title: Isometric strength of the cervical flexor, extensor, and rotator muscles in 220 healthy females aged 20 to 59 years.
abstract: METHODS
  Cross-sectional descriptive study.
  
  
  OBJECTIVE
  To determine the maximal isometric strength of the flexor, extensor, and rotator muscles of the cervical spine in healthy females of working age to document reference values for diagnostic and rehabilitation purposes.
  
  
  BACKGROUND
  Reference values for the isometric strength of the cervical muscles have often been based on small samples. To date, reference values for rotator muscles of the cervical spine have not been published.
  
  
  METHODS
  The group consisted of 220 volunteer healthy females in 4 age groups (20-29 years, n = 57; 30-39 years, n = 51; 40-49 years, n = 51; 50-59 years, n = 61) from Jyadskyla, Finland. Isometric cervical muscle strength in flexion, extension, and rotation was evaluated with a specially designed measurement system.
  
  
  RESULTS
  Across all age groups, mean (+/-SD) maximal isometric neck strength was 73.8 +/- 20.0 N in flexion and 190.8 +/- 31.3 N in extension. Mean (+/-SD) rotation strength was 8.1 +/- 2.3 Nm to the right and 7.9 +/- 2.3 Nm to the left. Absolute strength values did not differ among the age groups. A weak but significant correlation between body mass and neck flexion (r = 0.31, P<.01) and extension (r = 0.25, P<.01) strength was found. Intratester reliability varied from 0.87 to 0.96.
  
  
  CONCLUSIONS
  Women aged 20 to 59 years appear to have similar absolute isometric neck muscle strength levels. Thus these values can be used as reference for the working-age female population.
authors.affiliation: Department of Physical and Rehabilitation Medicine, Central Finland Health Care District, Jyväskylä. Petri.Salo@ksshp.fi
authors.forename: Petri K
authors.initials: PK
authors.lastname: Salo
authors.forename: Jari J
authors.initials: JJ
authors.lastname: Ylinen
authors.forename: Esko A
authors.initials: EA
authors.lastname: Mälkiä
authors.forename: Hannu
authors.initials: H
authors.lastname: Kautiainen
authors.forename: Arja H
authors.initials: AH
authors.lastname: Häkkinen
mesh_terms: D000328:Adult; D000886:Anthropometry; D001696:Biomechanical Phenomena / Q000295:instrumentation; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D007537:Isometric Contraction; D008875:Middle Aged; D009334:Neck Muscles / Q000502:physiology*; D012016:Reference Values; D017006:Rotator Cuff / Q000502:physiology