title: Kinetics of .VO2 and femoral artery blood flow during heavy-intensity, knee-extension exercise.
abstract: It has been suggested that, during heavy-intensity exercise, O(2) delivery may limit oxygen uptake (.VO2) kinetics; however, there are limited data regarding the relationship of blood flow and .VO2 kinetics for heavy-intensity exercise. The purpose was to determine the exercise on-transient time course of femoral artery blood flow (Q(leg)) in relation to .VO2 during heavy-intensity, single-leg, knee-extension exercise. Five young subjects performed five to eight repeats of heavy-intensity exercise with measures of breath-by-breath pulmonary .VO2 and Doppler ultrasound femoral artery mean blood velocity and vessel diameter. The phase 2 time frame for .VO2 and Q(leg) was isolated and fit with a monoexponent to characterize the amplitude and time course of the responses. Amplitude of the phase 3 response was also determined. The phase 2 time constant for .VO2 of 29.0 s and time constant for Q(leg) of 24.5 s were not different. The change (Delta) in .VO2 response to the end of phase 2 of 0.317 l/min was accompanied by a DeltaQ(leg) of 2.35 l/min, giving a DeltaQ(leg)-to-Delta.VO2 ratio of 7.4. A slow-component .VO2 of 0.098 l/min was accompanied by a further Q(leg) increase of 0.72 l/min (DeltaQ(leg)-to-Delta.VO2 ratio = 7.3). Thus the time course of Q(leg) was similar to that of muscle .VO2 (as measured by the phase 2 .VO2 kinetics), and throughout the on-transient the amplitude of the Q(leg) increase achieved (or exceeded) the Q(leg)-to-.VO2 ratio steady-state relationship (ratio approximately 4.9). Additionally, the .VO2 slow component was accompanied by a relatively large rise in Q(leg), with the increased O(2) delivery meeting the increased Vo(2). Thus, in heavy-intensity, single-leg, knee-extension exercise, the amplitude and kinetics of blood flow to the exercising limb appear to be closely linked to the .VO2 kinetics.
authors.affiliation: Canadian Centre for Activity and Aging, University of Western Ontario, 1490 Richmond St., London, Ontario, Canada N6G 2M3. dpaterso@uwo.ca
authors.forename: Nicole D
authors.initials: ND
authors.lastname: Paterson
authors.forename: John M
authors.initials: JM
authors.lastname: Kowalchuk
authors.forename: Donald H
authors.initials: DH
authors.lastname: Paterson
mesh_terms: D000328:Adult; D001783:Blood Flow Velocity / Q000502:physiology; D005080:Exercise Test; D005260:Female; D005263:Femoral Artery / Q000502:physiology*; D006801:Humans; D007700:Kinetics; D007719:Knee Joint / Q000502:physiology*; D008168:Lung / Q000502:physiology*; D008297:Male; D009119:Muscle Contraction / Q000502:physiology; D018482:Muscle, Skeletal / Q000098:blood supply* / Q000502:physiology*; D010100:Oxygen / Q000378:metabolism; D010101:Oxygen Consumption / Q000502:physiology*; D010807:Physical Endurance / Q000502:physiology*; D005082:Physical Exertion / Q000502:physiology
chemical_list: D010100:Oxygen