title: Relationship between sleep stages and nocturnal trapezius muscle activity.
abstract: OBJECTIVE
  Former studies reported a relationship between increased nocturnal low level trapezius muscle activity and neck or shoulder pain but it has not been explored whether trapezius muscle relaxation is related to sleep stages. The goal of the present study was to investigate whether trapezius muscle activity is related to different sleep stages, as measured by polysomnography.
  
  
  METHODS
  Twenty one healthy subjects were measured on four consecutive nights in their homes, whereas the first night served as adaptation night. The measurements included full polysomnography (electroencephalography (EEG), electrooculography (EOG), electromyography (EMG) and electrocardiography (ECG)), as well as surface EMG of the m. trapezius descendens of the dominant arm.
  
  
  RESULTS
  Periods with detectable EMG activity of the trapezius muscle lasted on average 1.5% of the length of the nights and only in four nights it lasted longer than 5% of sleeping time. Neither rest time nor the length of periods with higher activity levels of the trapezius muscle did significantly differ between sleep stages.
  
  
  CONCLUSIONS
  We found no evidence that nocturnal trapezius muscle activity is markedly moderated by the different sleep stages. Thus the results support that EMG measurements of trapezius muscle activity in healthy subjects can be carried out without concurrent polysomnographic recordings.
authors.affiliation: Occupational Health Management, SBB AG, Swiss Federal Railways, Hilfikerstrasse 1, 3000 Bern, Switzerland.
authors.forename: Christian
authors.initials: C
authors.lastname: Müller
authors.affiliation: ETH Zürich, Department of Health Sciences and Technology, Sensory-Motor Systems Lab, Sonneggstrasse 3, ML G57, CH-8092 Zurich, Switzerland.
authors.forename: Corinne
authors.initials: C
authors.lastname: Nicoletti
authors.affiliation: Umwelt und Energie, Kanton of Lucerne, 6002 Lucerne, Switzerland.
authors.forename: Sarah
authors.initials: S
authors.lastname: Omlin
authors.affiliation: Swiss Federal Office for the Environment, 3003 Bern, Switzerland.
authors.forename: Mark
authors.initials: M
authors.lastname: Brink
authors.affiliation: ETH Zürich, Department of Health Sciences and Technology, Sensory-Motor Systems Lab, Sonneggstrasse 3, ML G57, CH-8092 Zurich, Switzerland.
authors.forename: Thomas
authors.initials: T
authors.lastname: Läubli
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D004569:Electroencephalography / Q000379:methods / Q000592:standards; D004576:Electromyography / Q000379:methods* / Q000592:standards; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D017286:Polysomnography / Q000379:methods* / Q000592:standards; D012894:Sleep Stages / Q000502:physiology*; D064171:Superficial Back Muscles / Q000502:physiology*; D055815:Young Adult
keywords: EMG; Polysomnography; Sleep quality; Sleep stages; Trapezius