Submitted on December 19, 2008
Revised on May 29, 2009
Accepted on June 2, 2009
Effect of prior exercise on pulmonary O2 uptake and estimated muscle capillary blood flow kinetics during moderate-intensity field running in man
Martin Buchheit1*, Paul B. Laursen2, and Said Ahmaidi3
1 Faculty of Sport Sciences, University of Picardie, Jules Verne, 80025, Amiens, France
2 Edith Cowan University
3 Exercise Physiology Lab. EA3300,
* To whom correspondence should be addressed. E-mail: martin.buchheit{at}u-picardie.fr.
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 males presenting with either moderately-fast (16s<
VO2p<30s; MFK) or very-fast (VO2p<16s; VFK) VO2p kinetics (i.e., primary time constant, VO2p). 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 (MRTQm) was estimated by rearranging the Fick equation, using VO2p and deoxy-[Hb+Mb] as proxies of muscle VO2 and arterio-venous difference, respectively. HR, blood lactate concentration, total hemoglobin and Qm were elevated prior to Mod2 compared with Mod1 (all P<0.05). VO2p was shorter in VFK compared to 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). MRTQm was shorter in VFK compared to 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 VO2p between Mod1 and Mod2 was related to MRTQm 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 uptake kinetic during the onset of moderate-intensity field-based running exercise, at least in subjects exhibiting moderately-fast O2 uptake kinetics.
