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3 Phases of Golf Swing� Preparatory Phase
� Grip
� Posture & Stance� Ball Position
� Execution Phase� Backswing and Downswing
� Follow-Through Phase
Grip� Purpose: Hands & wrist work together to transfer
energy
� Muscles: Flexor Pollicis Brevis, Abductor Pollicisbrevis and Palmaris Longus
Posture, Stance and Ball Placement
� Feet should be shoulder width apart, even weight distribution
� Slightly bend knees
� Straight Left arm vsflexed right arm
� Head aligned with ball
� Ball Placement varies*
Execution Phase:� Swing in two planes:
� Back swing plane and down swing plane
� 3 dimensions to take into account:� Vertical (hands)
� Lateral (arms)� Rotary movement
around body (pivot of body)
The Backswing� Goal: establish a balanced, powerful position at top of swing
� Best way to do this: stay within backswing plane
� Club head, hands and shoulders start in one motion
� Weight shifted laterally (F à B)
� Increases range of hip rotation and flatten swing arc
� Two ways to increase acceleration:
� Stretch-reflex principle
� Shorten radius of lever arm
The Downswing� Initiated by rotation of the hips
� Simultaneous weight transfer
� Golfer must lengthen lever arm
� Summation of forces
� At impact, wrists straighten to produce maximum hitting effort
The Follow-Through� Right arm begins to rotate and right hand climbs
over left.
� Head is rotated forward by the momentum of the swing
� Important to accelerate through impact
Bryson DeChambeau: “The Golf Scientist”
� Single Golf Plane: Zero Shifting� Angle of club (to ground) never changes from 70
degrees� Each shaft 37.5 inches and club head 278 grams
� Allows for better muscle memory
Close Game� It is believed that the best players on the PGA Tour
distinguish themselves from the rest of the competition by a more accurate short game.
Bunker Shot� Sometimes, your ball will fall into a “bunker”
� Important things to consider with shot:� Stance� Grip
� Swing� Spin
� Trajectory
Club Entrance• Very important to
enter the sand 1 – 3 inches before making contact
• This increases the angle of the club-head upward on ball = higher trajectory and less backspin
• Goal is to “push” the ball forward
My Focus� Analysis between two of the most common close
game shots: bunker and pitch shot� Club head velocity and acceleration� Ball velocity/acceleration
� Conversion of Energy in Swing
� Wrist-Cock Angle
Methods & Analysis� Shot with an IPhone 6 at 240fps
� Made sure that shots analyzed were playable shots
� Logger pro for analysis
� Excel for calculations/graphs
� Markers on Club head and Hands
� Club is a Titleist Vokey Design SM5 58 degree Lob wedge
Weight of Club (Total): .48kg Weight of Shaft: .130kg
Weight of ball: .045kg Weight of Grip: .052kg
Length of Club: .889m Weight of Clubhead: .298kg
0
5
10
15
20
25
30
35
40
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7
Velo
city
(m
/s)
Time (s)
Club Head Speed Comparison
Pitch Shot
Bunker Shot
36.51
23.4
Kinetic Energy of Club head before impact: 1/2mv^2Bunker Shot: ½(.298kg)(36.51 m/s)^2 = 198.6 JPitch Shot: ½(.298kg)(23.4 m/s)^2 = 81.6 J
Momentum of Club head at Impact: m*dVBunker Shot: .298kg*36.51m/s = 10.88 kg*m/sPitch Shot: .298kg*23.4m/s = 6.97 kg*m/s
Acceleration of Club head before Impact: dV/dTBunker Shot: 36.51 (m/s) / (.25s) = 146.04 m/s^2Pitch Shot: 23.4m/s / .33s = 70.9 m/s^2
Force of Club head before impact: F=maBunker Shot: .298kg*146.04m/s^2 = 43.52 NPitch Shot: .298kg*70.9m/s^2 = 21.13 N
Power of Club headBunker Shot: (198.6J) / (.25s) = 794.4WPitch Shot: (81.6J) / (.33s) = 247.3 W
Club head ComparisonPitch Shot Bunker Shot
Power (W) 247.3 794.4
KE (J) 81.6 198.6
Momentum (kg*m/s) 6.97 10.88
Max velocity (m/s) 23.4 36.51
Acceleration (m/s^2) 70.9 146.04
Force (N) 21.13 43.52
Bunker shot yielded higher numbers in all 6...
Does this make sense??
Max velocity of Ball: Pitch Shot: 20.29 m/s (45.39mph)Bunker Shot: 11.73 m/s (26.24mph)
Max acceleration of Ball:Pitch Shot: (20.29m/s) / (.0833s) = 243 m/s^2Bunker Shot: (11.73 ms) / (.0833s) = 140.76 m/s^2
KE of Ball:Pitch Shot: ½ (.045kg)(20.29m/s)^2 = 9.26JBunker Shot: ½ (.045kg)(11.73m/s)^2 = 3.1J
Force of BallPitch Shot: .045kg*243m/s^2 = 10.94NBunker Shot: .045kg*140.76 m/s^2 = 6.33N
Ball Kinetics
Pitch Shot Bunker Shot
Max velocity (m/s) 20.29 11.73
Max acceleration (m/s^2) 243 140.76
Kinetic Energy (Joules) 9.26 3.1
Force (N) 10.94 6.33
Pitch Shot had higher #’s in all ball comparisons
What’s Happening!?!
Conversion of EnergyPitch Shot KE of club head after collision
½(.298kg)(16.3m/s)^2 = 39.6 J
Bunker Shot KE of club head after collision
(½)(.298kg)(16.48m/s) = 40.5 J
Pitch Shot Energy not accounted for
81.6 J – 39.6J – 9.26 J = 32.74J (40% Energy Lost)
Bunker Shot Energy not accounted for:
198.6 J – 40.5J – 3.1J = 155 J (78 % Energy Lost)
Energy Loss and an Extra Stroke
KE of Club head before impact: ½(.298kg)(48.1m/s)^2 = 344.7J
KE of Club head after impact:½(.298kg)(23.4m/s)^2 = 88.0 J
344.7J – 88.0J = 256.7 J
(256.7J / 344.7 J)*100 = 74.5% of energy lost upon contact with sand
Wrist-Cock/Torque
• Diverging directions of hands/club head = Large tension in shaft
• Tension causes club head to accelerate and hands to decelerate• Differing directions
ultimately responsible for energy transfer
• Wrist cock angle and wrist torque important
Wrist-Cock Angle
115.3 degrees
133.2 degrees
Increasing wrist-cock = increasing efficiency of swing = increased club velocity
Conclusions� Club-head speed and Power for bunker shot = higher
� Club-head hitting sand before ball dissipated 78% energy
� Ball kinetics from bunker shot = lower� Makes sense because of sand contact
� Larger wrist-cock in bunker shot increased club-head velocity
Limitations & Future Directions
� Amateur golf swing= not best for analysis
� Resolution of video = some noisy data
� Golf swing is DIFFICULT to analyze
� Compare to people with better/more consistent swings
� Film with multiple cameras
� Larger sample size
ReferencesJolly, Tom. “What Are the Biomechanical Principles for the Bunker Shot in
Golf?” What are the Biomechanical Principles for the Bunker Shot in Golf?”. 20 June 2014. Web. 1 April 2016.
Maddalozzo, John. “An Anatomical and Biochemical Analysis of the Full Golf Swing.” National Strength and Conditioning Association 9.4 (1987). November 1987. Web. 1 April 2016.
McCormick, Cameron. “The Short Game Explained.” Golf Digest. 11 November 2014. Web. 1 April 2016.
White, Rod. “Golf Swing Physics.” Swing Physics. 17 April. 2016