• Korean Journal of Applied Biomechanics
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• v.18 no.1
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• pp.11-19
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• 2008

This study was conducted with 8 male table tennis players who won national competitions. Of the subjects, 4 used a racket of penholder grip and 4 used one of shake hand grip, and all of them were right.handers. We analyzed three-dimensional angular characteristics such as angular component, swing trajectory and swing posture related to the racket swing motions of forehand drive and smash in table tennis, and drew conclusions as follows. Racket angle(p<.05) and racket swing angle(p<.01) were significantly different between the two motions. In smash, the back swing posture maintained the racket angle large by holding the racket upright and made the racket swing angle small for high ball speed. In addition, the height of the racket head in back swing posture was also significantly different between the two motions. In phg on impact, the open angle of the long axis of the racket was significantly different between the two motions. This shows that impact was applied a bit behind for giving top spin to the ball. In the back swing of drive, the gradient of the upper body was slightly larger in shg than in phg probably because of the structural difference of the racket grip in the neutral posture.

• Korean Journal of Applied Biomechanics
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• v.20 no.2
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• pp.139-148
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• 2010

The purpose of this study was to comparatively analyze the kinematic variables between the squash backhand and racquetball backhand strokes through three-dimensional cinematography. Three expert racquetball players and three expert squash players were involved in the data gathering process. The horizontal, vertical and lateral displacement of racket and trunk segment, intersegmental angular velocity of the wrist, elbow and shoulder joints, and the linear velocity of the racket were descriptively analyzed, and the followings were concluded. The racket of the squash backhand stroke showed an 'U' shaped movement where the racket moved rapidly downward and moved forward to make an impact and followed through to a front-top finish, while the racket of racquetball backhand stroke showed an 'O' shaped movement where the racket showed circular movement through the rear and bottom positions for the impact, and showed rotation through the lower-front and upper front to a upper-rear-ward finish during the follow-through. The peak velocity of racket was found before the impact point in the squash backhand stroke and at the impact point in the racquetball backhand stroke. For the final conclusion, for the squash backhand stoke, instructors might be better to make the racket move downward to make highest velocity before the impact and finished short follow-through, while for the racquetball backhand stroke, to make the racket move forward to make highest velocity at the impact and finished rather long follow-through.

• Korean Journal of Applied Biomechanics
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• v.17 no.1
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• pp.53-60
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• 2007

Recently tennis techniques has been changed in stance patterns. Stance is consist of square stance, open stance and semi-open stance. The purpose of this study was to analyze the kinematics variables of racket head velocity during forehand stroke by stance patterns. Eight high school tennis players were chosen for the study who use semi western grip right-handed person more than career 7 years. They performed horizontal swing and vertical swing that it was done each five consecutive trial in the condition of square, open and semi-open stance. The results showed that racket head velocity significant difference was not observed in stance types between swings at impact. Y and Z components of racket head velocity for horizontal and vertical swing at second prior to impact and at impact were that y components velocity was faster horizontal swing than vertical swing and z components velocity was later horizontal swing than vertical swing. Statistically significant variable to racket head velocity and Pearson's correlation were drawn as follows. 1. Z components of racket head velocity in square stance was significant correlation by right knee joint. 2. Y components of racket head velocity in semiopen stance was significant correlation by left hip joint. 3. Y components of racket head velocity in open stance was significant correlation by left ankle joint.

• Korean Journal of Applied Biomechanics
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• v.17 no.1
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• pp.41-52
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• 2007

The present study analyzed the two hand backhand stroke motion of six female high school tennis players who won the championship at the National Athletic Meeting in 2006, and drew conclusions as follows. The open angle of the racket at the moment of impact was 90 degree without significant difference among the players, making a wide contact between the ball and the racket. The racket angle was 43 degree at take back and 91 at impact, showing a style of holding the racket rather upright in general. In back swing from the top to the impact, the shoulders and the hips turned by 97 degree and 40 degree, respectively. At the moment of impact, the height of the impact was 54%H, and the position of the impact was 10%H ahead of and 37%H left from the central axis of the body. The right hand made a continental grip and the left hand made a Western or semi Western grip. Through the entire swing motion, the grip angle of the left hand was smaller than that of the right hand, and those who maintained a large grip angle of the right hand at the moment of take back put the racket head slightly farther from the body. In the swing of the racket head from the lowest point to the impact, the vertical length of movement was 11%H and the horizontal length of movement was 60%H, quite long.

• The Journal of Korean Physical Therapy
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• v.31 no.4
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• pp.228-235
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• 2019

Purpose: This study examined the injury and rehabilitation of athletes with disabilities in racket sports projects (i.e., badminton, table tennis, and wheelchair tennis). In addition, the characteristics of each project and the differences among those projects are discussed. Methods: Business team athletes with disabilities in racket sport were enrolled as subjects (i.e., 19 badminton athletes, 19 table tennis athletes, and 19 wheelchair tennis athletes). The real conditions of the injury, injury severity, injury site, symptoms, and rehabilitation methods after injury were analyzed. Results: No significant differences were observed among the actual condition, injury severity, symptoms and the methods of rehabilitation on racket sport for athletes (i.e., badminton, table tennis, and wheelchair tennis athletes) with disability. The differences were focused mainly on the injury sites due to the characteristics of the different projects, and specific technical actions. Conclusion: This study examined the real condition of the injury, injury severity, injury site, symptoms and rehabilitation methods after the injury on the rackets (i.e., badminton, table tennis, and wheelchair tennis) athletes with disabilities. The data can be used to eliminate the incidence of injury and minimize the injury severity for racket athletes with disabilities. In addition, it can also be used for the disabled, who like racket projects, as the fundamental material to prevent injury and assist in recovery.

• Korean Journal of Applied Biomechanics
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• v.19 no.2
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• pp.337-345
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• 2009

The purpose of this study were to find out the differences in kinematic variables of racket movement by performing the tennis serve. Three top male tennis players participated in this study. Three synchronized high-speed cameras were used to record the service action of top players for Three dimensional video analysis. The results of this study showed that (1) the velocity of the tennis racket at impact is important to the generation of racket velocity to Y-axis. This result indicates that forward motion and upward movement of the racket; (2) with respect to racket angular velocity at impact, the fast angular momentum of X-axis is important to generate the velocity of the tennis ball. This result indicate upward movement of the racket with a strong flexor of wrist joint; (3) the velocity of the tennis ball was influenced by the change of angular linking the Z-axis to -X-axis. This result indicates that the high velocity of the tennis ball is obtained from having the racket unitedly moving to the direction of the bill's flight at the acceleration interval and acquiring the distance of acceleration with the racket head vertically to the ground at the back scratching.

• Transactions of the Korean Society of Mechanical Engineers
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• v.12 no.1
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• pp.95-105
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• 1988

The dynamic characteristics of a tennis racket were identified by experimental modal analysis and the sweet spot due to these was calculated. A tennis racket was selected as a model reference and modal parameters of the racket were estimated from the transfer function measured by experiment. The transfer function was reconstructed by the modified modal parameters on the assumption that the racket was locally modified, for example, a change in the material of the frame and the attachment of a damping material to the grip. The change of the dynamic characteristics, especially natural frequency and magnitude of the second and the third vibrational modes, were evaluated from the reconstructed transfer function. The change of the sweet spot due to the modified modal parameters was estimated and visualized through computer graphic simulation by the criterion of the sweet spot measured before structural modification. The modal parameters for improvement of the dynamic characteristics.

• Journal of radiological science and technology
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• v.32 no.1
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• pp.107-110
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• 2009

The research was about the relation between the dorsal side dose measured by using the phantom body (Alderson Rando Phantom) and factors like contacted material of the patients, the size of the field, angle of incidence. Compared with mylar (tennis racket), the dose on $10{\times}10\;cm^2$ field size of cotton was increased by 2% and by 8% in the case of breast board. In the case of $15{\times}15\;cm^2$ field size, the dose was increased by 6% compared with $10{\times}10\;cm^2$ size. The field size of $20{\times}20\;cm^2$ resulted in 10% increase of dose, while $5{\times}5\;cm^2$ produced 13% decrease. Compared with incident angle $0^{\circ}$, the cases for the incident angle $5^{\circ}$ had 0.4% less dose for breast board, 0.5% for tennis racket, 1.1% for cotton. The cases for the incident angle $10^{\circ}$ had 1.5% less dose for breast board, 1.9% for tennis racket, 2.6% for cotton. For the incident angle $15^{\circ}$, breast board, tennis racket, cotton caused decrease of dose by 3.9%, 2.6%, 3.86% respectively. Resultantly carbon material can cause more skin dose in treatment field. By the results of this study, we recommend that one should avoid the contact between the carbon material and skin.

• Korean Journal of Applied Biomechanics
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• v.12 no.1
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• pp.221-231
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• 2002

The purpose of this study was to clarify the differences in service patterns of a forward and backward soft tennis players using 3D motion analyzer. Subjects were 4 forward players of $24.0\pm5.23$yrs and 4 backward players of $23.5\pm1.73$yrs. The results were as following: 1. There was no difference among each positions on swinging-time. The longest racket swinging-time was in the phase of takeback, the second one was in follow-through. The shortest one was in the phase of forward-swing so called force production phase, which had an influence on ball's velocity. 2. The racket speed on impact was 16.3m/s in forward subject and 19.53m/s in backward subject, when each velocity of balls was 44.6m/s, 52.9m/s. Although there was no significant difference along by positions, backward subject showed faster result. 3. The maximum speed of each performance was reached before the impact, and the speed at impact along by positions did not show any significant difference. The summation of velocity was measured in good order as following; hip, shoulder, elbow, wrist, top of racket. 4. In the angular velocity of all examine except one, the angular velocity of forearm was bigger than the one of racket top although there was no statistically significant difference between forward and backward subject. 5. The service grip of the forward players was shorter than that of backward players.

• Journal of the Korean Applied Science and Technology
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• v.38 no.4
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• pp.1143-1155
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• 2021

The results of the analysed to compare the kinematic variables of backhand backwall boast shot motion between the expert and novice subjects through three dimensional cinematography. First, the expert took shorter time than novice to finish the motion. Second, the racket of expert showed side-horizontally higher, vertically lower and front-horizontally higher displacement than novice in the downswing phase. Third, the racket of expert showed vertically and front-horizontally lower displacements than novice during the follow through phase. Fourth, the velocity of racket was faster for the novice. Five, the velocity of lower arm was faster for the novice.