alignment
During the set-up, 50–60% of the golfer’s weight should be on the back foot, the knees should be flexed to 20–25°, the trunk flexed to approximately 45° at the hips (Hume, Keogh, & Reid, 2005). In conjunction with the golfer’s knees and trunk, their should also be right, lateral bending in the spine, thus,with all these phases combined, this position is said to be optimal for creating power and maintaining control of the golf swing (Hume, Keogh, & Reid, 2005). This can be seen in the picture below.
Additionally, balance and stability are highly important as they act as a base support for the full swing it be completed successfully. The golf swing must start with a solid base of support with the feet shoulder-width apart, and weight evenly distributed with slight flexion in the knees (“Teaching Golf To Beginners: A Simplified Approach”, 2016). With this understanding, the common misconception that the golf swing requires all upper body strength is proven wrong as “in golf, loading the back foot during the back swing and transferring the weight onto the front foot during the downswing and acceleration phases can achieve a greater club-head velocity at impact” (Hume et al., p.435).Thus, by transferring the majority of the weight to the back leg also engages ground reaction force (GRF). This demonstrates Newton’s third law which states “for every action, there is an equal and opposite reaction” (Blazevich, 2007, p. 43), allowing the player to push off the ground to get more force in the strike.
Backswing
The aim of the backswing is to align and prepare the golfers body and club head so to equate to the most benefit in the downswing phase. It does this by creating a solid foundation for the kinetic chain, positioning the body in preparation for the impending throw-like movement as well as stretching the muscles and joints that aid in generating power in the downswing (Hume et al., 2005).
The backswing begins once the set up phase finishes and the body is in the prescribed position. For elite golfers this phase is generally completed in less than a second (Hume et al., 2005). Initially, the shoulders start to turn across the spine, moving the club head backwards from the ball in a perpendicular line with the toes, preserving the triangle created by the arms (PGA, 2011a). After approximately 50cm of backwards club head movement, the shoulder rotation is coupled with hip rotation and flexion of the elbows (Hume et al., 2005). This dual elbow flexion finishes when the hands reach the hip level, as now only flexion of the support elbow continues and the support arm abducts and rotates outwards (Hume et al., 2005). The lead arm does the opposite, adducting and rotating inwardly. The shaft of the club moves smoothly across a swing plane. These movements increase the range of motion available in the following swing phases and keeps the rotation around a fixed base of support, shoulders rotating perpendicular to the spine, without lateral body displacement, which then increases the speed of the swing and in turn the club head velocity, as described in the following video (PGA, 2011a). This is opposed to shifting the weight on a lateral plane as the body rotates backwards, which can cause the golfer’s centre of mass to move too far away from the base of support, resulting in too much difficulty in controlling the swing, potentially sacrificing swing speed and technique which benefits the kinetic chain, angular velocity, impulse, momentum and torque, for the possibility of only a minimal increase in linear velocity (Blazevich, 2007; Hume et al., 2005; PGA, 2011a).
How to make a proper shoulder turn video from PGA (2011a)
http://www.pga.com/video-embed/video/instruction/2011/06/17/Shoulder%20The%20Load.pga
Nearing the top of the backswing, as the angle between the club and forearm becomes perpendicular, the right arm is approximately abducted to 75 – 90° and rotated externally roughly 90°, the left elbow is extended, the left shoulder in rotated inwards and adducted horizontally across the chest, and the left scapula is abducted, raised and rotated outwards (Hume et al., 2005). At the top of the backswing, the wrists and hands are cocked to achieve a square hand and club face position, creating tautness in the wrist tendons (Hume et al., 2005). The reason for this movement is to tension the abdominal and shoulder muscles and tendons so the elastic energy from their extension is maximized, fostering the body’s kinetic chain, as well as increasing the angular velocity, acceleration, impulse, momentum and torque available to be placed on the ball and the force available to overcome the club heads inertia, abiding by Newton’s first law of motion which states “An object will remain at rest or continue to move with constant velocity as long as the net force equals zero”(Biewener & Roberts, 2000; Blazevich, 2007, p. 42).
The left shoulder and spines range of motion govern the overall length of he backswing. At the final stage of the backswing the lead hand is roughly in line with the vertical plane, the lead leg is holding approximately 40% of the weight of the body and is rotated externally due to the right pelvic rotation (Hay, 1993). If not enough internal rotation of the right femur (less than 30°) occurs, this can compromise the ideal body position for keeping the rotation swing around a fixed base of support, without lateral movement, which increases the speed of the swing, aiding momentum, angular velocity, impulse and torque of the lever (Blazevich, 2007; Hume et al., 2005).
Downswing
The aim of the downswing is to bring the club head back to the ball along the plane of the swing, ensuring accurate connection whilst maximizing velocity and energy to impart on the ball (Hume et al., 2005). The downswing begins a tenth of a second before the back swing phase reaches its top, when the wrists and hands are cocked in the square hand and club face position. The throw-like movement pattern is initiated almost by the snap back of the body’s previous rotation (Hay, 1993). Firstly, by the feet pushing into the ground, in which the earth exerts an opposing force, known as the ground reaction force, abiding by Newton’s third law which (Blazevich, 2007, p. 43). The legs and hips also begin moving forwards, followed by the trunk and shoulders (Hume et al., 2005). The applicable muscles and tendons that were in tension now contract, imparting their elastic energy savings on the ball, enhancing force for the kinetic chain with low energy cost (Biewener & Roberts, 2000). Then the hands and wrists move down and uncock, achieving the formation of the body’s kinetic chain (Hume et al., 2005). This order of simultaneous joint movement ensures a greater summation of forces from the kinetic chain, creating higher amounts of momentum from the body, increases velocity, recoil, and results in imparting more force on the ball at impact (Blazevich, 2007; Hume et al., 2005). Ensuring this throw-like movement pattern moves in a sequential order, activating the torque generators from proximal to distal, is a critical technique for maximizing club head speed at impact (Hume et al., 2005).
Optimal torque for the golf drive is generated from a passive-active wrist technique, utilizing both the negative torque when the wrists are fully cocked at the top of the back, and positive torque when the wrists uncock at the end of the downswing (Chen et al., 2007). This combination of both positive and negative torque, as well as the torque created by the rotating of arms, shoulders and abdominal muscles, maximizes the amount of torque generated and results in more force able to be placed on the ball (Chen et al., 2007; Blazevich, 2007; Hume et al., 2005).
Emphasis is still placed on keeping the hub body position within the fixed base of support, rotating perpendicular to the spine, to increase the speed of the swing and in turn the club head velocity (Hume et al., 2005; PGA, 2011a). A lever is formed by the lead arm and club shaft, with the lead arm guiding the lever down and the support arm imparting force onto it (Hume et al., 2005). As the arms add length to the golf club, the velocity able to be created by the lever is increased (Blazevich, 2010). This lever continually increases angular velocity throughout the swing as the force summation and elastic energy increase the levers acceleration, centrifugal force and impulse, as well as maximizing the conservation of angular momentum (Blazevich, 2010; Hume et al., 2005). For elite golfers the downswing phase is generally completed in a quarter of a second, therefore maximizing the impulse in that time is crucial to maximizing momentum and therefore the force to be applied to the golf ball (Hume et al., 2005). Maximizing the impulse is aided by ensuring the wrist uncocking is at last moment, almost acting as a hinge to the arm’s lever, providing an increase in acceleration and force to the swing, optimizing the angular velocity of the club head (Hume et al., 2005).
The plane the drive swing travels along is slightly shallower than the backswing plane, this ensures an accurate ‘sweet spot’ connection, transferring the maximum amount of energy from the club head to the ball at impact, ensuring optimal distance (Hume et al., 2005).
Follow through
The aim of the follow through movement phase is to accurately impart as much of the energy gathered so far on the ball, at optimal trajectory, so that it may cause maximum displacement, and then decelerate the body and club head (Hume et al., 2005). As the club head makes impact with the ball, body weight should be shifted onto the lead leg from the support leg, as this causes the body’s momentum to be moving in the direction of the projectile and employ’s the ground reaction force to increase the kinetic chains force, in turn, increasing the impacting club head velocity (Hume et al., 2005). This abides by Newton’s second law which states, “The acceleration of an object is proportional to the net force acting on it and inversely proportional to the mass of the object” (Blazevich, 2007, p. 43).
The slightly shallower plane the drive swing travels back along allows for precise connection with the club heads ‘sweet spot’, as depicted in the image below, which is necessary for transferring as much energy from the force summation to achieve optimal displacement (Smith, 2000).
Ensuring a flush connecting with the ‘sweet spot’ is an important aspect to technique as the way the club face hits the ball can effect the direction the ball travels in, which many result in a hindering of the distance achieved (Blazevich, 2007). The way the club face it is orientated or the side it connects with can impart spin on the ball, causing the ball to swerve in the direction the club was facing, or drop short (Blazevich, 2007). This is due to the magnus effect, which in relation to the golf drive means that the spinning ball ‘grabs’ the air flowing past it due to friction between the air and the ball, and the air particles begin to spin with the ball (Blazevich, 2007). The spinning builds up and causes the oncoming air on one of the sides to slow down, whilst on the other side the air moves past almost normally. The air speed on one side is therefore less than the other, resulting in a pressure differential and the balls swerve (Blazevich, 2007). A swerve in direction caused by side spin, a drop in ball path caused by top spin, or too much rise in ball path caused by back spin, will result in a non optimal drive for distance as the path the ball travels is not the optimal path for maximum distance, as depicted in the image below. However, the magnus effect can be beneficial, as imparting subtle back spin on the ball can cause a slight rise in the ball path, increasing vertical travel and not hindering horizontal travel (Blazevich, 2007). This is why golf drivers have a slight backwards angle to their club face, so to increase hitting distance (Blazevich, 2007).
The trajectory of the projectile is also an important technique aspect when impacting with the ball, as optimal distance will be achieved when the trajectory angle is optimal. In most sports the optimal angle of release is around 45° due to having an equal magnitude of vertical and horizontal velocity (Blazevich, 2007). However due to an increased vertical velocity from the golf ball having to face wind resistance, backspin which increases flight time combatting with gravity, and turbulent flow, the optimal launch angle is lower (Blazevich, 2007). For the golf drive, the optimal angle of trajectory at impact is around 12°, which increases the horizontal velocity to compensate for the increased vertical velocity and results in optimal ball displacement (Winfield & Tan, 2000). Also, it is important to consider the relative height of projection, as if the projection point is higher than the landing surface, the optimal angle of projection decreases. If the projection point is lower than the landing surface, the optimal angle of projection increases (Blazevich, 2007). It is important to compensate impact technique for the relative height of projection.
After impact with the ball, the hands and wrists follow the plane the drive swing travels along, the lead arm abducts and rotates outwards, whilst the support arm adducts and rotates outwards (Hume et al., 2005). When the hands get to shoulder height, the elbows flex to decrease the acceleration of the arms and body rotation whilst maintaining balance (Hume et al., 2005). The lead leg rotates, absorbing weight, the left ankle supinates, and the golfer faces the targeted direction (Hume et al., 2005). At the finishing point, the hands should be behind the lead ear and the head should be facing the targeted direction due to the body’s rotation and the momentum from the swing (Hume et al., 2005).
How else can we use this information?
The biomechanical principals of the golf drive, as discussed in this blog, can be applied to many other sports. The following video emphasizes this view (PGA, 2011b).
Understanding the basics of the golf swing (PGA 2011b)
http://www.pga.com/video-embed/video/instruction/2011/06/17/Body%20In%20Motion.pga
Understanding the biomechanical principals of levers, coefficient of restitution, the magnus effect, air resistance, impulse-momentum, kinetic chain, torque, balance, drag, centre of mass, inertia, angular momentum, angular velocity, Newton’s three laws of motion, throw-like movement patterns, velocity, acceleration, and projectile motion (angle of trajectory), as well as understanding what aspects of technique foster these principals, allows a transfer of skill to other sports, particularly sports which feature hitting or throw-like movement patterns. For example, cricket, where both batting and bowling involve this throw-like movement pattern as well as force summation, angle of projection and balance. Tennis and volleyball also utilize the kinetic chain force summation, balance and throw-like movements. These two sports also involve angle of projection and the magnus effect. Understanding the magnus effect and techniques to use it as an advantage can be very effective skill, transferrable to sports such as soccer, tennis, volleyball, rugby, AFL and cricket. Being able to impart spin and therefore curve of a soccer ball in soccer, or tennis ball in tennis can be a valuable skill, with which the biomechanical principles learnt in golf can foster.
Levers play a big role in golf, therefore developing an understanding of how impart the most amount of force on the ball, particularly through increasing angular velocity, momentum and club head velocity, can be transferred to baseball, cricket, hockey, badminton, squash, croquet and many other sports involving a ball and racquet, bat, stick or any form of lever.
Newton’s laws discussed in this blog can also be applied to athletic events, such as running, jumping and sprinting, as gaining the most energy from the ground reaction force is crucial to optimizing performance. Throwing events also benefit from many of the principals mentioned, such as angle of projection, balance, the magnus effect, kinetic chain, angular velocity, momentum and impulse, to achieve maximum displacement.
Reference List
Biewener, A. & Roberts, T. (2000). Muscle and Tendon Contributions to Force, Work, and Elastic Energy Savings: A Comparative Perspective. Journal of Exercise and Sports Science Reviews.
Blazevich, A. (2007). Sports biomechanics, the basics: Optimising human Performance (1st ed.). London: A. & C. Black.
Blazevich, A. (2010). Sports biomechanics (2nd ed.). London: A & CB.
Burglund, B. & Street, R. (2011). Golf Ball Flight Dynamics.
Chen, C., Inoue, Y. & Shibara, K. (2007). Numerical study on the wrist action during the golf downswing. Journal of Sports Engineering. Volume 10, (1). pp. 23-31.
Driver Head Coefficient of Restitution and/or Characteristic Time. (2016). Golfclub-technology.com. Retrieved from: http://www.golfclub-technology.com/coefficient-of-restitution.html
Golf Grip – Strong, Weak or Neutral. (2015). The Grateful Golfer. Retrieved from: https://thegratefulgolfer.com/2015/01/25/golf-grip-strong-weak-or-neutral/
Hay, J (1993). The biomechanics of Sports Techniques (4th ed). Prentice Hall: New Jersey.
Hume, P., Keogh, J., & Reid, D. (2005). The Role of Biomechanics in Maximising Distance and Accuracy of Golf Shots. Sports Medicine, 35(5), 429-449. Retrieved from: http://dx.doi.org/10.2165/00007256-200535050-00005
Image identifying the arm-club lever. (2016). Retrieved from: https://shipsimplemachines12.wikispaces.com/lever+-+third+class
Maddalozzo, J. (1987). An anatomical and biomechanical analysis of the full golf swing. Department Of Physical Education And Leisure Studies, 9(4).
Perfect Golf Swing. (2016). Perfectgolfswingreview.net. Retrieved from: http://perfectgolfswingreview.net/index.html
PGA (2011a). How to make a proper shoulder turn. PGA: PGA. Retrieved from: http://www.pga.com/golf-instruction/instruction-feature/fundamentals/shoulder-turn-in-your-swing-video
PGA (2011b). Understanding the basics of the golf swing. PGA: PGA. Retrieved from: http://www.pga.com/golf-instruction/instruction-feature/fundamentals/understanding-basics-golf-swing-video
Smith, S. (2000) from the Golf digest labs: Hitting the sweet spot. Golf Digest, 51 (8), 25.
Street, R. & Burglund, B. (2011). Golf Ball Flight Dynamics (1st ed.). Retrieved from: http://home2.fvcc.edu/~dhicketh/DiffEqns/Spring11projects/Brett_Burglund_Ryan_Street/Diff%20Q/pdfscreen/projectoutline.pdf
Teaching Golf To Beginners: A Simplified Approach. (2016). Streetdirectory.com. Retrieved from: http://www.streetdirectory.com/travel_guide/44899/golf_guide/teaching_golf_to_beginners_a_simplified_approach.html
Winfield, D. & Tan, T. (2000). Optimization of club-head loft and swing elevation angles for maximum distance of the golf drive. Department of Mechanical Engineering, 53 (1), 19-25.
Wishon, T. (2012). How Does COR Affect Your Golf Game?. Clubfitting, Golf Club Technology. Retrieved from: http://wishongolf.com/how-does-cor-affect-your-golf-game/
YouTube (2012). mygolfinstructor, Ideal Ball Position and Set Up for Hitting a Driver. Retrieved from: https://www.youtube.com/watch?v=UU2z7KA0VrI&feature=youtu.be
YouTube (2014). PGA TOUR, Bubba Watson records 424-yard drive at Bridgestone Invitational. Retrieved from https://www.youtube.com/watch?v=zDb_AeI-bH8&feature=player_embedded
Pictures Retrieved From (In the order they appear):
http://blog.anytimefitness.com/wp-content/uploads/2012/08/golf-tutorial-how-to-improve-1050×591.jpg
http://www.golfwrx.com/wp-content/uploads/2014/04/Screen-Shot-2014-04-25-at-10.45.37-AM.png
http://elisebaldwin.blogspot.com.au/2013/04/what-are-biomechanics-involved-in-golf.html
hlpe 3531 golf biomechanics 
