Prolonged sitting and peripheral vascular function: potential mechanisms and methodological considerations

Abstract

Sitting time is associated with increased risks for subclinical atherosclerosis and cardiovascular disease development, and this is thought to be partially due to sitting-induced disturbances in macro- and microvascular function as well as molecular imbalances. Despite surmounting evidence supporting these claims, contributing mechanisms to these phenomena remain largely unknown. In this review, we discuss evidence for potential mechanisms of sitting-induced perturbations in peripheral hemodynamics and vascular function and how these potential mechanisms may be targeted using active and passive muscular contraction methods. Furthermore, we also highlight concerns regarding the experimental environment and population considerations for future studies. Optimizing prolonged sitting investigations may allow us to not only better understand the hypothesized sitting-induced transient proatherogenic environment but to also enhance methods and devise mechanistic targets to salvage sitting-induced attenuations in vascular function, which may ultimately play a role in averting atherosclerosis and cardiovascular disease development.

Keywords: macrovascular function; microcirculation; peripheral arterial disease; prolonged sitting; shear stress.

Graphical abstract

Figure 1.

The effects of the bent leg position and intermittent active muscular contractions (fidgeting, 1 min on/4 min off) during prolonged sitting on popliteal artery hemodynamics. A: the bent leg position associated with prolonged sitting produces reductions in popliteal artery blood flow when compared with an otherwise straight limb (mL/min), n = 12, *P < 0.05 vs. Baseline, †P < 0.05 vs. straight leg. B: mean popliteal artery shear rate (s⁻¹) was greater in the fidgeting leg compared with the nonfidgeting control leg when measured 2 min after the 1-min fidgeting bout. n = 11, *P < 0.05 vs. baseline †P < 0.05 vs. control leg. [Adapted and reused with permission from Walsh et al. (11), under a Creative Commons Attribution 4.0 International License, and from Morishima et al. (22).]

Figure 2.

Measurements of popliteal artery flow-mediated dilation (FMD) pre- and postprolonged sitting in a control group (CON, no movement), passive leg movement group (PASS, passive leg movements every 30 min for 2 min at 1 Hz), and active leg movement group (ACT, active leg movements every 30 min for 2 min at 1 Hz at a 13-W workload) and central arterial stiffness [assessed by carotid-to-femoral pulse-wave velocity (PWV)] in response to 3 h of prolonged sitting both with and without intermittent active skeletal muscle contractions (i.e., 10 calf raises at 0.33 Hz every 10 min). A: FMD decreased after sitting in CON and PASS but was preserved in ACT. n = 14, *P < 0.05 vs. Pre, †P < 0.05 vs. ACT. B: carotid-to-femoral PWV (m/s) increased after sitting in both conditions. n = 20, *P < 0.05 vs. Pre sit. [Adapted and reused with permission from Park et al. (8) and Evans et al. (42).]

Figure 3.

Measurements of microvascular function [tissue oxygenation index (TOI) recovery rate, % min⁻¹] pre- and postprolonged sitting in a control group (CON, no movement), passive leg movement group (PASS, passive leg movements every 30 min for 2 min at 1 Hz), and active leg movement group (ACT, active leg movements every 30 min for 2 min at 1 Hz at a 13 W workload). TOI recovery rate was lower after sitting in CON, and post-CON was less than post-PASS and post-ACT. Post-ACT was greater than post-CON and post-PASS. n = 14, *P < 0.05 vs. Pre, †P < 0.05 vs. PASS, ‡P < 0.05 vs. ACT. [Adapted and reused with permission from Park et al. (8).]

Figure 4.

Measurements of total plasma nitrate/nitrite to endothelin-1 ratio pre- and postprolonged sitting in a control group (CON, no movement), passive leg movement group (PASS, passive leg movements every 30 min for 2 min at 1 Hz), and active leg movement group (ACT, active leg movements every 30 min for 2 min at 1 Hz at a 13-W workload). Total plasma nitrate/nitrite to endothelin-1 ratio was lower in post-CON and post-PASS when compared with post-ACT. n = 14, †P < 0.05 vs. PASS. [Adapted and reused with permission from Park et al. (8).]