Analysis of Upper-Limb Movement Characteristics in Tennis Volleys Based on Skill-Level Differences: Kinematic Features of the Backhand Versus Forehand Volley

Background: In tennis, the volley is an important shot; however, studies describing its movement characteristics have been limited to the forehand volley (FV). In this study, we analyzed the characteristics of upper-limb movement during FV and backhand volley (BV) in skilled and less-skilled tennis players. Methods: Twelve tennis players with experience (skilled group) and eight with little experience (less-skilled group) were included. The participants stood in front of a simulated net and volleyed balls were fed toward the target. Movements were recorded using three video cameras, and three-dimensional coordinates were obtained using the direct linear transformation method. The measured variables were bilateral shoulder rotation angle, pelvic rotation angle, shoulder–pelvis twist angle, and the racket–forearm angle. A two-way analysis of variance (ANOVA) was conducted with player level (skilled vs. less skilled) and time point (backswing event vs. impact event) as factors. Results: In the FV, a significant main effect of time point was observed for the bilateral shoulder rotation angle (F1,18 = 7.471, p = 0.014, η2 = 0.293). In the BV, significant main effects at both player level and time point were observed for the pelvic rotation (player level; F1,18 = 8.759, p = 0.008, η2 = 0.327, time point; F1,18 = 13.351, p = 0.002, η2 = 0.426). Also, significant main effects at both player level and time point were observed for racket–forearm angles (player level; F1,18 = 6.752, p = 0.018, η2 = 0.273, time point; F1,18 = 10.213, p = 0.005, η2 = 0.362). However, a significant main effect of the player level was observed for the shoulder–pelvis twist angle (F1,18 = 12.124, p = 0.003, η2 = 0.402). Conclusions: In contrast to FV, BV prioritizes ball control by maintaining the shoulder–pelvis angular relationship without releasing the twist. These results suggest that skill-related differences in volleying are more pronounced in the BV than in the FV.