Combined Effects of Standing and Passive Heating on Attenuating Sitting-Induced Vascular Dysfunction

Abstract

Recent evidence suggests prolonged sitting strains the arteries through angulations that create turbulent blood flow. This turbulent flow reduces flow-mediated dilation (FMD), a key indicator of vascular health. The purpose of this study was to determine if arterial angulations (through sitting or standing), shear stress (through local heating), or a combination of these factors affected vascular function. In addition, we sought examined the impact of biological sex on these responses. MethodsTwenty-six healthy, young (18-40 years old) males (n=13) and females (n=13) participated. Participants completed two experimental trials (2-h sitting and 2-h standing), and, in a randomized fashion, one leg was passively heated. Flow-mediated dilation (FMD) at the superficial femoral artery (SFA), and central and peripheral pulse-wave velocity (PWV) were measured using vascular ultrasound. ResultsThere was a non-significant decrease in FMD (- 1.48%; p = .06) during sitting and the decline in FMD was not different between biological sexes (-1.96% vs -0.93%; p = .49, males and females respectively). Passive heating (1.42%; p < .05) and standing (1.42%; p < .05) both improved FMD in comparison to sitting. However, standing resulted in a significant increase in peripheral PWV (50 cm/s; p < .05). Interestingly, the standing was not well tolerated among female participants with seven participants having to stop their initial trial early due to lightheadedness. ConclusionsBoth interventions appear to be equally effective at mitigating reductions FMD associated with sitting, but standing increased peripheral PWV. In addition, it does not appear that biological sex moderates these physiological responses. New FindingsO_ST_ABSWhat is the central question of this study?C_ST_ABSProlonged sitting can cause acutely vascular dysfunction while interventions such as local heating or standing have been explored they have not been used in combination and the role of biological sex has not been fully explored. What is the main finding and its importance?In this study we demonstrate that either local heating or standing are effective at reducing some of the vascular dysfunction associated with prolonged sitting. Biological sex did not appear appear to play a role in this response. However, standing may also cause some negative effects such as increased arterial stiffness and increase the risk of syncope.