Influence of sympathetic vasoconstriction on muscle blood flow control during graded handgrip exercise in young and older adults (1165.2)

Abstract

With human aging there is a marked increase in resting sympathetic nervous system (SNS) activity, and older adults also exhibit attenuated vasodilation and skeletal muscle blood flow during exercise.We tested the hypothesis that SNS restraint of muscle (forearm) blood flow (FBF) is greater in older compared with young adults during graded handgrip exercise (5, 15, 25% maximal voluntary contraction (MVC)). FBF was measured (Doppler ultrasound) and vascular conductance (FVC) was calculated in 12 young (21±1 years) and 12 older (62±2 years) adults in control conditions and following local α+β‐adrenergic receptor blockade (intra‐arterial infusions of phentolamine and propranolol). Compared to young, older adults exhibited significantly lower FBF at 15% MVC (216±12 vs. 177±15 ml/min) and 25% MVC (344±24 vs. 277±17 ml/min; both P<0.05). Following local adrenergic blockade, the increase in FBF was similar in young and older adults across exercise intensities, and the age difference in FBF during exercise was similar to control conditions. Our data indicate that, during graded mild‐to‐moderate intensity handgrip exercise, the reduction in muscle blood flow in older healthy adults is not due to augmented sympathetic vasoconstriction, but rather due to impairments in local vasodilatory signaling with age.Supported by HL095573Grant Funding Source: Supported by HL095573