title: Independent and combined association of muscle strength and cardiorespiratory fitness in youth with insulin resistance and β-cell function in young adulthood: the European Youth Heart Study.
abstract: OBJECTIVE
  To examine the independent and combined association of isometric muscle strength of the abdomen and back and cardiorespiratory fitness (CRF) in youth with indices of glucose metabolism in young adulthood among boys and girls from the European Youth Heart Study.
  
  
  METHODS
  We used data from a population-based prospective cohort study among youth followed up for up to 12 years (n = 317). In youth, maximal voluntary contractions during isometric back extension and abdominal flexion were determined using a strain-gauge dynamometer and CRF was obtained from a maximal cycle ergometer test. Insulin resistance (homeostasis model assessment of insulin resistance [HOMA-IR]) and β-cell function (homeostasis model assessment of β-cell function [HOMA-B]) were estimated from fasting serum insulin and glucose that were obtained in youth and at follow-up in young adulthood.
  
  
  RESULTS
  For each 1-SD difference in isometric muscle strength (0.16 N/kg) in youth, fasting insulin, HOMA-IR, and HOMA-B in young adulthood changed by -11.3% (95% CI -17.0 to -5.2), -12.2% (-18.2 to -5.7), and -8.9% (-14.4 to -3.0), respectively, in young adulthood after adjustment for CRF and personal lifestyle and demographic factors. Results for CRF were very similar in magnitude, and the magnitude of associations for both exposures was unchanged with additional adjustment for general or abdominal adiposity in youth. Combined associations of muscle strength and CRF with fasting insulin, HOMA-IR, and HOMA-B were additive, and adolescents in the highest sex-specific tertile for both isometric muscle strength and CRF had the lowest levels of these glucose metabolism outcomes.
  
  
  CONCLUSIONS
  Increasing muscle strength and CRF should be targets in youth primordial prevention strategies of insulin resistance and β-cell dysfunction.
authors.affiliation: Institute of Sport Science and Clinical Biomechanics, Research Unit for Exercise Epidemiology, Centre of Research in Childhood Health, University of Southern Denmark, Odense M, Denmark. agroentved@health.sdu.dk
authors.forename: Anders
authors.initials: A
authors.lastname: Grøntved
authors.forename: Mathias
authors.initials: M
authors.lastname: Ried-Larsen
authors.forename: Ulf
authors.initials: U
authors.lastname: Ekelund
authors.forename: Karsten
authors.initials: K
authors.lastname: Froberg
authors.forename: Søren
authors.initials: S
authors.lastname: Brage
authors.forename: Lars B
authors.initials: LB
authors.lastname: Andersen
mesh_terms: D000293:Adolescent; D001786:Blood Glucose / Q000378:metabolism; D005260:Female; D006801:Humans; D007328:Insulin / Q000097:blood; D007333:Insulin Resistance / Q000502:physiology*; D050417:Insulin-Secreting Cells / Q000378:metabolism / Q000502:physiology*; D008297:Male; D053580:Muscle Strength / Q000502:physiology*; D010809:Physical Fitness / Q000502:physiology; D011446:Prospective Studies; D044465:White People
chemical_list: D001786:Blood Glucose; D007328:Insulin