title: Effect of prior exercise on pulmonary O2 uptake and estimated muscle capillary blood flow kinetics during moderate-intensity field running in men.
abstract: The effect of prior exercise on pulmonary O2 uptake (VO2p) and estimated muscle capillary blood flow (Qm) kinetics during moderate-intensity, field-based running was examined in 14 young adult men, presenting with either moderately fast (16 s<tauVO2p<30 s; MFK) or very fast VO2p kinetics (tauVO2p<16 s; VFK) (i.e., primary time constant, tauVO2p). On four occasions, participants completed a square-wave protocol involving two bouts of running at 90-95% of estimated lactate threshold (Mod1 and Mod2), separated by 2 min of repeated supramaximal sprinting. VO2p was measured breath by breath, heart rate (HR) beat to beat, and vastus lateralis oxygenation {deoxy-hemoglobin/myoglobin concentration (deoxy-[Hb+Mb])} using near-infrared spectroscopy. Mean response time of Qm (Qm MRT) was estimated by rearranging the Fick equation, using VO2p and deoxy-[Hb+Mb] as proxies of muscle O2 uptake (VO2) and arteriovenous difference, respectively. HR, blood lactate concentration, total hemoglobin, and Qm were elevated before Mod2 compared with Mod1 (all P<0.05). tauVO2p was shorter in VFK compared with MFK during Mod1 (13.1+/-1.8 vs. 21.0+/-2.5 s, P<0.01), but not in Mod2 (12.9+/-1.5 vs. 13.7+/-3.8 s, P=1.0). Qm MRT was shorter in VFK compared with MFK in Mod1 (8.8+/-1.9 vs. 17.0+/-3.4 s, P<0.01), but not in Mod2 (10.1+/-1.8 vs. 10.5+/-3.5 s, P=1.0). During Mod2, HR kinetics were slowed, whereas mean deoxy-[Hb+Mb] response time was unchanged. The difference in tauVO2p between Mod1 and Mod2 was related to Qm MRT measured at Mod1 (r=0.71, P<0.01). Present results suggest that local O2 delivery (i.e., Qm) may be a factor contributing to the VO2 kinetic during the onset of moderate-intensity, field-based running exercise, at least in subjects exhibiting moderately fast VO2 kinetics.
authors.affiliation: Laboratory of Exercise Physiology and Rehabilitation, EA 3300, Faculty of Sport Sciences, University of Picardie, Jules Verne, F-80025, Amiens, France. martin.buchheit@u-picardie.fr
authors.forename: Martin
authors.initials: M
authors.lastname: Buchheit
authors.forename: Paul B
authors.initials: PB
authors.lastname: Laursen
authors.forename: Said
authors.initials: S
authors.lastname: Ahmaidi
mesh_terms: D000222:Adaptation, Physiological; D000328:Adult; D015308:Anaerobic Threshold; D001944:Breath Tests; D002196:Capillaries / Q000502:physiology; D015444:Exercise; D006339:Heart Rate; D006454:Hemoglobins / Q000378:metabolism; D006801:Humans; D007700:Kinetics; D019344:Lactic Acid / Q000097:blood; D008297:Male; D008833:Microcirculation; D008954:Models, Biological; D009119:Muscle Contraction; D009211:Myoglobin / Q000378:metabolism; D010100:Oxygen / Q000097:blood*; D010101:Oxygen Consumption; D012123:Pulmonary Ventilation; D052097:Quadriceps Muscle / Q000098:blood supply* / Q000378:metabolism*; D012039:Regional Blood Flow; D012420:Running; D019265:Spectroscopy, Near-Infrared; D055815:Young Adult
chemical_list: D006454:Hemoglobins; D009211:Myoglobin; D019344:Lactic Acid; C100003:deoxyhemoglobin; D010100:Oxygen