title: Characterizing cerebral and locomotor muscle oxygenation to incremental ramp exercise in healthy children: relationship with pulmonary gas exchange.
abstract: OBJECTIVE
  To characterize the oxygenation responses at cerebral and locomotor muscle level to incremental exercise in children and to assess the interrelationship with the pulmonary gas exchange responses.
  
  
  METHODS
  Eighteen children (9 boys, 9 girls) (mean age 10.9 ± 1.0 years) performed incremental cycle ramp exercise to exhaustion. The concentration of cerebral and muscle oxygenated (O2Hb) and deoxygenated (HHb) hemoglobin (by means of near-infrared spectroscopy) and pulmonary gas exchange was recorded. Cerebral and muscle O2Hb and HHb values were expressed as functions of oxygen uptake (VO2) and breakpoints were detected by means of double linear model analysis. The respiratory compensation point (RCP) was determined. The breakpoints in cerebral and muscle O2Hb and HHb were compared and correlated to RCP.
  
  
  RESULTS
  The subjects reached peak power output of 105 ± 18 W and VO2peakof 43.5 ± 7.0 ml min-1kg-1. Cerebral O2Hb increased to an intensity of 89.4 ± 5.5 %VO2peak, where a breakpoint occurred at which cerebral O2Hb started to decrease. Cerebral HHb increased slightly to 88.1 ± 4.8 %VO2peak, at which the increase was accelerated. Muscle HHb increased to 90.5 ± 4.8 %VO2peakwhere a leveling-off occurred. RCP occurred at 89.3 ± 4.3 %VO2peak. The breakpoints and RCP did not differ significantly (P = 0.13) and were strongly correlated (r > 0.70, P < 0.05). There were no differences between boys and girls (P = 0.43) and there was no significant correlation with VO2peak(P > 0.05).
  
  
  CONCLUSIONS
  It was shown that cerebral and muscle oxygenation responses undergo significant changes as work rate increases and show breakpoints in the ongoing response at high intensity (85-95 %VO2peak). These breakpoints are strongly interrelated and associated with changes in pulmonary gas exchange.
authors.affiliation: Department of Pediatric Cardiology, Ghent University Hospital, Ghent, Belgium.
authors.forename: Kristof
authors.initials: K
authors.lastname: Vandekerckhove
authors.affiliation: Department of Pediatric Cardiology, Ghent University Hospital, Ghent, Belgium.
authors.forename: Ilse
authors.initials: I
authors.lastname: Coomans
authors.affiliation: Department of Anesthesiology, Ghent University Hospital, Ghent, Belgium.
authors.forename: Annelies
authors.initials: A
authors.lastname: Moerman
authors.affiliation: Department of Pediatric Cardiology, Ghent University Hospital, Ghent, Belgium.
authors.forename: Daniel
authors.initials: D
authors.lastname: De Wolf
authors.affiliation: Department of Movement and Sports Sciences, Ghent University, Watersportlaan 2, 9000, Ghent, Belgium. Jan.boone@ugent.be.|Center of Sports Medicine, Ghent University Hospital, Ghent, Belgium. Jan.boone@ugent.be.
authors.forename: Jan
authors.identifier: http://orcid.org/0000-0002-8485-6169
authors.initials: J
authors.lastname: Boone
mesh_terms: D001921:Brain / Q000502:physiology*; D002648:Child; D003198:Computer Simulation; D005080:Exercise Test; D005260:Female; D006801:Humans; D007866:Leg / Q000502:physiology; D008124:Locomotion / Q000502:physiology*; D008297:Male; D008954:Models, Biological; D018482:Muscle, Skeletal / Q000502:physiology*; D010100:Oxygen / Q000378:metabolism / Q000502:physiology; D010101:Oxygen Consumption / Q000502:physiology*; D005082:Physical Exertion / Q000502:physiology*; D011659:Pulmonary Gas Exchange / Q000502:physiology*; D013223:Statistics as Topic
chemical_list: D010100:Oxygen
keywords: Breakpoints; Oxygen demand; Oxygen supply; Respiratory compensation point; Whole-body VO2