Stride variability measures derived from wrist- and hip-worn accelerometers

TL;DR

This study introduces novel measures of stride variability from raw accelerometry data, comparing wrist and hip placements, and links these measures to gait performance in elderly individuals.

Contribution

It defines and estimates two new gait variability measures, AD and PD, from raw accelerometry data and evaluates their sensitivity to device placement and association with gait performance.

Findings

AD and PD are significantly associated with gait speed.

Device placement affects the sensitivity of variability measures.

New measures provide detailed insights into gait variability.

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 gait measures of temporal stride-to-stride 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 400 meter walk test. We also show that AD and PD have a statistically significant association with the gait speed and sit-to-stand test performance