title: Stability of measurement outcomes for voluntary task performance in participants with chronic ankle instability and healthy participants.
abstract: BACKGROUND
  Acceptable measurement stability during data collection is critically important to research. To interpret differences in measurement outcomes among participants or changes within participants after an intervention program, we need to know whether the measurement is stable and consistent.
  
  
  OBJECTIVE
  To determine the within-session stability of muscle activation patterns for a voluntary postural-control task in a group of noninjured participants and a group of participants with chronic ankle instability (CAI).
  
  
  METHODS
  Descriptive laboratory study.
  
  
  METHODS
  Musculoskeletal laboratory.
  
  
  METHODS
  Twenty control participants (8 men, 12 women; age = 21.8 ± 2.4 years, height = 164.3 ± 13.4 cm, mass = 68.4 ± 17.9 kg) and 20 participants with CAI (12 men, 8 women; age = 21.2 ± 2.1 years, height = 176 ± 10.2 cm, mass = 71.7 ± 11.3 kg).
  
  
  METHODS
  Participants performed 4 barefoot standing trials, each of which included a 30-second double-legged stance followed by a 30-second single-legged stance in 3 conditions: with vision, without vision, and with vision on a balance pad.
  
  
  METHODS
  The activity of 7 muscles of the lower limb was measured for the stance task in the 3 different conditions for each trial. The onset of muscle activity and muscle recruitment order were determined and compared between the first and the fourth trials for both groups and for each condition.
  
  
  RESULTS
  We found no differences in the onset of muscle activity among trials for both groups or for each condition. The measurement error was 0.9 seconds at maximum for the control group and 0.12 seconds for the CAI group. In the control group, 70% to 80% of the participants used the same muscle recruitment order in both trials. In the CAI group, 75% to 90% used the same recruitment order.
  
  
  CONCLUSIONS
  Within 1 session, measurement stability for this task was acceptable for use in further research. Furthermore, no differences were found in measurement stability across conditions in the control or CAI groups.
authors.affiliation: Research Centre for Musculoskeletal Rehabilitation, Katholieke Universiteit Leuven, Belgium. sara.vandeun@faber.kuleuven.be
authors.forename: Sara
authors.initials: S
authors.lastname: Van Deun
authors.forename: Karel
authors.initials: K
authors.lastname: Stappaerts
authors.forename: Oron
authors.initials: O
authors.lastname: Levin
authors.forename: Luc
authors.initials: L
authors.lastname: Janssens
authors.forename: Filip
authors.initials: F
authors.lastname: Staes
mesh_terms: D000328:Adult; D000843:Ankle Joint / Q000503:physiopathology*; D016022:Case-Control Studies; D002908:Chronic Disease; D004576:Electromyography; D005260:Female; D006801:Humans; D007593:Joint Instability / Q000503:physiopathology*; D035002:Lower Extremity / Q000502:physiology*; D008297:Male; D018482:Muscle, Skeletal / Q000294:innervation / Q000502:physiology*; D011187:Posture / Q000502:physiology*; D014785:Vision, Ocular; D055815:Young Adult