title: Shared muscle synergies in human walking and cycling.
abstract: The motor system may rely on a modular organization (muscle synergies activated in time) to execute different tasks. We investigated the common control features of walking and cycling in healthy humans from the perspective of muscle synergies. Three hypotheses were tested: 1) muscle synergies extracted from walking trials are similar to those extracted during cycling; 2) muscle synergies extracted from one of these motor tasks can be used to mathematically reconstruct the electromyographic (EMG) patterns of the other task; 3) muscle synergies of cycling can result from merging synergies of walking. A secondary objective was to identify the speed (and cadence) at which higher similarities emerged. EMG activity from eight muscles of the dominant leg was recorded in eight healthy subjects during walking and cycling at four matched cadences. A factorization technique [nonnegative matrix factorization (NNMF)] was applied to extract individual muscle synergy vectors and the respective activation coefficients behind the global muscular activity of each condition. Results corroborated hypotheses 2 and 3, showing that 1) four synergies from walking and cycling can successfully explain most of the EMG variability of cycling and walking, respectively, and 2) two of four synergies from walking appear to merge together to reconstruct one individual synergy of cycling, with best reconstruction values found for higher speeds. Direct comparison of the muscle synergy vectors of walking and the muscle synergy vectors of cycling (hypothesis 1) produced moderated values of similarity. This study provides supporting evidence for the hypothesis that cycling and walking share common neuromuscular mechanisms.
authors: Electronics Department, University of Minho, Azurém, Guimarães, Portugal; Bioengineering Group, Spanish National Research Council (CSIC), Arganda del Rey, Madrid, Spain; fbarroso@dei.uminho.pt.
authors: Filipe O
authors: FO
authors: Barroso
authors: Bioengineering Group, Spanish National Research Council (CSIC), Arganda del Rey, Madrid, Spain;
authors: Diego
authors: D
authors: Torricelli
authors: Bioengineering Group, Spanish National Research Council (CSIC), Arganda del Rey, Madrid, Spain;
authors: Juan C
authors: JC
authors: Moreno
authors: Sensorimotor Function Group-National Paraplegia Hospital SESCAM, Toledo, Spain; and.
authors: Julian
authors: J
authors: Taylor
authors: Sensorimotor Function Group-National Paraplegia Hospital SESCAM, Toledo, Spain; and Nursing and Physical Therapy School, Castilla la Mancha University, Toledo, Spain.
authors: Julio
authors: J
authors: Gomez-Soriano
authors: Bioengineering Group, Spanish National Research Council (CSIC), Arganda del Rey, Madrid, Spain; Sensorimotor Function Group-National Paraplegia Hospital SESCAM, Toledo, Spain; and.
authors: Elisabeth
authors: E
authors: Bravo-Esteban
authors: Bioengineering Group, Spanish National Research Council (CSIC), Arganda del Rey, Madrid, Spain;
authors: Stefano
authors: S
authors: Piazza
authors: Electronics Department, University of Minho, Azurém, Guimarães, Portugal;
authors: Cristina
authors: C
authors: Santos
authors: Bioengineering Group, Spanish National Research Council (CSIC), Arganda del Rey, Madrid, Spain;
authors: José L
authors: JL
authors: Pons
mesh_terms: D000328:Adult; D000465:Algorithms; D001696:Biomechanical Phenomena; D004576:Electromyography; D005080:Exercise Test; D005260:Female; D006801:Humans; D007866:Leg / Q000502:physiology; D008297:Male; D009043:Motor Activity; D018482:Muscle, Skeletal / Q000502:physiology*; D009415:Nerve Net / Q000502:physiology; D016138:Walking / Q000502:physiology*
keywords: cycling; electromyography; motor control; muscle synergies; walking