1. Ashwini Kulkarni
KINE 5397-001
Graduate Research Project with Dr. T. Ajisafe
Fall 2016
The Relationship between the Trunk and Lower limb
Muscle Activation and Serving velocity in NCAA
Division I Tennis players.

2. • Flat serve: basic serve
• Trunk :Kinetic chain - 54% force production (Akuthota & Nadler, 2004). Trunk
instability leads to decreased mobility (Leetun et al. 2004; Chow et al., 2003)
• Lower limb: Largest KE is produced by lower limb (Ladeira et. al., 2005),
muscle activation and Stretch Shortening Cycle leads to increase in racquet
speed (Bahamonde, 2000)
• Serving Velocity: Doppler effect (Girard et al. 2005). No literature on
correlation of radar gun use and effect on performance
• Significance of problem: Limited research
• Hypothesis: There will be a relationship between the trunk and the lower limb
muscle activation and serving velocity in NCAA division I tennis players.
Introduction

3. IRB application Participant recruitment
Voluntary participation
and
Confidentiality note
Informed consents Schedule testing day
Methodology(Before testing)

4. Methodology (Testing day)
Code numbers
Demographic
questionnaire
Anthropometri
c
characteristics
Instructions for EMG,
preparation of skin, and
electrode placement
Warm up
Electrode
placement
MVIC
Normalization
SENIAM guidelines
(Konrad 2005)
Practice trials +
Actual trials
Signal
processing
Serving velocity

5. • Raw data was processed using SENIAM guidelines
• SV was predicted using quadratic linear regression
y=a+b1x1+b2x2+b3x3+b4x4+b5x5+b6x6+b7x7
y= predicted score on serving velocity
a= intercept
b= slope
x1-x7= Observed score on independent variables
• SPSS version 21.0
• Pearson correlation coefficients
• Multicollinearity tests
• Relationship between muscle activation and serving velocity – quadratic model for
linear regression
Data Analysis

6. Descriptive Statistics
Mean Std. Deviation
Age (years) 20.2000 1.87380
Years 8.1000 2.68535
String tension (kg) 24.0550 2.20753
Height (cm) 177.4090 12.77516
Weight (kg) 75.9220 6.58799
BMI 24.1400 2.81906
Waist (inches) 36.1100 1.74448
Hip (inches) 39.7000 1.58465
WHR .9071 .05551
Arm length (cm) 53.8650 4.25591
Girth arm (cm) 28.5730 1.61870
Girth forearm (cm) 27.1660 2.02117
Limb length (cm) 94.5130 4.92965
Girth above knee (cm) 47.0030 5.02889
Girth below knee (cm) 37.1180 4.80419
SV (mph) 89.6600 7.09557
Results
Table 1: Descriptive statistics

7. Results
Correlations
RA TH MUL BF GAST RF TA
Pearson Correlation SV
.861 .724 .888 .761 .711 .880 .777
Sig. (2-tailed) SV .012 .024 .027 .038 .038 .046 .041
Table 2: Pearson correlation coefficients
• Represents strong correlation with serving velocity
• Alpha level of p < 0.05 was used

8. Results
Shapley’s Value Decomposition : Partial R2 Coefficients
Model
Unstandardized Coefficients
Shapley’s partial Coefficients
Beta Std. Error Beta % contribution
1
109.802 17.824
RA -11.288 2.56 .711 71.19
TH .959 2.36 .282 28.2
MUL 1.766 2.65 .325 32.5
BF .480 1.25 .352 35.2
GAST -9.408 1.98 .493 49.3
RF 2.109 1.10 .489 48.9
TA -1.638 3.12 .329 32.9
a. Dependent Variable: SV
Table 3: Individual Contributions

9. Results
Model R
R
Square
Adjusted
R Square
Std. Error
of the
Estimate
Change Statistics
Durbin-
Watson
R Square
Change
F
Change df1 df2 Sig.
1
.940a .885 .655 4.16999 .062 .066 7 2 .024* 1.896
Table 4 : Regression statistics
* Represents the model significance at p < 0.05

10. Storage of potential
energy in Rt Obliques,
ES, and Multifidus
Extension moment in
Thoracic ES- decreases
with synergistic activity
Lateral trunk flexion
and axial rotation
RA
Eccentric contractions
Greater angular
momentum
Transferred to racquet
SSC during loading
phase
Discussion and Conclusion
Lower limb
51-55% of KE and force
delivered to hand
Back leg to front leg
angular momentum
Arm drive upwards
large CSA of trunk and
legs with high moment of
inertia
Centripetal motion
Trunk and Lower Limb muscle activation are associated with serving velocity

11. • Increase sample size
• Standard and reliable test to measure
MVIC
• Different levels of tennis teams and
different phases should be studied
• Different warm up protocol
• Limited generalization
• Less sample size
• Significant variations in
normalization values
• Overestimated normalized
EMG levels
Limitations and future implications

12. • Akuthota, V. and S. F. Nadler (2004). "Core strengthening." Archives of physical medicine and
rehabilitation 85: 86-92.
• Leetun, D. T., et al. (2004). "Core stability measures as risk factors for lower extremity injury
in athletes." Medicine & Science in Sports & Exercise 36(6): 926-934.
• Chow, J., et al. (2003). "Lower trunk muscle activity during the tennis serve." Journal of
Science and Medicine in Sport 6(4): 512-518.
• Ladeira, C. E., et al. (2005). "Validation of an abdominal muscle strength test with
dynamometry." The Journal of Strength & Conditioning Research 19(4): 925-930.
• Bahamonde, R. E. (2000). "Changes in angular momentum during the tennis serve." Journal
of sports sciences 18(8): 579-592.
• Knudson, D. and B. Elliott (2003). "Analysis of advanced stroke production." Biomechanics of
advanced tennis: 143-160.
• Konrad, P. (2005). "The abc of emg." A practical introduction to kinesiological
electromyography 1: 30-35.
• Girard, O., Micallef, J.-P., & Millet, G. P. (2005). Lower-limb activity during the power serve
in tennis: effects of performance level. Med Sci Sports Exerc, 37(6), 1021-1029.
References