Received January 31, 2005
Revised March 15, 2005
Accepted after revision May 18, 2005

¹ Kansas State University

^* To whom correspondence should be addressed. E-mail: tbarsto{at}ksu.edu.

	Abstract

The kinetic characteristics of muscle capillary blood flow (Qcap) during recovery from exercise is controversial (e.g. one vs. two-phases). Further it is not clear how the overall Qcap kinetics are temporally associated with muscle oxygen uptake (VO2m) kinetics. To address these issues, we examined the kinetics of Qcap estimated from the rearrangement of the Fick equation [Qcap = VO2m/C(a-v)O2] using the kinetics of pulmonary VO2 (primary component) and deoxy-hemoglobin concentration ([HHb]) as indices of VO2m and C(a-v)O2 kinetics, respectively. VO2p (L/min) was measured breath-by-breath and [HHb] (µM) was measured by near infrared spectroscopy during moderate- (M; below Lactate Threshold, LT) and heavy-exercise (H, above LT) in nine subjects. The kinetics of Qcap were biphasic, with an initial fast phase (_I; M = 9.3 ± 4.9 s and H = 6.0 ± 3.8 s) followed by a slower phase 2 (_P; M = 29.9 ± 8.6 s and H = 47.7 ± 26.0 s). For moderate exercise, the overall kinetics of Qcap (mean response time [MRT], 36.1 ± 8.6 s) were significantly slower than the kinetics of VO2 (_P; 27.8 ± 5.3 s) and [HHb] (MRT-[HHb]; 16.2 ± 6.3 s). However, for heavy exercise, there was no significant difference between MRT-[HHb] (34.7 ± 10.4 s) and _P-VO2p (32.3 ±6.7 s), &while MRT- Qcap (48.7 ± 21.8 s) was significantly slower than MRT-[HHb] and _P-VO2p. In conclusion, during recovery from exercise the estimated Qcap kinetics were biphasic, showing an early rapid decrease in blood flow. In addition, the overall kinetics of Qcap were slower than the estimated VO2m kinetics.

Key Words: Exercise, Kinetics, Oxygen

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