Activity Monitors give an objective measure of usual walking performance. This study aimed to examine the test-retest reliability of the StepWatch Activity Monitor outputs (mean steps/day; peak activity index; sustained activity indices of 1, 5, 20, 30, 60 minutes; steps at high, medium, and low stepping rates).
Thirty healthy adults age 18 to 49 years wore the StepWatch for 2 3-day periods at least 1 week apart.
The intraclass correlation coefficients of the StepWatch outputs ranged from 0.44 to 0.91 over 3 days. The coefficient of variation ranged from 3.0% to 51.3% over the monitoring periods, with higher variation shown for shorter monitoring periods. The most reliable 5 outputs had 95% limits of agreement between 3-day periods that were less than 40%. These were mean steps/day (±39.1%), highest step rate in 1 (±17.3%) and 5 (±37.4%) minutes, peak activity index (±25.6%), and percentage of inactive time (±9.52%).
Mean steps/day, highest step rate in 1 and 5 minutes, peak activity index, and percentage of inactive time have good test-retest reliability over a 3-day monitoring period, with lower reliability shown by the other StepWatch outputs. Monitoring over 1 or 2 days is less reliable.
Mudge and Taylor are with the Health and Rehabilitation Research Centre, Auckland University of Technology, Auckland, New Zealand. Chang and Wong are with the Dept of Physiotherapy, Auckland University of Technology, Auckland, New Zealand.