title: Evaluating the Responsiveness of Accelerometry to Detect Change in Physical Activity.
abstract: The responsiveness to change of the Actical and ActiGraph accelerometers was assessed in children and adolescents. Participants (n=208) aged 6-16 years completed two simulated free-living protocols, one with primarily light-to-moderate physical activities (PA) and one with mostly moderate-to-vigorous PA. Time in sedentary, light, moderate, and vigorous PA was estimated using 8 previously developed cut-points (4 for Actical and 4 for ActiGraph) and 15-s and 30-s epochs. Accelerometer responsiveness for detecting differences in PA between protocols was assessed using standardized response means (SRM). SRM values ≥0.8 represented high responsiveness to change. Both accelerometers showed high responsiveness for all PA intensities (SRMs = 1.2-4.7 for Actical and 1.1-3.3 for ActiGraph). All cut-points and epoch lengths yielded high responsiveness, and choice of cut-points and epoch length had little effect on responsiveness. Thus, both the Actical and ActiGraph can detect change in PA in a simulated free-living setting, irrespective of cut-point selection or epoch length.
authors.affiliation: Department of Kinesiology, Michigan State University, East Lansing, Michigan.
authors.forename: Alexander H
authors.initials: AH
authors.lastname: Montoye
authors.affiliation: Department of Kinesiology, Michigan State University, East Lansing, Michigan.
authors.forename: Karin A
authors.initials: KA
authors.lastname: Pfeiffer
authors.affiliation: Movement Science Department, Grand Valley State University, Allendale, Michigan.
authors.forename: Darijan
authors.initials: D
authors.lastname: Suton
authors.affiliation: School of Human Movement Studies, The University of Queensland, St. Lucia, Queensland, Australia.
authors.forename: Stewart G
authors.initials: SG
authors.lastname: Trost
keywords: ActiGraph; Actical; accelerometer; children; sensitivity