Manipulating Initial Peak vGRF During Walking Affects Loading Throughout Stance in Individuals with ACL Reconstruction

Abstract

Gait alterations may be associated with osteoarthritis development following anterior cruciate ligament reconstruction (ACLR). Novel gait retraining paradigms are being developed to optimize peak vertical limb loading in the first half of stance; yet the effect of changing this single discrete variable on loading characteristics across the entire stance phase remain unknown. PURPOSE: Determine the effect of increasing and decreasing the first peak of the vertical ground reaction force (vGRF) by 5% during walking using real-time biofeedback (RTBF) of vGRF throughout stance. METHODS: 30 ACLR participants (21 females, 20.4±2.9 yrs, 172.7±10.8 cm, 73.2±16.1 kg, 47.8±4.2 months post-ACLR) completed one 20-minute control condition and two experimental conditions (high- and low-loading). For high- and low-load conditions, participants walked for 20 minutes on a force-measuring treadmill with RTBF displayed on a screen cuing a 5% increase (high) or decrease (low) in the first peak of the vGRF relative to vGRF collected in the control condition. VGRFs were collected at 1000 Hz throughout the 19th minute. Two functional analyses of variance were conducted to evaluate VGRF magnitude throughout stance. RESULTS: Figures 1A and 1C depict mean vGRF, normalized to body weight (BW), throughout the stance phase. Figures 1B and 1D depict pairwise comparison functions (solid black lines) and associated 95% confidence intervals (gray bands), indicating mean differences between the two conditions. Significant between-condition differences existed in the high-loading condition between 42 and 74% of stance, and in the low-loading condition (between 38 and 70%, and 76 and 97% of stance. CONCLUSION: RTBF, used to cue changes in the first vGRF peak, results in loading alterations throughout stance. Specifically, high loading results in lesser vGRF at midstance but a similar propulsive peak. Conversely, low loading increases vGRF during midstance and decreases vGRF during toe-off.