title: Enhanced oxygen extraction and reduced flow heterogeneity in exercising muscle in endurance-trained men.
abstract: The aim of this study was to investigate the effects of endurance training on skeletal muscle hemodynamics and oxygen consumption. Seven healthy endurance-trained and seven untrained subjects were studied. Oxygen uptake, blood flow, and blood volume were measured in the quadriceps femoris muscle group by use of positron emission tomography and [15O]O2, [15O]H2O, and [15O]CO during rest and one-legged submaximal intermittent isometric exercise. The oxygen extraction fraction was higher (0.49 +/- 0.14 vs. 0.29 +/- 0.12; P = 0.017) and blood transit time longer (0.6 +/- 0.1 vs. 0.4 +/- 0.1 min; P = 0.04) in the exercising muscle of the trained compared with the untrained subjects. The flow heterogeneity by means of relative dispersion was lower for the exercising muscle in the trained (50 +/- 9%) compared with the untrained subjects (65 +/- 13%, P = 0.025). In conclusion, oxygen extraction is higher, blood transit time longer, and perfusion more homogeneous in endurance-trained subjects compared with untrained subjects at the same workload. These changes may be associated with improved exercise efficiency in the endurance-trained subjects.
authors.affiliation: Turku PET Centre, University of Turku, FIN-20521 Turku, Finland. Kari.Kalliokoski@pet.tyks.fi
authors.forename: K K
authors.initials: KK
authors.lastname: Kalliokoski
authors.forename: V
authors.initials: V
authors.lastname: Oikonen
authors.forename: T O
authors.initials: TO
authors.lastname: Takala
authors.forename: H
authors.initials: H
authors.lastname: Sipilä
authors.forename: J
authors.initials: J
authors.lastname: Knuuti
authors.forename: P
authors.initials: P
authors.lastname: Nuutila
mesh_terms: D000328:Adult; D001794:Blood Pressure / Q000502:physiology; D001810:Blood Volume / Q000502:physiology; D006339:Heart Rate / Q000502:physiology; D006801:Humans; D007537:Isometric Contraction / Q000502:physiology; D008297:Male; D018482:Muscle, Skeletal / Q000098:blood supply / Q000000981:diagnostic imaging / Q000502:physiology*; D010101:Oxygen Consumption / Q000502:physiology*; D010807:Physical Endurance / Q000502:physiology*; D010809:Physical Fitness / Q000502:physiology; D012039:Regional Blood Flow / Q000502:physiology; D014055:Tomography, Emission-Computed