title: Spinal cord injury and time to instability in seated posture.
abstract: OBJECTIVE
  To investigate seated postural control in persons with spinal cord injury (SCI) compared with age-matched controls.
  
  
  METHODS
  Cohort.
  
  
  METHODS
  University research laboratory.
  
  
  METHODS
  Adults (N=36; mean age ± SD, 22.5 ± 3.2y): 7 persons with high SCI (HI group; injury level greater than T10), 11 persons with low SCI (LI group; injury level between T10 and L4), and 18 persons with non-SCI.
  
  
  METHODS
  Not applicable.
  
  
  METHODS
  Participants sat on a force platform on a custom-built wooden box with their arms by their side. Postural control was quantified in several ways. Participants completed a functional reach test. The amount of postural sway was quantified by characterizing the center of pressure (COP) trajectory by determining median velocity and root mean square of the signal. In addition, the virtual time to contact to the functional boundary was quantified. Last, the instability index was determined as the ratio of the COP area to the functional boundary.
  
  
  RESULTS
  There were no group differences in COP-based metrics (P>.05). There was no difference between SCI groups in functional reach (P>.05). The HI group had a smaller virtual time to contact (VTC) than the control group (.50 ± .20s vs .98 ± .24s, P<.05). Both SCI groups had a greater instability index than the control group, with the HI group having the largest amount of instability (P<.05).
  
  
  CONCLUSIONS
  The observations suggest that VTC analysis is appropriate to investigate seated postural control. It is proposed that including VTC of seated postural control as an outcome measure will provide novel information concerning the effectiveness of various rehabilitation approaches and/or technologies aimed at improving seated postural control in persons with SCI.
authors: Department of Kinesiology and Community Health, University of Illinois at Urbana-Champaign, Urbana, IL, USA.
authors: Sunghoon
authors: S
authors: Shin
authors: Jacob J
authors: JJ
authors: Sosnoff
mesh_terms: D000328:Adult; D016022:Case-Control Studies; D015331:Cohort Studies; D005260:Female; D006801:Humans; D008159:Lumbar Vertebrae; D008297:Male; D004856:Postural Balance / Q000502:physiology*; D011187:Posture / Q000502:physiology*; D012678:Sensation Disorders / Q000209:etiology / Q000503:physiopathology*; D013119:Spinal Cord Injuries / Q000150:complications* / Q000503:physiopathology*; D013647:Task Performance and Analysis; D013904:Thoracic Vertebrae; D013997:Time Factors; D055815:Young Adult
keywords: COP; HI; LI; Paraplegia; RMS; Rehabilitation; SCI; VTC; center of pressure; high injury; low injury; root mean square; spinal cord injury; virtual time to contact