The effect of walking mobility on the measurement of physical activity using accelerometry in multiple sclerosis

Objective: To examine whether accelerometry provides a measure of physical activity, walking ability or both in a sample of individuals with multiple sclerosis. The secondary purpose was to examine the validity of physical activity measures in people with multiple sclerosis who have ambulatory impairments. Participants: Forty-two individuals with multiple sclerosis without ambulatory impairment (Expanded Disability Status Scale (EDSS) score <= 4.5) and 32 individuals with multiple sclerosis with ambulatory impairment (EDSS >= 5.0). Method: Participants completed the Multiple Sclerosis Walking Scale-12 and Performance Scales, wore an accelerometer for seven days, and completed the Godin Leisure-Time Exercise Questionnaire and short-form of the International Physical Activity Questionnaire. Results: There were significant differences between groups on scores from the five measures. There were large correlations between the accelerometer counts with scores from both the self-report measures of physical activity and the self-report measures of walking mobility in the overall sample. There were large correlations between scores from both measures of physical activity in the overall sample and the subsample with ambulatory impairment. Conclusion: Our data suggest that accelerometers are measuring both physical activity and walking mobility in individuals with multiple sclerosis, whereas self-report measures are measuring physical activity in individuals with multiple sclerosis, including those with ambulatory impairment.