A Comparative Analysis of IMUs and Optical Systems in Layup Shot Biomechanics

The purpose of this study was to assess the validity and reliability of an inertial measurement unit (IMU) system against an optical motion capture system in detecting motion in the dynamically complex and constraint-governed task of the basketball layup shot. Ten basketball players performed 10 trials with and 10 without a defender. Key kinematic variables (jump height, take-off angle, joint angles, and centre of mass (COM) displacement) were derived, and agreement (intraclass correlation coefficient (ICC) and Bland–Altman plots) and disagreement (root mean square difference (RMSD) and statistical parametric mapping (SPM)) calculations were carried out for each trial. The IMU system provided agreeable results for jump height and take-off angle, while joint angles and COM displacement agreement were plane-specific. A between-condition analysis demonstrated the IMU system reliably detected joint angle differences between defended and undefended conditions comparable to the optical system for nine out of twelve joint angles, with shoulder flexion-extension and external-internal and elbow external-internal joint angles showing inconclusive results. Ultimately, the IMU system was generally able to detect similar magnitudes of difference between conditions to those detected by the optical motion-based system. Therefore, conclusions can be drawn for between-condition comparisons if data are derived from either system.