title: Sex differences in variances of multi-channel surface electromyography distribution of the vastus lateralis muscle during isometric knee extension in young adults.
abstract: OBJECTIVE
  The aim of the present study was to compare spatial electromyographic potential distribution during force production between healthy young female and male using multi-channel surface electromyography (multi-SEMG).
  
  
  METHODS
  Thirty healthy subjects (15 females) performed sustained isometric knee extension at 10% maximal voluntary contraction (MVC) task for 120 s. Multi-SEMG signals from the vastus lateralis muscle were detected and the modified entropy, coefficient of variation (CV), and correlation coefficient determined.
  
  
  RESULTS
  The modified entropy and CV showed significant interaction and difference between females and males at all time points during the 10% MVC task. The correlation coefficient in females was significantly lower at 90 and 120 s than that of males.
  
  
  CONCLUSIONS
  The multi-SEMG potential distribution pattern in females showed more varied motor unit recruitment during sustained low-intensity isometric contraction than that of males. Variations in motor unit recruitment may result from recruitment and/or de-recruitment of motor units.
authors.affiliation: Department of Clinical Neuroscience and Therapeutics, Hiroshima University Graduate School of Biomedical and Health Sciences, 1-2-3 Kasumi, Minami-ku, Hiroshima, 734-8551, Japan. yuichi@hiroshima-u.ac.jp.|Division of Rehabilitation, Department of Clinical Practice and Support, Hiroshima University Hospital, 1-2-3 Kasumi, Minami-ku, Hiroshima, 734-8551, Japan. yuichi@hiroshima-u.ac.jp.
authors.forename: Yuichi
authors.identifier: http://orcid.org/0000-0002-0088-8447
authors.initials: Y
authors.lastname: Nishikawa
authors.affiliation: Laboratory of Neuromuscular Biomechanics, School of International Liberal Studies, Chukyo University, 101-2 Yagotohonmachi, Showa-ku, Nagoya, 466-8666, Japan.
authors.forename: Kohei
authors.initials: K
authors.lastname: Watanabe
authors.affiliation: Department of Clinical Neuroscience and Therapeutics, Hiroshima University Graduate School of Biomedical and Health Sciences, 1-2-3 Kasumi, Minami-ku, Hiroshima, 734-8551, Japan.
authors.forename: Tetsuya
authors.initials: T
authors.lastname: Takahashi
authors.affiliation: Department of Clinical Neuroscience and Therapeutics, Hiroshima University Graduate School of Biomedical and Health Sciences, 1-2-3 Kasumi, Minami-ku, Hiroshima, 734-8551, Japan.
authors.forename: Naohisa
authors.initials: N
authors.lastname: Hosomi
authors.affiliation: Division of Rehabilitation, Department of Clinical Practice and Support, Hiroshima University Hospital, 1-2-3 Kasumi, Minami-ku, Hiroshima, 734-8551, Japan.
authors.forename: Naoya
authors.initials: N
authors.lastname: Orita
authors.affiliation: Department of Rehabilitation Medicine, Hiroshima University Hospital, 1-2-3 Kasumi, Minami-ku, Hiroshima, 734-8551, Japan.
authors.forename: Yukio
authors.initials: Y
authors.lastname: Mikami
authors.affiliation: Department of Clinical Neuroscience and Therapeutics, Hiroshima University Graduate School of Biomedical and Health Sciences, 1-2-3 Kasumi, Minami-ku, Hiroshima, 734-8551, Japan.
authors.forename: Hirofumi
authors.initials: H
authors.lastname: Maruyama
authors.affiliation: Department of Rehabilitation Medicine, Hiroshima University Hospital, 1-2-3 Kasumi, Minami-ku, Hiroshima, 734-8551, Japan.
authors.forename: Hiroaki
authors.initials: H
authors.lastname: Kimura
authors.affiliation: Department of Clinical Neuroscience and Therapeutics, Hiroshima University Graduate School of Biomedical and Health Sciences, 1-2-3 Kasumi, Minami-ku, Hiroshima, 734-8551, Japan.
authors.forename: Masayasu
authors.initials: M
authors.lastname: Matsumoto
mesh_terms: D000328:Adult; D004576:Electromyography; D005260:Female; D006801:Humans; D007537:Isometric Contraction; D007717:Knee / Q000502:physiology*; D008297:Male; D018482:Muscle, Skeletal / Q000502:physiology*; D012737:Sex Factors
keywords: Isometric contraction; Motor unit; Multi-channel surface electromyography; Vastus lateralis muscle; Young adult