title: Accelerometer Data Collection and Processing Criteria to Assess Physical Activity and Other Outcomes: A Systematic Review and Practical Considerations.
abstract: BACKGROUND
  Accelerometers are widely used to measure sedentary time, physical activity, physical activity energy expenditure (PAEE), and sleep-related behaviors, with the ActiGraph being the most frequently used brand by researchers. However, data collection and processing criteria have evolved in a myriad of ways out of the need to answer unique research questions; as a result there is no consensus.
  
  
  OBJECTIVE
  The purpose of this review was to: (1) compile and classify existing studies assessing sedentary time, physical activity, energy expenditure, or sleep using the ActiGraph GT3X/+ through data collection and processing criteria to improve data comparability and (2) review data collection and processing criteria when using GT3X/+ and provide age-specific practical considerations based on the validation/calibration studies identified.
  
  
  METHODS
  Two independent researchers conducted the search in PubMed and Web of Science. We included all original studies in which the GT3X/+ was used in laboratory, controlled, or free-living conditions published from 1 January 2010 to the 31 December 2015.
  
  
  RESULTS
  The present systematic review provides key information about the following data collection and processing criteria: placement, sampling frequency, filter, epoch length, non-wear-time, what constitutes a valid day and a valid week, cut-points for sedentary time and physical activity intensity classification, and algorithms to estimate PAEE and sleep-related behaviors. The information is organized by age group, since criteria are usually age-specific.
  
  
  CONCLUSIONS
  This review will help researchers and practitioners to make better decisions before (i.e., device placement and sampling frequency) and after (i.e., data processing criteria) data collection using the GT3X/+ accelerometer, in order to obtain more valid and comparable data.
  CRD42016039991.
authors.affiliation: PROFITH "PROmoting FITness and Health through physical activity" Research Group, Department of Physical Education and Sports, Faculty of Sport Sciences, University of Granada, Ctra. Alfacar s/n, 18011, Granada, Spain. jairohm@ugr.es.
authors.forename: Jairo H
authors.identifier: http://orcid.org/0000-0003-0366-6935
authors.initials: JH
authors.lastname: Migueles
authors.affiliation: PROFITH "PROmoting FITness and Health through physical activity" Research Group, Department of Physical Education and Sports, Faculty of Sport Sciences, University of Granada, Ctra. Alfacar s/n, 18011, Granada, Spain.
authors.forename: Cristina
authors.initials: C
authors.lastname: Cadenas-Sanchez
authors.affiliation: Department of Sport Medicine, Norwegian School of Sport Sciences, Oslo, Norway.|MRC Epidemiology Unit, Institute of Metabolic Science, University of Cambridge, Addenbrooke's Hospital Hills Road, Cambridge, UK.
authors.forename: Ulf
authors.initials: U
authors.lastname: Ekelund
authors.affiliation: Department of Biosciences and Nutrition, Karolinska Institutet, Huddinge, Sweden.
authors.forename: Christine
authors.initials: C
authors.lastname: Delisle Nyström
authors.affiliation: PROFITH "PROmoting FITness and Health through physical activity" Research Group, Department of Physical Education and Sports, Faculty of Sport Sciences, University of Granada, Ctra. Alfacar s/n, 18011, Granada, Spain.
authors.forename: Jose
authors.initials: J
authors.lastname: Mora-Gonzalez
authors.affiliation: Department of Biosciences and Nutrition, Karolinska Institutet, Huddinge, Sweden.|Department of Clinical and Experimental Medicine, Faculty of the Health Sciences, Linköping University, Linköping, Sweden.
authors.forename: Marie
authors.initials: M
authors.lastname: Löf
authors.affiliation: Department of Nutrition and Food Science, University of the Basque Country, UPV-EHU, Vitoria-Gasteiz, Spain.
authors.forename: Idoia
authors.initials: I
authors.lastname: Labayen
authors.affiliation: PROFITH "PROmoting FITness and Health through physical activity" Research Group, Department of Physical Education and Sports, Faculty of Sport Sciences, University of Granada, Ctra. Alfacar s/n, 18011, Granada, Spain.|Department of Biosciences and Nutrition, Karolinska Institutet, Huddinge, Sweden.
authors.forename: Jonatan R
authors.initials: JR
authors.lastname: Ruiz
authors.affiliation: PROFITH "PROmoting FITness and Health through physical activity" Research Group, Department of Physical Education and Sports, Faculty of Sport Sciences, University of Granada, Ctra. Alfacar s/n, 18011, Granada, Spain.|Department of Biosciences and Nutrition, Karolinska Institutet, Huddinge, Sweden.
authors.forename: Francisco B
authors.initials: FB
authors.lastname: Ortega
mesh_terms: D061725:Accelerometry; D000293:Adolescent; D000368:Aged; D002648:Child; D004734:Energy Metabolism; D015444:Exercise; D005260:Female; D006801:Humans; D007231:Infant, Newborn; D008297:Male; D015203:Reproducibility of Results; D057185:Sedentary Behavior; D012890:Sleep / Q000502:physiology
keywords: Indirect Calorimetry; Multivariate Adaptive Regression Spline; Physical Activity Intensity; Sedentary Time; Vigorous Physical Activity