title: Step detection using multi- versus single tri-axial accelerometer-based systems.
abstract: Multiple sensors are often considered necessary for increased step count accuracy. However, subject adherence to device-wear increases using a minimal number of activity monitors (AMs). The study aims were to determine and compare the validity of using multiple AMs versus a single AM to detect steps by comparison to video using a modification of an algorithm previously developed for a four-accelerometer AM system capable, unlike other algorithms, of accurate step detection for gait velocities as low as 0.1 m s(-1). Twelve healthy adults wore ankle, thigh and waist AMs while performing walking/jogging trials at gait velocities from 0.1-4.8 m s(-1) and a simulated free-living dynamic activities protocol. Nineteen older adults wore ankle and waist AMs while walking at velocities from 0.5-2.0 m s(-1). As little as one AM (thigh or waist) accurately detected steps for velocities  >0.5 m s(-1). A single ankle AM accurately detected steps for velocities  ⩾0.1 m s(-1). Only the thigh AM could not accurately detect steps during the dynamic activities. Only the thigh-ankle combination or single waist AM could accurately distinguish between walking and jogging steps. These laboratory-based results suggest that the presented algorithm can accurately detect steps in a free-living environment using only one ankle or waist AM.
authors.affiliation: Motion Analysis Laboratory, Division of Orthopedic Research, Charlton North L-110L, Mayo Clinic, Rochester, MN 55905, USA.
authors.forename: E
authors.initials: E
authors.lastname: Fortune
authors.forename: V A
authors.initials: VA
authors.lastname: Lugade
authors.forename: S
authors.initials: S
authors.lastname: Amin
authors.forename: K R
authors.initials: KR
authors.lastname: Kaufman
mesh_terms: D061725:Accelerometry / Q000295:instrumentation*; D000328:Adult; D000465:Algorithms; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D011187:Posture; D016138:Walking; D055815:Young Adult