Acute Ascorbic Acid Ingestion Does Not Blunt Sympathetically‐Mediated Vasoconstriction During Handgrip Exercise in Older Adults

Abstract

The normal ability of contracting skeletal muscle to blunt sympathetic vasoconstriction is impaired in older adults, potentially contributing to the age‐associated impairment in skeletal muscle blood flow during exercise. Acute ingestion of 2g of ascorbic acid (AA) improves forearm blood flow (FBF) during moderate intensity handgrip exercise in older adults. We tested the hypothesis that acute AA ingestion improves the ability to blunt a sympathetically‐mediated vasoconstrictor stimulus during handgrip exercise (15% maximal voluntary contraction: MVC) in 10 older (63±2 years) adults. FBF was measured (Doppler ultrasound) and vasoconstriction was calculated (%Δ forearm vascular conductance [FVC]) in response to reflex sympathetic activation achieved via 2 minutes of ‐40mmHg lower body negative pressure (LBNP) at rest and during steady‐state handgrip exercise prior to and 2h post ingestion of AA. Compared to control, AA increased FBF during exercise (185±15 vs. 212±19 ml/min P<0.05) however there was no change in the amount of vasoconstriction to LBNP at rest (ΔFVC = ‐16±2 vs. ‐16±2%) or during exercise (ΔFVC= ‐12±2 vs. ‐11±4 %). We conclude that acute oral AA is capable of improving FBF during handgrip exercise in healthy older adults but does not improve the ability to blunt sympathetically‐mediated vasoconstriction.Supported by HL095573