Young-Hoo Kwon, Chris Como, Ki Hoon Han, Sangwoo Lee, & Kunal Singhal Biomechanics Laboratory, Texas Woman’s University, Denton, TX 6 th World Scientific.

Decomposition of the Clubhead Velocity:Assessment of the Contributions of the Joint/Segment Motions in Golf Drives

Young-Hoo Kwon,Chris Como, Ki Hoon Han, Sangwoo Lee, & Kunal SinghalBiomechanics Laboratory, Texas Woman’s University, Denton, TX

6th World Scientific Congress of Golf, Phoenix, AZ

2

Planar Double-Pendulum Model

X-Factor

(Cochran & Stobbs, 1968; Hume et al., 2005; Hellstrom, 2009)

Stretch-Shortening Cycle

Triple-pendulum model

3

Planarity & Functional SP

R ElbowL Hand

R ShoulderL Shoulder

FSP

MDMF

FSP

Motion Planes

(Kwon et al., 2012)

4

New Double-Pendulum Model

Hand Path Determined by: • Trunk motion &• Arm motions

Trunk Motion:• Flexion/extension• Lateral flexion• Rotation• Elevation/depression

Projected Hand

Projected Clubhead

New Hub

Arm Motions:• Shoulder motions• Elbow motions

5

0 10 20 30 40 50 60 70 80 90 100

-200

-100

0

100

200

300

400

500

P: P/A TiltP: R/L TiltP: L/R RotT: R/L Lat FlT: L/R Rot

Normalized Time (%)

(de

g/s

)

0 10 20 30 40 50 60 70 80 90 100

-300-200-100

0100200300400500

S: Fl/ExtS: Abd/AddS: E/I Rot

Normalized Time (%)

(de

g/s

)

New Kinematic Sequence: Joint Angular Velocities

Meaningfulness of the trunk rotation and the X-factor?

6

X-Factor Studies

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

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

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:• Wiffle balls• 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

TB ED MD BI MF

Top of BS Early DS Mid DS Ball Impact Mid FT

12

Functional Swing Plane (FSP)

nro

ii

ij

ik

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 axisX-Factor Computation:• Shoulder & hip lines• Projected to the FSP

frame

13

1

2 3

45

A

B

CD

1v 1 2 21

3 31

4 41

5 51

6 61

71

7

F

v r

r

r

r

r

r

v

Wrist (2 + 1 DOFs)

Elbow (1)

Shoulder Joint (3)

Mid-Shoulder (1)

L4/L5 (3)E

6

7F

Pelvis Rotation (3)

Mid-Hip Translation

Decomposition of CH Velocity

1 2 3 4 5 6 7 ( )FSPFSP Gv T v v v v v v

Max contributionContribution at BIContribution

Time Function:

14

Tangential Velocity Contribution

0 10 20 30 40 50 60 70 80 90 1000

5

10

15

20

25

30

CH

Wrist

Pr/Sup

SJ

Trunk

Pelvis

Normalized Time (%)

(BH

/s)

100%

ED: 67.0%

MD: 86.9%

BI: 100%

46.9%

16.8%

19.2%

15.7%

18.5%

TB: 0%

(5)(12)(1)

15

Velocity Contribution

CH Wrist Pr/Sup

Elbow SJ Trunk Pelvis MH-5

0

5

10

15

20

25

30

MaxChange

Joint/Segment

(BH

/s)

r = 0.724

r = 0.539r = 0.501

r = -0.475

(p < 0.05)vs. Max CH Velocity

(3)(1)

16

X-Factor Parameters

0 10 20 30 40 50 60 70 80 90 100

-60

-40

-20

0

20

40

60

80

100

120

140

Hip LineShoulder LineX-Factor

Normalized Time (%)

(deg

)

17

X-Factor Parameters

0 10 20 30 40 50 60 70 80 90 100

-60

-40

-20

0

20

40

60

80

100

120

140

Hip LineShoulder LineX-Factor

Normalized Time (%)

(deg

)

X-Factor Stretch

1.5 ± 2.2 deg

18

X-Factor Parameters

X-Factor Hip Line Shoulder Line-150

-100

-50

0

50

100

150

MaxImpactChange

X-Factor Parameter

(deg

)

r = -0.486*

(*p < 0.05)vs. Max CH Velocity

r = -0.568*

r = -0.461*

CV = (15, 79, 18)%CV = (21, 25, 17)%CV = (10, 31, 11)%

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

Ball Plate

Club

Static Posture Motion Trial Processed Motion Trial

25

Kinematic Chain Analysis

1

2 3

45

A

BC

D

1v

1 1 2

2 3

3 4

4 5

5 6

6 7

7

v v v

v v

v v

v v

v v

v v

v

1 2 21

2 3 4 5 6 21

A

F

v v r

r

E

6

7F

CH Velocity:

Relative Velocity of CH to Wrist:

26

1

2 3

45

A

BC

D

1v

E

6

7F

1 2 3 4 5 6 21

3 4 5 6 32

4 5 6 43

5 6 54

6 65

76

7

F

F

F

F

F

F

v r

r

r

r

r

r

v

2 21

3 32 21

4 43 32 21

5 54 43 32 21

6 65 54 43 32 21

76 65 54 43 32 21

7

F

r

r r

r r r

r r r r

r r r r r

r r r r r r

v

1

2 3

45

A

BC

D

1v

E

6

7F

Segment Perspective:

Joint Perspective:

27

1

2 3

45

A

B

CD

1v 1 2 21

3 31

4 41

5 51

6 61

71

7

F

v r

r

r

r

r

r

v

Wrist (2 + 1 DOFs)

Elbow (1)

Shoulder Joint (3)

Mid-Shoulder (1)

L4/L5 (3)E

6

7F

Pelvis Rotation (3)

Mid-Hip Translation

Decomposition of CH Velocity

1 2 3 4 5 6 7 v v v v v v v Max contributionContribution at BIContribution

1 2 3 4 5 6 7 dt dt dt dt dt dt dtv v v v v v v

Time Function:

28

Normal Velocity Contribution

0 10 20 30 40 50 60 70 80 90 100

-10

-8

-6

-4

-2

0

2

4

6

8

10

CH

Wrist

Pr/Sup

SJ

Pelvis

Normalized Time (%)

(BH

/s) Up

Down

29

Radial Velocity Contribution

0 10 20 30 40 50 60 70 80 90 100

-2

-1.5

-1

-0.5

0

0.5

1

1.5

CHWristPr/SupSJTrunkPelvis

Normalized Time (%)

(BH

/s)

Away

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

Study Methods Results

Cheetham et al. (2000)

10 skilled9 less skilled ( 15)

Skilled > less skilled (max)

Zheng et al. (2007)

18 professional (0)18 low HC (3.22)18 mid HC (12.5)18 high HC (21.3)

Pro > high (TB)

Myers et al. (2007)

21 low ball velocity (15.1)65 medium ball velocity (7.8)14 high ball velocity (1.8)

Low, med. < high (TB)Low < med. < high (max)Correlation (TB, max)

Lephart et al. (2007)

15 golfers (12.1)8-week golf-specific training

Pre < Post (shoulder rotation, x-factor)

Cole & Grimshaw (2009)

7 low HC ( 10)8 high HC (12-18)

None

33

X-Factor Studies (cont.)

Study Methods Results

Chu et al. (2010)

266 males & 42 females (8.4) Multiple regression (TB)

Joyce et al. (2010)

Method studyOrientation angle approach

Comparison among rotation sequences

Meister et al. (2011)

10 professional (scratch or better)5 amateur (4, 15, 30, two novice) 3 effort levels (easy, medium, & hard)

Within subject correlation (professional; max, impact)

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

Maximum(BH/s)

At Impact(BH/s)

Change(BH/s)

Clubhead 25.21 ± 1.82 24.86 ± 1.85(r = 0.997*) -0.35 ± 0.15

Wrist 11.87 ± 2.08(r = 0.724*)

10.32 ± 2.16(r = 0.633*) -1.55 ± 1.05

Pr/Sup 4.17 ± 2.23 4.14 ± 2.24 -0.03 ± 0.08

Elbow 1.94 ± 1.10 0.75 ± 1.93 -1.19 ± 1.20(r = 0.501*)

SJ 4.82 ± 0.63 2.71 ± 2.24 -2.11 ± 2.14

Trunk 3.95 ± 0.67 3.25 ± 1.30 -0.70 ± 0.88

Pelvis 4.67 ± 0.84(r = 0.539*) 3.97 ± 0.94 -0.70 ± 0.58

M Hip0.35 ± 0.15

(r = -0.402; p = 0.10)

-0.04 ± 0.15 -0.39 ± 0.23(r = -0.475*)

Correlation: vs. Max Clubhead Velocity

35

TB-ED(BH)

TB-MD(BH)

TB-BI(BH)

Clubhead 0.75 ± 0.10 1.60 ± 0.13 2.41 ± 0.36

Wrist 0.02 ± 0.09 0.34 ± 0.10 0.73 ± 0.17

SJ 0.12 ± 0.06 0.31 ± 0.08 0.41 ± 0.11

Trunk 0.24 ± 0.06 0.36 ± 0.08 0.46 ± 0.08

Pelvis 0.28 ± 0.08(r = 0.544*)

0.47 ± 0.11(r = 0.420; p =

0.08)

0.62 ± 0.14(r = 0.468*)

Correlation: vs. Max Clubhead Velocity

36

X-Factor Parameters

Maximum(deg)

At BI(deg)

Change(deg)

X-Factor 58.2 ± 8.9 10.7 ± 8.5 -47.5 ± 8.5

Hip LineAngle 38.4 ± 7.9 -38.7 ± 9.8

(r = -0.486*)

-77.1 ± 13.4(r = -0.461; p =

.05)

Shoulder Line

Angle

95.1 9.4(r = 0.415; p =

0.08)

-28.0 ± 8.8(r = -0.400; p =

0.10)

-123.1 ± 13.0(r = -0.568*)

Correlation: vs. Max Clubhead Velocity (BH/s)

37

Velocity Contribution

CH Wrist Pr/SupElbow SJ Trunk Pelvis M Hip-5

0

5

10

15

20

25

30

MaxImpactChange

Joint/Segment

(BH

/s)

r = 0.997*

r = 0.724*r = 0.633*

r = 0.539*

r = 0.501*r = -0.475*

(*p < 0.05)vs. Max CH Velocity

38

Pelvis Max

Elbow Max

Wrist Max Pr/Sup Max

MH -0.471

Pelvis -0.553 0.607

Trunk -0.536

El/Depr -0.476

Elbow 0.503 -0.631

Inter-Joint/Segment Correlations (p < 0.05)

Pelvis Max

SJ Max Wrist Max Pr/Sup Max

MH Max 0.470

El/Depr Max

0.497

Elbow Max

0.493

Wrist Max -0.674

39

Accumulated Contribution

0 10 20 30 40 50 60 70 80 90 1000

0.5

1

1.5

2

2.5

3

CH

Wrist

SJ

Trunk

Pelvis

Normalized Time (%)

(BH

) 29.9%

17.1%

19.3%

25.6%

100%

40

Trajectory Contribution

CH Wrist SJ Trunk Pelvis0

0.5

1

1.5

2

2.5

3

TB-EDTB-MDTB-BI

Joint/Segment

(BH

)

r = 0.544*

(*p < 0.05)

r = 0.468*

vs. Max CH Velocity

41

0 10 20 30 40 50 60 70 80 90 100

-300-200-100

0100200300400500

P: P/A TiltP: R/L TiltP: L/R RotT: R/L Lat FlT: L/R RotS: Fl/ExtS: Abd/AddS: E/I RotE: Fl/Ext

Normalized Time (%)

(de

g/s

)

0 10 20 30 40 50 60 70 80 90 100

-1500-1000

-5000

500100015002000

F: Sup/PrW: Fl/ExtW: R/U Dev

Normalized Time (%)

(de

g/s

)