Actigraphy as a measure of physical activity for wheelchair users with spinal cord injury.
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.
Warms
Catherine A
CA
Bio-behavioral Nursing and Health Systems, School of Nursing, University of Washington, Seattle, 98195-7266, USA. cwarms@u.washington.edu
Belza
Basia L
BL
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