Prolonged Leg Vasodilator Kinetics across an Exercise Transient in Older Adults

Abstract

Aging is associated with attenuated exercise hyperemia at the onset of exercise as well as during steady‐state exercise. How these two exercise states are related, and whether age‐associated impairments at the onset of exercise carry‐over into steady‐state exercise are unclear. The purpose of this study was to examine leg vasodilator kinetics preceding steady‐state exercise, as well as examine whether kinetic responses are altered with aging. Sedentary to recreationally active young (n=9), and older adults (n=13) performed single and rhythmic dynamic leg contractions at 20% and 40% work‐rate maximum (WRmax). Femoral artery diameter and blood velocity were measured by Doppler ultrasound. Vascular conductance (VC; ml·min−1·mmHg−1) was calculated using blood flow (ml·min−1) and mean arterial pressure (mmHg). Single contraction responses were described by peak (magnitude) and total (volume) responses. Kinetic responses for VC were modeled using an exponential model, expressed as mean response time (MRT; duty‐cycles). Older adults exhibited reduced peak VC responses to single contractions relative to young adults at both 20% and 40% WRmax (P<0.05). There were no differences in VC MRT between older and young at 20% WRmax (P=0.49). Older adults exhibited prolonged VC MRT at 40% WRmax vs. young (37±4 duty‐cycles vs. 24±4 duty‐cycles; P<0.05). When matched for a similar absolute workload (~9W) older adults exhibited prolonged VC MRT relative to young (38±5 vs. 25±4 duty‐cycles; P<0.05). Peak responses to single contractions were inversely associated with MRT at 40% WRmax (r=−0.61; P<0.05) but not 20% (r=−0.02; P=0.94) or 9W (r=−0.10; P=0.67) in the group as a whole. Our data suggest 1) advancing age prolongs the kinetics of vasodilation leading up to steady‐state exercise at both relative and absolute exercise intensities; and 2) single contraction responses are inversely related to the kinetics of vasodilation preceding relative exercise intensity steady‐state exercise, perhaps indicative of a feed‐forward mechanism towards steady‐state.Support or Funding InformationFunded by NIH HL‐105467 (DPC)This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.