Sympathetic nervous system activation reduces contraction-induced rapid vasodilation in the leg of humans independent of age

We examined whether the age-related reduction in contraction-induced vasodilation in the leg is also due to a sympathetic vasoconstrictive mechanism. Thirteen young (24 ± 1 yr) and twelve older adults (67 ± 1 yr) performed single-leg knee extension at 20 and 40% of work-rate maximum (WRmax) during control and cold-pressor test (CPT) conditions. Femoral artery diameter and blood velocity were measured using Doppler ultrasound. Vascular conductance (VC; ml·min–1·mmHg–1) was calculated using blood flow (ml/min) and mean arterial pressure (mmHg). Peak (VC from baseline) and total VC were blunted in older adults during control conditions across exercise intensities (P < 0.05). Peak and total VC were reduced during CPT in both age groups across exercise intensities (P < 0.05). The relative change (i.e., %reduction; CPT vs. control) in peak (–25 ± 5 vs. –22 ± 4% at 20% WRmax; and –21 ± 6 vs. –27 ± 5% at 40% WRmax; P = 0.42–0.55) and total VC (–28 ± 5 vs. –36 ± 6% at 20% WRmax; and –22 ± 8 vs. –33 ± 5% at 40% WRmax; P = 0.23–0.34) were similar between young and older adults. When matched for absolute workload (~10 W), age differences persisted in peak VC (P < 0.05) under both conditions, with similar relative changes in peak and total VC during CPT. Our data suggest that 1) sympathetic stimulation reduces contraction-indu...
Source: Journal of Applied Physiology - Category: Physiology Authors: Tags: RESEARCH ARTICLE Source Type: research