Reliability of daily step activity monitoring in adults with incomplete spinal cord injury

Abstract

We determined the number of days of step activity monitoring required to establish stable measures of walking activity in adults with incomplete spinal cord injury (iSCI). Eleven individuals with iSCI (mean age 49 +/- 14 years) wore a StepWatch Activity Monitor during waking hours for 7 consecutive days. We used generalizability theory to identify sources of variance in daily step counts and determine the minimum number of days necessary to obtain a reliability coefficient (G-coefficient) greater than or equal to 0.80. Average daily step activity (DSA) was 1,281 +/- 1,594 steps. Participants and days accounted for 70.9% and 1.3% of total variance in DSA, respectively, while unidentifiable error accounted for 27.8% of the total variance in DSA. A minimum of 2 days was required to achieve a G-coefficient greater than or equal to 0.80. An acceptably stable measure of walking activity in adults with iSCI can be obtained by averaging step count values from any 2-day period in a week. Results from this investigation should be useful in evaluating the effect of activity-based programs designed to enhance locomotor function in persons with iSCI.