title: Differences in cervical multifidus muscle thickness during isometric contraction of shoulder muscles: a comparison between patients with chronic neck pain and healthy controls.
abstract: OBJECTIVE
  The purposes of this study were to (1) measure the thickness of cervical multifidus muscle (CMM) in different maximal voluntary contraction percentages of isometric contraction of shoulder muscles, (2) evaluate the differences of the CMM thickness in different directions of the shoulder movement, and (3) compare the changes in the CMM thickness of participants with neck pain and also of healthy individuals.
  
  
  METHODS
  Twenty healthy men (age, 27.45 ± 4.37 years; height, 177 ± 4.66 cm; weight, 72.85 ± 6.46 kg) and 20 men with chronic mechanical neck pain (age, 28.90 ± 5.53 years; height, 176 ± 5.98 cm; weight, 73.15 ± 7.82 kg) participated in the study. Both the right and left CMM thicknesses were measured using an ultrasound device while participants performed isometric contraction of shoulder muscles in 6 movement directions.
  
  
  RESULTS
  In both groups, an increment of CMM thickness followed as the increase of isometric force (P < .01).The increase of muscle thickness of healthy participants was substantially more than the chronic mechanical neck pain participants (P = .03). Although no significant difference of CMM thickness was seen among the effects of the 6 force directions (P > .05), there was a significant difference of activity noted between the left and right sides (P = .047).
  
  
  CONCLUSIONS
  The results of the present study indicate that isometric contraction of shoulder muscles caused an increase in the CMM thickness regardless of force direction. This increase was seen in both groups of healthy participants and patients with neck pain. However, less thickness changes were observed in participants with neck pain, which may be interpreted as reduced CMM activity in such people.
authors.affiliation: Assistant Professor of Physiotherapy, Department of Physiotherapy, University of Social Welfare and Rehabilitation Sciences, Tehran, Iran. Electronic address: lrahnama@gmail.com.
authors.forename: Leila
authors.initials: L
authors.lastname: Rahnama
authors.affiliation: Professor of Physiotherapy, Faculty of Rehabilitation, Physiotherapy Research Center, Shahid Behesht University of Medical Sciences, Tehran, Iran.
authors.forename: Asghar
authors.initials: A
authors.lastname: Rezasoltani
authors.affiliation: Assistant Professor of Physiotherapy, Faculty of Rehabilitation, Department of Physiotherapy, Shahid Behesht University of Medical Sciences, Tehran, Iran.
authors.forename: Minoo Khalkhali
authors.initials: MK
authors.lastname: Zavieh
authors.affiliation: Radiologist, Specialist Doctor, Department of Radiology, Medical Imaging Research Center, Shiraz University of Medical sciences, Shiraz, Iran.
authors.forename: Farhang
authors.initials: F
authors.lastname: NooriKochi
authors.affiliation: Associate Professor of Biostatistics, Faculty of Rehabilitation, Department of Basic Sciences, Shahid Behesht University of Medical Sciences, Tehran, Iran.
authors.forename: Alireza Akbarzadeh
authors.initials: AA
authors.lastname: Baghban
mesh_terms: D000328:Adult; D059350:Chronic Pain / Q000503:physiopathology*; D006801:Humans; D007537:Isometric Contraction; D008297:Male; D009334:Neck Muscles / Q000033:anatomy & histology* / Q000000981:diagnostic imaging; D019547:Neck Pain / Q000503:physiopathology*; D009929:Organ Size; D064170:Paraspinal Muscles / Q000033:anatomy & histology* / Q000000981:diagnostic imaging; D012782:Shoulder / Q000503:physiopathology*; D014463:Ultrasonography
keywords: Isometric Contraction; Muscle Size; Neck Muscle; Neck Pain; Shoulder; Ultrasonography