Author(s): XU, C.1,2, MARTÍNEZ-GALLEGO, R.2, CUI, Y.1, Institution: UNIVERSITY OF VALENCIA, Country: SPAIN, Abstract-ID: 1974

INTRODUCTION:
Disguised strokes are critical tactical weapon in modern tennis, enabling players to delay opponent’s anticipation and disrupt court positioning. However, empirical research on their underlying kinematic characteristics—particularly across different skill levels—remains limited. This study aimed to i) quantify kinematic differences between conventional and disguised forehand strokes, and ii) examine features of disguise execution between elite and sub-elite players.
METHODS:
Twenty healthy right-handed national elite and sub-elite tennis players (10 each, age: 22.2 ± 2.33 years) with no injuries in the past six months were recruited. Kinematic data were captured using a validated multi-camera markerless tracking system, comprising high-definition cameras (120 Hz) and a 3D calibration frame s). Each player performed six baseline forehand conditions: 1) Open-Stance (OS) Cross-Court (CC) (conventional,); 2) OS Down-The-Line (DTL) (disguised); 3) Neutral-Stance (NS) DTL (conventional); 4) NS CC (disguised); 5) Combined disguised trails (2+4); 6) Combined conventional trials (1+3). Key events—backswing (B), impact (C), and follow-through completion (D) and phases (B–C, C–D) were analyzed for Z-axis(Z) displacement, joint angles, angular velocity/acceleration, and rotation amplitude at the shoulder, elbow, wrist, hip, knee, and ankle, using 3D motion analysis system.
RESULTS:
Elite players modulated kinematics to disguise shots: in OS, disguised DTL strokes showed greater bilateral shoulder and hip X-axis (X) angles at B, larger right ankle resultant angle and right knee resultant angular acceleration at C. In NS, disguised CC strokes showed larger bilateral shoulder X angles at C, larger Z displacement of right elbow/knee and bilateral shoulder/hip X angles at D, larger right shoulder Z displacement difference at C-D. Sub-elite players showed technical flaws in disguise strokes: in OS, disguised DTL strokes showed smaller shoulder Z displacement difference (0.6 ≤ |d| ≤ 1.2), with greater right ankle/knee resultant angles (0.6 ≤ |d| ≤ 1.2) at C, shorter duration with greater bilateral shoulder/hip X‑angle and angular velocity (0.6 ≤ |d| ≤ 1.2) at B–C, greater bilateral shoulder X‑angle angular velocity at C–D. In NS, disguised CC showed larger bilateral shoulder X angles at B, larger right knee resultant angle and resultant angular acceleration at C, larger bilateral shoulder and hip X angle and angular velocity at B-C. (P < 0.05, 0.2 ≤ |d| ≤ 0.6) .
CONCLUSION:
Compared to conventional strokes, elite players executed disguised forehands with deeper ankle flexion, greater shoulder-hip rotation, and more pronounced elbow extension in open-stance strokes; and elevated hand position, upright trunk posture, and greater shoulder fluctuation in neutral-stance crosscourt disguises. Sub-elite players displayed excessive shoulder-height discrepancy, limited trunk rotational range and speed, and underutilization of lower-limb drive, suggesting less efficient disguised strategies.