Gait asymmetries are exacerbated at faster walking speeds in individuals with acute anterior cruciate ligament reconstruction.

Previous research suggests more biomechanically demanding tasks (e.g., stair descent, hopping) magnify biomechanical asymmetries compared with walking after anterior cruciate ligament (ACL) reconstruction. However, it is unclear if modifying task-specific constraints, like walking speed also elicits greater biomechanical asymmetries in this population. We examined the effects of manipulating walking speed on ground reaction force (GRF) asymmetries in individuals with ACL reconstruction and uninjured controls. Thirty individuals with ACL reconstruction (age = 20.6 ± 5.4 years, body mass index [BMI] = 23.9 ± 3.3 kg/m2 ) and 15 controls (age = 23.1 ± 4.5 years, BMI = 23.6 ± 2.7 kg/m2 ) were tested on an instrumented treadmill at three speeds (100%, 120%, and 80% self-selected speed). Bilateral vertical and posterior-anterior GRFs were recorded at each speed. GRF asymmetries were calculated by subtracting the uninjured from the injured limb at each percent of stance. Statistical parametric mapping was used to evaluate the effects of speed on GRF asymmetries across stance. We found vertical and posterior GRF asymmetries were exacerbated at faster speeds and reduced at slower speeds in ACL individuals but not controls (p < .05). No differences in anterior GRF asymmetries were observed between speeds in either group (p > .05). Our results suggest increasing walking speed magnifies GRF asymmetries in individuals with ACL reconstruction. Statement of Clinical Significance: Evaluating both preferred and fast walking speeds may aid in characterizing biomechanical asymmetries in individuals with ACL reconstruction which may be valuable in earlier rehabilitative time points when more difficult tasks like hopping and running are not feasible.