title: Using Accelerometer and Gyroscopic Measures to Quantify Postural Stability.
abstract: BACKGROUND
  Force platforms and 3-dimensional motion-capture systems provide an accurate method of quantifying postural stability. Substantial cost, space, time to administer, and need for trained personnel limit widespread use of biomechanical techniques in the assessment of postural stability in clinical or field environments.
  
  
  OBJECTIVE
  To determine whether accelerometer and gyroscope data sampled from a consumer electronics device (iPad2) provide sufficient resolution of center-of-gravity (COG) movements to accurately quantify postural stability in healthy young people.
  
  
  METHODS
  Controlled laboratory study.
  
  
  METHODS
  Research laboratory in an academic medical center.
  
  
  METHODS
  A total of 49 healthy individuals (age = 19.5 ± 3.1 years, height = 167.7 ± 13.2 cm, mass = 68.5 ± 17.5 kg).
  
  
  METHODS
  Participants completed the NeuroCom Sensory Organization Test (SOT) with an iPad2 affixed at the sacral level.
  
  
  METHODS
  Primary outcomes were equilibrium scores from both systems and the time series of the angular displacement of the anteroposterior COG sway during each trial. A Bland-Altman assessment for agreement was used to compare equilibrium scores produced by the NeuroCom and iPad2 devices. Limits of agreement was defined as the mean bias (NeuroCom - iPad) ± 2 standard deviations. Mean absolute percentage error and median difference between the NeuroCom and iPad2 measurements were used to evaluate how closely the real-time COG sway measured by the 2 systems tracked each other.
  
  
  RESULTS
  The limits between the 2 devices ranged from -0.5° to 0.5° in SOT condition 1 to -2.9° to 1.3° in SOT condition 5. The largest absolute value of the measurement error within the 95% confidence intervals for all conditions was 2.9°. The mean absolute percentage error analysis indicated that the iPad2 tracked NeuroCom COG with an average error ranging from 5.87% to 10.42% of the NeuroCom measurement across SOT conditions.
  
  
  CONCLUSIONS
  The iPad2 hardware provided data of sufficient precision and accuracy to quantify postural stability. Accuracy, portability, and affordability make using the iPad2 a reasonable approach for assessing postural stability in clinical and field environments.
authors.affiliation: Department of Biomedical Engineering, Cleveland Clinic, OH;|Center for Neurological Restoration, Cleveland Clinic, OH;|Cleveland Clinic Concussion Center, Cleveland Clinic, OH;|Cleveland Functional Electrical Stimulation Center, L. Stokes Cleveland VA Medical Center, OH.
authors.forename: Jay L
authors.initials: JL
authors.lastname: Alberts
authors.affiliation: Department of Biomedical Engineering, Cleveland Clinic, OH;|Cleveland Clinic Concussion Center, Cleveland Clinic, OH;
authors.forename: Joshua R
authors.initials: JR
authors.lastname: Hirsch
authors.affiliation: Department of Biomedical Engineering, Cleveland Clinic, OH;
authors.forename: Mandy Miller
authors.initials: MM
authors.lastname: Koop
authors.affiliation: Department of Biomedical Engineering, Cleveland Clinic, OH;|Cleveland Clinic Concussion Center, Cleveland Clinic, OH;
authors.forename: David D
authors.initials: DD
authors.lastname: Schindler
authors.affiliation: Department of Biomedical Engineering, Cleveland Clinic, OH;
authors.forename: Daniel E
authors.initials: DE
authors.lastname: Kana
authors.affiliation: Department of Biomedical Engineering, Cleveland Clinic, OH;|Cleveland Clinic Concussion Center, Cleveland Clinic, OH;
authors.forename: Susan M
authors.initials: SM
authors.lastname: Linder
authors.affiliation: Department of Biomedical Engineering, Cleveland Clinic, OH;|Cleveland Clinic Concussion Center, Cleveland Clinic, OH;
authors.forename: Scott
authors.initials: S
authors.lastname: Campbell
authors.affiliation: Department of Biomedical Engineering, Cleveland Clinic, OH;|Center for Neurological Restoration, Cleveland Clinic, OH;
authors.forename: Anil K
authors.initials: AK
authors.lastname: Thota
mesh_terms: D061725:Accelerometry; D001696:Biomechanical Phenomena / Q000502:physiology; D001827:Body Height / Q000502:physiology; D001835:Body Weight / Q000502:physiology; D005260:Female; D006801:Humans; D008297:Male; D009038:Motion; D009068:Movement / Q000502:physiology*; D004856:Postural Balance / Q000502:physiology*; D011597:Psychomotor Performance / Q000502:physiology; D013997:Time Factors; D055815:Young Adult
keywords: biomechanics; concussions; motor control; motor function
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