title: Repeatability of electromyography and force measurements of the neck muscles in adolescents with and without headache.
abstract: BACKGROUND
  Reliable measurements are needed to study the dysfunction of the neck muscles. The aim of this study was to determine the intra-tester repeatability of EMG and isometric force measurements of the neck muscles in adolescents with headache and headache-free controls.
  
  
  METHODS
  A group of 30 adolescents with migraine-type headache, 29 with tension-type headache, and 30 headache-free controls were recruited. Maximal isometric neck muscle force with simultaneous recording of surface EMG from the cervical erector spinae and the sternocleidomastoideus muscles was measured twice during one day.
  
  
  RESULTS
  For all groups, intra-class correlation coefficients (ICC) and coefficients of variation (CV) showed acceptable repeatability of all measurements. (Force measurements: ICC 0.98-0.99, CV 0.7-3.7%; EMG measurements: ICC 0.95-0.99, CV 4.9-10.1%.) On the individual level, variation between the consecutive measurements was found to be low in all groups.
  
  
  CONCLUSIONS
  The present EMG and force measurements of neck muscles indicate acceptable intra-tester repeatability in adolescents. The repeatability was comparable in migraine- and tension-type headache and headache-free groups. The EMG and the force measurements offer the possibility to investigate neck muscle dysfunction in adolescent headache.
authors.affiliation: Department of Physical and Rehabilitation Medicine, Turku University Central Hospital, P.O. Box 52, FIN-20521 Turku, Finland. airi.oksanen@tyks.fi
authors.forename: Airi
authors.initials: A
authors.lastname: Oksanen
authors.forename: Jari J
authors.initials: JJ
authors.lastname: Ylinen
authors.forename: Tapani
authors.initials: T
authors.lastname: Pöyhönen
authors.forename: Pirjo
authors.initials: P
authors.lastname: Anttila
authors.forename: Katri
authors.initials: K
authors.lastname: Laimi
authors.forename: Heikki
authors.initials: H
authors.lastname: Hiekkanen
authors.forename: Jouko J
authors.initials: JJ
authors.lastname: Salminen
mesh_terms: D000293:Adolescent; D016022:Case-Control Studies; D004576:Electromyography; D005260:Female; D006801:Humans; D007537:Isometric Contraction / Q000502:physiology*; D008297:Male; D008881:Migraine Disorders / Q000503:physiopathology*; D053581:Muscle Strength Dynamometer; D009334:Neck Muscles / Q000502:physiology*; D015203:Reproducibility of Results; D012399:Rotation; D018781:Tension-Type Headache / Q000503:physiopathology*