title: Nature of the coupling between neural drive and force-generating capacity in the human quadriceps muscle.
abstract: The force produced by a muscle depends on both the neural drive it receives and several biomechanical factors. When multiple muscles act on a single joint, the nature of the relationship between the neural drive and force-generating capacity of the synergistic muscles is largely unknown. This study aimed to determine the relationship between the ratio of neural drive and the ratio of muscle force-generating capacity between two synergist muscles (vastus lateralis (VL) and vastus medialis (VM)) in humans. Twenty-one participants performed isometric knee extensions at 20 and 50% of maximal voluntary contractions (MVC). Myoelectric activity (surface electromyography (EMG)) provided an index of neural drive. Physiological cross-sectional area (PCSA) was estimated from measurements of muscle volume (magnetic resonance imaging) and muscle fascicle length (three-dimensional ultrasound imaging) to represent the muscles' force-generating capacities. Neither PCSA nor neural drive was balanced between VL and VM. There was a large (r = 0.68) and moderate (r = 0.43) correlation between the ratio of VL/VM EMG amplitude and the ratio of VL/VM PCSA at 20 and 50% of MVC, respectively. This study provides evidence that neural drive is biased by muscle force-generating capacity, the greater the force-generating capacity of VL compared with VM, the stronger bias of drive to the VL.
authors.affiliation: School of Health and Rehabilitation Sciences, The University of Queensland, NHMRC Centre of Clinical Research Excellence in Spinal Pain, Injury and Health, Brisbane, Australia Laboratory EA 4334 'Movement, Interactions, Performance', University of Nantes, Nantes, France francois.hug@univ-nantes.fr.
authors.forename: François
authors.identifier: http://orcid.org/0000-0002-6432-558X
authors.initials: F
authors.lastname: Hug
authors.affiliation: Laboratory EA 4334 'Movement, Interactions, Performance', University of Nantes, Nantes, France.
authors.forename: Clément
authors.initials: C
authors.lastname: Goupille
authors.affiliation: School of Biomedical Sciences, The University of Queensland, Brisbane, Australia, and.
authors.forename: Daniel
authors.initials: D
authors.lastname: Baum
authors.affiliation: School of Human Movement and Nutrition Sciences, Centre for Sensorimotor Performance, The University of Queensland, Brisbane, Australia.
authors.forename: Brent J
authors.initials: BJ
authors.lastname: Raiteri
authors.affiliation: School of Health and Rehabilitation Sciences, The University of Queensland, NHMRC Centre of Clinical Research Excellence in Spinal Pain, Injury and Health, Brisbane, Australia.
authors.forename: Paul W
authors.initials: PW
authors.lastname: Hodges
authors.affiliation: School of Health and Rehabilitation Sciences, The University of Queensland, NHMRC Centre of Clinical Research Excellence in Spinal Pain, Injury and Health, Brisbane, Australia School of Biomedical Sciences, The University of Queensland, Brisbane, Australia, and.
authors.forename: Kylie
authors.identifier: http://orcid.org/0000-0003-4976-7483
authors.initials: K
authors.lastname: Tucker
mesh_terms: D000328:Adult; D001696:Biomechanical Phenomena; D004576:Electromyography; D005260:Female; D006801:Humans; D007537:Isometric Contraction; D008297:Male; D018763:Muscle Fatigue; D052097:Quadriceps Muscle / Q000502:physiology*; D055815:Young Adult
keywords: electromyography; physiological cross-sectional area; quadriceps