title: Relationship between percentage of VO2max and type of physical activity in obese and non-obese adolescents.
abstract: OBJECTIVE
  The objective of the present study was to determine oxygen uptake (VO(2)) and percentage of maximum oxygen uptake (%VO2max) in obese and non-obese adolescents during various activities in standardised conditions, and the corresponding %VO2max in free-living conditions.
  
  
  METHODS
  Twenty-seven obese and 50 non-obese adolescents aged 12 to 16 years participated in this study. Body composition was assessed by bioelectrical impedance analysis and dual energy X-ray absorptiometry (DXA), VO2max by treadmill tests, VO2 corresponding to various activities by whole body calorimetry, and time and % VO2max corresponding to various activities in free-living conditions using the heart-rate recording method and a physical activity diary.
  
  
  RESULTS
  VO2max (l/min) was 27.4% higher in obese than in non-obese subjects (p<0.001), but not significantly different after adjustment for fat-free mass (FFM). In the whole body calorimeters, with the same activity program, % VO2max corresponding to sleep and sedentary activities were lower in obese than in non-obese girls (-15.1% and -12.3%, p<0.05), but not significantly different between obese and non-obese boys. However, walking at 4-5-6 km/h corresponded to 47-59% and 71% of VO2max, respectively, in obese, and 34-41% and 48% of VO2max in non-obese subjects (p<0.001). In free-living conditions, moderate physical activities and sports corresponded to 52% vs 35%, and 39% vs 51% of VO2max, respectively, in obese and non-obese adolescents.
  
  
  CONCLUSIONS
  In standardised conditions %VO2max did not correspond to the same type of physical activity in obese compared to non-obese adolescents. Consequently, % VO2max is inadequate for comparing the types of physical activities of obese and non-obese adolescents in free-living conditions.
authors.affiliation: Energy and Protein Metabolism Research Unit, INRA, University of Auvergne, CRNH, Clermont-Ferrand, France.
authors.forename: S
authors.initials: S
authors.lastname: Lazzer
authors.forename: Y
authors.initials: Y
authors.lastname: Boirie
authors.forename: A
authors.initials: A
authors.lastname: Bitar
authors.forename: I
authors.initials: I
authors.lastname: Petit
authors.forename: M
authors.initials: M
authors.lastname: Meyer
authors.forename: M
authors.initials: M
authors.lastname: Vermorel
mesh_terms: D015502:Absorptiometry, Photon; D000293:Adolescent; D000704:Analysis of Variance; D001823:Body Composition; D002648:Child; D017097:Electric Impedance; D004734:Energy Metabolism; D005260:Female; D006339:Heart Rate / Q000502:physiology; D006801:Humans; D008297:Male; D009043:Motor Activity / Q000502:physiology*; D009765:Obesity / Q000503:physiopathology*; D010101:Oxygen Consumption / Q000502:physiology*