Calibration of Accelerometer Output for Ambulatory Adults With Multiple Sclerosis

Motl RW, Snook EM, Agiovlasitis S, Suh Y. Calibration of accelerometer output for ambulatory adults with multiple sclerosis.ObjectivesTo examine the association between the rates of accelerometer activity counts and energy expenditure during walking in persons with multiple sclerosis (MS) versus controls and then to calibrate the output of accelerometers for computing time spent in light, moderate, and vigorous physical activity based on common metabolic equivalent unit categories in persons with MS.DesignMixed-model design.SettingLaboratory.ParticipantsPeople with MS (n=24) and people without MS (n=24) who were similar in age, sex, height, and weight.InterventionsThe participants undertook three 6-minute periods of walking at 3.2, 4.8, and 6.4km·h−1 on a motor-driven treadmill.Main Outcome MeasuresActivity counts and energy expenditure were measured with an accelerometer worn on the right hip and open-circuit spirometry, respectively.ResultsThe results indicated that (1) persons with MS had greater energy expenditure, but not activity counts, during walking on a treadmill than did controls; (2) there was a strong linear relationship between activity counts and energy expenditure during treadmill walking, but the slope of the relationship was steeper in persons with MS than in controls; and (3) the cut-points for light, moderate, and vigorous physical activity were lower in persons with MS than in controls.ConclusionsSuch findings provide evidence for a strong linear relationship between activity counts and energy expenditure during walking in persons with MS and cut-points based on counts per minute for quantifying time spent in light, moderate, and vigorous physical activity using accelerometers in this population.