Leg Blood Flow During Large Muscle Dynamic Exercise

It is currently unclear to what extent aging impairs blood flow to active muscles during large muscle dynamic exercise. To investigate this issue, femoral vein thermodilution measurements of total leg blood flow (leg Q) were compared between older (62–71 yr; n = 4) and younger (22–30 yr; n = 2) sedentary healthy men during upright cycling at similar absolute and relative work intensities. Systemic VO2, mean arterial pressure (MAP; radial artery catheter), and cardiac output (acetylene rebreathe) were also measured. Leg Q and leg vascular conductance (Q/MAP) were both ∼20% less in the older men at the same submaximal power outputs (20, 40, 60, 80, & 100 watts). At similar relative intensities (60% and 100% VO2peak), leg Q and conductance were both 40–42% less in the older group, with no evidence of an age difference in the slope of the leg Q vs. %VO2peak relation. Cardiac outputs were modestly reduced (∼1.0L/min) in the older group at similar absolute intensities. These results suggest that total leg blood flow during dynamic large muscle exercise is reduced with age in sedentary men. The reduced level of leg vasodilation seen in these older men could be due to an age-related decline in leg oxygen demand, augmented vasoconstrictor tone, and/or diminished vasodilator reactivity.