Regional differences in blood flow and oxygen consumption in resting muscle and their relationship during recovery from exhaustive exercise

This investigation evaluated regional differences in blood flow and oxygen consumption and their relationship in exercised muscle during recovery from exhaustive exercise. Five healthy men performed exhaustive one-legged cycling exercise. Positron emission tomography was used to measure blood flow, oxygen uptake, and oxygen extraction in the quadriceps femoris muscle before and after exercise. Regions of interest included five areas of the muscle (two proximal, one central, and two distal), which were evenly spaced across the muscle. Before exercise, blood flow and oxygen consumption decreased significantly (P < 0.05) in the direction from the proximal to the distal portions; blood flow declined from 2.0 ± 0.5 to 1.4 ± 0.3 ml·100 g ^-1·min^-1, and oxygen consumption decreased from 0.21 ± 0.04 to 0.17 ± 0.02 ml·100 g^-1· min^-1. In contrast, these gradients in blood flow and oxygen consumption diminished during recovery after exercise. Consequently, there was a positive relationship between changes in blood flow and oxygen consumption in an exercised muscle during recovery after exercise (r = 0.963, P < 0.01). These changes became larger in the direction from proximal to distal portions: blood flow increased from 2.9 ± 0.7 to 3.9 ± 0.8 and oxygen consumption from 1.4 ± 0.1 to 1.8 ± 0.4 times resting values. These results suggest that hemodynamic variables are heterogeneous within a muscle both at rest and during recovery from exercise and that there is a systematic difference in these variables in the direction from proximal to distal regions within the quadriceps femoris muscle.