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 acceler-ometer output in MS. Ambulatory persons (5 males/17 females; 13 without aid/9 with aid) with MS wore a triaxial accelerome-ter (ActiGraph GT3X, Health One Technologies; Fort Walton Beach, Florida) as well as an IDEEA system (MiniSun, Inc; Fresno, Florida) over the course of a single day. Outcome mea-sures 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 corre-lations (r) were used to examine the associations between out-comes 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 ante-rior-posterior (r = 0.69) axes. Significant correlations were fur-ther 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 obser-vations further support accelerometry as an objective marker of community ambulation in persons with MS.