title: Time-of-day influences on static and dynamic postural control.
abstract: BACKGROUND
  Assessment of postural control is used extensively in clinical and research applications. Time of day affects aspects of physical performance, but whether it also affects postural control is unknown.
  
  
  OBJECTIVE
  To determine the influence of time of day on static and dynamic postural control.
  
  
  METHODS
  For each static postural control variable, a separate 3-way (day, time, eye) repeated-measures analysis of variance (ANOVA) was performed. For the dynamic postural control variable, a 2-way (day, time) repeated-measures ANOVA was performed.
  
  
  METHODS
  University research laboratory.
  
  
  METHODS
  Thirty healthy college-aged subjects.
  
  
  METHODS
  Static and dynamic postural control of each subject was assessed in a laboratory at 10:00, 15:00, and 20:00 on 2 consecutive days.
  
  
  METHODS
  Unilateral static postural control was assessed with eyes open and closed on a forceplate using center-of-pressure velocity in the anterior-posterior and medial-lateral planes as the dependent variables. Dynamic postural control was assessed with the anterior reaching direction of the Star Excursion Balance Test using reach distances normalized to leg length as the dependent variable.
  
  
  RESULTS
  For static postural control, velocity scores in both directions were lower at 10:00 than at 15:00 and 20:00 on day 1 (P < .05). For dynamic postural control, normalized reach distance was greater at 10:00 than at 15:00 and 20:00 (P < .05).
  
  
  CONCLUSIONS
  Time of day had a consistent influence on dynamic postural control that suggests performance of this task may be better in the morning than in the afternoon or evening. The influence of time of day on static postural control was not as consistent and we feel requires further investigation. These findings have implications for researchers and clinicians when implementing and interpreting postural control testing.
authors.affiliation: University of Toledo, Toledo, OH 43606, USA. phillip.gribble@utoledo.edu
authors.forename: Phillip A
authors.initials: PA
authors.lastname: Gribble
authors.forename: W Steven
authors.initials: WS
authors.lastname: Tucker
authors.forename: Paul A
authors.initials: PA
authors.lastname: White
mesh_terms: D000328:Adult; D000704:Analysis of Variance; D005260:Female; D006801:Humans; D008297:Male; D009068:Movement; D018763:Muscle Fatigue / Q000502:physiology*; D004856:Postural Balance / Q000502:physiology*; D011597:Psychomotor Performance / Q000502:physiology*; D016059:Range of Motion, Articular / Q000502:physiology*; D015203:Reproducibility of Results; D012307:Risk Factors; D012494:Sampling Studies; D012680:Sensitivity and Specificity; D013314:Stress, Mechanical; D013997:Time Factors