Quadriceps Strength Does Not Associate with Gait Adaptation Ability in Individuals with Anterior Cruciate Ligament Reconstruction.

CONTEXT: Postoperative muscle weakness contributes to the development of aberrant gait biomechanics that persist following traditional anterior cruciate ligament reconstruction (ACLR). However, it is unknown if quadriceps weakness impedes the ability of ACLR patients to modify gait biomechanics using a real-time gait biofeedback (RTGBF) intervention. OBJECTIVE: The purpose was to determine if quadriceps strength associates with the ability to modify vertical ground reaction force (vGRF) during a RTGBF intervention. DESIGN: Cross-Sectional Study. SETTING: Research Laboratory. PARTICIPANTS: 35 individuals with unliateral ACLR (Time since ACLR= 32 ± 16 months; 22 Females, 13 Males). MAIN OUTCOME MEASURES: Peak vGRF was evaluated during a baseline walking trial, and three 250-step randomized RTGBF walking trials which cued an increased average peak vGRF of the baseline walking trial by 5%, 10%, or 15%. The ability to modify gait was reported as changes in pvGRF (ΔpvGRF; BW) and root mean square error (RMSE) of the peak vGRF relative to the feedback target (pvGRF RMSE; BW). We also calculated quadriceps strength. RESULTS: There were no significant associations between strength (Mean: 2.56 ± 0.75 Nm/kg, Range: 0.84-4.6 Nm/kg) and ΔpvGRF (5% ΔpvGRF: 0.04 ± 0.03 BW, 10% ΔpvGRF: 0.10 ± 0.03 BW, 15% ΔpvGRF: 0.15 ± 0.04 BW) nor strength and RMSE (5% RMSE: 0.04 ± 0.02 BW, 10% RMSE: 0.05 ± 0.02 BW, 15% RMSE: 0.08 ± 0.04 BW) for any of the 3 RTGBF trials (R2: 0.003-0.025; P: 0.37-0.77). CONCLUSIONS: The magnitude of quadriceps strength did not influence the ability to modify gait using RTGBF. These data suggest that it may be unnecessary to wait for quadriceps full strength recovery to capitalize on the benefits of RTGBF following ACLR.