The impact of a 12-week high-intensity interval training program on popliteal vascular responses to prolonged sitting

We examined the impact that 12-weeks of high-intensity interval training (HIIT) had on aerobic fitness and popliteal artery endothelium-dependent (flow-mediated dilation, FMD) and -independent dilatory function (nitroglycerin-mediated dilation, NMD) in response to an acute bout of prolonged sitting.

Twenty-one healthy adults were assigned to HIIT (n = 11, 7♀, 24 ± 8 years) or Control groups (n = 10, 6♀, 22 ± 1 years). Popliteal artery FMD response to 5-min distal cuff occlusion and NMD were assessed via duplex ultrasonography before and after ~ 2-h of uninterrupted sitting. Peak oxygen consumption (relative V̇O₂peak) was assessed using a maximal cycle ergometer protocol. All assessments were repeated following the HIIT (2 × 20-min bouts alternating between 15-s intervals at 100% of peak aerobic power and passive recovery) or Control (usual physical activity) periods.

The 12-week HIIT intervention 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). Pre-sitting popliteal artery FMD and NMD did not differ from Baseline to Follow-up in either group (all, P ≥ 0.173). In both groups, prolonged sitting attenuated FMD and NMD at Baseline and Follow-up (all, P ≤ 0.076). Sitting-induced changes in popliteal artery FMD (HIIT: -1.4 ± 2.6 to -1.7 ± 1.9%; Control: -2.9 ± 2.2 to -2.0 ± 2.3%) and NMD (HIIT: -3.1 ± 2.9 to -3.2 ± 2.5%; Control: -3.0 ± 2.9 to -3.8 ± 3.7%) were not different between Baseline and Follow-up in either group (all, P ≥ 0.327).

A 12-week HIIT intervention improved aerobic fitness but did not provide protection against prolonged sitting-induced impairments in popliteal artery endothelial function or vascular smooth cell function.