title: Correlation between electromyographic spectral changes and subjective assessment of lumbar muscle fatigue in subjects without pain from the lower back.
abstract: OBJECTIVE
  The purpose of this study was to correlate objective measurements of muscle fatigue in the lower back to the subject's own assessment of fatigue.
  
  
  METHODS
  Muscle fatigue in the lower back was assessed in healthy subjects using electromyography (EMG), endurance time and the Borg scale.
  
  
  BACKGROUND
  Muscle fatigue, measured with EMG and endurance time, in the lower back, is significant for patients with pain in the lower back.
  
  
  METHODS
  Fifty healthy subjects participated. EMG was detected from the lumbar extensor muscles during a modified Sørensen's test, an isometric contraction for the back extensors until exhaustion. During the test, subjects rated their subjective fatigue on a Borg CR-10 scale.
  
  
  RESULTS
  Borg scale ratings correlated with endurance time (0.68) and EMG median- and mean power frequency slopes (0.41-0.50). At a Borg rating of 3, median- and mean power frequency and endurance time were reduced by 30%. At a Borg rating of 5, median- and mean power frequency and endurance time were reduced by 50%. At a Borg rating of 7, median- and mean power frequency and endurance time were reduced by 60-70%.
  
  
  CONCLUSIONS
  Significant correlation between the Borg scale, EMG and endurance time suggests a close relationship between subjective and objective assessment of muscle fatigue.
authors.affiliation: Department of Orthopedics, Karolinska Hospital, Stockholm, Sweden.
authors.forename: A
authors.initials: A
authors.lastname: Dedering
authors.forename: G
authors.initials: G
authors.lastname: Németh
authors.forename: K
authors.initials: K
authors.lastname: Harms-Ringdahl
mesh_terms: D000328:Adult; D004576:Electromyography; D005080:Exercise Test; D005260:Female; D006801:Humans; D007537:Isometric Contraction / Q000502:physiology*; D017116:Low Back Pain / Q000175:diagnosis / Q000503:physiopathology; D008159:Lumbar Vertebrae; D008297:Male; D018763:Muscle Fatigue / Q000502:physiology*; D018482:Muscle, Skeletal; D010358:Patient Participation; D010807:Physical Endurance / Q000502:physiology*; D012016:Reference Values; D018709:Statistics, Nonparametric