Author(s): KASAI, N., IHARA, H., IEMITSU, M., MORISHIMA, T., Institution: DOSHISHA UNIVERSITY, Country: JAPAN, Abstract-ID: 2265

INTRODUCTION:
Prolonged sitting disrupts lower-limb endothelial function, likely because of reduced shear stress and decreased microvascular reactivity [1]. However, it remains unclear whether aerobic capacity-enhancing training modifies sitting-induced endothelial dysfunction and microvascular function as assessed by flow-mediated dilation (FMD) in response to prolonged sitting. Therefore, the present study was examined whether high-intensity interval training (HIIT) mitigates sitting-induced vascular dysfunction.
METHODS:
Twenty two healthy active men and women were randomly assigned to a control group (men = 7, women = 4) or a training group (men = 7, women = 4), in which we completed 8 weeks of HIIT (4 sessions/week) using a cycling and bodyweight exercises. Cycling HIIT consisted of 7–8 sets of 20-s cycling at an intensity of approximately 170% of VO2max at 90 rpm, with a 10-s rest between each round. The structure of the bodyweight exercises HIIT, exercise duration, rest duration, and number of sets, was the same as that of cycling HIIT. Before and after the intervention period, maximal oxygen uptake (VO2max) testing and 3 h of sitting testing, in which popliteal artery FMD and hyperemic blood flow were conducted. A baseline blood sample was collected to measure plasma endothelin-1 (ET-1) and nitrate/nitrite (NOx) concentrations. A three-way repeated measures analysis of variance (ANOVA) was conducted on sitting-involved variables with Bonferroni’s post hoc multiple comparisons test. To determine the group differences in post-sitting popliteal FMD following the intervention period, while controlling for potential covariates, an analysis of covariance (ANCOVA) was performed. VO2max and blood parameters were determined using a two-way ANOVA with Bonferroni’s post hoc test.
RESULTS:
After the intervention period, the training group exhibited a significant increase in VO2max, which was also significantly higher compared with that of the control group (p < 0.05). Circulating levels of plasma NOx and ET-1 were unchanged following the intervention. During the sitting protocol, blood flow and shear rate were significantly decreased in both groups, regardless of the intervention (p < 0.05). Popliteal artery FMD was significantly decreased after sitting in both groups before the intervention and remained lower in the training group following the intervention (p < 0.05); however, post-sitting FMD was significantly higher in the training group compared with that in the control group, even after adjusting for pre-sitting FMD (p < 0.05). The post-sitting blood-flow area under the curve was significantly decreased with sitting in both groups before and after the intervention period (p < 0.05).
CONCLUSION:
Eight weeks of HIIT did not preserve microvascular function or prevent sitting-induced endothelial dysfunction. However, HIIT partially attenuated the decline in conduit-artery function after prolonged sitting.

1. Padilla and Fadel (2017)