KINEMATICS OF SOCCER INSTEP KICKING: A COMPARISON OF TWO-DIMENSIONAL AND THREE-DIMENSIONAL ANALYSIS

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The influence of two- and three-dimensional filming procedures on the calculation of soccer instep kicking kinematics was examined in this study. The knee angular velocity calculated three-dimensionally was compared with the data obtained from the following two procedures: 1. the angular velocity vector was computed as a perpendicular component to the sagittal plane (2D projection); 2. the angular velocity was computed only from the two-dimensional coordinates (2D standard). A distorted changing pattern was produced by the 2D standard approach which was most likely caused by computing segmental angular velocities from quasi-planar projection. It is suggested that researchers treat with caution any comparisons in the literature between three-dimensional angular kinematics and those computed two-dimensionally.