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The Journal of Sports Medicine and Physical Fitness 2016 Oct 20


language: English

Altered gas-exchange at peak exercise in obese adolescents: implications for verification of effort during cardiopulmonary exercise testing

Nastasia MARINUS 1, Liene BERVOETS 2, Guy MASSA 1, 3, Kenneth VERBOVEN 1, An STEVENS 1, Tim TAKKEN 4, Dominique HANSEN 1, 5

1 REVAL, Rehabilitation Research Center, BIOMED-Biomedical Research Center, Faculty of Medicine and Life Sciences, Hasselt University, Diepenbeek, Belgium; 2 Faculty of Medicine and Life Sciences, Hasselt University, Hasselt, Belgium; 3 Jessa Hospital, Department of Pediatrics, Hasselt, Belgium; 4 Child Development & Exercise Center, Wilhelmina Children’s Hospital, University Medical Center Utrecht, Utrecht, The Netherlands; 5 Jessa Hospital, Heart Centre Hasselt, Hasselt, Belgium


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).
CONCLUSION: RERpeak is significantly lowered in obese adolescents. This may have important methodological implications for cardiopulmonary exercise testing in this population.

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