title: The interrelationship between muscle oxygenation, muscle activation, and pulmonary oxygen uptake to incremental ramp exercise: influence of aerobic fitness.
abstract: We investigated whether muscle and ventilatory responses to incremental ramp exercise would be influenced by aerobic fitness status by means of a cross-sectional study with a large subject population. Sixty-four male students (age: 21.2 ± 3.2 years) with a heterogeneous peak oxygen uptake (51.9 ± 6.3 mL·min(-1)·kg(-1), range 39.7-66.2 mL·min(-1)·kg(-1)) performed an incremental ramp cycle test (20-35 W·min(-1)) to exhaustion. Breath-by-breath gas exchange was recorded, and muscle activation and oxygenation were measured with surface electromyography and near-infrared spectroscopy, respectively. The integrated electromyography (iEMG), mean power frequency (MPF), deoxygenated [hemoglobin and myoglobin] (deoxy[Hb+Mb]), and total[Hb+Mb] responses were set out as functions of work rate and fitted with a double linear function. The respiratory compensation point (RCP) was compared and correlated with the breakpoints (BPs) (as percentage of peak oxygen uptake) in muscle activation and oxygenation. The BP in total[Hb+Mb] (83.2% ± 3.0% peak oxygen uptake) preceded (P < 0.001) the BP in iEMG (86.7% ± 4.0% peak oxygen uptake) and MPF (86.3% ± 4.1% peak oxygen uptake), which in turn preceded (P < 0.01) the BP in deoxy[Hb+Mb] (88.2% ± 4.5% peak oxygen uptake) and RCP (87.4% ± 4.5% peak oxygen uptake). Furthermore, the peak oxygen uptake was significantly (P < 0.001) positively correlated to the BPs and RCP, indicating that the BPs in total[Hb+Mb] (r = 0.66; P < 0.001), deoxy[Hb+Mb] (r = 0.76; P < 0.001), iEMG (r = 0.61; P < 0.001), MPF (r = 0.63; P < 0.001), and RCP (r = 0.75; P < 0.001) occurred at a higher percentage of peak oxygen uptake in subjects with a higher peak oxygen uptake. In this study a close relationship between muscle oxygenation, activation, and pulmonary oxygen uptake was found, occurring in a cascade of events. In subjects with a higher aerobic fitness level this cascade occurred at a higher relative intensity.
authors.affiliation: a Department of Movement and Sport Sciences, Ghent University, Ghent, Belgium.|b Center of Sports Medicine, Ghent University Hospital, Ghent, Belgium.
authors.forename: Jan
authors.initials: J
authors.lastname: Boone
authors.affiliation: c Department of Kinesiology, Kansas State University, Manhattan, KS 66506, USA.
authors.forename: Thomas J
authors.initials: TJ
authors.lastname: Barstow
authors.affiliation: a Department of Movement and Sport Sciences, Ghent University, Ghent, Belgium.
authors.forename: Bert
authors.initials: B
authors.lastname: Celie
authors.affiliation: d Laboratoire CIAMS, Equipe MHAPS, Université Paris Sud-Université d'Orléans, Orléans, France.
authors.forename: Fabrice
authors.initials: F
authors.lastname: Prieur
authors.affiliation: a Department of Movement and Sport Sciences, Ghent University, Ghent, Belgium.|b Center of Sports Medicine, Ghent University Hospital, Ghent, Belgium.
authors.forename: Jan
authors.initials: J
authors.lastname: Bourgois
mesh_terms: D000293:Adolescent; D015992:Body Mass Index; D003430:Cross-Sectional Studies; D004576:Electromyography; D015444:Exercise / Q000502:physiology*; D006454:Hemoglobins / Q000378:metabolism; D006801:Humans; D008297:Male; D018482:Muscle, Skeletal / Q000378:metabolism*; D009211:Myoglobin / Q000378:metabolism; D010100:Oxygen / Q000378:metabolism*; D010101:Oxygen Consumption; D010809:Physical Fitness; D019265:Spectroscopy, Near-Infrared; D055815:Young Adult
chemical_list: D006454:Hemoglobins; D009211:Myoglobin; D010100:Oxygen
keywords: V̇O2 de crête; V̇O2 pulmonaire; V̇O2peak; activation musculaire; critical power; muscle activation; muscle oxygenation; oxygénation musculaire; point de compensation respiratoire; puissance critique; pulmonary V̇O2; respiratory compensation point