Direction-Dependent Limb Asymmetries in Female Lateral Jumps: A Ground Reaction Force and Knee Torque Study

Background: Movement symmetry in the lower limbs is critical for biomechanical efficiency, injury prevention, and athletic performance. Lateral (sideways) jumping challenges force production and control in the frontal plane and provide a unique assessment of neuromuscular coordination that may not be detected through sagittal-plane tasks such as running or vertical jumping. This study aimed to evaluate limb asymmetries in isometric knee muscle torque and ground reaction forces (GRFs) during lateral jumps in healthy young women, using the Symmetry Index (SI) to quantify differences between limbs. Methods: Twenty right-limb dominant females (mean age: 20.65 ± 4.51 years) participated in the study. Isometric torque of the knee flexors and extensors was measured using a dynamometric testing station. Lateral jumps were performed onto dual force platforms, with GRF components (vertical (PD), anterior–posterior (AP), mediolateral (ML)) recorded separately for rightward and leftward jumps. SI was calculated for all parameters to determine side-to-side asymmetries, and paired Student’s t-tests were used for statistical comparisons. Results: Right-limb dominance was evident in both knee flexor and extensor torque. Significant asymmetries were observed across all GRF components, varying with jump direction. The trailing limb in each jump direction typically generated greater propulsion forces. In lateral jumps, the trailing limb is generally the leg positioned opposite to the direction of travel, playing a primary role in generating propulsion and absorbing forces during take-off. SI values revealed both inter-individual variability and consistent direction-dependent asymmetry patterns. Conclusions: The or-posterior and vertical components, with greater loading on the dominant leg. Muscle torque measurements also revealed imbalances, with flexors showing more symmetry than extensors. These findings underline the importance of assessing load symmetry to prevent injury and guide rehabilitation.