title: Assessment of the variability of vastii myoelectric activity in young healthy females during walking: a statistical gait analysis.
abstract: The study was designed to assess the natural variability of the activation modalities of vastus medialis (VM) and vastus lateralis (VL) during walking at a self-selected speed and cadence of 30 young, healthy, females. This was achieved by conducting statistical gait analysis on the surface electromyographic signals from hundreds of strides for each subject. Results revealed variability in the number of activations, occurrence frequency, and onset-offset instants across the thousands of strides analyzed. However, despite the variability, there was one activation occurrence which remained consistent across subjects for both VM and VL. This occurred from terminal swing to the following loading response (observed in 100% of strides). A second, less frequent, activation occurred between mid-stance up to pre-swing (observed in 39.3±22.4% of strides for VM and in 35.1±20.6% for VL). No significant differences (p>0.05) were observed in the onset-offset instants or in the occurrence frequency, which suggest a simultaneous recruitment of VM and VL. This "normality" pattern represents the first attempt at developing a reference frame for vastii sEMG activity during walking, that is able to include the physiological variability of the phenomenon and control the confounding effects of age and gender.
authors.affiliation: Department of Information Engineering, Università Politecnica delle Marche, 60131 Ancona, Italy. Electronic address: f.dinardo@univpm.it.
authors.forename: Francesco
authors.initials: F
authors.lastname: Di Nardo
authors.affiliation: Department of Information Engineering, Università Politecnica delle Marche, 60131 Ancona, Italy; Posture and Movement Analysis Laboratory, Italian National Institute of Health and Science on Aging (INRCA), 60131 Ancona, Italy.
authors.forename: Elvira
authors.initials: E
authors.lastname: Maranesi
authors.affiliation: Department of Information Engineering, Università Politecnica delle Marche, 60131 Ancona, Italy.
authors.forename: Alessandro
authors.initials: A
authors.lastname: Mengarelli
authors.affiliation: Posture and Movement Analysis Laboratory, Italian National Institute of Health and Science on Aging (INRCA), 60131 Ancona, Italy.
authors.forename: Giacomo
authors.initials: G
authors.lastname: Ghetti
authors.affiliation: Department of Information Engineering, Università Politecnica delle Marche, 60131 Ancona, Italy.
authors.forename: Laura
authors.initials: L
authors.lastname: Burattini
authors.affiliation: Department of Information Engineering, Università Politecnica delle Marche, 60131 Ancona, Italy.
authors.forename: Sandro
authors.initials: S
authors.lastname: Fioretti
mesh_terms: D000328:Adult; D003627:Data Interpretation, Statistical; D004576:Electromyography / Q000379:methods / Q000592:standards*; D005260:Female; D005684:Gait; D006801:Humans; D008297:Male; D018482:Muscle, Skeletal / Q000502:physiology; D012016:Reference Values; D016138:Walking
keywords: Knee-flexor muscles; Quadriceps femoris; Statistical gait analysis; Surface electromyography; Variability