The effects of prolonged sitting with a mild hypercapnic environment on vascular function in elderly adults: A pilot study

Abstract

Introduction: Prolonged Sitting (PS), defined a sitting for 2+ hours at a time, has been identified as an independent risk factor for cardiovascular disease (CVD). We previously reported that an acute bout of PS can attenuate macrovascular function in healthy young adults. Additionally, we reported that PS in mild hypercapnic environments (elevated CO2 concentrations) can further exacerbate these impairments in healthy young adults, and these impairments can be partially prevented by intermittent bouts of passive and active leg movements. However, the effects of prolonged sitting with a mild hypercapnic environment in the elderly population have not been studied. Therefore, the purpose of this study was to examine the impact of prolonged sitting with a mild hypercapnic condition on macrovascular function, arterial stiffness, and leg muscle metabolism. Additionally, we have further examined the effects of passive and active movements to negate the negative effects of prolonged sitting in elderly adults. Hypothesis: We hypothesized that 1) prolonged sitting in a hypercapnic environment will attenuate vascular function and leg metabolism, 2) both passive and active leg movements will preserve endothelial function and leg metabolism. Methods: Healthy elderly adults (n=2, 2 males, 69 ± 2.83 yrs) participated in three experimental visits consisting of 2.5h of prolonged sitting in a mild hypercapnic condition (CO2 = 1500ppm): control (CON), passive (PASS, passive leg movement), and active (ACT, active leg movement). Popliteal and brachial artery endothelial function was measured using flow-mediated dilation (FMD). Peripheral and central arterial stiffness was assessed using pulse wave velocity. Leg muscle metabolism was assessed using near infrared spectroscopy and a thermal camera. All measurements were taken pre- and post-siting. Results: Popliteal FMD was reduced in the CON condition compared to both the PASS and ACT (Δ -3.559 ± 0.499 vs Δ -1.799 ± 0.824 vs Δ 0.601 ± 1.958, respectively). Brachial FMD was attenuated in the CON condition compared to both compared to both the PASS and ACT (Δ -2.368 ± 0.215 vs Δ -0.285 ± 1.578 vs Δ 1.116 ± 1.174, respectively). The CON condition showed a greater reduction in leg temperature compared to both the PASS and ACT (Δ -2.4 vs Δ -1.6 ± 0.599 vs Δ 0.1 ± 0.224, respectively). No changes in central or peripheral arterial stiffness were observed. Conclusion: This preliminary data shows that uninterrupted prolonged sitting induces impairments in both local and systemic vascular function, leg muscle metabolism, but not arterial stiffness. Additionally, intermittent bouts of passive and active movements can partially preserve leg vascular function and metabolism during PS. This research was supported by the UNO Graduate Research and Creative Activity Grant, National Institutes of Health (RO1HD106911) and the Great Plains IdeaA-CTR (U54 GM115448). This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.