Kinematic study of serve velocity of Hong Kong elite tennis players

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Kinematic study of serve velocity of Hong Kong elite tennis players

 

Author: Wong, Kam Hung Francis
Title: Kinematic study of serve velocity of Hong Kong elite tennis players
Degree: D.H.Sc.
Year: 2012
Subject: Tennis -- Serve.
Tennis players -- China -- Hong Kong.
Human mechanics.
Hong Kong Polytechnic University -- Dissertations
Department: Faculty of Health and Social Sciences
Pages: xviii, 122 leaves : ill. (some col.) ; 30 cm.
Language: English
InnoPac Record: http://library.polyu.edu.hk/record=b2551433
URI: http://theses.lib.polyu.edu.hk/handle/200/6840
Abstract: Effective training for improving serve velocity is important for elite tennis players. Kinematic analysis of tennis serve is scarce. Only a few studies have compared and correlated ball velocity using real time tennis serve kinematic data. Twelve Hong Kong Tennis Team male players (mean age 20.5±3.8 years, height 174.8±7.1cm and body weight 68.2±12.2kg) were recruited. Body, racket and ball kinematics of tennis serves performed by elite Hong Kong players were monitored by a motion analysis system (Vicon MX, Oxford Metric, Oxford, UK) and correlated with the ball velocity. The data were also compared with a previous study of the World Class tennis players in the Olympic 2000. Tennis serve of each subject was analyzed in sequence of movements and the temporal coordination of the body kinematics. The tennis serve was analyzed in 4 phases: (I) Back Swing Phase (i.e. Preparation Phase) defined from the instant of maximum shoulder internal rotation (MSIR) to the instant of maximum front knee joint flexion (MKF), (II) Lead Leg Drive Phase defined from the instant of MKF to the instant of maximum shoulder external rotation (MSER), (III) Forward Swing Phase defined from the instant of MSER to the instant of racket-ball impact (IMP); and (IV) Follow-Through Phase defined from the instant of IMP to the instant of foot contact with the ground. Our data showed that at the instant of ball impact, there were statistically significant differences in shoulder abduction, elbow flexion, trunk angle relative to horizontal and front knee flexion and the differences between the Hong Kong elite players and the World Class Olympic 2000 tennis players were 10°, 11°, 17° and 15° respectively. At the instant of maximum shoulder external rotation, there were statistically significant differences in shoulder external rotation, shoulder abduction, elbow flexion, wrist extension, trunk angle relative to horizontal and front knee flexion between the two groups and the differences were 19°, 14°, 12°, 22°, 36° and 7° respectively. It was found that the World Class Olympic Games 2000 Players were faster than those of the Hong Kong elite players with 1.9 times in front knee peak extension velocity, 1.6 times trunk peak right rotation velocity, 1.2 times elbow peak extension velocity and 1.4 times wrist peak flexion velocity.
The mean serve velocity of Olympic players (50.81±3.9 m/s) was significantly faster than that of the Hong Kong elite players (40.39±5.5 m/s; range: 33-50 m/s). The velocity of tennis serve of the Hong Kong elite players was similar to the national standard of lower-level tournament western players. The slower ball velocity of the Hong Kong elite players might be due to the differences in kinematic profile during the tennis serve. It was also found that the racket-side rear knee range of motion in the sagittal plane during phase II and III (r=0.705; p<0.05), racket-side rear knee peak extension velocity during phase II (r=0.751; p<0.01), racket-side rear hip peak extension velocity in the sagittal plane during phase II (r=0.657; p< 0.05), racket-side shoulder range of motion in the coronal plane during phase III (r=0.616; p<0.05), racket-side elbow peak extension velocity during phase III (r=0.708; p<0.01) and body mass index (r=0.577; p<0.05) were significantly correlated with the ball velocity. Kinematic analysis of ball motion showed that the theoretical maximum ball velocity that a player could serve is affected by the impact height and racket inclination angle at impact. Kinematic analysis of ball motion of individual Hong Kong elite player's serve showed that ball velocity was found to be significantly correlated with racket inclination angle at impact (r=0.821; p<0.01) and ball landing distance in serve box (r=0.652; p<0.05). Impact height was found to be significantly correlated with racket inclination angle at impact (r=0.860; p<0.01), range of racket inclination angle at impact (r=0.961, p<0.01) and range of ball velocity (r=0.958, p<0.01), range of ball landing distance in serve box (r=0.792, p<0.01). The mean ball velocity of local elite players (145.4±20.5m/s) was significantly slower than the international elite players (Fleisigs: 182.9±14 m/s, Girard: 169.6±11.3 m/s and Elliott: 152.6±8.3 m/s). The calculated racket angle at impact for local elite players (4.883°) was also significantly smaller than that of the international elite players (Fleisigs: 6.548°, Girard: 6.083° and Elliott: 5.425°). In this study, the body, racket and ball kinematic of tennis serves of the elite Hong Kong players were measured. The body kinematics and body height were shown to have significant effects on ball velocity of tennis serve. The impact height and ball-racket inclination angle at impact of each individual local player were recommended to be used to enhance the quality of tennis serve in elite Hong Kong players through tailor-make training program.

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