title: Concurrent Validity of Wearable Activity Trackers Under Free-Living Conditions.
abstract: Brooke, SM, An, H-S, Kang, S-K, Noble, JM, Berg, KE, and Lee, J-M. Concurrent validity of wearable activity trackers under free-living conditions. J Strength Cond Res 31(4): 1097-1106, 2017-The purpose of this study is to evaluate the concurrent validity of wearable activity trackers in energy expenditure (EE) and sleep period time (SPT) under free-living conditions. Ninety-five (28.5 ± 9.8 years) healthy men (n = 34) and women (n = 61) participated in this study. The total EE and SPT were measured using 8 monitors: Nike+ FuelBand SE (NFB), Garmin VivoFit (VF), Misfit Shine (MF), Fitbit Flex (FF), Jawbone UP (JU), Polar Loop (PL), Fitbit Charge HR (FC), and SenseWear Armband Mini (SWA) (criterion measures: SWA for EE and a sleep log for SPT). The mean absolute percent error (MAPE) for EE was 13.0, 15.2, 15.5, 16.1, 16.2, 22.8, and 24.5% for PL, MF, FF, NFB, FC, JU, and VF, respectively. Mean absolute percent errors were calculated for SPT to be 4.0, 8.8, 10.2, 11.5, 12.9, 13.6, 17.5, and 21.61% for VF, FF, JU, FC, MF, SWA laying down, PL, and SWA, respectively. Concurrent validity was examined using equivalence testing on EE (equivalence zone: 2,889.7-3,531.9 kcal); 2 trackers fell short of falling in the zone: PL (2,714.4-3,164.8 kcal) and FC (2,473.8-3,066.5 kcal). For SPT (equivalence zone: 420.6-514.0 minutes), several monitors fell in the zone: PL (448.3-485.6 minutes), MS (442.8-492.2 minutes), and FF (427.7-486.7 minutes). This study suggests that the PL and FC provide a reasonable estimate of EE under free-living conditions. The PL, FC, and MF were the most valid monitors used for measuring SPT.
authors.affiliation: 1School of Health, Physical Education, and Recreation, University of Nebraska Omaha, Omaha, Nebraska; and 2Graduate School of Education, Yong-In University, Yongin-si, South Korea.
authors.forename: Skyler M
authors.initials: SM
authors.lastname: Brooke
authors.forename: Hyun-Sung
authors.initials: HS
authors.lastname: An
authors.forename: Seoung-Ki
authors.initials: SK
authors.lastname: Kang
authors.forename: John M
authors.initials: JM
authors.lastname: Noble
authors.forename: Kris E
authors.initials: KE
authors.lastname: Berg
authors.forename: Jung-Min
authors.initials: JM
authors.lastname: Lee
mesh_terms: D000328:Adult; D004734:Energy Metabolism / Q000502:physiology; D005260:Female; D000072936:Fitness Trackers / Q000592:standards*; D006801:Humans; D008297:Male; D015203:Reproducibility of Results; D012890:Sleep / Q000502:physiology; D055815:Young Adult