title: Electromyography and ratings of lumbar muscle fatigue using a four-level staircase protocol.
abstract: OBJECTIVE
  The purpose of the study was to explore whether a relationship existed between subject's experience and objective measurements of back-muscle fatigue in healthy subjects. This may be used as reference material later.
  
  
  METHODS
  Muscle fatigue in the lower back was measured in healthy subjects using a staircase protocol.
  
  
  BACKGROUND
  Muscle fatigue measurement in the lower back is of importance when assessing patients with low-back pain. The subject's experience of muscle fatigue needs to be explored further.
  
  
  METHODS
  Twenty healthy subjects with informed consent participated. Borg CR-10 scale responses and electromyography measurements were obtained from low-back muscles of the subjects following a staircase protocol with sustained contractions at 20%, 40%, 60%, and 80% of maximum voluntary contraction.
  
  
  RESULTS
  A strong correlation was found between Borg ratings and force (r=0.83) and between slope and force (r= -0.72) but not between Borg ratings and slopes which was at best 0.43 (/r/< or =0.43).
  
  
  CONCLUSIONS
  Although subjective ratings and slopes showed a low correlation; increases in force with a concomitant increase in fatigue was reflected both by the subjective ratings and the slope. One cannot use subjective ratings for prediction of the slope for this type of protocol. However, a more complete description of muscle fatigue needs both the slope and the Borg ratings.
  
  
  CONCLUSIONS
  In clinical testing, both subjective and objective measures of muscle fatigue must be considered since they measure different aspects of muscle fatigue. The median frequency slope probably reflects "physical discomfort" but the Borg ratings add a factor of "lack of energy".
authors.affiliation: Department of Physical Therapy, Karolinska Institute/Karolinska Hospital, Neuro R1:07, S-171 76 Stockholm, Sweden. asa.dedering@kirurgi.ki.se
authors.forename: Asa
authors.initials: A
authors.lastname: Dedering
authors.forename: Lars
authors.initials: L
authors.lastname: Oddsson
authors.forename: Karin
authors.initials: K
authors.lastname: Harms-Ringdahl
authors.forename: Gunnar
authors.initials: G
authors.lastname: Németh
mesh_terms: D000328:Adult; D001696:Biomechanical Phenomena; D004576:Electromyography; D005080:Exercise Test / Q000379:methods*; D005260:Female; D006801:Humans; D017116:Low Back Pain / Q000503:physiopathology; D008159:Lumbar Vertebrae; D008297:Male; D009119:Muscle Contraction / Q000502:physiology; D018763:Muscle Fatigue / Q000502:physiology*; D018482:Muscle, Skeletal / Q000502:physiology*; D011446:Prospective Studies; D012016:Reference Values; D012680:Sensitivity and Specificity