Prolonged Sitting Results in Microvascular, but not Macrovascular, Dysfunction in Healthy Young Women

Abstract

On average, Americans spend more than half of their waking hours sitting. Previous work has demonstrated impairments in leg micro‐ and macro‐vascular function following prolonged sitting, as assessed by reactive hyperemia and flow‐mediated dilation (FMD), respectively. However these studies were performed predominantly in young men, and the effects of sitting in women have yet to be identified. This is important given known differences in vascular function between sexes. Accordingly, we assessed popliteal artery reactive hyperemia and FMD, before (PreSIT) and after (PostSIT) a 3 hr sitting period in 12 women and 8 age‐ and BMI‐matched men. Popliteal artery hemodynamics (duplex Doppler ultrasound), heart rate (ECG), and calf circumference were measured throughout. During sitting, resting popliteal artery shear rate was reduced in women (−48.5±8.4 s−1) and men (−52.9±12.3 s−1; P = 0.448); which was accompanied by similar increases in calf circumference in both groups (P = 0.370). Following the sitting period, popliteal artery FMD (ANCOVA‐corrected for hyperemic shear rate AUC), was significantly reduced in men (PreSIT: 5.6±0.7%, PostSIT: 1.5±0.7%; P = 0.001) but not women (PreSIT: 4.5±0.6%, PostSIT: 3.5±0.6%; P = 0.502), whereas both groups exhibited similar reductions in hyperemic shear rate AUC (women: −33,199±8,516 a.u., men: −24,350±8,803 a.u.; P = 0.494). These preliminary findings indicate that with prolonged sitting, the leg vasculature is susceptible to similar microvascular impairments in men and women, however macrovascular function appears protected from sitting in young women.Support or Funding InformationSupported by UTA College of Nursing and Health Innovation.