Age-related decreases in basal limb blood flow in humans: time course, determinants and habitual exercise effects.

1. Basal whole-limb blood flow is lower in older than in young healthy sedentary men due to a lower limb vascular conductance. 2. In Study 1, we determined whether age-associated reductions in basal whole-leg (femoral artery) blood flow and vascular conductance are modulated by habitual physical activity by studying 89 healthy men aged 20-35 or 55-75 years (26 sedentary, 31 physically active and 32 endurance exercise trained). Femoral blood flow (duplex Doppler) and vascular conductance were similar to 20-30% lower (P < 0.01) in the older men in all three physical activity groups. 3. In Study 2, to determine the temporal pattern and relation to local metabolism and lean tissue mass of the age-associated reductions in femoral blood flow we studied 142 healthy men aged 18-79 years. Femoral blood flow (r= -0.40) and vascular conductance (r = -0.51) were linearly and inversely related to age (both P < 0.001). Leg fat-free mass (r = -0.48) and estimated leg oxygen consumption (r = -0.49) declined with advancing age (both P < 0.001), and were strongly and positively related (r = 0.75; P < 0.001). The age associated decline in femoral blood flow correlated with the corresponding reductions in leg fat-free mass and estimated leg oxygen consumption (both r = 0.47; P < 0.001). 4. We concluded that: (1) basal whole-limb blood flow and vascular conductance decrease progressively with advancing age in healthy men; (2) reductions in both limb fat-free mass and oxygen consumption are related to the decline in whole-limb blood flow with age; and (3) habitual aerobic exercise does not appear to modulate the age-related reductions in basal limb blood flow and vascular conductance.