Age and regional specificity of peak limb vascular conductance in men

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Abstract
Because of methodological variation in previous studies, age-associated changes in peak limb vascular conductance (VCpeak; 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 VCpeak. Peak conductance (plethysmographic flow/brachial mean arterial pressure) of the forearm (forearm VCpeak) and calf (calf VCpeak) 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 VCpeak with age (−6.6% per decade; P < 0.001) was greater than the decline in calf VCpeak (−3.4% per decade; P = 0.004). Limb VCpeak 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, V̇o2 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.