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Objectives: Quadriceps neuromuscular dysfunction is a recognized sequela of anterior cruciate ligament reconstruction (ACLR) and may persist despite clinical recovery. Persistent activation deficits impair functional performance and elevate reinjury risk. This pilot study investigated quadriceps neuromuscular activation asymmetry after ACLR using a publicly available electromyographic (EMG) dataset, comparing activation symmetry between reconstructed and contralateral limbs and relative to healthy controls. Methods: In this pilot secondary observational analysis, surface EMG recordings from isokinetic knee extension were analyzed from a publicly available Dryad dataset. The dataset comprised 22 participants: 12 with prior ACLR and 10 healthy controls. Vastus lateralis EMG was recorded at 90°/s and 180°/s. Peak EMG amplitude and root-mean-square (RMS) activation were extracted per participant. Limb symmetry indices (LSIs) were calculated from involved and uninvolved limbs. Between-group comparisons used independent samples t -tests or nonparametric equivalents. Results: Individuals with ACLR demonstrated greater variability in quadriceps EMG activation patterns compared with healthy controls. LSI analysis revealed persistent neuromuscular asymmetry in reconstructed limbs, most pronounced during higher-velocity contractions. Healthy participants exhibited consistently balanced bilateral activation, whereas the ACLR group demonstrated substantially wider dispersion of symmetry values during isokinetic knee extension tasks. Conclusion: Quadriceps neuromuscular activation asymmetry persists after ACLR and is detectable using surface EMG during isokinetic testing, with velocity-dependent deficits most apparent at higher contraction speeds. These pilot findings provide effect size estimates to support the design of future adequately powered prospective studies.
Khafagy et al. (2026) studied this question.