title: Quantification of isometric cervical strength at different ranges of flexion and extension.
abstract: BACKGROUND
  Studies have demonstrated that cervical strength is affected by injury to the neck. Cervical strength measurements are influenced by the protocol used for the measurements. Previous studies have determined the isometric cervical strength only at a few degrees of range of neck motion. The present study was aimed at quantifying cervical strength at neutral, 25%, 50% and 75% of flexion and extension.
  
  
  METHODS
  Using a correlation study design, 39 volunteers in the age range of 18-30 years were recruited in two sessions, one for flexion and the other extension. Their sequence was randomized. The cervical strength was measured using a force measuring device. The device was firmly bolted in the floor. A rotating metal tube was pivoted, adjustably counterweighted and attached to the device at one end and an immovable object with a load cell in its path at the other. The neck was positioned in the desired posture and isometric efforts were exerted on the horizontal resistance arm.
  
  
  RESULTS
  Cervical strength was found to be highest in the neutral posture for both flexion (19.8 N females and 31.4 N males) and extension (39.5 females and 45.1 males) and significantly decreased with an increasing angular deviation of the neck (P<0.01). Males exerted significantly higher forces than females. The overall flexion-extension ratio was 1:1.7 (P<0.01).
  
  
  CONCLUSIONS
  The maximum force was exerted in the neutral posture of the neck and it was directionally dependent being less in flexion than extension (P<0.01). Males were stronger than females. The findings may assist in targeting rehabilitation goals.
authors.affiliation: Faculty of Rehabilitation Medicine, Department of Physical Therapy, 3-75 Corbett Hall, Ergonomics Research Laboratory, University of Alberta, Edmonton, Canada T6G2G4.
authors.forename: Laxmi
authors.initials: L
authors.lastname: Suryanarayana
authors.forename: Shrawan
authors.initials: S
authors.lastname: Kumar
mesh_terms: D000293:Adolescent; D000328:Adult; D002574:Cervical Vertebrae / Q000502:physiology*; D005260:Female; D006801:Humans; D007537:Isometric Contraction / Q000502:physiology*; D008297:Male; D009334:Neck Muscles / Q000502:physiology*; D010808:Physical Examination / Q000379:methods*; D005082:Physical Exertion / Q000502:physiology*; D011187:Posture / Q000502:physiology*; D016059:Range of Motion, Articular / Q000502:physiology*; D013314:Stress, Mechanical