title: Altered gas-exchange at peak exercise in obese adolescents: implications for verification of effort during cardiopulmonary exercise testing.
abstract: BACKGROUND
  Cardiopulmonary exercise testing is advised ahead of exercise intervention in obese adolescents to assess medical safety of exercise and physical fitness. Optimal validity and reliability of test results are required to identify maximal exercise effort. As fat oxidation during exercise is disturbed in obese individuals, it remains an unresolved methodological issue whether the respiratory gas exchange ratio (RER) is a valid marker for maximal effort during exercise testing in this population.
  
  
  METHODS
  RER during maximal exercise testing (RERpeak), and RER trajectories, was compared between obese and lean adolescents and relationships between RERpeak, RER slope and subject characteristics (age, gender, Body Mass Index [BMI], Tanner stage, physical activity level) were explored. Thirty-four obese (BMI: 35.1±5.1 kg/m²) and 18 lean (BMI: 18.8±1.9 kg/m²) adolescents (aged 12-18 years) performed a maximal cardiopulmonary exercise test on bike, with comparison of oxygen uptake (VO2), heart rate (HR), expiratory volume (VE), carbon dioxide output (VCO2), and cycling power output (W).
  
  
  RESULTS
  RERpeak (1.09±0.06 vs. 1.14±0.06 in obese vs. lean adolescents, respectively) and RER slope (0.03±0.01 vs. 0.05±0.01 per 10% increase in VO2, in obese vs. lean adolescents, respectively) was significantly lower in obese adolescents, and independently related to BMI (P<0.05). Adjusted for HRpeak and VEpeak, RERpeak and RER slope remained significantly lower in obese adolescents (P<0.05). RER trajectories (in relation to %VO2peak and %Wpeak) were significantly different between groups (P<0.001).
  
  
  CONCLUSIONS
  RERpeak is significantly lowered in obese adolescents. This may have important methodological implications for cardiopulmonary exercise testing in this population.
authors.affiliation: REVAL (Rehabilitation Research Center), BIOMED (Biomedical Research Center), Faculty of Medicine and Life Sciences, Hasselt University, Diepenbeek, Belgium.
authors.forename: Nastasia
authors.initials: N
authors.lastname: Marinus
authors.affiliation: Faculty of Medicine and Life Sciences, Hasselt University, Hasselt, Belgium.
authors.forename: Liene
authors.initials: L
authors.lastname: Bervoets
authors.affiliation: REVAL (Rehabilitation Research Center), BIOMED (Biomedical Research Center), Faculty of Medicine and Life Sciences, Hasselt University, Diepenbeek, Belgium.|Department of Pediatrics, Jessa Hospital, Hasselt, Belgium.
authors.forename: Guy
authors.initials: G
authors.lastname: Massa
authors.affiliation: REVAL (Rehabilitation Research Center), BIOMED (Biomedical Research Center), Faculty of Medicine and Life Sciences, Hasselt University, Diepenbeek, Belgium.
authors.forename: Kenneth
authors.initials: K
authors.lastname: Verboven
authors.affiliation: REVAL (Rehabilitation Research Center), BIOMED (Biomedical Research Center), Faculty of Medicine and Life Sciences, Hasselt University, Diepenbeek, Belgium.
authors.forename: An
authors.initials: A
authors.lastname: Stevens
authors.affiliation: Child Development and Exercise Center, Wilhelmina Children's Hospital, University Medical Center Utrecht, Utrecht, The Netherlands.
authors.forename: Tim
authors.initials: T
authors.lastname: Takken
authors.affiliation: REVAL (Rehabilitation Research Center), BIOMED (Biomedical Research Center), Faculty of Medicine and Life Sciences, Hasselt University, Diepenbeek, Belgium - dominique.hansen@uhasselt.be.|Heart Center Hasselt, Jessa Hospital, Hasselt, Belgium.
authors.forename: Dominique
authors.initials: D
authors.lastname: Hansen
mesh_terms: D000293:Adolescent; D015992:Body Mass Index; D016022:Case-Control Studies; D002648:Child; D015444:Exercise / Q000502:physiology*; D005080:Exercise Test / Q000379:methods*; D005260:Female; D006801:Humans; D008297:Male; D009765:Obesity / Q000503:physiopathology*; D010809:Physical Fitness / Q000502:physiology; D011659:Pulmonary Gas Exchange / Q000502:physiology*; D015203:Reproducibility of Results; D012129:Respiratory Function Tests