Effects Of Uninterrupted Sitting: Are There Differences Across Sex In Vascular And Inflammatory Biomarkers?

A single bout of uninterrupted sitting impairs vascular function in the legs, which may be due to reductions in blood flow and shear stress. Preliminary evidence suggests men and women may experience differing acute physiological responses to a bout of sitting. PURPOSE: To investigate whether the effects of a single bout of uninterrupted sitting on hemodynamics and vascular and inflammatory biomarkers were different between middle-aged men and women. Based on previous literature, we hypothesized women would experience less adverse physiological changes after sitting compared to men. METHODS: Thirty adults (14 men, 16 women; age, 46.6 ± 8.8 y; body fat, 28.9 ± 8.7%) completed 3 h of uninterrupted sitting in a laboratory. Hemodynamic variables including blood pressure (BP), mean arterial pressure (MAP), and blood pooling via calf circumference were measured at baseline and each hour over 3 h of sitting. Additionally, superficial femoral artery (SFA) diameter and blood velocity were measured using Doppler ultrasound, and SFA blood flow and shear rate were calculated. Serum vascular and inflammatory biomarkers were measured pre and post sitting. Linear mixed-effects modeling was used to assess changes in dependent variables over time and between men and women. RESULTS: There were no time by sex interaction effects for any of the outcome variables (p > 0.05). Systolic BP, MAP, and calf circumference increased (p < 0.01 for all) over 3 h of sitting in both men and women. In all participants, SFA blood flow, blood velocity and shear rate decreased over time (p < 0.05 for all), whereas SFA arterial diameter did not change (p = 0.12). Endothelin-1 (baseline: 8.3 ± 13.4 pg/mL, post: 81.1 ± 103.0 pg/mL; p < 0.001) and interleukin-6 (baseline: 0.08 ± 0.06 pg/mL, post: 0.11 ± 0.11 pg/mL; p = 0.03) increased post sitting compared to baseline in all adults. CONCLUSIONS: Although a single bout of uninterrupted sitting induced unfavorable changes in vascular and inflammatory biomarkers, systolic BP, MAP, calf circumference, and SFA blood flow, velocity, and shear rate, there were no differences between men and women. Unfavorable changes in hemodynamic variables from repeated exposure to uninterrupted sitting throughout the lifespan may help explain the increased risk for cardiometabolic disease with excessive amounts of sedentary behavior.