The Influencing Factors On The Ball Speed During Table Tennis Forward-loop Strokes In Male Athletes

Purpose: The forward-loop is considered to be the most common table tennis stroke.It is also regarded as the most offensive stroke style,the main characteristics of forward-loop stroke included fast velocity,strong rotation and large force of forward direction.Ball speed is one of the most important indicators to evaluate the performance of playing forward-loop strokes,thus the purpose of this study was to explore the relationship between muscle strength,joint kinematics,segment kinematics and table tennis speed in different stroke conditions as well as compare the above parameters between shakehand-grip and penhold-grip players.Method: A total of thirty-five male table tennis athletes at the Chinese national level I or II participated.The motor-driven dynamometer was used to measure joint/segment torque,work,power of lower-extremity drive,trunk rotation and shoulder,elbow,forearm and wrist in the corresponding motion plane of the playing side separately.In addition,Participants completed three successful forward-loop strokes with forehand or backhand strokes against topspin or backspin balls using their habitual grips.Kinematic data were collected at a sampling rate of 100 Hz using a10-camera motion capture system.Three-dimensional joint/segment angular velocities of pelvis,trunk and upper extremity were extracted at the peak resultant velocity of the table tennis racket.Result:1.For shakehand-grip athletes: positive correlations between ball speed and isokinetic strengths were observed,including between shoulder flexion(r=0.467),trunk left rotation(r=0.471)and lower-extremity drive(r=0.448)during topspin forehand condition;between shoulder horizontal adduction(r=0.417),trunk left rotation(r=0.481)and lower-extremity drive(r=0.412)during backspin forehand condition;between wrist adduction(r=0.416)and lower-extremity drive(r=0.419)during topspin backhand condition.For penhold-grip athletes: positive correlations between ball speed and isokinetic strengths were observed,including between elbow extension(r=0.867)and trunk left rotation(r=0.767)during topspin backhand condition.2.For shakehand-grip athletes: positive correlation between ball speed and internal rotation angular velocity of shoulder joint was observed(r=0.519)during topspin forehand condition.For penhold-grip athletes: positive correlations between ball speed and joint/segment angular velocities were observed,including between elbow adduction(r=0.833)and forearm pronation(r=0.783)during topspin forehand condition;between shoulder internal rotation(r=0.733)and racket abduction(r=0.850)during backspin forehand condition;between shoulder flexion(r=0.767)during topspin backhand condition.3.For shakehand-grip athletes: joint/segment works of 180 °/s wrist adduction,60 °/s shoulder horizontal adduction and 50 mm/s lower-extremity drive can explain 65%of ball speed during topspin backhand condition;For penhold-grip athletes:joint/segment torques/forces of 180 °/s wrist extension,500 mm/s lower-extremity drive and 180 °/s shoulder horizontal adduction can explain 94% of ball speed during backspin backhand condition.4.For shakehand-grip athletes: joint/segment angular velocities of pelvis left rotation,trunk left lean,trunk left rotation,shoulder adduction,shoulder internal rotation,racket flexion and racket internal rotation can explain 63% of ball speed during backspin forehand condition.For penhold-grip athletes: joint/segment angular velocities of pelvis right lean,trunk right lean,elbow abduction and racket abduction can explain 99% of ball speed during topspin backhand condition.5.Shakehand-grip and penhold-grip athletes demonstrated similar ball speed but increased shoulder flexion and racket internal rotation angular velocities were found in penhold-grip athletes during forehand conditions.However,shankhand-grip athletes resulted in increased ball speed together with increased racket extension angular velocity during backhand conditions.6.Penhold-grip athletes demonstrated increased elbow flexion torque,elbow flexion work,forearm pronation torque,forearm pronation work and forearm pronation torque compared to shankhand-grip athletes at both 60 °/s and 180 °/s test conditions.Conclusion:1.In order to develop ball speed of playing forward-loop strokes,it is necessary to develop angular velocities of each joint/segment together with general muscle strength in the daily training.2.Muscle strength plays important roles in developing ball speed of playing forward-loop strokes.For shakehand-grip athletes,the joint/segment strength of shoulder flexion,shoulder horizontal adduction,wrist adduction,trunk left rotation and lower-extremity drive are of great significance to develop ball speed;For penhold-grip athletes,the joint/segment strength of elbow extension and trunk left rotation are of great significance to develop ball speed.3.The angular velocity of upper-extremity movement is an important indicator to influence the ball speed of playing forward-loop strokes,but the influence of the angular velocities of core locations such as pelvis and trunk can't be ignored.For shakehand-grip athletes,angular velocities of the pelvis and trunk play important roles during backspin forehand and backspin backhand conditions.For penhold-grip athletes,angular velocities of the pelvis and trunk play important roles during topspin backhand and backspin backhand conditions.4.Penhold-grip athletes demonstrated increased muscle strength of elbow flexion and forearm pronation compared to shakehand-grip players.Shakehand-grip and penhold-grip athletes demonstrated similar ball speed but different shoulder and racket kinematics in forehand strokes.However,Shakehand-grip players resulted in increased ball speed compared to penhold-grip players in backhand strokes.