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Young-Hoo Kwon, Chris Como, Ki Hoon Han, Sangwoo Lee, & Kunal Singhal

Young-Hoo Kwon, Chris Como, Ki Hoon Han, Sangwoo Lee, & Kunal Singhal Biomechanics Laboratory, Texas Woman’s University, Denton, TX. Decomposition of the Clubhead Velocity: Assessment of the Contributions of the Joint/Segment Motions in Golf Drives.

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Young-Hoo Kwon, Chris Como, Ki Hoon Han, Sangwoo Lee, & Kunal Singhal

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  1. Young-Hoo Kwon, Chris Como, Ki Hoon Han, Sangwoo Lee, & Kunal Singhal Biomechanics Laboratory, Texas Woman’s University, Denton, TX Decomposition of the Clubhead Velocity:Assessment of the Contributions of the Joint/Segment Motions in Golf Drives 6th World Scientific Congress of Golf, Phoenix, AZ

  2. Planar Double-Pendulum Model Triple-pendulum model X-Factor Stretch-Shortening Cycle (Cochran & Stobbs, 1968; Hume et al., 2005; Hellstrom, 2009)

  3. Planarity & Functional SP Motion Planes L Shoulder R Shoulder MD R Elbow MF L Hand FSP FSP (Kwon et al., 2012)

  4. New Double-Pendulum Model • Hand Path Determined by: • Trunk motion & • Arm motions Projected Clubhead New Hub • Trunk Motion: • Flexion/extension • Lateral flexion • Rotation • Elevation/depression Projected Hand • Arm Motions: • Shoulder motions • Elbow motions

  5. New Kinematic Sequence: Joint Angular Velocities Meaningfulness of the trunk rotation and the X-factor?

  6. X-Factor Studies • Trends: • Comparison among different skill levels (Cheetham et al. 2000; Zheng et al., 2007; Cole & Grimshaw, 2009) • Comparison among different ball velocity groups (Myers et al., 2007) • Comparison among different effort levels (Meister et al., 2011) • Correlation/regression (Myers et al., 2007; Chu et al., 2010) • Training effects (Lephart et al., 2007) • Methodology (Joyce et al., 2010) *p < 0.05 • Issues: • ANOVA/correlation/regression with heterogenous samples • No direct relationship between CH velocity and X-factor • Influence of the planar swing model / stretch-shorting cycle • Projected to the horizontal plane

  7. Purposes To assess the contributions of the joint/segment motions to the clubhead velocity: • Homogenous sample • Normalized CH velocity • Direct relationship between the CH velocity and the trunk motion To assess the relationship between the X-factor parameters and the CH velocity: • Projected to the functional swing plane • Homogenous sample • Normalized CH velocity

  8. Participants • 18 Male Skilled Golfers: • Recruited from North Texas (Dallas) area • Handicap: -0.6 ± 2.1 • Height: 1.81 ± 0.05 m • Mass: 82.6 ± 10.4 kg • Clubhead Velocity: • 45.48 ± 2.85 m/s (102.3 ± 6.4 mph; CV = 6.3%) • 25.21 ± 1.82 BH/s (CV = 7.2%)

  9. Data Collection • Motion Capture: • 10-camera VICON system (Centennial, CO) • Captured at 250 Hz • ‘TWUGolfer’ marker set (65 markers) • 2 AMTI force plates (250 Hz) • 4 different types of trials (ball plate, club, static posture, & motion trials) captured • Laboratory Study: • Wiffleballs • Ball mat • 5 driving trials per golfer collected

  10. Data Processing • ‘TWUGolfer’ Body Model: • 89 points • 13 joints / 24 computed points • 18 bodies / 6 additional reference frames • Data Processing: • C3D importing • Kwon3D (Visol, Seoul, Korea) • Cutoff frequency: 20/10 Hz • Interpolated to 2,000 Hz

  11. Events BI ED MD TB MF Mid FT Mid DS Ball Impact Top of BS Early DS

  12. Functional Swing Plane (FSP) FSP (Kwon et al., 2012): • Plane formed by the clubhead trajectory (MD to MF) • Projected trajectory Moving FSP Reference Frame: • Instantaneous rotation centers & arms • Normal, tangential, & radial axis n ro X-Factor Computation: • Shoulder & hip lines • Projected to the FSP frame

  13. Decomposition of CH Velocity Wrist (2 + 1 DOFs) Elbow (1) 1 Shoulder Joint (3) A 4 Mid-Shoulder (1) D 5 C L4/L5 (3) E B Pelvis Rotation (3) 3 6 2 F Mid-Hip Translation 7 Time Function: Max contribution Contribution at BI Contribution

  14. Tangential Velocity Contribution 100% TB: 0% ED: 67.0% 46.9% MD: 86.9% 16.8% BI: 100% 19.2% 15.7% (1) (12) 18.5% (5)

  15. Velocity Contribution vs. Max CH Velocity (p < 0.05) r = 0.724 r = 0.539 r = 0.501 r = -0.475 (1) (3)

  16. X-Factor Parameters

  17. X-Factor Parameters X-Factor Stretch 1.5 ± 2.2 deg

  18. X-Factor Parameters CV = (15, 79, 18)% CV = (10, 31, 11)% CV = (21, 25, 17)% vs. Max CH Velocity r = -0.461* (*p < 0.05) r = -0.486* r = -0.568*

  19. Discussion • Velocity Contribution: • Wrist motion: the main source of the CH velocity • Pelvis motion: larger contributions than the trunk motion • Wrist & pelvis contributions: correlated to the max CH velocity • Trunk motion: no notable contribution / correlation to the max CH velocity • Velocity Decomposition: • Decomposed velocities  causal relationships • 3-D modeling studies needed: to establish the causal relationship

  20. Discussion (cont.) • X-Factor: • Not the X-factor but the hip & shoulder parameters were correlated to the max CH velocity. • Direct relationship between max CH velocity and X-factor is questionable. • Inter-group difference in X-factor may mean fundamental differences in swing style. • The X-factor could be an indicator of the golfer’s skill level.

  21. Discussion (cont.) • Golf swing: •  a planar motion around a hub (Cochran & Stobbs, 1968) • Planar perspective, X-factor, & SSC: • Popular menus • Time to reassess their meaningfulness • Trunk & arms: work together to achieve a planar CH motion in the delivery zone • Future studies: trunk-arm coordination

  22. Conclusion Velocity decomposition revealed that contribution of the trunk motion to the max CH velocity was minor. Not the X-factor, but the hip and shoulder line position/ROM showed significant correlations to the max CH velocity. The link between the X-factor/stretch-shortening cycle perspective and CH velocity generation is questionable. Future studies need to focus on hip and shoulder line position/ROM vs. downswing motion patterns.

  23. Thank you for your attention!

  24. Trial Types Static Posture Motion Trial Processed Motion Trial Club Ball Plate

  25. Kinematic Chain Analysis CH Velocity: 1 A 4 D 5 C E B 3 6 2 F 7 Relative Velocity of CH to Wrist:

  26. Segment Perspective: 1 1 A A 4 4 D D 5 5 C C E E B B 3 3 6 6 2 2 F F 7 7 Joint Perspective:

  27. Decomposition of CH Velocity Wrist (2 + 1 DOFs) Elbow (1) 1 Shoulder Joint (3) A 4 Mid-Shoulder (1) D 5 C L4/L5 (3) E B Pelvis Rotation (3) 3 6 2 F Mid-Hip Translation 7 Time Function: Max contribution Contribution at BI Contribution

  28. Normal Velocity Contribution Up Down

  29. Radial Velocity Contribution Toward

  30. Golf Performance Factors Goal: • Accuracy & consistency in distance & direction • Maximization of the distance Impact Conditions: • Motion of the clubhead (velocity) • Orientation of the clubface at impact • Location of impact on the clubface • Distance: function of the CH velocity at impact

  31. Motion Planes

  32. X-Factor Studies

  33. X-Factor Studies (cont.) • Issues: • Heterogenous samples • No direct relationship between CH velocity and X-factor • Influence of the planar swing model / stretch-shorting cycle • No normalization of the CH velocity to body size

  34. Correlation: vs. Max Clubhead Velocity

  35. Correlation: vs. Max Clubhead Velocity

  36. X-Factor Parameters Correlation: vs. Max Clubhead Velocity (BH/s)

  37. Velocity Contribution vs. Max CH Velocity r = 0.997* (*p < 0.05) r = 0.724* r = 0.633* r = 0.539* r = 0.501* r = -0.475*

  38. Inter-Joint/Segment Correlations (p < 0.05)

  39. Accumulated Contribution 100% 29.9% 17.1% 19.3% 25.6%

  40. Trajectory Contribution vs. Max CH Velocity (*p < 0.05) r = 0.468* r = 0.544*

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