Peak Vertical Ground Reaction Force Modifies Gait Biomechanics Bilaterally Following ACL Reconstruction: A Randomized Experiment.

Vertical ground reaction force (vGRF) is a promising target for modifying aberrant gait biomechanics in individuals post-anterior cruciate ligament reconstruction (ACLR). However, an adequate sample size and arandomized, mechanistic study is needed to determine acute effects of vGRF biofeedback on biomechanical outcomes. The purpose of the study is to determine differences in discrete gait biomechanical variables (i.e., first and second peak vGRF, midstance vGRF, peak knee flexion angle (KFA), KFA range-of-motion (ROM), peak knee extension moment (KEM), and peak knee abduction moment (KAM) following a treadmill walking protocol between limbs and across four separate conditions in individuals 6-12 months post-ACLR. We utilized a randomized, cross-over mechanistic trial where participants walked for 3000 steps for three visual feedback conditions (i.e., HIGH, LOW, and SYMMETRICAL vGRF loading) and a control condition on a dual-belt treadmill. We constructed a mixed effects linear model to determine within-subject biomechanical changes between limbs and conditions. The HIGH condition elicited greater first peak vGRF, sagittal plane motion (i.e., peak KFA, KFA ROM), and peak KEM compared to the control condition (p < 0.01). The LOW condition observed first peak vGRF and KFA ROM decreases but increased peak KFA and KEM (p < 0.01) compared to the control condition. No notable biomechanical changes were observed between the SYMMETRICAL and control conditions. The HIGH condition produced acute, sagittal plane kinematic and kinetic profile improvements in ACLR individuals. vGRF is a viable target for modifying gait biomechanics; future work should determine the long-term health effects of vGRF-driven feedback treatment to improve gait profiles post-ACLR.