title: Stride variability measures derived from wrist- and hip-worn accelerometers.
abstract: Many epidemiological and clinical studies use accelerometry to objectively measure physical activity using the activity counts, vector magnitude, or number of steps. These measures use just a fraction of the information in the raw accelerometry data as they are typically summarized at the minute level. To address this problem, we define and estimate two measures of temporal stride-to-stride gait variability based on raw accelerometry data: Amplitude Deviation (AD) and Phase Deviation (PD). We explore the sensitivity of our approach to on-body placement of the accelerometer by comparing hip, left and right wrist placements. We illustrate the approach by estimating AD and PD in 46 elderly participants in the Developmental Epidemiologic Cohort Study (DECOS) who worn accelerometers during a 400m walk test. We also show that AD and PD have a statistically significant association with the gait speed and sit-to-stand test performance.
authors.affiliation: Department of Biostatistics, Johns Hopkins Bloomberg School of Public Health, 615 N. Wolfe Street, Baltimore, MD 21205, United States. Electronic address: jurbane2@jhu.edu.
authors.forename: Jacek K
authors.initials: JK
authors.lastname: Urbanek
authors.affiliation: Department of Epidemiology and Biostatistics, School of Public Health, Indiana University, Bloomington, United States.
authors.forename: Jaroslaw
authors.initials: J
authors.lastname: Harezlak
authors.affiliation: Center for Aging and Population Health, Department of Epidemiology, Graduate School of Public Health, University of Pittsburgh, United States.
authors.forename: Nancy W
authors.initials: NW
authors.lastname: Glynn
authors.affiliation: Laboratory of Epidemiology, Demography, and Biometry, National Institute on Aging, United States.
authors.forename: Tamara
authors.initials: T
authors.lastname: Harris
authors.affiliation: Department of Biostatistics, Johns Hopkins Bloomberg School of Public Health, 615 N. Wolfe Street, Baltimore, MD 21205, United States.
authors.forename: Ciprian
authors.initials: C
authors.lastname: Crainiceanu
authors.affiliation: Department of Biostatistics, Johns Hopkins Bloomberg School of Public Health, 615 N. Wolfe Street, Baltimore, MD 21205, United States.
authors.forename: Vadim
authors.initials: V
authors.lastname: Zipunnikov
mesh_terms: D061725:Accelerometry; D000368:Aged; D000375:Aging; D015331:Cohort Studies; D015444:Exercise; D005260:Female; D005684:Gait; D006621:Hip Joint / Q000502:physiology*; D006801:Humans; D008297:Male; D016138:Walking; D014955:Wrist Joint / Q000502:physiology*
keywords: Accelerometry; Gait asymmetry; Stride variability; Wearable computing