Post-processed EMG data normalized to MVIC (used for analysis): Analysis of Muscle Activity During Active Straight Leg Raise with a Knee Extension Brace - Potential Implications for Rehabilitation in Patients with Arthrogenic Muscle Inhibition

Objective:To evaluate quadriceps activity during active straight leg raise (ASLR) in a knee extension brace and assess its potential as an adjunctive tool in managing arthrogenic muscle inhibition (AMI). Design: Prospective, within-subject observational study. Methods:Thirty-nine young and healthy adults. Outcome measures included: surface electromyography (sEMG) activity (root mean square (RMS), values normalized to maximal voluntary isometric contraction at 90° knee flexion (MVIC90) recorded during four ASLR conditions: without brace (p1), with brace and no additional instruction (p2), with brace and maximal voluntary quadriceps contraction (p3), with brace and volitional quadriceps relaxation (p4, as AMI simulation). Electrodes were placed according to SENIAM guidelines. Results:The brace did not affect rectus femoris (RF) (p = 0.322, 95%CI [-0.156, 0.475]) and vastus medialis oblique (VMO) activity (p = 0.160, δ 0.05, 95%CI [-0.21, 0.30]), but significantly reduced vastus lateralis oblique (VLO) activity (p = 0.026, δ 0.18, 95%CI [-0.08, 0.42]). Muscle activation ranked as follows: p3 > p1 > p2 > p4. All pairwise comparisons were significant except p1–p2 for RF and VMO. Conclusion:The knee extension brace reduces VLO activity without affecting RF and VMO during ASLR. Ranking muscle activation across trials allows precise progression and regression of the ASLR. These findings are specific to this setting and motivate hypothesis-testing trials in AMI populations.