Marker location and knee joint constraint affect the reporting of overhead squat kinematics in elite youth football players

Motion capture systems are used in the analysis and interpretation of athlete movement patterns for a variety reasons, but data integrity remains critical regardless. The extent to which marker location or constraining degrees freedom (DOF) biomechanical model impacts on this lacks consensus. Ten elite academy footballers performed bilateral overhead squats using marker-based motion system. Kinematic were calculated four different sets with 3DOF 6DOF configurations three joint rotations right knee. Root mean squared error differences between ranged sagittal plane 1.02 4.19 larger values frontal (1.30–6.39 degrees) transverse planes (1.33 7.97 degrees). cross-correlation function knee kinematic time series all eight marker-sets from excellent (>0.99) reduced both coronal (<0.9). Two-way ANOVA repeated measures at peak flexion revealed significant (p < 0.05). Pairwise comparisons showed some sets. Marker DOF while measuring relatively large ranges population important considerations integrity.