title: Central circulatory and peripheral O2 extraction changes as interactive facilitators of pulmonary O2 uptake during a repeated high-intensity exercise protocol in humans.
abstract: It has frequently been demonstrated that prior high-intensity exercise facilitates pulmonary oxygen uptake [Formula: see text] response at the onset of subsequent identical exercise. To clarify the roles of central O(2) delivery and/or peripheral O(2) extraction in determining this phenomenon, we investigated the relative contributions of cardiac output (CO) and arteriovenous O(2) content difference [Formula: see text] to the [Formula: see text] transient during repeated bouts of high-intensity knee extension (KE) exercise. Nine healthy subjects volunteered to participate in this study. The protocol consisted of two consecutive 6-min KE exercise bouts in a supine position (work rate 70-75% of peak power) separated by 6 min of rest. Throughout the protocol, continuous-wave Doppler ultrasound was used to measure beat-by-beat CO (i.e., via simultaneous measurement of stroke volume and the diameter of the arterial aorta). The phase II [Formula: see text] response was significantly faster and the slow component (phase III) was significantly attenuated during the second KE bout compared to the first. This was a result of increased CO during the first 30 s of exercise: CO contributing to 100 and 56% of the [Formula: see text] speeding at 10 and 30 s, respectively. After this, the contribution of [Formula: see text] became increasingly more predominant: being responsible to an estimated 64% of the [Formula: see text] speeding at 90 s, which rose to 100% by 180 s. This suggests that, while both CO and [Formula: see text] clearly interact to determine the [Formula: see text] response, the speeding of [Formula: see text] kinetics by prior high-intensity KE exercise is predominantly attributable to increases in [Formula: see text].
authors.affiliation: Department of Exercise Science and Physiology, School of Health Sciences, Prefectural University of Hiroshima, 1-1-71, Ujina-Higashi, Hiroshima, Japan. fukuba@pu-hiroshima.ac.jp
authors.forename: Yoshiyuki
authors.initials: Y
authors.lastname: Fukuba
authors.forename: Masako Yamaoka
authors.initials: MY
authors.lastname: Endo
authors.forename: Yukie
authors.initials: Y
authors.lastname: Ohe
authors.forename: Yuiko
authors.initials: Y
authors.lastname: Hirotoshi
authors.forename: Asami
authors.initials: A
authors.lastname: Kitano
authors.forename: Chiaki
authors.initials: C
authors.lastname: Shiragiku
authors.forename: Akira
authors.initials: A
authors.lastname: Miura
authors.forename: Osamu
authors.initials: O
authors.lastname: Fukuda
authors.forename: Hatsumi
authors.initials: H
authors.lastname: Ueoka
authors.forename: Motohiko
authors.initials: M
authors.lastname: Miyachi
mesh_terms: D000222:Adaptation, Physiological / Q000502:physiology; D000328:Adult; D002302:Cardiac Output / Q000502:physiology*; D005260:Female; D006801:Humans; D007719:Knee Joint / Q000502:physiology*; D008297:Male; D010100:Oxygen / Q000097:blood*; D010101:Oxygen Consumption / Q000502:physiology*; D010807:Physical Endurance / Q000502:physiology*; D005082:Physical Exertion / Q000502:physiology*; D011659:Pulmonary Gas Exchange / Q000502:physiology*
chemical_list: D010100:Oxygen