The Skeletal Muscle Metaboreflex is Attenuated in Healthy Older Adults

Abstract

A previous study reported that healthy aging attenuated the exercise pressor reflex (EPR); however, whether this is due to alterations in the metabolic or mechanical component of the EPR remains unclear. Thus, the goal of this study was to comprehensively assess the influence of age on the metabolic component of the EPR using graded intensities of muscle metaboreflex activation. In young (n=18; 23±1 yr; resting blood pressure (BP) 111±3/69±3 mmHg) and older (n=23; 60±1 yr; resting BP 112±1/69±2 mmHg) normotensive subjects graded isolation of the muscle metaboreflex was achieved by post exercise ischemia (PEI) following moderate (PEI‐M) and high (PEI‐H) intensity static handgrip performed at 30% and 40% maximum voluntary contraction, respectively. BP (Finometer) and muscle sympathetic nerve activity (MSNA; peroneal microneurography) were measured continuously. The increases in mean BP and MSNA burst frequency were significantly less in older subjects compared to younger subjects during both PEI‐M (15±2 young v 10±1 older mmHg and 13±3 young v 2±2 older bursts/min; both P<0.05) and PEI‐H (20±2 young v 13±1 older mmHg and 12±3 young v 4±2 older burst/min; both P<0.05). These data indicate that older normotensive adults have blunted neurocirculatory responses to PEI compared to young adults, suggesting that the metaboreflex is attenuated in healthy aging.Supported by NIH Grant HL‐074851‐02 and 2 P20 RR016472‐11 (to W.B.F.); HL‐093167‐03 (to P.J.F.); AHA 11PRE7580029 (to J.L.G.)