Impaired popliteal artery flow-mediated dilation caused by reduced daily physical activity is prevented by increased shear stress

We recently showed that 5 days of reduced daily physical activity impair popliteal artery, but not brachial artery, flow-mediated dilation (FMD). However, the mechanisms by which physical inactivity causes leg vascular dysfunction are unclear. We reason that a reduction in leg blood flow-induced shear stress is a primary underlying mechanism by which reduced daily physical activity impairs popliteal artery FMD. Thus the purpose of this study was to determine whether increased leg blood flow and shear stress during inactivity prevent the reduction in popliteal artery FMD. Bilateral popliteal artery FMD measures were performed at baseline and after 5 days of a transition from high (>10,000 steps/day) to low levels (<5,000 steps/day) of physical activity in 13 healthy and physically active men [20 ± 2 (SD) yr]. During the inactive period, one foot was submerged in ~42°C water (i.e., heated leg) three times a day for 30 min each period, to increase blood flow and thus shear stress, whereas the contralateral leg remained dry and served as internal control (i.e., nonheated leg). During heating, popliteal artery mean shear rate was increased in the heated leg (change of 119.3 ± 26.4%, P < 0.01) but slightly decreased in the nonheated leg (change of –21.8 ± 7.5%, P = 0.03). Popliteal artery FMD was impaired after 5 days of reduced daily physical activity in the control nonheated leg (P < 0.01) but was unchanged in the heated leg (P = 0.34). ...

Source: Journal of Applied Physiology - July 1, 2017 Category: Physiology Authors: Teixeira, A. L., Padilla, J., Vianna, L. C. Tags: RESEARCH ARTICLE Source Type: research