Concurrent validity of IMU and phone-based markerless systems for lower-limb kinematics during cognitively-challenging landing tasks

Alternative technologies, such as IMU and low-cost markerless systems, may overcome the drawbacks of optoelectronic marker-based motion capture systems (OMS) in sports non-contact injury risk screening, but the precision of collected kinematic data must be validated in comparison to OMS. This study assessed the concurrent validity of the Xsens IMU and phone-based OpenCap systems for lower-limb kinematics during cognitively-challenging landing tasks. Thirty competitive athletes (13 females, 17 males) performed unplanned jump-land-jump tasks towards lateral secondary directions while kinematics was simultaneously recorded with OMS, Xsens, and OpenCap. The agreement of lower limb joint discrete (initial contact and peak) values was assessed using Bland-Altman plots. Kinematic waveforms validity and similarity were evaluated through RMSE, normalized RMSE (NRMSE), and coefficient of multiple correlation (CMC). All systems were also compared using statistical parametric mapping (SPM) ANOVA. ...