title: Effect of trunk-muscle fatigue and lactic acid accumulation on balance in healthy subjects.
abstract: OBJECTIVE
  This study sought to determine the effects of trunk-muscle fatigue and blood lactic acid elevation on static and dynamic balance.
  
  
  METHODS
  Fatigue was induced by an isokinetic protocol, and static and dynamic balance were assessed during bilateral stance using a Kinesthetic Ability Trainer. Subjects participated in a fatigue protocol in which continuous concentric movements at 60 degrees/s were performed until the torque output for both trunk flexion and extension dropped below 25% of the calculated peak torque for 3 consecutive movements.
  
  
  METHODS
  Before and immediately after the fatigue protocol, blood lactic acid measurements and static- and dynamic-balance measurements were recorded.
  
  
  RESULTS
  An increase in lactic acid levels was detected in all subjects. According to a dependent-samples t test, significant differences in balance and lactic acid values were found after the fatigue protocol. There was no correlation between lactic acid accumulation (change between prefatigue and postfatigue levels) and balance-score differences.
  
  
  CONCLUSIONS
  Trunk-muscle fatigue has an adverse effect on static and dynamic balance.
authors.affiliation: Dept of Hydrotherapy, Baskent University, Ankara, Turkey.
authors.forename: Ozgur
authors.initials: O
authors.lastname: Surenkok
authors.forename: Ayse
authors.initials: A
authors.lastname: Kin-Isler
authors.forename: Aydan
authors.initials: A
authors.lastname: Aytar
authors.forename: Zuhal
authors.initials: Z
authors.lastname: Gültekin
mesh_terms: D000054:Acceleration; D000328:Adult; D015444:Exercise / Q000502:physiology*; D005080:Exercise Test; D006801:Humans; D019344:Lactic Acid / Q000097:blood; D008297:Male; D009119:Muscle Contraction / Q000502:physiology*; D018763:Muscle Fatigue / Q000502:physiology*; D018482:Muscle, Skeletal / Q000502:physiology*; D010865:Pilot Projects; D011187:Posture; D016059:Range of Motion, Articular; D019415:Torque
chemical_list: D019344:Lactic Acid