Sex-related differences in rapid-onset vasodilation: Impact of aging

Abstract

Rapid-onset vasodilation (ROV) in response to a single muscle contraction is attenuated with aging. Moreover, sex-related differences in muscle blood flow and vasodilation during dynamic exercise have been observed in young and older adults. The purpose of the present study was to explore if sex-related differences in ROV exist in young (n = 36, 25±1yr) and older (n = 32, 66±1yr) adults. Subjects performed single forearm contractions at 10%, 20%, and 40% maximal voluntary contraction. Brachial artery blood velocity and diameter were measured with Doppler ultrasound, and forearm vascular conductance (mL·min-1·100mmHg-1) was calculated from blood flow (mL·min-1) and mean arterial pressure (mmHg) and used as a measure of ROV. Peak ROV was attenuated in women across all relative intensities in the younger and older groups (P < 0.05). In a subset of subjects with similar absolute workloads (∼5kg and ∼11 kg), age-related differences in ROV were observed among both women and men (P < 0.05). However, only older women demonstrated an attenuated peak ROV compared with men (91±6 vs. 121±11 mL·min-1·100mmHg-1, P < 0.05), a difference not observed in the young group (134±8 vs. 154±11 mL·min-1·100mmHg-1, P = 0.15). Additionally, examining the slope of peak ROV across contraction intensities indicated a blunted response in older women compared with their younger counterparts (P < 0.05), with no differences observed between older and young men (P = 0.38). Our data suggest that sex-related differences in the rapid vasodilatory response to single muscle contractions exist in older but not young adults, such that older women have a blunted response compared with older men.