A non-invasive assessment of variability in sEMG signals from lower limb muscles during gait

Surface electromyography (sEMG) is commonly used in gait analysis for detecting muscle activity in a non-invasive way, preserving the normal mobility of the subject. Aim of this study was to assess the variability of sEMG signals acquired from lower limb muscles during gait at self-selected speed and cadence, in terms of onset-offset muscular activation and frequency of occurrence. To this aim, a statistical analysis of sEMG signals from Tibialis Anterior, Gastrocnemius Lateralis, Rectus Femoris, Biceps Femoris and Vastus Lateralis was performed in twenty-two healthy young volunteers. Findings illustrated that a single muscle can show a different number of activation intervals in different strides of the same walk. Moreover, muscles showed activity also in phases of the gait cycle usually not reported in healthy adults that could be related to tasks different from the typical sagittal plane movement, as foot inversion, balance improvement during single support and control of joint dynamic stability. The concomitance of these results indicates a large variability in onset-offset muscular activation and occurrence frequency, which should be considered in discriminating pathological from physiological behaviour and for designing more focused gait studies.