Emerging evidence suggests that lower quadriceps rate of torque development (RTD) following anterior cruciate ligament reconstruction (ACLR) may be associated with altered landing mechanics. However, the influence of quadriceps RTD magnitude and RTD limb symmetry on landing mechanics limb symmetry remains unknown.
To assess the influence of quadriceps RTD magnitude and RTD limb symmetry on sagittal plane landing mechanics limb symmetry in females with and without ACLR during functional landing tasks.
Thirty-eight females (ACLR=19, 19.2±1.8 years-old, 164.1±7.0 cm, 63.8±7.6 kg, Time after surgery: 20.1±9.5 months; Control=19, 21.1±3.3 years-old, 167.3±7.3 cm, 67.3±9.3 kg).
Landing mechanics were assessed during double-leg and single-leg jump-landing tasks (DL and SL), and a side-cut task (SC). Quadriceps RTD was collected during isometric muscle contractions. Separate stepwise multiple linear regression models determined the amount of variance in limb symmetry in sagittal plane knee moment at initial contact (IC), peak vertical ground reaction force (vGRF), and loading rate that could be explained by quadriceps RTD magnitude or RTD limb symmetry, group (ACLR or Control), and their interaction.
In ACLR females, greater quadriceps RTD limb symmetry was associated with greater symmetry in sagittal plane knee moment at IC during DL (P=.004). Peak vGRF and loading rate could not be predicted by quadriceps RTD magnitude or RTD limb symmetry, group, or their interaction during all tasks.
Developing greater quadriceps RTD symmetry, but not RTD magnitude, likely enables more symmetrical sagittal plane knee landing mechanics during double-leg task in ACLR females, and thus may reduce the risk of a second ACL injury. Such protective effect was not found during single-leg tasks that may not allow for a compensatory landing mechanism of shifting load to the uninvolved limb as is possible during a double-leg task.