Objective: To assess the feasibility, acceptability, and psychometric properties of Actical accelerometers in people with multiple sclerosis (MS).
Design: Participants attended 2 testing sessions 7 days apart in which they completed 6 activities ranging in intensity while wearing an Actical accelerometer and Polar heart rate monitor. Perceived exertion was recorded after each activity.
Setting: University research center.
Participants: People (N=31) with a definite diagnosis of MS were purposefully selected, aiming for diversity in level of reported disability, age, sex, and type of MS.
Interventions: Not applicable.
Main outcome measures: Actical accelerometer, Polar S810i and RS800sd heart rate monitors, Borg rating of perceived exertion, six-minute walk test (6MWT), 30-second chair stand test.
Results: Accelerometers had good feasibility and acceptability in people with MS. Test-retest reliability was poor for sedentary and free-living activities, with low to moderate intraclass correlation coefficients (.00-.75), but was better for more vigorous or rhythmic activities (.85-.90). Bland-Altman 95% limits of agreement for average accelerometer counts were wide, ranging from +/-16 (newspaper reading) to +/-1330 (6MWT). Validity was not established with 95% prediction intervals showing high variability for all activities.
Conclusions: The psychometric problems highlighted here suggest Actical accelerometers should be used with caution in people with MS as a measure of physical activity, particularly when measuring comparatively sedentary or free-living activities.