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 sede ntary men due to a lower limb vascular conductance. 2. In Study 1, we determined whether age-associated reductions in basal who le-leg (femoral artery) blood flow and vascular conductance are modulated b y habitual physical activity by studying 89 healthy men aged 20-35 or 55-75 years (26 sedentary, 31 physically active and 32 endurance exercise traine d). Femoral blood flow (duplex Doppler) and vascular conductance were simil ar to 20-30% lower (P < 0.01) in the older men in all three physical activi ty groups. 3. In Study 2, to determine the temporal pattern and relation to local meta bolism and lean tissue mass of the age-associated reductions in femoral blo od 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 re lated 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 a ge associated decline in femoral blood flow correlated with the correspondi ng reductions in leg fat-free mass and estimated leg oxygen consumption (bo th r = 0.47; P < 0.001). 4. We concluded that: (1) basal whole-limb blood flow and vascular conducta nce decrease progressively with advancing age in healthy men; (2) reduction s in both limb fat-free mass and oxygen consumption are related to the decl ine in whole-limb blood flow with age; and (3) habitual aerobic exercise do es not appear to modulate the age-related reductions in basal limb blood fl ow and vascular conductance.