The Acute and Prolonged Impact of Knee-Flexion Angle on Popliteal Hemodynamics and Flow-Mediated Dilation Responses to Sitting

Abstract

The purpose of this study was to determine the impact of prolonged sitting (~2.5 h) at knee-flexion angles of 0°, 45°, and 90° on popliteal blood flow (PBF) and endothelial-dependent, flow-mediated dilation (FMD). 8 participants (24±2 yr; 4 females) was assessed PBF at the start (pre-sitting), 0.5-h, 1.0-h, post-sitting, and popliteal FMD at pre- and post-sitting. Two sitting bouts were completed on separate days with one leg positioned at 0° or 90° and the opposite leg at 45° knee-flexion. At pre-sitting, PBF was lower during 90° (36±15 mL•min-1) versus 0° (53±15 mL•min-1, P=0.021). Following prolonged sitting, PBF was lower at 45° (33±10 mL•min-1) and 90° (30±12 mL•min-1) versus 0° (42±15 mL•min-1, both P≤0.026). Sitting-induced reductions in popliteal FMD were similar among all knee-flexion angles (all, P>0.674). During an acute prolonged sitting, greater knee-flexion angles negatively impacted PBF, but did not further impair endothelial-dependent vasodilatory responses.