title: Acute respiratory muscle unloading by normoxic helium-O₂ breathing reduces the O₂ cost of cycling and perceived exertion in obese adolescents.
abstract: OBJECTIVE
  In obesity, an increased work of breathing contributes to a higher O2 cost of exercise and negatively affects exercise tolerance. The purpose of the study was to determine whether, in obese adolescents, acute respiratory muscle unloading via normoxic helium-O2 breathing reduces the O2 cost of cycling and perceived exertion.
  
  
  METHODS
  Nine males [age 16.8 ± 1.6 (x ± SD) years, body mass 109.9 ± 15.0 kg] performed on a cycle ergometer, breathing room air (AIR) or a 21 % O2-79 % helium mixture (He-O2): an incremental exercise, for determination of [Formula: see text]O2 peak and gas exchange threshold (GET); 12 min constant work rate (CWR) exercises at 70 % of GET (<GET) and 120 % of GET (>GET) determined in AIR.
  
  
  RESULTS
  [Formula: see text]O2 peak was not different in the two conditions. From the 3rd to the 12th minute of exercise (both during CWR < GET and CWR > GET), [Formula: see text]O2 was lower in He-O2 vs. AIR (end-exercise values: 1.40 ± 0.14 vs. 1.57 ± 0.22 L min(-1) <GET, and 2.23 ± 0.31 vs. 2.54 ± 0.27 L min(-1) >GET). During CWR > GET in AIR, [Formula: see text]O2 linearly increased from the 3rd to the 12th minute of exercise, whereas no substantial increase was observed in He-O2. The O2 cost of cycling was ~10 % (<GET) and ~15 % (>GET) lower in He-O2 vs. AIR. Heart rate and ratings of perceived exertion for dyspnea/respiratory discomfort and leg effort were lower in He-O2.
  
  
  CONCLUSIONS
  In obese adolescents, acute respiratory muscle unloading via He-O2 breathing lowered the O2 cost of cycling and perceived exertion during submaximal moderate- and heavy-intensity exercise.
authors.affiliation: Department of Medical and Biological Sciences, University of Udine, Piazzale M. Kolbe 4, 33100, Udine, Italy.
authors.forename: Desy
authors.initials: D
authors.lastname: Salvadego
authors.forename: Alessandro
authors.initials: A
authors.lastname: Sartorio
authors.forename: Fiorenza
authors.initials: F
authors.lastname: Agosti
authors.forename: Gabriella
authors.initials: G
authors.lastname: Tringali
authors.forename: Alessandra
authors.initials: A
authors.lastname: Patrizi
authors.forename: Antonella Lo
authors.initials: AL
authors.lastname: Mauro
authors.forename: Andrea
authors.initials: A
authors.lastname: Aliverti
authors.forename: Bruno
authors.initials: B
authors.lastname: Grassi
mesh_terms: D000293:Adolescent; D015444:Exercise / Q000502:physiology*; D006371:Helium / Q000378:metabolism*; D006801:Humans; D008297:Male; D009765:Obesity / Q000378:metabolism / Q000503:physiopathology*; D010100:Oxygen / Q000378:metabolism; D010101:Oxygen Consumption; D010465:Perception; D005082:Physical Exertion; D012119:Respiration; D012132:Respiratory Muscles / Q000502:physiology*
chemical_list: D006371:Helium; D010100:Oxygen