title: Neuromuscular adjustments of gait associated with unstable conditions.
abstract: A compact description of coordinated muscle activity is provided by the factorization of electromyographic (EMG) signals. With the use of this approach, it has consistently been shown that multimuscle activity during human locomotion can be accounted for by four to five modules, each one comprised of a basic pattern timed at a different phase of gait cycle and the weighting coefficients of synergistic muscle activations. These modules are flexible, in so far as the timing of patterns and the amplitude of weightings can change as a function of gait speed and mode. Here we consider the adjustments of the locomotor modules related to unstable walking conditions. We compared three different conditions, i.e., locomotion of healthy subjects on slippery ground (SL) and on narrow beam (NB) and of cerebellar ataxic (CA) patients on normal ground. Motor modules were computed from the EMG signals of 12 muscles of the right lower limb using non-negative matrix factorization. The unstable gait of SL, NB, and CA showed significant changes compared with controls in the stride length, stride width, range of angular motion, and trunk oscillations. In most subjects of all three unstable conditions, >70% of the overall variation of EMG waveforms was accounted for by four modules that were characterized by a widening of muscle activity patterns. This suggests that the nervous system adopts the strategy of prolonging the duration of basic muscle activity patterns to cope with unstable conditions resulting from either slippery ground, reduced support surface, or pathology.
authors.affiliation: Centre of Space Biomedicine, University of Rome Tor Vergata, Rome, Italy; Laboratory of Neuromotor Physiology, Istituto di Ricovero e Cura a Carattere Scientifico, Santa Lucia Foundation, Rome, Italy; g.martino@hsantalucia.it.
authors.forename: G
authors.initials: G
authors.lastname: Martino
authors.affiliation: Laboratory of Neuromotor Physiology, Istituto di Ricovero e Cura a Carattere Scientifico, Santa Lucia Foundation, Rome, Italy;
authors.forename: Y P
authors.initials: YP
authors.lastname: Ivanenko
authors.affiliation: Laboratory of Neuromotor Physiology, Istituto di Ricovero e Cura a Carattere Scientifico, Santa Lucia Foundation, Rome, Italy; Department of Biomedical Sciences and Morphological and Functional Images, University of Messina, Messina, Italy;
authors.forename: A
authors.initials: A
authors.lastname: d'Avella
authors.affiliation: Rehabilitation Centre Policlinico Italia, Rome, Italy; Department of Medical and Surgical Sciences and Biotechnologies, Sapienza University of Rome, Latina, Italy;
authors.forename: M
authors.initials: M
authors.lastname: Serrao
authors.affiliation: Istituto Nazionale per l'Assicurazione Contro gli Infortuni sul Lavoro, Department of Occupational and Environmental Medicine, Epidemiology and Hygiene, Monte Porzio Catone, Rome, Italy; and.
authors.forename: A
authors.initials: A
authors.lastname: Ranavolo
authors.affiliation: Istituto Nazionale per l'Assicurazione Contro gli Infortuni sul Lavoro, Department of Occupational and Environmental Medicine, Epidemiology and Hygiene, Monte Porzio Catone, Rome, Italy; and.
authors.forename: F
authors.initials: F
authors.lastname: Draicchio
authors.affiliation: Centre of Space Biomedicine, University of Rome Tor Vergata, Rome, Italy;
authors.forename: G
authors.initials: G
authors.lastname: Cappellini
authors.affiliation: Department of Medical and Surgical Sciences and Biotechnologies, Sapienza University of Rome, Latina, Italy;
authors.forename: C
authors.initials: C
authors.lastname: Casali
authors.affiliation: Centre of Space Biomedicine, University of Rome Tor Vergata, Rome, Italy; Laboratory of Neuromotor Physiology, Istituto di Ricovero e Cura a Carattere Scientifico, Santa Lucia Foundation, Rome, Italy; Department of Systems Medicine, University of Rome Tor Vergata, Rome, Italy.
authors.forename: F
authors.initials: F
authors.lastname: Lacquaniti
mesh_terms: D000328:Adult; D000368:Aged; D001696:Biomechanical Phenomena; D002524:Cerebellar Ataxia / Q000503:physiopathology*; D004576:Electromyography / Q000379:methods*; D005260:Female; D005684:Gait; D006801:Humans; D008124:Locomotion; D035002:Lower Extremity / Q000294:innervation / Q000503:physiopathology; D008297:Male; D008875:Middle Aged; D018482:Muscle, Skeletal / Q000294:innervation / Q000503:physiopathology*
keywords: central pattern generator; cerebellar ataxia; muscle synergies; slippery surface; unstable conditions