title: Physical activity, cardiovascular fitness, and insulin sensitivity among U.S. adolescents: the National Health and Nutrition Examination Survey, 1999-2002.
abstract: OBJECTIVE
  The purpose of this study was to examine the association of physical activity and cardiovascular fitness (CVF) with insulin sensitivity in a nationally representative sample of U.S. youth.
  
  
  METHODS
  The study included 1,783 U.S. adolescents (11% Mexican American, 14% non-Hispanic black, 63% non-Hispanic white, and 12% other) aged 12-19 years who were examined in the 1999-2002 National Health and Nutrition Examination Survey. Physical activity was assessed by questionnaire and expressed in units of MET hours per week. Predicted maximal oxygen uptake (Vo(2max), expressed in milliliters per kilogram of body weight per minute), a measure of CVF, was determined by a submaximal multistage treadmill test. Insulin sensitivity was defined by the Quantitative Insulin Sensitivity Check Index.
  
  
  RESULTS
  Boys were more likely than girls to be highly active (>or=30 MET h/week; 51 vs. 37%, P < 0.001) and had higher levels of CVF (mean Vo(2max) 47 vs. 39 ml x kg(-1) x min(-1), P < 0.001). Sex-specific multiple regression models controlled for age, race/ethnicity, and BMI showed that in boys, high levels of physical activity and high levels of CVF were significantly and positively associated with insulin sensitivity (beta = 0.84, P < 0.001 and beta = 0.82, P = 0.01, respectively). Among girls, insulin sensitivity was not significantly associated with physical activity or with CVF but was inversely and significantly associated with BMI.
  
  
  CONCLUSIONS
  Increasing physical activity and CVF may have an independent effect of improving insulin sensitivity among boys. For girls, the primary role of physical activity may be in weight maintenance.
authors.affiliation: Division of Diabetes Translation, National Center for Chronic Disease Prevention and Health Promotion, Centers for Disease Control and Prevention, 4770 Buford Highway, NE MS-K10, Atlanta, GA 30341, USA. gai5@cdc.gov
authors.forename: Giuseppina
authors.initials: G
authors.lastname: Imperatore
authors.forename: Yiling J
authors.initials: YJ
authors.lastname: Cheng
authors.forename: Desmond E
authors.initials: DE
authors.lastname: Williams
authors.forename: Janet
authors.initials: J
authors.lastname: Fulton
authors.forename: Edward W
authors.initials: EW
authors.lastname: Gregg
mesh_terms: D000293:Adolescent; D001786:Blood Glucose / Q000378:metabolism; D002320:Cardiovascular Physiological Phenomena; D015444:Exercise / Q000502:physiology*; D005080:Exercise Test; D005260:Female; D006339:Heart Rate; D006801:Humans; D007328:Insulin / Q000097:blood*; D007333:Insulin Resistance; D016014:Linear Models; D008297:Male
chemical_list: D001786:Blood Glucose; D007328:Insulin