title: Cross validation of ROC generated thresholds for field assessed aerobic fitness related to weight status and cardiovascular disease risk in Portuguese young people.
abstract: OBJECTIVE
  To examine the efficacy of aerobic fitness thresholds in predicting weight status and cardiovascular disease risk (CVD) in young people.
  
  
  METHODS
  A cross-sectional school-based study was conducted on 414 Portuguese young people (235 girls and 179 boys) aged 10-16 years (Mean age ± SD = 13.6 ± 1. 8 years). Height and mass were assessed to determine body mass index (BMI). The 20 m multistage shuttle-fitness test (MSFT) was used as an estimate of aerobic fitness. Capillary blood sampling was used to determine: total cholesterol, triglycerides, high-, and low-density lipoprotein. These were combined with measures of systolic blood pressure as z-scores and summed to create a CVD risk score.
  
  
  RESULTS
  Analysis of covariance, controlling for sexual maturation, indicated a significant main effect for BMI as a result of fitness category (P = 0.0001). When applied to CVD risk data, there was no difference between "fit" and "unfit" groups (P = 0.136). Subsequent receiver operating curve (ROC) analysis indicated significant diagnostic accuracy of 20 mMSFT performance for boys and girls (both P = 0.0001) with subsequent cut-offs of estimated VO2 peak of 49.5 ml kg(-1) min(-1) for girls and 47.7 ml kg(-1) min(-1) for boys. When applied to BMI and CVD risk data, there was a significant main effect as a result of fitness category for BMI (P = 0.0001) and CVD risk score (P = 0.0001).
  
  
  CONCLUSIONS
  Recently established cut-points proposed by Boddy et al. (Boddy et al. [2012]: PLoS One 7(9): e45755) show validity in distinguishing between weight status but not CVD risk in Portuguese young people. Alternative ROC generated cut points significantly predicted BMI and CVD risk in this sample.
authors.affiliation: Sport and Exercise Applied Research Group, Faculty of Health and Life Sciences, Coventry University, Coventry, United Kingdom.
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Duncan
authors.forename: Susana
authors.initials: S
authors.lastname: Vale
authors.forename: Maria Paula
authors.initials: MP
authors.lastname: Santos
authors.forename: José Carlos
authors.initials: JC
authors.lastname: Ribeiro
authors.forename: Jorge
authors.initials: J
authors.lastname: Mota
mesh_terms: D000293:Adolescent; D001774:Blood Chemical Analysis; D001794:Blood Pressure; D015992:Body Mass Index; D001835:Body Weight; D002318:Cardiovascular Diseases / Q000453:epidemiology*; D002648:Child; D003430:Cross-Sectional Studies; D005080:Exercise Test; D005260:Female; D006801:Humans; D008297:Male; D010809:Physical Fitness; D011174:Portugal / Q000453:epidemiology; D012372:ROC Curve; D012307:Risk Factors