Accelerometer output and its association with energy expenditure in persons with multiple sclerosis.

Limited data support the strong association between rates of accelerometer activity counts and energy expenditure during dynamic activity in persons with multiple sclerosis (MS). This study examined the association between rates of activity counts and energy expenditure during walking by using two models of accelerometers and generated cut-points representing moderate-to-vigorous physical activity (MVPA) in persons with MS. Participants were 43 persons with MS and 43 controls who undertook 5 min of seated rest and up to five 6 min periods of walking at five different speeds on a treadmill. While walking, participants wore two models of accelerometers and a mouthpiece in-line with an open-circuit spirometry system for measuring energy expenditure (rate of oxygen consumption). Strong linear associations were found between accelerometer activity counts and energy expenditure, and the magnitude did not differ between MS and controls for both accelerometer models. The mean slopes of the linear relationships were steeper in persons with MS than controls and resulted in distinct cut-points for MVPA based on accelerometer counts for persons with MS and controls. The strong linear relationship between activity counts and energy expenditure and cut-points for quantifying time spent in MVPA should allow for better understanding of physical activity and examination of its predictors and consequences when using accelerometers in MS.