Age and regional specificity of peak limb vascular conductance in men

Abstract

Because of methodological variation in previous studies, age-associated changes in peak limb vascular conductance (VC_peak; a functional index of arterial structure) and its determinants remain poorly defined. The objectives of this study were to describe and compare age-associated changes in peak forearm and calf conductance across a broad age range and to identify physiological characteristics that are predictive of variation in limb-specific VC_peak. Peak conductance (plethysmographic flow/brachial mean arterial pressure) of the forearm (forearm VC_peak) and calf (calf VC_peak) after 10 min of arterial occlusion was measured twice in 68 healthy, normally active men aged 20–79 yr. Aerobic capacity (cycle peak oxygen consumption), arterial health (ankle-brachial index, pulse wave velocity), and limb-specific measures of muscle mass (dual-energy X-ray absorptiometry) and isometric strength (grip, plantar flexion) were also assessed. The relative decline in forearm VC_peak with age (−6.6% per decade; P < 0.001) was greater than the decline in calf VC_peak (−3.4% per decade; P = 0.004). Limb VC_peak per kilogram of muscle declined with age in the forearm (−3.8% per decade; P = 0.004) but not in the calf ( P = 0.35). Age, V̇o_{2 peak}, and regional muscle mass were significant predictors of peak conductance in both limbs; however, these predictors explained considerably less variance in the calf than in the forearm. These results suggest that healthy aging is associated with a linear decline in limb vasodilator capacity in men, but the magnitude of this effect is reduced in the calf relative to the forearm. This could reflect regional differences in habitual muscle use with aging in normally active men.