title: A methodological model for collecting high-quality data on physical activity in developing settings-the experience of the 1993 Pelotas (Brazil) Birth Cohort study.
abstract: BACKGROUND
  Prospective studies on physical activity (PA), diet, and body composition in adolescents are lacking, particularly outside high-income countries.
  
  
  OBJECTIVE
  To describe the methods used to assess these variables in the 1993 Pelotas (Brazil) Birth Cohort and to discuss the fieldwork challenges faced and alternatives to overcome them.
  
  
  METHODS
  In 2006-07 a subsample of the 1993 Pelotas cohort was revisited. PA was estimated using questionnaires, a combined heart-rate and motion sensor (Acti-Heart), and the ActiGraph GT1M accelerometer. Diet was investigated by questionnaire. Total body water was determined by stable isotopes. Thirty individuals had their total energy expenditure assessed by doubly labeled water. All data were collected at participants' home.
  
  
  RESULTS
  The logistics of the fieldwork and the difficulties in undertaking the study and alternatives to overcome them are presented. Preliminary analyses show that 511 individuals were traced (response rate = 90.0%). Compliance of both adolescents and their families for the motion sensors and body-composition measurements was excellent.
  
  
  CONCLUSIONS
  The authors conclude that it is feasible to carry out high-quality studies on PA in developing countries. They hope the article will be useful to other researchers interested in carrying out similar studies.
authors: Department of Physical Education, State University of Londrina, Brazil.
authors: Felipe Fossati
authors: FF
authors: Reichert
authors: Ana Maria Batista
authors: AM
authors: Menezes
authors: Jonathan Charles
authors: JC
authors: Kingdom Wells
authors: Elf
authors: E
authors: Ekelund
authors: Fabiane Machado
authors: FM
authors: Rodrigues
authors: Pedro Curi
authors: PC
authors: Hallal
mesh_terms: D000886:Anthropometry; D015992:Body Mass Index; D001834:Body Water; D001938:Brazil; D015331:Cohort Studies; D003625:Data Collection / Q000592:standards; D003906:Developing Countries; D004734:Energy Metabolism; D006801:Humans; D008962:Models, Theoretical; D008991:Monitoring, Physiologic / Q000295:instrumentation; D009043:Motor Activity; D012107:Research Design; D011795:Surveys and Questionnaires