Yoon-Seok Choi, Junkyung Song, Dawon Park, Jaeho Park, Jaebum Park, Jaebum Park, Jaebum Park
In this study, we examined multiple hypotheses concerning the variations in tennis forehand strokes contingent on the velocity of the incoming ball and the player's proficiency. The experiment involved seven expert tennis players and six novice players, who were tasked with striking a ball projected from a ball machine under three randomized speed conditions: slow (mean ± SD: 7.54 ± 0.65 m/s), medium (10.83 ± 0.59 m/s), and fast (14.42 ± 0.50 m/s). Participants were instructed to execute a forehand drive toward the ball machine as accurately as possible while exerting maximum effort, without compromising accuracy. A motion capture system equipped with eight infrared cameras was employed to measure reflective markers affixed to the subjects' bodies and rackets. The objective of this study was to analyze the angular motion of each segment involved in the forehand stroke in the transverse plane, with a particular focus on angular displacement and maximum angular velocity. Furthermore, a comparison was made of the synergy indices computed from the segment angles at impact. The results indicated a decline in angular displacement with increasing ball speed, consistent with the hypothesis. In comparison with the novice group, the expert group demonstrated significantly greater usage of the distal segment with a decoupling strategy, as well as proper adjustments of other segments, particularly the trunk, depending on ball speed. The synergy index exhibited an increase with increasing ball speed; however, no significant difference was observed between the two groups.