title: Fatigue's effect on eversion force sense in individuals with and without functional ankle instability.
abstract: BACKGROUND
  Force sense (FS), the proprioceptive ability to detect muscle-force generation, has been shown to be impaired in individuals with functional ankle instability (FAI). Fatigue can also impair FS in healthy individuals, but it is unknown how fatigue affects FS in individuals with FAI.
  
  
  OBJECTIVE
  To assess the effect of fatigue on ankle-eversion force-sense error in individuals with and without FAI.
  
  
  METHODS
  Case control with repeated measures.
  
  
  METHODS
  Sports medicine research laboratory.
  
  
  METHODS
  32 individuals with FAI and 32 individuals with no ankle sprains or instability in their lifetime. FAI subjects had a history of ≥1 lateral ankle sprain and giving-way ≥1 episode per month.
  
  
  METHODS
  Three eversion FS trials were captured per load (10% and 30% of maximal voluntary isometric contraction) using a load cell before and after a concentric eversion fatigue protocol.
  
  
  METHODS
  Trial error was the difference between the target and reproduction forces. Constant error (CE), absolute error (AE), and variable error (VE) were calculated from 3 trial errors. A Group × Fatigue × Load repeated-measures ANOVA was performed for each error.
  
  
  RESULTS
  There were no significant 3-way interactions or 2-way interactions involving group (all P > .05). CE and AE had a significant 2-way interaction between load and fatigue (CE: F1,62 = 8.704, P = .004; AE: F1,62 = 4.024, P = .049), and VE had a significant main effect for fatigue (F1,62 = 5.130, P = .027), all of which indicated increased FS error with fatigue at 10% load. However, at 30% load only VE increased with fatigue. The FAI group had greater error as measured by AE (F1,62 = 4.571, P = .036) but not CE or VE (P > .05).
  
  
  CONCLUSIONS
  Greater AE indicates that FAI individuals are less accurate in their force production. Fatigue impaired force sense in all subjects equally. These deficits provide evidence of impaired proprioception with fatigue and in individuals with FAI.
authors: Health and Physical Education Dept, Marywood University, Scranton, PA, USA.
authors: Cynthia J
authors: CJ
authors: Wright
authors: Brent L
authors: BL
authors: Arnold
mesh_terms: D000293:Adolescent; D000328:Adult; D016512:Ankle Injuries / Q000150:complications / Q000503:physiopathology*; D000843:Ankle Joint / Q000503:physiopathology; D016022:Case-Control Studies; D056228:Feedback, Sensory / Q000502:physiology*; D005260:Female; D006801:Humans; D007537:Isometric Contraction / Q000502:physiology; D007593:Joint Instability / Q000209:etiology / Q000503:physiopathology*; D008297:Male; D018763:Muscle Fatigue / Q000502:physiology*; D018482:Muscle, Skeletal / Q000503:physiopathology; D013180:Sprains and Strains / Q000150:complications / Q000503:physiopathology*; D055815:Young Adult