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.
To assess the suitability and validity of actigraphy as a measure of free-living physical activity for wheelchair users with spinal cord injury.
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.
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.
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.
Catherine A. Warms, PhD, RN, is Postdoctoral Fellow; and Basia L. Belza, PhD, RN, is Associate Professor, Bio-behavioral Nursing and Health Systems, School of Nursing, University of Washington, Seattle.
Accepted for publication November 20, 2003.
Funded by Biobehavioral Nursing Training Grant NINR T32NR407106, the Hester McLaws Scholarship Fund of the University of Washington School of Nursing and Sigma Theta Tau Psi Chapter.
Corresponding author: Catherine Warms, PhD, RN, Department of Biobehavioral Nursing and Health Systems, School of Nursing, University of Washington, Box 357266, Seattle, WA 98195-7266. (e-mail:firstname.lastname@example.org).