Does a waist-worn ActiGraph accelerometer quantify community ambulation in persons with multiple sclerosis?

Abstract: Accelerometry has been recognized as a method of objectively measuring community ambulation in persons with multiple sclerosis (MS). However, the assumption that walking itself serves as a major contributor to the accelerometer signal has yet to be tested. This study examined the assumption that community-based walking is a primary contributor to accelerometer output in MS. Ambulatory persons (5 males/17 females; 13 without aid/9 with aid) with MS wore a triaxial accelerometer (ActiGraph GT3X) as well as an IDEEA system (MiniSun, Inc; Fresno, Florida) over the course of a single day. Outcome measures for the accelerometer included movement counts/hour for the vertical, anterior-posterior, and mediolateral axes. Outcomes for the IDEEA system included percent time walking, sitting, and standing, as well as walking speed. Pearson product correlations (r) were used to examine the associations between outcomes from the accelerometer and IDEEA system. Significant correlations were observed between percent walking time and movement counts/hour along the vertical (r = 0.84) and anterior-posterior (r = 0.69) axes. Significant correlations were further noted between movement counts/hour along the vertical axis and walking speed (r = 0.45) and self-report walking impairment (r = −0.50) and disability (r = −0.46). Such observations further support accelerometry as an objective marker of community ambulation in persons with MS.