Key result
Standing and passive heating both significantly improved flow-mediated dilation compared to sitting, although standing increased peripheral arterial stiffness and was poorly tolerated by females.
Why the study?
Prolonged sitting strains arteries through angulations that reduce flow-mediated dilation, but whether arterial angulations, shear stress via local heating, or their combination affect vascular function across biological sexes was unknown.
Do standing and passive heating improve flow-mediated dilation compared to prolonged sitting in healthy young adults?
RCT (n=26)
Open-label
Randomized counterbalanced order
No
Do standing and passive heating improve flow-mediated dilation compared to prolonged sitting in healthy young adults?
Mean Difference: 1.42 (95% CI 0.18–2.66)
p-value: p=0.025
Both standing and local passive heating acutely mitigate sitting-induced vascular dysfunction, though standing may increase arterial stiffness and the risk of lightheadedness, particularly in females.
Hypothesis-generating for acute vascular effects; should not change practice without confirmatory trials.
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. Methods Twenty-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. Results There 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. Conclusions Both 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 Findings What is the central question of this study? Prolonged 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.
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Caldwell et al. (2020) conducted an RCT in Healthy (n=26). Standing and passive heating vs. Sitting and non-heated control was evaluated on Flow-mediated dilation (FMD) (MD 1.42%, 95% CI 0.18, 2.66, p=0.025). Standing and passive heating both significantly improved flow-mediated dilation compared to sitting, although standing increased peripheral arterial stiffness and was poorly tolerated by females.
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