Contraction-induced rapid vasodilation is attenuated similarly in the upper and lower limbs of older adults. In the forearm, this attenuation is in part due to a greater sympathetic vasoconstriction. 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±1yr) and twelve older adults (67±1yr) 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-1) and mean arterial pressure (mmHg). Peak (ΔVC 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 (~10W), 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-induced rapid vasodilation in the leg of young and older adults similarly; and 2) enhanced sympathetic vasoconstriction does not fully explain age-related differences in contraction-induced vasodilation within the leg.
- rapid vasodilation
- Copyright © 2017, Journal of Applied Physiology