title: Actigraphy as a measure of physical activity for wheelchair users with spinal cord injury.
abstract: BACKGROUND
  Research has indicated that actigraphy is valid and reliable for measuring low levels of physical activity among ambulatory individuals, and that it may be a valid indicator of energy expenditure for wheelchair users in laboratory conditions, but there are no reports of its evaluation in free-living conditions.
  
  
  OBJECTIVE
  To assess the suitability and validity of actigraphy as a measure of free-living physical activity for wheelchair users with spinal cord injury.
  
  
  METHODS
  In a methodologic descriptive correlational study, measures of physical activity by an actigraph and a self-report physical activity record were obtained for six individuals in laboratory conditions and 22 individuals in free-living conditions during a 4-day period. At the completion of the home monitoring trial, all the participants completed a questionnaire about their experience wearing the monitor and maintaining the record.
  
  
  RESULTS
  Mean activity counts by actigraphy during active tasks were significantly different from the counts during inactive tasks (p =.003). During home monitoring, the participants wore the monitor, on the average, 95% of the prescribed wearing time, rated it as very comfortable, and were willing to wear it again. Pearson correlation coefficients of activity counts with self-reported activity intensity varied from.30 to.77 (p <.01) for individual participants. The mean correlation across the sample was.60 (p <.01). Activity counts varied with reported activity, indicating concurrence between the two activity measurement methods.
  
  
  CONCLUSIONS
  Actigraphy is suitable as a measurement of activity for people with spinal cord injury. This initial investigation suggests that it has concurrent validity with a self-report measure of activity intensity and frequency, as evidenced in this sample of wheelchair users in free-living conditions.
authors.affiliation: Bio-behavioral Nursing and Health Systems, School of Nursing, University of Washington, Seattle, 98195-7266, USA. cwarms@u.washington.edu
authors.forename: Catherine A
authors.initials: CA
authors.lastname: Warms
authors.forename: Basia L
authors.initials: BL
authors.lastname: Belza
mesh_terms: D000328:Adult; D000368:Aged; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D018670:Monitoring, Ambulatory / Q000295:instrumentation; D009043:Motor Activity; D013119:Spinal Cord Injuries / Q000145:classification*; D014910:Wheelchairs