The Acute Effects of Prolonged Uninterrupted Sitting on Vascular Function: A Systematic Review and Meta-analysis

A Single Bout of Prolonged Sitting Augments Very Short-Term Blood Pressure Variability

BACKGROUND

More habitual time spent engaging in prolonged sedentary behaviors increases the risk of developing hypertension. Beat-by-beat systolic (SBPV) and diastolic blood pressure variability (DBPV) are more pronounced in persons with hypertension and may be an early manifestation of blood pressure dysregulation. We tested the hypothesis that a single bout of prolonged sitting augments very short-term SBPV and DBPV. The secondary aim was to explore sex differences in prolonged sitting-induced increases in SBPV and DBPV.

METHODS

Thirty-three adults (22.9 ± 1.9 years; 17 females) completed a single, 3-hour bout of prolonged sitting with beat-by-beat arterial pressure determined at baseline, 1.5-hour, and 3-hour via finger photoplethysmography.

RESULTS

There were no sex differences observed for baseline brachial SBP (males: 122 ± 10 mm Hg; females: 111 ± 9 mm Hg), SBPV (males: 1.87 ± 0.63 mm Hg; females: 1.51 ± 0.38 mm Hg), DBP (males: 68 ± 6 mm Hg; females: 66 ± 8 mm Hg), or DBPV (males: 1.40 ± 0.41 mm Hg; females: 1.27 ± 0.32 mm Hg) (all, P > 0.41). In the pooled sample, baseline SBPV (1.68 ± 0.54 mm Hg) remained unchanged after 1.5 hours (1.80 ± 0.60 mm Hg; P = 0.59) but increased after 3.0 hours (1.84 ± 0.52 mm Hg; P = 0.01). This post-sitting increase was driven by males (P = 0.009), with no difference observed in females (P = 1.00). Similarly, baseline DBPV (1.33 ± 0.36 mm Hg) was similar after 1.5 hours (1.42 ± 0.41 mm Hg; P = 0.72) but was increased at 3 hours (1.50 ± 0.34 mm Hg; P = 0.02). However, no sex differences in DBPV (all, P > 0.07) were observed across the time points.

CONCLUSIONS

In young, normotensive adults, a single bout of prolonged sitting augmented beat-by-beat blood pressure variability, which may provide a link between uninterrupted sitting and the development of blood pressure dysregulation.

Interventions to reduce sedentary behaviour in adults with type 2 diabetes: A systematic review and meta-analysis

Treatment and management of Type 2 Diabetes (T2D) includes physical activity, nutrition, and pharmacological management. Recently, the importance of reducing and breaking up sedentary behaviour has become recognized. This review aimed to summarize and synthesize the effectiveness of interventions in reducing and/or breaking up sedentary behaviour and cardiometabolic biomarkers in adults with T2D. A study protocol was preregistered on PROSPERO (CRD42022357281) and a database search (PubMed, EMBASE, Scopus, Web of Science, PsycINFO, SPORTDiscus, CINAHL, and Cochrane Library) was conducted on 16/09/2022 and updated on 03/01/2024. This review followed PRISMA guidelines and study quality was assessed with the Cochrane risk of Bias Tools. Twenty-eight articles were included in the review. The meta-analysis of short-term (Range: 3 hours- 4 days) sedentary behaviour interventions found significant improvement in continuous interstitial glucose measured for 24 hours after the sedentary behaviour intervention compared to control (SMD:-0.819,95%CI:-1.255,-0.383,p<0.001). Similarly, there was a significant improvement in postprandial interstitial glucose after the sedentary behaviour intervention compared to control (SMD:-0.347,95%CI:-0.584,-0.110,p = 0.004). Ten out of eleven longer-term (Range: 5 weeks- 3 years) sedentary behaviour interventions improved at least one measure of sedentary behaviour compared to control. Eight out of eight longer-term sedentary behaviour interventions improved at least one cardiometabolic biomarker compared to control. Reducing sedentary behaviour, independent of physical activity, can improve glycemic control in adults with T2D. Further, sedentary behaviour may be a feasible/ sustainable behaviour change.

Prolonged Sitting Induces Elevated Blood Pressure in Healthy Young Men: A Randomized Crossover Trial

Introduction Prolonged sitting-induced blood pooling in the lower legs can increase blood pressure through increased sympathetic nerve activity and peripheral vascular resistance, an aspect that has been understudied as a primary outcome. This study compared the effects of prolonged sitting with those of prolonged supination on blood pressure in healthy young men. Methods This randomized crossover study included 16 healthy young men (mean age: 21.6 ± 0.7 years) who were randomly assigned to a three-hour supine (CON) or three-hour sitting (SIT) condition, followed by a washout period of at least one week. Systolic blood pressure (SBP), diastolic blood pressure (DBP), mean arterial pressure (MAP), heart rate (HR), low-frequency/high-frequency (LF/HF) ratio derived from heart rate variability, and leg circumference were measured at 60, 120, and 180 minutes from baseline. These indices were compared by two-way (time × conditions) analysis of variance (ANOVA). Results In the SIT condition, DBP, MAP, HR, LF/HF ratio, and leg circumference increased significantly over time (P < 0.05) and were significantly higher than those in the CON condition (P < 0.05). However, SBP showed no significant change over time and between conditions. Conclusions The findings indicate the involvement of sympathetic nerve activity and increased peripheral vascular resistance induced by fluid retention in the lower legs with increased DBP and MAP in healthy young men.

Exercise breaks prevent attenuation in cerebrovascular function following an acute bout of uninterrupted sitting in healthy children

The purpose of this study was to examine the effect of an acute bout of prolonged sitting with and without exercise breaks on cerebrovascular function in 7- to 13-year-old children. Forty-two children and adolescents were recruited to a crossover trial, with 15 girls (mean age 10.1 ± 2.5 years) and 16 boys (mean age 10.5 ± 1.3 years) completing the two trial conditions: SIT, uninterrupted sitting for 3 h and CYCLE, 3 h of sitting interrupted hourly with a 10-min moderate intensity exercise break. Cerebrovascular function was measured Pre and Post SIT and CYCLE from blood flow (Q ̇ ${\dot{Q}}$ ), diameter, and shear rate of the internal carotid artery (ICA) at rest and in response to CO2 . Blood velocity in the middle (MCA) and posterior (PCA) cerebral arteries was assessed at rest, during a neurovascular coupling task (NVC) and in response to CO2 . We demonstrate that SIT but not CYCLE reduced ICA cerebrovascular reactivity to CO2 (%Δ ICAQ ̇ ${\dot{Q}}$ /Δ end-tidal CO2 : SIT: Pre 5.0 ± 2.4%/mmHg to Post 3.3 ± 2.8%/mmHg vs. CYCLE: Pre 4.4 ± 2.3%/mmHg to Post 5.3 ± 3.4%/mmHg, P = 0.05) and slowed the MCA blood velocity onset response time to hypercapnia (SIT: Pre 57.2 ± 32.6 s to Post 76.6 ± 55.2 s, vs. CYCLE: Pre 64.1 ± 40.4 s to Post 52.3 ± 28.8 s, P = 0.05). There were no changes in NVC. Importantly, breaking up prolonged sitting with hourly exercise breaks prevented the reductions in cerebrovascular reactivity to CO2 and the slowed intracranial blood velocity onset response time to hypercapnia apparent with uninterrupted sitting in children. NEW FINDINGS: What is the central question of this study? What are the effects of interrupting prolonged sitting on cerebrovascular function in children? What is the main finding and its importance? Prolonged sitting results in declines in cerebrovascular reactivity, a valuable index of cerebrovascular health. Breaking up prolonged sitting with hourly 10 min exercise breaks prevented these changes. These initial findings suggest excessive sedentary behaviour does impact cerebrovascular function in childhood, but taking exercise breaks prevents declines.

Physiology of sedentary behavior

Sedentary behaviors (SB) are characterized by low energy expenditure while in a sitting or reclining posture. Evidence relevant to understanding the physiology of SB can be derived from studies employing several experimental models: bed rest, immobilization, reduced step count, and reducing/interrupting prolonged SB. We examine the relevant physiological evidence relating to body weight and energy balance, intermediary metabolism, cardiovascular and respiratory systems, the musculoskeletal system, the central nervous system, and immunity and inflammatory responses. Excessive and prolonged SB can lead to insulin resistance, vascular dysfunction, shift in substrate use toward carbohydrate oxidation, shift in muscle fiber from oxidative to glycolytic type, reduced cardiorespiratory fitness, loss of muscle mass and strength and bone mass, and increased total body fat mass and visceral fat depot, blood lipid concentrations, and inflammation. Despite marked differences across individual studies, longer term interventions aimed at reducing/interrupting SB have resulted in small, albeit marginally clinically meaningful, benefits on body weight, waist circumference, percent body fat, fasting glucose, insulin, HbA1c and HDL concentrations, systolic blood pressure, and vascular function in adults and older adults. There is more limited evidence for other health-related outcomes and physiological systems and for children and adolescents. Future research should focus on the investigation of molecular and cellular mechanisms underpinning adaptations to increasing and reducing/interrupting SB and the necessary changes in SB and physical activity to impact physiological systems and overall health in diverse population groups.

Relationship between sedentary behavior and endothelial dysfunction in a cross-sectional study in China

Sedentary behavior is a risk factor for several diseases, and previous studies have mostly reported the effects of acute sedentary behavior on vascular endothelial function. Data on the relationship between sedentary lifestyle habits and vascular function in large sample populations are lacking. Therefore, the aim of this study was to assess the correlation between self-reported sedentary behavior and peripheral vascular function in a check-up population from real-world data.

Methods

We recruited 13,220 participants from two health management centers of general tertiary hospitals located in northern and southern China between 2017 and 2021. All participants had undergone both questionnaires and brachial artery flow-mediated dilation (FMD) measurements.

Results

In total, 3,205 participants with FMD ≤ 5.0% were identified to have endothelial dysfunction. In a multivariable regression model including lifestyle habits such as sedentary behavior and cardiovascular risk factors, taking leisure sedentary time <2 h/day as a reference, the risk of vascular endothelial dysfunction gradually increased with time: 2-4 h/day (OR = 1.182, 95% CI: 1.058-1.321, P = 0.003), 4-6 h/day (OR = 1.248, 95% CI: 1.100-1.414, P = 0.001) and >6 h/day (OR = 1.618, 95% CI: 1.403-1.866, P < 0.001).

Conclusion

Longer leisure sedentary time is associated with a higher prevalence of vascular endothelial dysfunction. These findings suggest that leisure sedentary behavior is a risk factor for the occurrence of vascular endothelial dysfunction in the Chinese check-up population.

An acute bout of prolonged sitting blunts popliteal endothelium-independent dilation in young, healthy adults

A single bout of prolonged uninterrupted sitting increases oxidative stress, reduces popliteal blood flow-induced shear stress, and diminishes endothelium-dependent, flow-mediated dilation (FMD). The FMD response is also influenced by the sensitivity of vascular smooth muscle cells to nitric oxide (i.e., endothelium-independent dilation), which is also attenuated by elevated oxidative stress. However, it is currently unknown whether prolonged sitting impacts popliteal endothelium-independent dilation responses, which may uncover a novel mechanism associated with sitting-induced vascular dysfunction. This study tested the hypothesis that prolonged sitting attenuates both popliteal FMD and endothelium-independent, nitroglycerin-mediated dilation responses (NMD, 0.4 mg sublingual dose). Popliteal blood flow (mL/min), relative FMD (%), and NMD (%) were assessed via duplex ultrasonography before and after a ∼3-h bout of sitting in 14 young, healthy adults (8♀; 22 ± 2 yr). Prolonged sitting attenuated resting blood flow (57 ± 23 to 32 ± 16 mL/min, P < 0.001), relative FMD (4.6 ± 2.8% to 2.2 ± 2.5%; P = 0.001), and NMD (7.3 ± 4.0% to 4.6 ± 3.0%; P = 0.002). These novel findings demonstrate that both endothelium-dependent and independent mechanisms contribute to the adverse vascular consequences associated with prolonged bouts of sitting.NEW & NOTEWORTHY We demonstrate that lower-limb vascular smooth muscle function is attenuated in young, healthy adults after an acute bout of prolonged sitting. These data indicate that prolonged sitting-induced vascular dysfunction involves both endothelium-dependent and -independent mechanisms.

Effects of physical activity breaks during prolonged sitting on vascular and executive function—A randomised cross-over trial

Objectives

High sedentary behaviour is associated with adverse effects on central vascular function and cognitive function. Although interventions to mitigate the adverse effects of workplace sitting are intriguing, evidence of the efficacy of such interventions remains lacking. This randomised cross-over trial was aimed at exploring the effectiveness of prolonged sitting, with or without physical activity breaks, on central, peripheral vascular and cognitive function in adults.

Methods

Twenty one healthy adults completed 4 h of simulated work conditions in three experimental visits: (1) uninterrupted sitting (SIT); (2) sitting interrupted by 3 min of walking every hour (LIT); and (3) sitting interrupted by 3 min of stair climbing every hour (MIT). Carotid (CA) and superficial femoral artery (SFA) diameter, velocity, shear rate and blood flow were measured with Duplex ultrasound at 50 MHz at three time points (hours 0, 2 and 4), and executive function was assessed with the computer based Eriksen Flanker task every hour.

Results

The decreases in reaction time (-30.59%) and accuracy (-10.56%) during SIT conditions were statistically significant, and less of a decrease was observed under LIT and MIT conditions. No significant differences in CA and SFA function were observed with LIT and MIT interventions.

Conclusion

Physical activity breaks of varying intensity during prolonged sitting improve reaction time. However, the vascular benefits of physical activity breaks should be confirmed in the future through long term studies in natural environment.

Aortic stiffness increases during prolonged sitting independent of intermittent standing or prior exercise

INTRODUCTION

Adverse vascular responses can occur during prolonged sitting, including stiffening of the aortic artery which may contribute to cardiovascular disease. Few studies have investigated the impact of intermittent standing and/or prior exercise as strategies to attenuate these potentially deleterious vascular changes.

PURPOSE

To investigate central vascular health responses during prolonged sitting, with and without intermittent standing and/or prior exercise.

METHODS

Fifteen males aged 18 to 31 years were recruited. Subjects completed a control condition [Sitting Only (SO)], and three randomized strategy conditions [Sitting Plus Standing (SSt), Exercise Plus Sitting (ES), Exercise Plus Sitting Plus Standing (ESSt)]. For all conditions, measurements of carotid-femoral pulse wave velocity (cfPWV) were taken at pre- and post-intervention, and brachial and central blood pressure (BP) at pre-, 1-h, 2-h, and 3-h intervention.

RESULTS

cfPWV significantly increased from pre- to post-intervention for all conditions (all p ≤ 0.043), as did brachial mean arterial pressure (MAP) and diastolic BP, and central MAP and diastolic BP for the control condition (all p ≤ 0.022). Brachial and central systolic BP were significantly higher during SO compared to ESSt at 1 h, and compared to ES for central systolic BP (all p ≤ 0.036).

CONCLUSIONS

Strategies of intermittent standing and/or prior exercise may not prevent aortic stiffening during sitting but may attenuate BP elevations in the brachial and aortic arteries. Future research should investigate causal mechanistic links between sitting and aortic stiffening, and other attenuation strategies.

A Privacy-Preserving Desk Sensor for Monitoring Healthy Movement Breaks in Smart Office Environments with the Internet of Things

Smart workplace Internet of Things (IoT) solutions rely on several sensors deployed efficiently in the workplace environment to collect accurate data to meet system goals. A vital issue for these sensor-based IoT solutions is privacy. Ideally, the occupants must be monitored discreetly, and the strategies for maintaining privacy are dependent on the nature of the data required. This paper proposes a new sensor design approach for IoT solutions in the workplace that protects occupants' privacy. We focus on a novel sensor that autonomously detects and captures human movements in the office to monitor a person's sedentary behavior. The sensor guides an eHealth solution that uses continuous feedback about desk behaviors to prompt healthy movement breaks for seated workers. The proposed sensor and its privacy-preserving characteristics can enhance the eHealth solution system's performance. Compared to self-reporting, intrusive, and other data collection techniques, this sensor can collect the information reliably and timely. We also present the data analysis specific to this new sensor that measures two physical distance parameters in real-time and uses their difference to determine human actions. This architecture aims to collect precise data at the sensor design level rather than to protect privacy during the data analysis phase.

The behavioural epidemiology of sedentary behaviour in inflammatory arthritis: where are we, and where do we need to go?

In the last decade, studies into sedentary behaviour in inflammatory arthritis have raised important questions regarding its role in this condition. Specifically, evidence is needed on whether sedentary behaviour might exacerbate adverse inflammatory arthritis outcomes, and whether reducing sedentary behaviour might offer an effective avenue for self-management in this population. Research exploring these important research questions is still very much in its infancy and lacks the direction and scientific rigour required to inform effective intervention design, delivery and evaluation. Behavioural epidemiology refers to research that aims explicitly to understand and influence health behaviour patterns to prevent disease and improve health. To this end, the Behavioural Epidemiology Framework specifies a focused approach to health behaviour research, which leads to the development of evidence-based interventions directed at specific populations. In this review, we introduce the Behavioural Epidemiology Framework in the context of research into sedentary behaviour in inflammatory arthritis and ask: where are we, and where do we need to go?

Prior beetroot juice ingestion offsets endothelial dysfunction following prolonged sitting

Nutritional strategies to prevent endothelial dysfunction following prolonged sitting remain largely unknown. Given that beetroot juice (BRJ) ingestion enhances nitric oxide (NO) bioavailability, we aimed to evaluate whether prior BRJ ingestion would prevent sitting-induced endothelial dysfunction in the leg. Eleven healthy young males (n = 7) and females (n = 4) underwent two experimental trials of prolonged sitting with prior: 1) placebo ingestion (PL trial) and 2) BRJ ingestion (BRJ trial). All subjects ingested 140 ml of PL or BRJ (~0.0055 or ~12.8 mmol of nitrate, respectively) immediately before 3 h of sitting. Pre and post-sitting measurement of popliteal artery flow-mediated dilation (FMD) and blood pressure, and blood collection were undertaken. During the sitting period, an hourly assessment of popliteal artery diameter and blood velocity, blood pressure, and blood collection was performed. Popliteal artery blood flow and shear rate were significantly and similarly reduced during the sitting period in both trials (p < 0.001). Plasma nitrate and NOx (total nitrite and nitrate) concentrations were significantly increased relative to baseline in the only BRJ trial, and the overall concentrations were significantly higher in the BRJ trial (p < 0.001). Popliteal artery FMD was significantly reduced after the sitting period in the PL trial (p < 0.05), whereas no reduction was observed in the BRJ trial. Therefore, prior BRJ ingestion would prevent sitting-induced leg endothelial dysfunction via enhancing NO bioavailability.