title: Comparison of two Actigraph models for assessing free-living physical activity in Indian adolescents.
abstract: This aim of this study was to compare the new Actigraph (GT1M) with the widely used Model 7164. Seven days of free-living physical activity were measured simultaneously using both the Model 7164 and GT1M in 30 Indian adolescents (mean age 15.8 years, s = 0.6). The GT1M was on average 9% lower per epoch than model 7164, thus a correction factor of 0.91 is suggested for comparison between the two monitors. The differences between monitors increased in magnitude with intensity of activity (P < 0.001) but remained randomly distributed (r = 0.01, P = 0.96). No significant difference was observed between monitors for time spent in moderate (P = 0.31) and vigorous (P = 0.34) physical activity when using the same epoch length. The Model 7164 classified less time as sedentary (P < 0.001) and more time as light-intensity activity (P < 0.001) than the GT1M. In conclusion, data from the GT1M can be compared with historical data using average counts per minute with a correction factor, and the two models might be comparable for assessing time spent in moderate to vigorous physical activity in children when using the same epoch length.
authors.affiliation: MRC Epidemiology Unit, Institute of Metabolic Science, Box 285 Addenbrooke's Hospital, Cambridge CB2 0QQ, UK. kirsten.corder@mrc-epid.cam.ac.uk
authors.forename: Kirsten
authors.initials: K
authors.lastname: Corder
authors.forename: Søren
authors.initials: S
authors.lastname: Brage
authors.forename: Ambady
authors.initials: A
authors.lastname: Ramachandran
authors.forename: Chamukuttan
authors.initials: C
authors.lastname: Snehalatha
authors.forename: Nicholas
authors.initials: N
authors.lastname: Wareham
authors.forename: Ulf
authors.initials: U
authors.lastname: Ekelund
mesh_terms: D000054:Acceleration; D000293:Adolescent; D015444:Exercise; D005080:Exercise Test; D005260:Female; D006801:Humans; D007194:India; D008297:Male; D008954:Models, Biological; D008962:Models, Theoretical; D018670:Monitoring, Ambulatory / Q000295:instrumentation* / Q000379:methods; D008991:Monitoring, Physiologic; D009043:Motor Activity / Q000502:physiology*; D009068:Movement / Q000502:physiology*