The Impact of a 12-week High-Intensity Interval Training Program on Popliteal Vascular Responses to Prolonged Sitting

Abstract

Prolonged, uninterrupted sitting (≥1-h) impairs lower-limb flow-mediated dilation (FMD), nitroglycerin-mediated dilation (NMD), and resistance vessel responses. The benefits of regular aerobic exercise on vascular health are well established. However, conflicting evidence exists regarding the influence of aerobic fitness on sitting induced-reductions in lower-limb arterial function. To explore the impact that 12-weeks of high-intensity interval training (HIIT, 3 sessions/week) had on popliteal FMD, NMD, and reactive hyperemic responses to a bout of prolonged sitting. Twenty-one healthy adults were randomly assigned to HIIT (n=7, 24±8 years, 7♀) or Control groups (n=10, 22±1 years, 6♀). Relative FMD responses (% peak increase from baseline diameter) to 5-min distal cuff occlusion (250 mmHg) and relative NMD responses (% peak increase from baseline diameter) to sublingual nitroglycerin administration (0.4 mg), as well as post-occlusive peak red cell velocity (RBCv) were assessed via duplex ultrasonography before and after a ~3-h bout of uninterrupted sitting. Peak oxygen consumption (relative V̇O2peak, indirect calorimetry) using a maximal cycle ergometer protocol graded cycle ergometry was also assessed. These assessments were repeated following the HIIT (2×20-min bouts of alternating between 15-s intervals at 100% of peak aerobic power and passive recovery) or Control (habitual physical activity) periods. 12-week HIIT improved relative V̇O2peak (35.4±7.8 to 39.5±6.1 ml/kg/min, P=0.005), with no changes observed in the Control group (P=0.306). Sitting-induced changes in popliteal FMD (HIIT: -1.4±2.6 to -1.7±1.9%; Control: -2.9±2.2 to -2.0±2.3%), NMD (HIIT: -3.1±2.9 to -3.2±2.5%; Control: -3.0±2.9 to -3.8±3.7%), or peak hyperemic responses (HIIT: -12.8±6.1 to -12.5±11.0 cm/s; Control: -26.0±14.4 to -9.5±24.7 cm/s) did not change at follow-up in either group (all, P≥0.105). These results indicate that a 12-week HIIT intervention did not provide protection against prolonged sitting-induced lower-limb vascular dysfunction.