| Objective and implications: The world table tennis champion Wu Yang’s forehand chopping technique is the core among her technical collections in that she could chop heavy or no spin balls effortlessly and on purpose.The study aimed to examine the similarities and differences of the kinematic and muscular characteristics of racket arm and racket between chopping no-spin and back spin ball in order to provide research-based evidence for coaches and regular players to conceptually understand this type of technique and to correct or refine the chopping techniques for the low-level players.Wu Yang may choose to retire in the nearly future because of ageing.Therefore,it is necessary to use biomechanical approaches to quantify and record the core components of her technics(chopping no spin and back spin ball)since she is still in her time of top performanceMethod: The world table tennis champion,Wu Yang,participated in this study.Qualisys motion-capturing system and DYLSYS surface EMG system were utilized to collect the kinematic and EMG data.Factorial repeated measure ANOVA was employed to analyze the data.Results:Wu Yang spent similar amount of time between chopping no spin and backspin ball in the introductory phase.The racket moved primarily backward and right during this phase.The degree of flexion and adduction of the wrist was higher in the backspin condition compared to no-spin condition.The racket moved more backward and less right in the backspin condition.The racket angle was larger in the backspin condition due to less degree of internal rotation of the shoulder and elbow joints at the end of the introductory phase.The wrist underwent fast extension and abduction directly before the end of the introductory phase in the backspin condition.Wu Yang spent less time in the backspin condition compared to the no spin condition in the hitting phase.The racket moved more in the forward and rightward direction in the backspin condition compared to the no-spin condition.Similar to the introductory phase,the increase in the average degree of internal rotation of the shoulder and elbow joints contributed to the rise of the racket angle in the backspin condition in the hitting phase.The average angular and linear velocity of each joint and racket was greater in the backspin compared to no-spin situation in the hitting phase partly because of the muscular activity increase of the biceps,upper deltoid,brachioradialis,radial wrist flexor,and ulnar carpi flexor.Wrist joint underwent a tremendous change of direction from extension and abduction to flexion and adduction immediately before the contact moment.In the follow-through phase,Wu Yang spent less time in the backspin condition compared to the no spin condition.The player adopted a skill called “voluntary brake” to quickly reduce the linear speed of the racket and therefore to limit the displacement of it by increasing the muscular activity of brachioradialis,radial wrist flexor,and ulnar carpi flexor.Unlike topspin forehand,the resultant maximum racket velocity appeared directly after the contact moment.Suggestions: 1.Compared to chopping no-spin ball,choppers should increase the racket angle more in both introductory and hitting phases by decreasing the internal rotation of the shoulder and elbow joints.2.The increase of the angular velocity of the shoulder and elbow joints in the hitting phase is suggested in order to increase the linear velocity of paddle to chop heavy backspin ball.3.They should flex and adduct wrist joint closely before racket-ball contact.4.They should also swiftly restore through “voluntary brake” in the follow-through phase.5.It was recommended that the results of this study could not be interpreted as unvarying standards or solutions for the ordinary table tennis learners.Rather,beginning-or intermediate-level choppers should learn from the movement pattern Wu Yang used to switch between chopping no-spin and backspin balls based on the encountered circumstances. |
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