Calibration of Accelerometer Output for Children

Abstract

Understanding the determinants of physical activity behavior in children and youths is essential to the design and implementation of intervention studies to increase physical activity. Objective methods to assess physical activity behavior using various types of motion detectors have been recommended as an alternative to self-report for this population because they are not subject to many of the sources of error associated with children's recall required for self-report measures. This paper reviews the calibration of four different accelerometers used most frequently to assess physical activity and sedentary behavior in children. These accelerometers are the ActiGraph, Actical, Actiwatch, and the RT3 Triaxial Research Tracker. Studies are reviewed that describe the regression modeling approaches used to calibrate these devices using directly measured energy expenditure as the criterion. Point estimates of energy expenditure or count ranges corresponding to different activity intensities from several studies are presented. For a given accelerometer, the count cut points defining the boundaries for 3 and 6 METs vary substantially among the studies reviewed even though most studies include walking, running and free-living activities in the testing protocol. Alternative data processing using the raw acceleration signal is recommended as a possible alternative approach where the actual acceleration pattern is used to characterize activity behavior. Important considerations for defining best practices for accelerometer calibration in children and youths are presented.

Validity of wrist worn accelerometers and comparability between hip and wrist placement sites in estimating physical activity behaviour in preschool children

“…Despite this, given the problems with interpreting energy expenditure in young children, observational methods offer a behavioural approach to calibration as an alternative. In addition, this approach is argued to be valuable in studies of young children, particularly if there is an interest in 'type' or 'patterns' of physical activity (Freedson et al 2005).…”

Measuring physical activity using accelerometry in 13–15-year-old adolescents: the importance of including non-wear activities

“…Using the age-specific equation of Freedson (48) , 57?7 % met the PA recommendations without inclusion of the non-wear activities compared with 64?7 % with inclusion of the nonwear activities.…”

Why are early maturing girls less active? Links between pubertal development, psychological well-being, and physical activity among girls at ages 11 and 13

“…The age-specific count thresholds corresponding to the aforementioned intensity levels were derived from the MET prediction equation developed by Freedson and co-workers (Freedson, Pober, & Janz, 2005;Trost, Pate, Sallis, Freedson, Taylor, Dowda et al, 2002). To accommodate the 30-sec epoch length, count thresholds were divided by 2 (Nilsson, Ekelund, Yngve, & Sjostrom, 2002).…”