Influence of Age on Leg Vo2 Determinants During Large Muscle Dynamic Exercise

The purpose was to assess the impact of age-associated reductions in leg blood flow on leg oxygen uptake responses to exercise. We measured leg blood flow (femoral vein thermodilution), arterial-venous (A-V) O2 contents (radial artery and deep femoral vein), and whole body VO2 in healthy sedentary younger (22–30 yr) and older (62–71 yr) men during upright cycle ergometer exercise. Leg VO2 and its determinants were assessed at peak exercise (whole body VO2; younger = 3.15, older = 2.0 L/min) and during a functionally relevant submaximal work intensity for older adults (i.e., whole body VO2 of ∼1.15 L/min). Mean values (for 2 legs) are shown in the table. Leg O2 delivery at both work intensities was less in the older group, due primarily to their lower absolute leg blood flows vs. young controls. Leg A-V O2 difference was 2.0 ml/dl higher in the older compared to younger men during the submaximal workload (14.4 vs. 12.4 ml/dl, respectively). The present results suggest that leg muscle efficiency and O2 extraction capacity are fairly well maintained with age in healthy sedentary men. However, due to their diminished leg blood flow response, older men utilize a higher percentage of their O2 extraction “reserve” during light workloads to meet the required O2 demand. Supported by: NIH AG18246 and M01 RR10732Table