Accuracy and responsiveness of the stepwatch activity monitor and ActivPAL in patients with COPD when walking with and without a rollator

Purpose: To evaluate the measurement properties of the StepWatch^™ Activity Monitor (SAM) and ActivPAL in COPD. Method: Whilst wearing both monitors, participants performed walking tasks at two self-selected speeds, with and without a rollator. Steps obtained using the monitors were compared with that measured by direct observation. Results: Twenty participants aged 73 ± 9 years (FEV₁ = 35 ± 13% pred; 8 males) completed the study. Average speeds for the slow and normal walking tasks were 34 ± 7 m·min⁻¹and 46 ± 10 m·min⁻¹, respectively. Agreement between steps recorded by the SAM with steps counted was similar irrespective of speed or rollator use (p = 0.63) with a mean difference and limit of agreement (LOA) of 2 steps·min⁻¹ and 6 steps·min⁻¹, respectively. Agreement for the ActivPAL was worse at slow speeds (mean difference 7 steps·min⁻¹; LOA 10 steps·min⁻¹) compared with normal speeds (mean difference 4 steps·min⁻¹; LOA 5 steps·min⁻¹) (p = 0.03), but was unaffected by rollator use. The change in step rate between slow and normal walking via direct observation was 12 ± 7 steps·min⁻¹ which was similar to that detected by the SAM (12 ± 6 steps·min⁻¹) and ActivPAL (14 ± 7 steps·min⁻¹). Conclusions: The SAM can be used to detect steps in people who walk very slowly including those who use a rollator. Both devices were sensitive to small changes.