Impaired leg vasodilation during dynamic exercise in healthy older women

The purpose of the present study was to test the hypothesis that leg blood flow responses during leg cycle ergometry are reduced with age in healthy non-estrogen-replaced women. Thirteen younger (20-27 yr) and thirteen older (61-71 yr) normotensive, non-endurance-trained women performed both graded and constant-load bouts of leg cycling at the same absolute exercise intensities. Leg blood flow (femoral vein thermodilution), mean arterial pressure (MAP; radial artery), mean femoral venous pressure, cardiac output (acetylene rebreathing), and blood O₂ contents were measured. Leg blood flow responses at light workloads (20-40 W) were similar in younger and older women. However, at moderate workloads (50-60 W), leg blood flow responses were significantly attenuated in older women. MAP was 20-25 mmHg higher (P < 0.01) in the older women across all work intensities, and calculated leg vascular conductance (leg blood flow/estimated leg perfusion pressure) was lower (P < 0.05). Exercise-induced increases in leg arteriovenous O₂ difference and O₂ extraction were identical between groups (P > 0.6). Leg O₂ uptake was tightly correlated with leg blood flow across all workloads in both subject groups (r² = 0.80). These results suggest the ability of healthy older women to undergo limb vasodilation in response to submaximal exercise is impaired and that the legs are a potentially important contributor to the augmented systemic vascular resistance seen during dynamic exercise in older women.