Lower limb movement symmetry cannot be assumed when investigating the stop-jump landing

Purpose: When investigating lower limb landing biomechanics researchers often assume movement symmetry between a participant's right and left lower limbs for the simplicity of data collection and analysis, despite the fact that landing tasks often involve dual-limb motion. However, whether lower limb symmetry can be assumed when investigating dynamic, sport-specific movements such as the stop-jump, has not been investigated. Therefore, this study aimed to determine whether there were any significant differences in selected kinetic, kinematic and muscle activation patterns characterising lower limb biomechanics displayed by the dominant limb compared to the non-dominant limb of participants during a stop-jump task.Methods: Sixteen male athletes with normal patellar tendons on diagnostic imaging performed five successful stop-jump trials. Patellar tendon forces (FPT), ground reaction forces, three-dimensional kinematics, and electromyographic activity of seven lower limb muscles were recorded for the dominant and non-dominant lower limb during each trial.Results: During the horizontal landing phase, the dominant lower limb sustained a significantly higher FPT, and peak net knee joint extension moment compared to the non-dominant lower limb. Furthermore, during the vertical landing phase, the dominant lower limb sustained significantly lower vertical but higher posterior ground reaction forces compared to the non-dominant lower limb. Other variables did not significantly vary as a function of lower limb dominance.Conclusions: It is recommended that researchers clearly identify their primary outcome variables and ensure their experimental design, particularly in terms of lower limb dominance, provides an appropriate framework to investigate possible mechanics underlying unilateral and bilateral knee joint injuries during dual-limb movements such as the stop-jump task.