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Transcript of Young-Hoo Kwon, Chris Como, Ki Hoon Han, Sangwoo Lee, & Kunal Singhal Biomechanics Laboratory, Texas...
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
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.
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
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
)