Sex does not influence impairments in popliteal endothelial-dependent vasodilator or vasoconstrictor responses following prolonged sitting.

Abstract

An acute bout of prolonged sitting (PS) impairs the popliteal artery flow-mediated dilation (FMD) response. Despite equivocal reductions in mean shear rate, young women demonstrate an attenuated decline in popliteal FMD versus young men. However, it is uncertain whether popliteal endothelial-dependent vasoconstrictor responses [low-flow mediated constriction (L-FMC)] are similarly affected by PS and/or if sex differences exist. We tested the hypothesis that women would have attenuated reductions in both popliteal FMD and L-FMC responses following an acute bout of PS. Popliteal FMD, and L-FMC responses were assessed via duplex ultrasonography before and after a 3-hour bout of PS. These responses were then compared between 10 men (24±2 years) and 10 women (23±2 years) matched (P>0.13) for habitual levels of objectively measured physical activity (via PiezoRx) and sedentary time (via activPAL). At baseline, men and women exhibited similar (P>0.46) popliteal FMD (4.8±1.2% vs. 4.5±0.6%) and L-FMC (-1.7±1.0% vs. -1.9±0.9%) responses. Both sexes experienced identical (group: P>0.76; time: P<0.001) PS-induced impairments in popliteal FMD (-2.8±1.4% vs. -2.6±0.9%) and L-FMC (1.3±0.7% vs. 1.4±0.7%). In young adults, sex did not influence the negative PS-induced FMD, L-FMC or microvascular responses in the lower limb. As such, our findings suggest that young men and women are similarly susceptible to the acute negative vascular effects of PS. Future studies should extend these findings to older, less physically active adults and/or patients with vascular disease.