Lower limb movement asymmetry exists during volleyball stop-jump landing: Insights from markerless motion capture.

Patellar tendinopathy is a highly prevalent injury associated with high knee angular accelerations. However, collecting kinematic data on the volleyball court remains challenging. This study investigated landing kinematics between dominant and non-dominant lower limbs during stop-jumps on the volleyball court and analysed landing variables to identify biomechanical patterns associated with high knee angular accelerations. Landing kinematics were quantified using 3D markerless motion capture (OpenCap) with two cameras. Fourteen male and 5 female elite volleyball players performed 10 stop-jump landings while approaching the net to spike a ball over the net. Asymmetry was found with the dominant limb landing in greater plantarflexion and hip flexion but less knee flexion. The dominant limb exhibited higher knee angular velocities (mean ± standard deviation: dominant = 274 ± 62°/s, non-dominant = 169 ± 84°/s; p < 0.001) and accelerations (dominant = 3924 ± 2221°/s², non-dominant = 1441 ± 4278°/s²; p = 0.032), suggesting greater biomechanical load. High knee accelerations were significantly correlated with limited knee and hip flexion in the dominant limb, closer foot position, greater trunk flexion at non-dominant limb touchdown, and longer contact time with the non-dominant limb (Pearson's correlation coefficient; |0.55| ≤ r ≤ |0.79|, p < 0.018). OpenCap provided valuable insights into volleyball stop-jump kinematics. Therefore, markerless motion capture can provide coaches and scientists with a deeper understanding of landing performance and related injury mechanisms.