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

Abstract

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.

Implications for Rehabilitation

• The evaluation of physical activity (PA) before and after pulmonary rehabilitation in people with chronic obstructive pulmonary disease (COPD) has evolved to be an important outcome measure.

• Selecting an appropriate device to obtain valid measures of PA remains a challenge, especially for those individuals who walk slowly or use a rollator to assist with ambulation.

• The StepWatchTM Activity Monitor and the ActivPAL have been shown in this study to be sensitive to small changes in step rate, thus these devices can be used to assess changes in physical activity in individuals with COPD such as following pulmonary rehabilitation, including those who walk slowly or use a walking aid such as a rollator.

Keywords::

• Ambulatory/instrumentation
• COPD
• motor activity

Acknowledgements

We acknowledge Faith Png and Sandy Dumas at Bentley Hospital and Nola Cecins from Sir Charles Gairdner Hospital (Perth, Western Australia) for their contribution to patient recruitment as well as all the participants who took part in this study. We acknowledge Thomas Dolmage (West Park Healthcare Centre, Toronto, Ontario) for providing the audio-recordings to set walking speed.

Declaration of Interest: Funds for this study were provided by Sir Charles Gairdner Hospital Research Advisory Committee. We certify that no party having a direct interest in the results of the research supporting this article has or will confer a benefit on us or on any organization with which we are associated AND, if applicable, we certify that all financial and material support for this research (e.g. NIH or NHS grants) and work are clearly identified in the title page of the manuscript. The StepWatchTM Activity Monitor is FDA approved for the indicated usage in the United States. The ActivPAL that is the subject of this manuscript is/are exempt from FDA regulations because it quantifies activity using a posture sensing mechanism combined with step counting algorithms, and it is exported under the Harmonized Tariff for pedometers (HTS#9029.10.80.00).