Increasing dynamic limb-level loading via real-time biofeedback decreases cumulative loading impulse during gait post-anterior cruciate ligament reconstruction.

BACKGROUND: Dynamic gait loading patterns (greater peak vertical ground reaction force [vGRF]; lesser midstance vGRF) are associated with better outcomes post-anterior cruciate ligament reconstruction (ACLR). Real-time gait biofeedback (RTGBF) can elicit dynamic loading patterns by cuing an increase in peak vGRF; however, effects on cumulative limb-level loading and joint-moment impulses remain unclear. We determined the effects of cuing increases and decreases in peak vGRF via RTGBF on stance phase vGRF impulse, and absolute sagittal- and frontal-plane knee-moment impulses in individuals 6-12 months post-ACLR. METHODS: Thirty-nine individuals (46% male; 21 ± 4 years; 24.7 ± 3.2 kg/m2) completed dynamic (5% body weight [BW] increase in peak vGRF) and sustained (5% BW decrease) RTGBF sessions. Participants walked 3000 steps on an instrumented treadmill at self-selected speed with continuous RTGBF. Stance-phase vGRF and knee-moment impulses were compared between conditions. FINDINGS: vGRF impulse was significantly lower (p = 0.03) during dynamic loading compared with sustained loading (0.51 ± 0.07 vs 0.54 ± 0.06 BW·s). No statistically significant differences were detected in absolute sagittal- (0.15 ± 0.04 vs 0.17 ± 0.10 Nm/kg·s) and frontal-plane (0.07 ± 0.04 vs 0.07 ± 0.04 Nm/kg·s) knee-moment impulses. INTERPRETATION: Cuing increased peak vGRF resulted in lower cumulative limb-level compressive loading and no statistically significant differences in absolute knee-moment impulses were detected. The clinical significance of the observed vGRF impulse difference remains unknown as no established clinically meaningful threshold exists. It does seem clear from our findings that on average promoting dynamic loading via RTGBF in future gait-retraining studies will not substantially increase the overall impulsive loading applied to the limb during each step.