title: Asymmetrical and smaller size of trunk muscles in combat sports athletes with lumbar intervertebral disc degeneration.
abstract: BACKGROUND
  Lumbar intervertebral disc degeneration (LDD) frequently occurs in athletes. Associations between LDD and trunk muscles still remain unclear.
  
  
  OBJECTIVE
  This study examined whether there is an association between the prevalence of LDD and the symmetry and size of the cross-sectional areas (CSAs) of the trunk muscles in combat sports athletes.
  
  
  METHODS
  Participants in this study were 151 collegiate male combat sports athletes. A total of 755 lumbar intervertebral discs from L1-2 to L5-S1 in 151 athletes were assessed using magnetic resonance imaging (MRI) and a comprehensive grading system of LDD (grades I-V). All 151 athletes were divided into 2 groups: LDD and non-LDD. CSAs of trunk muscles at the L3-4 disc level were measured using MRI.
  
  
  RESULTS
  Sixty-nine athletes had LDD at 1 or more disc levels (45.7 %). The LDD grade for the lower 2 disc levels was significantly higher than that for the other disc levels (p < 0.001). The CSAs of the left and right sides in trunk muscles were significantly asymmetrical, independent of the LDD which was prevalent in the disc levels (obliques: p = 0.040; quadratus lumborum: p < 0.001). The relative CSAs of trunk muscles to their body weight in the LDD group were significantly smaller than those in the non-LDD group (rectus abdominis: p = 0.011; obliques: p = 0.024; quadratus lumborum: p = 0.006; lumbar erector spinae plus multifidus: p = 0.001).
  
  
  CONCLUSIONS
  This study suggests that the prevalence of LDD is associated with asymmetrical and relatively smaller CSAs of trunk muscles in combat sports athletes.
authors.affiliation: School of Kinesiology, Western University, 1151 Richmond Street, London, ON N6A 3K7 Canada ; Hiroshima Maritime College, National Institute of Technology, 4272-1 Higashino Osakikamijima-cho, Toyota-gun, Hiroshima, 725-0231 Japan.
authors.forename: Kazunori
authors.identifier: 0000-0001-8353-3520
authors.initials: K
authors.lastname: Iwai
authors.affiliation: Department of Judotherapy, Tokyo Ariake University of Medical and Health Science, 2-9-1 Ariake, Koto-ku, Tokyo, 135-0063 Japan.
authors.forename: Koji
authors.initials: K
authors.lastname: Koyama
authors.affiliation: Faculty of Sport Science, Nippon Sport Science University, 7-1-1 Fukasawa, Setagaya-ku, Tokyo, 158-8508 Japan.
authors.forename: Takashi
authors.initials: T
authors.lastname: Okada
authors.affiliation: Graduate School of Health and Sport Science, Nippon Sport Science University, 7-1-1 Fukasawa, Setagaya-ku, Tokyo, 158-8508 Japan.
authors.forename: Koichi
authors.initials: K
authors.lastname: Nakazato
authors.affiliation: School of Kinesiology, Western University, 1151 Richmond Street, London, ON N6A 3K7 Canada.
authors.forename: Ray
authors.initials: R
authors.lastname: Takahashi
authors.affiliation: Sports Methodology (Wrestling), Nippon Sport Science University, 1221-1, Kamoshida-cho, Aoba-ku, Yokohama, Kanagawa 227-0033 Japan.
authors.forename: Shingo
authors.initials: S
authors.lastname: Matsumoto
authors.affiliation: Sports Methodology (Judo), Nippon Sport Science University, 7-1-1 Fukasawa, Setagaya-ku, Tokyo, 158-8508 Japan.
authors.forename: Yosuke
authors.initials: Y
authors.lastname: Yamamoto
authors.affiliation: Graduate School of Health and Sport Science, Nippon Sport Science University, 7-1-1 Fukasawa, Setagaya-ku, Tokyo, 158-8508 Japan.
authors.forename: Kenji
authors.initials: K
authors.lastname: Hiranuma
keywords: Asymmetrical anatomy; Contact sports; Muscle atrophy; Radiological abnormality