Matching of blood flow to metabolic rate during recovery from moderate exercise in humans

Abstract

It is unclear whether measurement of limb or conduit artery blood flow during recovery from exercise provides an accurate representation of flow to the muscle capillaries where gas exchange occurs. To investigate this, we: (a) examined the kinetic responses of femoral artery blood flow (), estimated muscle capillary blood flow () and estimated muscle oxygen uptake () following cessation of exercise; and (b) compared these responses to verify the adequacy of O2 delivery during recovery. Pulmonary () was measured breath by breath, was measured using Doppler ultrasonography, and deoxy-haemoglobin/ myoglobin (deoxy-[Hb/Mb]) was estimated by near-infrared spectroscopy over the rectus femoris in nine healthy subjects during a series of transitions from moderate knee-extension exercise to rest. The time course of was estimated by rearranging the Fick equation [i.e. ], using the primary component of to represent and deoxy-[Hb/Mb] as a surrogate for arteriovenous O2 difference. There were no significant differences among the overall kinetics of (τ, 31.4 ± 8.2 s), [mean response time (MRT), 34.5 ± 20.4 s] and (MRT, 31.7 ± 14.7 s). The kinetics were also significantly correlated (P < 0.05) with those of both and. Both and appear to be coupled with during recovery from moderate knee-extension exercise, such that extraction falls (thus cellular energetic state is not further compromised) throughout recovery. © 2008 The Authors.