Impact of prolonged sitting on lower and upper limb micro- and macrovascular dilator function

Novel biomarkers in the saliva of healthy young males and females in a randomized crossover study on sedentary time: An exploratory analysis

Several known biomarkers have been used to understand the physiological responses of humans to various short and long-term interventions such as exercise or dietary interventions. However, little exploratory work has been conducted to identify novel biomarkers in human saliva that could enable non-invasive physiological research to understand acute responses to interventions such as reducing sedentary time. The purpose of this study was to identify novel biomarkers in the saliva (cytokines, growth factors and vascular factors) that respond to prolonged (4 hours) and interrupted sitting (4 hours of sitting interrupted by 3 minutes of walking at 60% of maximal heart rate every 27 minutes) in young, healthy males and females. We also sought to determine whether responsive biomarkers would differ by sex. Participants (n = 24, 21.2 ± 2.2 years, 50% female) completed a prolonged sitting (PS) session and an interrupted sitting (IS) session in random order. Individual saliva samples were pooled into a male sample and a female sample to identify responsive biomarkers using a human cytokine antibody membrane array (42 targets). Several novel biomarkers were responsive in both sexes (e.g., IL-8, Angiogenin, VEGF, and EGF), in females only (e.g., TNF-α and IL-13), and in males only (e.g., IL-3, RANTES, and IL-12p40/p70). Importantly, several biomarkers appear to be responsive to the 4-hour prolonged and interrupted sitting sessions (e.g., TNF-α, IL-8, IL-3, RANTES, EGF, Angiogenin, and VEGF). This work highlights new directions for researchers aiming to investigate the effect of short-term or acute interventions on different physiological pathways using non-invasive methods. Our work clearly indicates that human saliva samples can provide a wealth of insight into physiological responses, and that a number of biomarkers can be used to understand changes induced by acute interventions such as interrupting prolonged sitting.

Resistance exercise breaks during prolonged sitting augment the blood flow response to a subsequent oral glucose load in sedentary adults

Sitting-induced impairments in postprandial blood flow are an important link between sedentary behaviour and cardiometabolic disease risk. The objective of this work was to examine the effects of resistance exercise breaks (REB) performed every 30 min during an otherwise sedentary 3-h period on the vasodilatory response to a subsequent oral glucose load in sedentary adults. Twenty-four sedentary adults (27 ± 7 years, 16 females) completed two conditions. Fasting blood glucose, insulin, popliteal artery blood flow (PABF) and gastrocnemius perfusion were measured immediately before standardized breakfast consumption. After breakfast, the 3-h REB or uninterrupted (SIT) intervention period commenced. Participants sat at a workstation, and popliteal artery shear rate (PASR) was measured 60 and 120 min into this period. In the REB condition, participants performed a 3-min REB (3 × [20 s squats, 20 s high knees, 20 s calf raises]) every 30 min. Following the intervention period, baseline measurements were repeated. Participants then consumed a 75 g glucose beverage, and PABF and perfusion were measured every 30-60 min for the following 120 min. Relative to SIT, REB increased PASR at 60 min (+31.4 ± 9.2/s, P = 0.037) and 120 min (+37.4 ± 10.2/s, P = 0.019) into the intervention period. Insulin and glucose increased (P < 0.001) in response to glucose consumption, with no differences between conditions (P ≥ 0.299). In response to the glucose load, perfusion (1.57 vs. 1.11 mL/100 mL/min, P = 0.023) and PABF (+45.3 ± 11.8 mL/min, P = 0.001) were greater after REB versus SIT. Performing 3-min REB every 30 min during an otherwise sedentary 3-h period augmented leg blood flow responses to an oral glucose load. HIGHLIGHTS: What is the central question of this study? Can 3-min resistance exercise breaks (REB) performed during an otherwise sedentary 3-h period augment the vasodilatory response to a subsequent oral glucose load in sedentary adults? What is the main finding and its importance? Performing 3-min REB, which included squats, high knees, and calf raises, every 30 min augmented lower limb blood flow responses to a subsequent oral glucose load compared to 3 h of uninterrupted sitting in sedentary adults. Sitting-induced impairment in postprandial vasodilatory function has been identified as a link between sedentary behaviour and cardiometabolic disease. Thus, the current study presents a potentially effective strategy to offset this risk.

Sitting knee-flexion angle does not influence endothelial-dependent vasodilation in laboratory or free-living conditions

INTRODUCTION

Single bouts of prolonged bent-legged sitting attenuate popliteal endothelial-dependent vasodilation (as assessed via flow-mediated dilation [FMD]), which is partially attributed to arterial 'kinking'. However, the impact of knee-flexion angle on sitting-induced popliteal FMD is unknown. The objective of this study was to perform separate laboratory and free-living studies to test the hypotheses that: (1) popliteal FMD impairments would be graded between knee flexions at 90° (bent-legged sitting) > 45° > 0° (straight-legged sitting) following a 3-hour bout of sitting; and (2) more habitual time spent bent-legged sitting (< 45°) would be associated with lower FMD.

METHODS

The laboratory study included eight young, healthy adults (24 ± 2 years; four women) who underwent two sitting bouts over 2 days with one leg positioned at a knee-flexion angle of 0° or 90° and the opposite leg at 45° knee flexion. Popliteal FMD was assessed at pre- and postsitting timepoints.

RESULTS

Sitting-induced reductions in FMD were similar between all knee-flexion angles (all, p > 0.674). The free-living study included 35 young, healthy adults (23 ± 3 years; 16 women) who wore three activPAL monitors (torso, thigh, shin) to determine detailed sedentary postures. Time spent sedentary (624 ± 127 min/day), straight-legged sitting (112 ± 98 min/day), and bent-legged sitting (442 ± 106 min/day) were not related to relative FMD (5.3 ± 1.8%; all, p > 0.240).

CONCLUSION

These findings suggest that knee-flexion angle-mediated arterial 'kinking' during sitting is not a major contributor toward sitting-induced popliteal endothelial-dependent vasodilatory dysfunction.

Effect of Exercise Prior to Sedentary Behavior on Vascular Health Parameters: A Systematic Review and Meta-Analysis of Crossover Trials

BACKGROUND

Sedentary behavior has been shown to negatively affect parameters of endothelial function and central hemodynamics, both of which are closely associated with vascular health. Exercise prior to sedentary behavior has demonstrated potential as a preventive strategy to mitigate these detrimental effects. To evaluate the impact of exercise prior to sedentary behavior on vascular health parameters in the adult population, a systematic review and meta-analysis were conducted, synthesizing the available body of knowledge.

METHODS

A literature search was carried out in 6 databases. For each outcome, standard error and mean difference or standardized mean difference were calculated, as appropriate. An analysis was performed using a random effects model with a 95% confidence interval, using the inverse variance statistical method. Risk of bias assessment was performed using ROB2 and considerations for crossover trials. The quality of evidence was assessed using the GRADE system.

RESULTS

Exercise performed prior to prolonged sedentary behavior resulted in increased flow-mediated vasodilation at the first and third hours of sedentary time, compared with the control condition of sedentary behavior without prior exercise [MD: 1.51% (95% CI: 0.57 to 2.45) and MD: 1.36% (95% CI: 0.56 to 2.16), respectively]. Moreover, prior exercise led to increased shear rate at the first and third hours of sedentary time [MD: 7.70 s^-1 (95% CI: 0.79 to 14.61) and MD: 5.21 s^-1 (95% CI: 1.77 to 8.43), respectively]. Furthermore, it increased blood flow at the third hour [SMD: 0.40 (95%CI: 0.07 to 0.72)], compared with the control condition of prolonged sedentary behavior without prior exercise. Regarding hemodynamic parameters, exercise prior to prolonged sedentary behavior decreased mean arterial pressure during the first and third hours of sedentary behavior [MD: -1.94 mmHg (95% CI: -2.77 to -1.11) and MD: -1.90 mmHg (95% CI: -3.27 to -0.53), respectively], and an increase in heart rate during the first hour [MD: 4.38 beats per minute (95%CI: 2.78 to 5.98)] compared with the control condition of prolonged sedentary behavior without prior exercise.

CONCLUSIONS

The findings of this research suggest that prior exercise may prevent the impairment of vascular health parameters caused by sedentary behavior. However, the quality of the evidence was estimated as moderate. Therefore, further experimental studies and high-quality clinical trials are needed in this field to strengthen the results and conclusions drawn.

PROSPERO REGISTRATION NUMBER

CRD42023393686.

Non-neuronal cell-derived acetylcholine, a key modulator of the vascular endothelial function in health and disease

Vascular endothelial cells play an important role in regulating peripheral circulation by modulating arterial tone in the microvasculature. Elevated intracellular Ca2+ levels are required in endothelial cells to induce smooth muscle relaxation via endothelium-dependent mechanisms such as nitric oxide production, prostacyclin, and endothelial cell hyperpolarization. It is well established that exogenous administration of acetylcholine can increase intracellular Ca2+ concentrations, followed by endothelium-dependent vasodilation. Although endogenous acetylcholine's regulation of vascular tone remains debatable, recent studies have reported that endogenously derived acetylcholine, but not neuronal cell-derived acetylcholine, is a key modulator of endothelial cell function. In this minireview, we summarize the current knowledge of the non-neuronal cholinergic system (NNCS) in vascular function, particularly vascular endothelial cell function, which contributes to blood pressure regulation. We also discuss the possible pathophysiological impact of endothelial NNCS, which may induce the development of vascular diseases due to endothelial dysfunction, and the potential of endothelial NNCS as a novel therapeutic target for endothelial dysfunction in the early stages of metabolic syndrome, diabetes, and hypertension.

Seated Elliptical Exercise, But Not Periodic Standing, Alleviates Sitting-Induced Changes to Arterial Wave Reflections

PURPOSE

Sedentary behavior may contribute to increased central wave reflection due to associated peripheral vasoconstriction, yet its impact on central hemodynamics and the mitigating effects of interventional strategies have not been thoroughly investigated. We tested whether standing or seated elliptical breaks alleviate the deleterious effects of prolonged sitting on central wave reflections.

METHODS

Eighteen healthy adults (9 9 females, 25 ± 3 yr) completed three 3-h protocols on separate days: uninterrupted sitting, sitting with periodic standing, and sitting with periodic seated elliptical activity. Central wave reflection, central pulse wave velocity, and lower-limb pulse wave velocity were measured before and after each intervention.

RESULTS

Central relative wave reflection magnitude (RM) increased during sitting (0.31 ± 0.05 to 0.35 ± 0.05; P < 0.01) but did not change after standing (0.30 ± 0.05 to 0.32 ± 0.04; P = 0.19) or elliptical protocols (0.30 ± 0.05 to 0.30 ± 0.04; P > 0.99). The change in RM during prolonged sitting (ΔRM) was attenuated with elliptical activity (0.04 ± 0.05 vs 0.00 ± 0.03; P = 0.02) but not with periodic standing (0.04 ± 0.04 vs 0.02 ± 0.05; P = 0.54). In addition, augmentation index and central pulse wave velocity increased after sitting (both P < 0.01) and periodic standing (both P < 0.01) but were unchanged after elliptical activity. Lower limb pulse wave velocity did not change after sitting ( P = 0.73) or standing ( P = 0.21) but did decrease after elliptical activity ( P = 0.03).

CONCLUSIONS

Prolonged sitting without interruptions increased central wave reflection, whereas elliptical but not standing interruptions were able to ameliorate multiple sitting-induced vascular consequences. More work is required to examine the long-term effectiveness of interruption strategies, as well as the optimal type, frequency, and duration for reducing vascular risk associated with sedentary behaviors.

Joint associations of sedentary behavior and domain-specific physical activity on C-reactive protein in Korea

Sedentary behavior (SB) and physical activity (PA) exert opposing effects on inflammatory markers. This study examined the associations of a more subdivided combination of PA and SB with high-sensitivity C-reactive protein (hs-CRP). Using the 2014-2019 Korean National Health and Nutrition Examination Survey, this cross-sectional study analyzed 20,541 adults. The independent variables were SB, defined as ≥10 h of sitting per day, and three domains of PA: occupational PA (OPA) during work, leisure-time PA (LPA) during leisure time, and transportation PA (TPA) or active commuting. The dependent variable was hs-CRP ≥ 1.0 mg/L. Besides exploring the individual association of SB and each PA with hs-CRP, the combined association of SB and each PA with hs-CRP was also examined using multiple logistic regression. The analyses indicated that concurrent exposure to SB and OPA (odds ratio [OR] 1.36, 95% confidence interval [CI] 1.02-1.80) significantly raised the likelihood of increased hs-CRP, while SB without LPA (OR 1.26, 95% CI 1.11-1.41) or TPA (OR 1.19, 95% CI 1.08-1.31) significantly increased risk of higher hs-CRP, compared to their respective reference. The absence of non-occupational PA such as LPA or TPA combined with SB was associated with the increased hs-CRP risk, whereas OPA increased the risk when present concurrently with SB. Reducing SB and OPA while increasing LPA and TPA, is necessary to reduce inflammatory conditions.

Active workstations: A literature review on workplace sitting

The purpose of this paper is to further understand current literature on prolonged sitting, sitting posture and active sitting solutions. This paper is divided into three sections: The first section (Part I) is a comprehensive overview of the literature on how a static prolonged seated posture can affect: spinal health, trunk posture, contact pressure/discomfort development and vascular issues. The second section (Part II) reviews and qualitatively compares the four working postures recognized in ANSI/HFES 100-2007: reclined sitting, upright sitting, declined sitting and standing. The final section (Part III) is a summary of research on active chairs that revolves around the two types of movement patterns: 1- sustaining continual movement over a range of postures, occasionally reaching neutral lordosis, and 2- maintaining high frequency and duration of daily light contractile activity in the legs (or lower limbs).

Reducing thrombotic risks in video gamers: investigating the benefits of walking and compression sleeves on blood hemodynamics

With the growing popularity of video gaming, deep vein thromboses are increasingly being reported in gamers. This study aimed to compare the effects of lower leg graduated compression sleeves and a 6-min walking break during prolonged gaming on blood flow and hemodynamics in competitive sport players to help mitigate this risk. Ten healthy gamers (19.6 ± 1.2 yr old; 9 men) consented to participate in this mixed-model crossover design study that consisted of three visits. In visit 1, participants engaged in continuous 2-h video game play wearing no compression (continuous). Visits 2 and 3 involved 2-h play wearing compression sleeves (compression) and 2-h game play interrupted at 1 h by a 6-min walk (walk). Doppler ultrasound measurements of the left popliteal artery were taken at 30, 60, 90, and 120 min, to record vessel diameter, blood flow velocity, and blood flow volume. Participants completed a survey to assess their perception of each approach. There was a significant interaction between conditions for blood flow and blood velocity (P = 0.01, P < 0.001). Post hoc analysis demonstrated a greater decrease in blood flow and blood velocity in the continuous group compared with the walk group at the 90-min mark (P = 0.04, P = 0.01). No differences were found between the compression and walk groups or between the continuous and compression groups (P = 0.42, P = 0.69). No interactions were observed in diameter, mean arterial pressure, or heart rate. This study suggests that incorporating a 6-min walk every 60 min during prolonged gaming is advisable to counteract the negative effects on blood flow hemodynamics.NEW & NOTEWORTHY A 6-min light-intensity walking break during gaming can effectively combat the adverse effects of prolonged sitting, surpassing compression garments. Prolonged sitting reduces blood flow velocity, potentially leading to deep vein thrombosis (DVT). Compression sleeves help, with superior results after a 6-min walk at 60 min. Although compression stockings offer moderate improvements, a 6-min active break proves more effective. These findings offer promising interventions for gamers' health, initiating guidelines to mitigate DVT risk during gaming.

Cardiovascular Effects From Venous Blood Pooling in the Lower Limbs During Prolonged Sitting

PURPOSE

To investigate whether venous blood pooling in the lower limbs from prolonged sitting induces harmful cardiovascular effects by reducing stroke volume (SV) and cardiac output (CO).

METHODS

A randomized crossover trial involving 16 participants (mean age = 24.8 years ± 6.0 years, 44% women, 1 dropout) was conducted. The trial consisted of 2 conditions: cuff and noncuff, both involving 2 hours of prolonged sitting with tourniquets placed proximal to each knee. In the cuff condition, the tourniquets were inflated to subdiastolic pressure, allowing arterial inflow but preventing venous outflow. Venous blood pooling was assessed by measuring calf circumference. Cardiac Doppler sonography was used to measure CO, SV, and heart rate (HR) before and after the sitting period.

RESULTS

Although the interaction effect between venous blood pooling and CO was not statistically significant (P = .190), there was a significant main effect for time (effect size [ES] = 0.36, β = -0.238, 5.42% decrease). A medium-sized time-by-condition interaction effect for SV was observed (ES = 0.37, β = 6.165), with a 5.87% decrease in the cuff condition and a 2.81% increase in the noncuff condition. Furthermore, there was a large interaction effect for venous blood pooling as measured by calf circumference (ES = 1.98, β = -0.987), with a 3.69% increase in the cuff condition and a 0.03% increase in the noncuff condition.

DISCUSSION

Understanding the physiological adaptations that occur during prolonged sitting can provide insight into how and how often to interrupt sitting to prevent deleterious cardiovascular effects. SV decreased during the sitting period of 120 minutes in the cuff condition and increased slightly during in the noncuff condition. However, the changes in CO and HR were more variable and were not perfectly in line with the authors' hypotheses.

CONCLUSION

The findings indicate that as venous blood pooling increases during prolonged sitting, SV decreases, suggesting venous blood pooling influences certain hemodynamic changes associated with prolonged sitting.

Sitting leg vasculopathy: potential adaptations beyond the endothelium

Increased sitting time, the most common form of sedentary behavior, is an independent risk factor for all-cause and cardiovascular disease mortality; however, the mechanisms linking sitting to cardiovascular risk remain largely elusive. Studies over the last decade have led to the concept that excessive time spent in the sitting position and the ensuing reduction in leg blood flow-induced shear stress cause endothelial dysfunction. This conclusion has been mainly supported by studies using flow-mediated dilation in the lower extremities as the measured outcome. In this review, we summarize evidence from classic studies and more recent ones that collectively support the notion that prolonged sitting-induced leg vascular dysfunction is likely also attributable to changes occurring in vascular smooth muscle cells (VSMCs). Indeed, we provide evidence that prolonged constriction of resistance arteries can lead to modifications in the structural characteristics of the vascular wall, including polymerization of actin filaments in VSMCs and inward remodeling, and that these changes manifest in a time frame that is consistent with the vascular changes observed with prolonged sitting. We expect this review will stimulate future studies with a focus on VSMC cytoskeletal remodeling as a potential target to prevent the detrimental vascular ramifications of too much sitting.

Occupational physical activity as a determinant of daytime activity patterns and pregnancy and infant health

Though physical activity (PA) is recommended during pregnancy, it remains unclear how occupational physical activity (OPA) and sedentary behavior (SB) contribute to activity patterns and health during pregnancy. The purpose of this secondary analysis was to determine if OPA pattern is a determinant of all-day PA and evaluate associations with pregnancy/infant health outcomes. Data was from two prospective cohorts with study visits each trimester: MoM Health (Pittsburgh, PA; n = 120) and PRAMS (Iowa City, Iowa; n = 20). Using employment status/job hours (self-reported in demographic questionnaires) and OPA from the Pregnancy Physical Activity Questionnaire, latent class analysis identified three groups: sitting (n = 61), part-time mixed (n = 9), and active (n = 29). A fourth group included non-working participants (n = 32). Device-based PA (ActiGraph GT3X), SB (activPAL3 micro), and blood pressure were measured each trimester. Glucose screening test, gestational age, gestational weight gain, adverse pregnancy outcomes (APOs: gestational hypertension, preeclampsia, eclampsia, gestational diabetes, intrauterine growth restriction, and preterm birth), and infant outcomes (length, weight, and sex) were abstracted from medical records. Associations between groups with APOs and pregnancy/infant health were calculated using linear/logistic regression with adjustment for age, pre-pregnancy BMI, education, and race. Self-reported participant characteristics were similar across groups, except education which was higher in the sitting versus other groups. All-day device-based PA differed across groups; for example, the sitting group had the highest SB across trimester (all p<0.01) while the active group had the highest steps per day across trimesters (all p<0.01). Pregnancy/infant health did not differ between groups (all p>0.09). Compared to the non-working group, the risk of any APO was non-significantly higher in the sitting (OR = 2.27, 95%CI = 0.63-8.18) and active groups (OR = 2.40, 95%CI = 0.66-9.75), though not the part-time mixed (OR = 0.86, 95%CI = 0.08-9.1). OPA pattern is a determinant of all-day PA during pregnancy. Future studies with larger samples should examine associations between pregnancy OPA patterns and pregnancy/infant health.

Blood pressure and heart rate variability responses following an acute bout of vinyasa yoga and a prolonged seated control: A randomized crossover trial

Vinyasa yoga is moderate-intensity physical activity, yet physiological responses are poorly characterized. The purpose of this study was to examine the effect of a vinyasa yoga session on autonomic/cardiovascular functioning in healthy adults. A randomized crossover design took place at the Physical Activity and Weight Management laboratory (Pittsburgh, PA; n = 18), and included two experimental conditions: 60 minutes of vinyasa yoga or a seated control, and measurements were taken at baseline, 5-minutes, and 65-minute post-conditions. The primary cardiovascular-related outcomes of this study included blood pressure (BP), heart rate (HR), and HR variability (HRV) measures [natural log transformed (ln) standard deviation of normal-to-normal R-R intervals (SDNN), root mean square of successive differences (RMSSD), high frequency (HF), and low frequency to high frequency ratio (LF/HF ratio)]. Linear mixed effects models were used for data analyses. Systolic BP was 8.14 mmHg lower at 5 minutes post yoga (p<0.001) but was not different 65 minutes post, compared to the control. HR was higher at 5- and 65-minutes post yoga compared to the control (10.49/4.70 bpm, respectively, both p<0.01). HRV was lower (worse) at 5 and 65 minutes post for lnSDNN, lnRMSSD, and lnHF (all p<0.01). LF/HF ratio was higher (worse) at 5 minutes post yoga compared to the control (difference = +0.38, p = 0.025), but not different at 65 minutes post between conditions. Compared to prolonged sitting, vinyasa yoga had variable effects on post-session autonomic function including favorable BP responses and unfavorable HR and HRV responses, further investigation is warranted.

The effect of sedentary time on cardiovascular disease risk in middle-aged and elderly patients with type 2 diabetes mellitus

Sedentary lifestyle has become quite prevalent lately, and it has been associated with cardiovascular diseases (CVDs). CVD is a primary cause of premature death in patients with type 2 diabetes mellitus (T2DM). Some studies have focused on the association between sedentary behavior and blood glucose among T2DM patients. However, the occurrence and development of CVD involves many factors, such as blood glucose, blood lipid and so on. Therefore, we comprehensively examined the association of sedentary time with overall CVD risk and various metabolic risk factors in T2DM patients. A total of 775 middle-aged and elderly patients with T2DM were assessed. Framingham risk equation was employed to assess their overall CVD risk, while the sedentary time was self-reported. Demographic data and anthropometric and cardiac metabolic indicators were separately analyzed for both genders. The median age of the respondents was 55 (range: 45-75) years, and 39.23% were women. The overall risk of CVD in women was lower than that in men. Linear regression analysis revealed that sedentary time was significantly positively correlated with overall CVD risk and triglyceride level, but not with diastolic blood pressure and glycosylated hemoglobin and high-density lipoprotein cholesterol (HDL-C) levels. However, the correlation of sedentary time with fasting blood glucose level, body mass index, total cholesterol, and low-density lipoprotein cholesterol was only detected in women. In middle-aged and elderly patients with T2DM, prolonged sedentary time may increase the triglyceride levels and the overall risk of CVD. The adverse effects of sedentary time on fasting blood glucose, body mass index, total cholesterol, and low-density lipoprotein cholesterol may exhibit sex-based differences, as they were detected only in women.

The Impact of Sedentary Behavior on Renal Function Decline in 132,123 Middle Aged and Older Adults: A Nationwide Cohort Study

BACKGROUND Prior studies suggest that sedentary behavior is a well-known risk factor for cardiometabolic diseases. However, the longitudinal association between overall siting time and kidney function decline is not known. MATERIAL AND METHODS We performed a nationwide prospective cohort study in individuals aged more than 40 years enrolled in the China Cardiometabolic Disease and Cancer Cohort (4C) study. A total of 132 123 individuals were included in this study. Sitting time was measured with the short version of the International Physical Activity Questionnaire (IPAQ). Kidney function decline was defined as an eGFR <60 mL/min/1.73 m² or more than a 30% decrease in eGFR from baseline. Multivariate Cox proportional hazards regression analyses were conducted to estimate the adjusted hazard ratios (aHRs) and 95% confidence intervals (CIs) of the relation between kidney function decline and sitting time. RESULTS During a mean follow-up of 3.8 years, 3890 (2.9%) participants experienced kidney function decline. Longer sitting time was significantly associated with the risk of kidney function decline (aHR, 1.136; 95% CI, 1.036-1.247, P=0.007, comparing participants with baseline sitting time in the lowest quartile with those in the highest quartile) after adjustment for potential confounders. CONCLUSIONS Longer sitting time was independently and prospectively associated with a higher risk of kidney function decline. Sedentary behavior might represent a modifiable risk factor for chronic kidney disease (CKD) prevention.

Exercise Training on Anginal Threshold Does Not Improve Endothelial Function in Refractory Angina Patients

Refractory angina (RA) is a chronic condition of coronary artery disease (CAD). Endothelial function (EF) measured by flow-mediated dilation (FMD) is an important prognostic marker in CAD. Exercise training is a stimulus that improves EF in CAD. However, exercise training effects on EF in RA are unknown. Therefore, we aimed to verify the effects of exercise training on EF in RA. This was a longitudinal, non-randomized clinical study, involving patients with patients limited by angina, aged 45 to 75 years. Patients were prospectively allocated by convenience to either exercise trained (ET) or control group (C). Laboratory analysis, cardiopulmonary exercise test (CPET), and FMD were implemented at inclusion and after 12 weeks of exercise training or clinical treatment period. Exercise training included 60 minutes per session, 3 times a week, including 40 minutes of aerobic exercise on anginal threshold heart rate obtained on the CPET, 15 minutes of resistance training, and 5 minutes of stretching. A total of 38 patients were included (mean age 60 ± 9 years, 22 men); 21 were allocated to the ET and 17 to the C group. Baseline measures showed no differences between groups. After 12 weeks glycated hemoglobin and systolic blood pressure were lower in ET before than ET after (p = 0.004, and p = 0.05, respectively), and exercise time of the CPET was lower in ET before than ET after (p = 0.002). Exercise training did not change FMD. In conclusion, exercise training performed on anginal threshold increases exercise tolerance but causes no changes in EF in patients with RA.

Attenuated reactive hyperemia after prolonged sitting is associated with reduced local skeletal muscle metabolism: insight from artificial intelligence

Blunted post-occlusive reactive hyperemia (PORH) after prolonged sitting (PS) has been used as evidence of microvascular dysfunction. However, it has not been determined if confounding variables are responsible for the reduction in PORH after PS. Therefore, the purpose of this study was to examine the PS-mediated changes in cardiovascular and metabolic factors that affect PORH using artificial intelligence (AI). We hypothesized that calf muscle metabolic rate (MMR) is attenuated after PS, which may reduce tissue hypoxia during an arterial occlusion (i.e., oxygen deficit) and PORH. Thirty-one subjects (male = 13, female = 18) sat for 2.5 h. A rapid-inflation cuff was placed around the thigh above the knee to generate an arterial occlusion. PORH was represented by the reoxygenation rate (RR) of the near-infrared spectroscopy (NIRS) tissue oxygenation index (TOI) after 5-min of arterial occlusion. An artificial intelligence model (AI) defined the stimulus-response relationship between the oxygen deficit (i.e., ΔTOI and TOI deficit), and RR with 65 previous PORH recordings. If the AI predicts the experimental RRs, then the change in RR is related to the change in the oxygen deficit. RR (Δ -0.27 ± 0.55 lnTOI%·s-1, P = 0.001), MMR (Δ -0.46 ± 0.61 lnTOI%·s-1, P < 0.001), ΔTOI (Δ -0.34 ± 0.62 lnTOI%, P < 0.001), and the TOI deficit (Δ -0.42 ± 0.68 lnTOI%·s, P < 0.001) were reduced after PS. In addition, strong linear associations were found between MMR and the TOI deficit (r2 = 0.900, P < 0.001) and ΔTOI (r2 = 0.871, P < 0.001). Furthermore, the AI accurately predicted the RRs pre- and post-PS (P = 0.471, P = 0.328, respectively). Therefore, blunted PORH after PS may be caused by attenuated MMR and not microvascular dysfunction.NEW & NOTEWORTHY Prolonged sitting reduces lower leg skeletal muscle metabolic rate in healthy individuals. Artificial intelligence revealed that impaired post-occlusive reactive hyperemia after prolonged sitting is related to a reduced stimulus for vasodilation and may not be evidence of microvascular dysfunction. Current post-occlusive reactive hyperemia protocols may be insufficient to assess micro- and macrovascular function after prolonged sitting.

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.

Prolonged sitting and peripheral vascular function: potential mechanisms and methodological considerations

Sitting time is associated with increased risks for subclinical atherosclerosis and cardiovascular disease development, and this is thought to be partially due to sitting-induced disturbances in macro- and microvascular function as well as molecular imbalances. Despite surmounting evidence supporting these claims, contributing mechanisms to these phenomena remain largely unknown. In this review, we discuss evidence for potential mechanisms of sitting-induced perturbations in peripheral hemodynamics and vascular function and how these potential mechanisms may be targeted using active and passive muscular contraction methods. Furthermore, we also highlight concerns regarding the experimental environment and population considerations for future studies. Optimizing prolonged sitting investigations may allow us to not only better understand the hypothesized sitting-induced transient proatherogenic environment but to also enhance methods and devise mechanistic targets to salvage sitting-induced attenuations in vascular function, which may ultimately play a role in averting atherosclerosis and cardiovascular disease development.

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.

High physical activity alleviates the adverse effect of higher sedentary time on the incidence of chronic kidney disease

BACKGROUND

Low physical activity (PA) increases the prevalence of chronic kidney disease (CKD). This study aimed to investigate the effects of PA and sedentary time (ST) on the changes in renal function and the development of CKD in the middle-aged Korean population.

METHODS

From the Korean Genome and Epidemiology Study Database, 7988 participants in their 40s and 60s were identified and stratified by (1) PA: high-PA (>24 MET-h/day), moderate-PA (9-24 MET-h/day) and low-PA (<9 MET-h/day); and (2) ST: high-ST (>6 h/day), moderate-ST (3-6 h/day) and low-ST (<3 h/day). Incident CKD was defined as estimated glomerular filtration rate (eGFR) < 60 mL/min/1.73 m² following the Chronic Kidney Disease Epidemiology Collaboration equation.

RESULTS

The mean age of the participants was 52.0 years. The overall incidence of CKD was 16.8 per 1000 person-years over a median of 12 years. The lower the PA and the higher the ST, the lower the baseline eGFR. Relative to the high-PA, the coefficients of the annual eGFR decline were -0.12 (95% confidence interval [CI]: -0.26 to 0.001, P = 0.081) and -0.13 (95% CI: -0.27 to 0.01, P = 0.078) in the moderate- and low-PA groups, respectively. Similarly, relative to the low-ST, the coefficients of annual eGFR decline were -0.07 (59% CI: -0.19 to 0.05, P = 0.236) and -0.14 (95% CI: -0.28 to -0.01, P = 0.039) in the moderate- and high-ST groups, respectively. Incident CKD was higher with lower PA (hazard ratio: high-PA 1.00, moderate-PA 1.13 [1.00, 1.28, P = 0.056] and low-PA 1.25 [1.11, 1.24, P < 0.001]) and higher ST (hazard ratio: low-ST 1.00, moderate-ST 1.04 [0.94, 1.16, P = 0.440] and high-ST 1.19 [1.05, 1.34, P = 0.007]). The high-PA reduced the risk for the CKD development irrespective of the amount of ST.

CONCLUSIONS

Low-PA and high-ST are risk factors for the development of CKD in the middle-aged Korean population. High-PA recovers high-ST, inducing a harmful effect on the occurrence of CKD.

Does sex influence near-infrared spectroscopy-derived indicators of microvascular reactivity and the response to acute dietary capsaicin

Endothelial dysfunction is associated with cardiovascular disease development, nitric oxide (NO) deficiencies, and may be limb or sex-specific. Prior in vitro work indicated that the transient receptor potential vanilloid channel-1 (TRPV₁) is expressed in human arteries and the TRPV₁ agonist capsaicin alters vasodilation in an endothelium-dependent manner; however, it is unknown if this translates in vivo or is limb or sex-dependent. Therefore, we sought to determine if there was limb or sex-specificity in the effect of capsaicin on microvascular function using near-infrared spectroscopy (NIRS)-derived tissue oxygen saturation (StO₂) reperfusion slope. In a blinded placebo-controlled crossover design, 45 young males (M: n = 25) and females (F: n = 20), the reperfusion slopes of the forearm and quadriceps were assessed, and a urine sample obtained to assay for nitrate/nitrite (NOx) concentrations and antioxidant capacity after acutely ingesting placebo or capsaicin. Under placebo, females had greater reperfusion rates in both the forearm (M: 0.44 ± 0.24 vs. F: 0.98 ± 0.46 %/sec; p = 0.002, d = -1.50) and quadricep (M: 0.86 ± 0.31 vs. F: 1.17 ± 0.43 %/sec; p = 0.010, d = -0.85). Capsaicin decreased microvascular responsiveness in the forearm of females (placebo: 0.98 ± 0.45 vs. capsaicin: 0.84 ± 0.45 %/sec) as compared to males (placebo: 0.45 ± 0.24 vs. capsaicin: 0.38 ± 0.16 %/sec, interaction p < 0.001, η² = 0.475). There was a sex*treatment interaction for NOx concentrations, where males increased (placebo: 21.13 ± 12.83 vs. capsaicin: 23.82 ± 13.34 μM), while females decreased (placebo: 22.78 ± 14.40 vs. capsaicin: 14.43 ± 10.01 μM; p = 0.037, η² = 0.042). Using NIRS to assess microvascular function, there is apparent limb and sex-specificity, and, for the first-time, document that acute oral capsaicin alters reperfusion slope in a sexually divergent manner.

Three-minute bench step exercise as a countermeasure for acute mental stress-induced arterial stiffening

Acute mental stress (MS) induces a transient increase in arterial stiffness. We verified whether a single bout of bench step (BS) exercise for 3 minutes counteracts acute MS-induced arterial stiffening. Fifteen healthy young men (mean age, 21.7 ± 0.3 years) underwent two experimental trials: rest (RE) and exercise (EX) trials. Following a 5-minute MS task, the participants in the RE trial rested on a chair for 3 minutes (from 10 to 13 minutes after task cessation), whereas those in the EX trial performed the BS exercise for the same duration. The heart-brachial pulse wave velocity (PWV) (hbPWV), brachial-ankle PWV (baPWV), heart-ankle PWV (haPWV), and the cardio-ankle vascular index (CAVI) were measured at baseline and at 5 and 30 minutes after the task. In both trials, significant increases in hbPWV, haPWV, and CAVI occurred at 5 minutes after the task; these elevations persisted until 30 minutes after the task in the RE trial, but significantly decreased to baseline levels in the EX trial. baPWV was significantly elevated at 30 minutes after the task in the RE trial, but not in the EX trial. This study reveals that a 3-minute BS exercise offsets acute MS-induced arterial stiffening.

Patterns in Prenatal Physical Activity and Sedentary Behavior: Associations With Blood Pressure and Placental Features in the MoMHealth Cohort

BACKGROUND

Moderate to vigorous physical activity (MVPA) and sedentary behavior (SED) are associated with blood pressure (BP) and adverse pregnancy outcomes. The authors investigated associations of prenatal MVPA and SED patterns with BP and with placental malperfusion features.

METHODS

Women enrolled in this prospective cohort study in the first trimester. MVPA, SED, and BP were measured objectively each trimester. MVPA and SED trajectories were constructed. Placental examinations were conducted in a subset. Associations of trajectories with BPs were assessed with linear regression adjusted for age, race, education, prepregnancy body mass index, and gestational age. Associations with placental malperfusion lesions and weight were adjusted for key covariates.

RESULTS

One hundred eleven participants were included; placental exams were available in 50. Participants with high (vs low) SED were younger and more likely to have adverse pregnancy outcomes. High SED (vs low) was associated with higher first trimester systolic (β = 5.3; 95% confidence interval, 0.0 to 10.6) and diastolic (β = 5.0; 95% confidence interval, 1.4 to 8.6) and higher second trimester diastolic (β = 4.9; 95% confidence interval, 1.6 to 8.2) BP. Medium and high MVPA groups were associated with lower postpartum diastolic BP. Trajectories were not associated with placental malperfusion.

CONCLUSIONS

MVPA and SED patterns were differentially associated with prenatal and postpartum BP. Encouraging favorable levels of both might help women achieve lower BP during and after pregnancy.

Associations between noninvasive upper- and lower-limb vascular function assessments: extending the evidence to young women

Brachial artery (BA) flow-mediated dilation (FMD) is a well-established measure of peripheral vascular function prognostic of future cardiovascular events. The vasodilatory response to FMD (FMD%) reflects upper-limb conduit artery function, whereas reactive hyperemia (RH) following cuff-occlusion release reflects upper-limb resistance artery function. Comparatively, passive leg movement (PLM) is a newer, increasingly utilized assessment of lower-limb resistance artery function. To increase its clinical utility, PLM-induced leg blood flow (LBF) responses have been compared with hemodynamic responses to FMD, but only in men. Therefore, the purpose of this study was to retrospectively compare LBF responses to FMD% and RH responses in women. We hypothesized that LBF responses would be positively associated with both FMD% and RH, but to a greater extent with RH. FMD and PLM were performed on 72 women (23 ± 4 yr). Arterial diameter and blood velocity were assessed using Doppler ultrasound. Pearson correlation coefficients were used to evaluate associations. Measures of resistance artery function were weakly positively associated: change in BA blood flow ΔBABF and ΔLBF (r = 0.33, P < 0.01), BABF area under the curve (BABF AUC) and LBF AUC (r = 0.33, P < 0.01), and BABFpeak and LBFpeak (r = 0.37, P < 0.01). However, FMD% was not associated with any index of PLM (all P > 0.30). In women, indices of resistance artery function in the upper- and lower limbs were positively associated. However, contrary to the previous work in men, upper-limb conduit artery function was not associated with lower-limb resistance artery function suggesting these assessments capture different aspects of vascular function and should not be used interchangeably in women.NEW & NOTEWORTHY Upper- and lower-limb indices of resistance artery function are positively associated in young women when assessed by reactive hyperemia following brachial artery flow-mediated dilation (FMD) cuff-occlusion release and leg blood flow responses to passive leg movement (PLM), respectively. However, despite previous data demonstrating a positive association between upper-limb conduit artery function assessed by FMD and lower-limb resistance artery function assessed by PLM in young men, these measures do not appear to be related in young women.

Detrimental effects of physical inactivity on peripheral and brain vasculature in humans: Insights into mechanisms, long-term health consequences and protective strategies

The growing prevalence of physical inactivity in the population highlights the urgent need for a more comprehensive understanding of how sedentary behaviour affects health, the mechanisms involved and what strategies are effective in counteracting its negative effects. Physical inactivity is an independent risk factor for different pathologies including atherosclerosis, hypertension and cardiovascular disease. It is known to progressively lead to reduced life expectancy and quality of life, and it is the fourth leading risk factor for mortality worldwide. Recent evidence indicates that uninterrupted prolonged sitting and short-term inactivity periods impair endothelial function (measured by flow-mediated dilation) and induce arterial structural alterations, predominantly in the lower body vasculature. Similar effects may occur in the cerebral vasculature, with recent evidence showing impairments in cerebral blood flow following prolonged sitting. The precise molecular and physiological mechanisms underlying inactivity-induced vascular dysfunction in humans are yet to be fully established, although evidence to date indicates that it may involve modulation of shear stress, inflammatory and vascular biomarkers. Despite the steady increase in sedentarism in our societies, only a few intervention strategies have been investigated for their efficacy in counteracting the associated vascular impairments. The current review provides a comprehensive overview of the evidence linking acute and short-term physical inactivity to detrimental effects on peripheral, central and cerebral vascular health in humans. We further examine the underlying molecular and physiological mechanisms and attempt to link these to long-term consequences for cardiovascular health. Finally, we summarize and discuss the efficacy of lifestyle interventions in offsetting the negative consequences of physical inactivity.

Impact of Acute Uninterrupted Sitting on Cerebrovascular Hemodynamics

Reductions in brain blood flow are associated with reduced cognitive function and cerebrovascular disease. Acute periods of uninterrupted sitting can lead to endothelial dysfunction, namely due to a reduction in shear stress and subsequent reduction in nitric oxide bioavailability. Little is known of the impact of sitting on brain health. The purpose was to determine the total brain blood flow response following a 60-minute bout of uninterrupted sitting. Using a parallel design, this study evaluated the impact of 60-minutes of sitting on total brain blood flow. Fifteen participants (n=15; age=24 ± 1yr; BMI=25 ± 1 kg/m²) sat, uninterrupted, for 60-minutes during the SIT protocol. To ascertain the contribution of blood pooling effects on total brain blood flow, ten participants (n=10; age=23±2yr; BMI=27±4 kg/m²) sat in a modified sitting (MOD) for 60-minutes. Finally, thirteen participants (n=13; age=23±3yr; BMI=26±4 kg/m²) remained supine for the duration of the 60-minutes as a time-control (TC). Brain blood flow was quantified through Doppler-ultrasound measurements of blood flow through the internal carotid (ICA) and vertebral (VA) arteries: (ICA blood flow + VA blood flow) × 2. Following the 60-minutes of sitting (SIT), there was a significant reduction in brain blood flow with time (p=0.001, η _p ² =0.05). Total brain blood flow did not significantly change in MOD (p=0.69, η _p ² =0.05) or TC (p=0.06, η _p ² =0.58) conditions. These findings indicate 60-minutes of sitting may alter cerebrovascular hemodynamics characterized by a reduction in total brain blood flow.

Does active sitting provide more physiological changes than traditional sitting and standing workstations?

This cross-sectional study examined the physiological effects of two active chairs (AC1: had the feature to pedal and slide forward; AC2: was a multiaxial chair) compared to a traditional office chair and standing workstation. Twenty-four healthy participants computed at each of the workstations for 60 min. The active protocol was to alternate between a pedalling/side-to-side motion and sliding forward/front-to-back motion to the sound of a metronome operating at 40 bpm. The participants' physiological effects were recorded using near-infrared spectroscopy (NIRS); electrodermal activity (EDA) and a heart rate (HR) monitor for each collection period. Statistical analysis was conducted using a repeated measures analysis of variance for within-task and between-workstation comparisons. A Tukey's post hoc analysis was calculated for significant findings. Both active chairs significantly increased oxygenated blood in the gastrocnemius and participants' heart rate and EDA (stress) levels were affected slightly by task and time. However, participants felt more "productive" sitting in the control chair than in either of the active chairs.

Impact of prolonged sitting interruption strategies on shear rate, flow-mediated dilation and blood flow in adults: A systematic review and meta-analysis of randomized cross-over trials

Prolonged sitting has been shown to affect endothelial function. Strategies that promote interruption of sitting have shown varying results on the shear rate (SR), flow-mediated dilation (FMD) and blood flow (BF). Thus, we conducted a systematic review and meta-analysis to 1) increase the existing knowledge of the impact of sitting interruption in the prevention of endothelial dysfunction in adults and 2) determine the effect of the sitting interruption strategies on SR, FMD, BF. Literature search was carried out through 7 databases. A random effects model was used to provide the overall mean difference with a 95%CI, and forest plots were generated for pooled estimates of each study outcome. Assessment of biases was performed using ROB2 and considerations for crossover trials. Prolonged sitting interruption strategies showed a significant effect in increasing SR (MD: 7.58 s^-1; 95% CI: 3.00 to 12.17), FMD (MD: 1.74%; 95% CI: 0.55 to 2.93) and BF (MD: 12.08 ml/min; 95% CI: 7.61 to 16.55) when compared with the uninterrupted prolonged sitting condition. Prolonged sitting interruption strategies significantly increase SR, FMD and BF, therefore, they represent a considerable effective preventive method on endothelial dysfunction caused by acute exposure to uninterrupted prolonged sitting.

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.

Effects of the Follicular Menstrual Phase on Forearm Vascular Conductance in Abdominal Obese Premenopausal Women During Graded Handgrip Exercise

Purpose

Previous studies have reported a sympatholytic action of estrogen on the vasculature in response to increased sympathetic outflow, an effect most notable during exercise, providing for necessary increases in blood flow to working muscle. In contrast, elevated concentrations of progesterone can inhibit this action of estrogen, impairing increases in blood flow. We hypothesize that the peak concentration of estrogen during the proliferative portion of the follicular phase of the menstrual cycle in female humans will increase vascular conductance during exercise when the effects of progesterone are negligible. In addition, we hypothesize that overweight abdominally obese females will have an attenuated conductance response to dynamic exercise during the same menstrual phase.

Methods

Participants engaged in graded forearm exercise using an isotonic handgrip dynometer with sequential increases in resistance at a cadence of 30 contractions/minute until task failure. They performed exercise at time points of the menstrual cycle corresponding to low concentrations of both sex hormones and elevated estrogen, while progesterone remained low. Blood flow and vascular conductance were measured using Doppler ultrasound.

Results

This revealed a trend that abdominal obese women during a phase of low estrogen had a lower overall blood flow and vascular conductance response than healthy controls at matching resistance stages during rest and exercise. This group difference was attenuated during the proliferative phase with elevated circulating estrogen. There is not a statistically significant interaction between Ovarian Phase and Weight group (P = 0.778).

Conclusion

The results indicate that overweight women are at a disadvantage during exercise in increasing blood flow to working muscles, which can be detrimental to overall fitness improvement during the early and potentially late follicular phase of the menstrual cycle.

The effectiveness of bench step exercise for ameliorating acute mental stress-induced arterial stiffening

Purpose

This study aimed to evaluate the effectiveness of bench step (BS) exercise for ameliorating arterial stiffening caused by acute mental stress (MS).

Methods

Fifteen young healthy men participated in two randomized trials: rest (RE) and exercise (EX) trials. Following a 5-min MS task (first task), the RE trial participants rested on a chair for 10 min (from 10 to 20 min after task cessation); the EX trial participants performed BS exercise for the same duration. At 40 min after the first task, the participants performed the same task (second task) again. Heart–brachial pulse wave velocity (PWV) (hbPWV), brachial–ankle PWV (baPWV), heart–ankle PWV (haPWV), and the cardio-ankle vascular index (CAVI) were measured simultaneously at 5, 30, and 50 min after the first task.

Results

Both trials caused significant elevations in hbPWV, haPWV, and CAVI at 5 min after the first task; these changes persisted until 30 min after the task in the RE trial, while they were abolished in the EX trial. baPWV significantly increased at 30 min after the task in the RE trial, but not in the EX trial. After the second task (from 30 to 50 min after the first task), none of the parameters significantly increased in the RE trial, although the values remained above baseline levels. In the EX trial, hbPWV, haPWV, and CAVI showed significant elevations.

Conclusion

Our findings suggest that a 10-min BS exercise after acute MS can counteract stress-induced arterial stiffening, but has only a limited effect against subsequent acute MS.

Supplementary Information

The online version contains supplementary material available at 10.1007/s00421-022-04962-y.

Self-reported total sitting time on a non-working day is associated with blunted flow-mediated vasodilation and blunted nitroglycerine-induced vasodilation

We divided the 466 subjects into two groups based on information on sitting time on a non-working day and evaluated flow-mediated vasodilation (FMD) and nitroglycerine-induced vasodilation (NID). FMD was smaller in subjects with sitting time on a non-working day of ≥6 h/day than in subjects with sitting time on a non-working day of <6 h/day (2.5 ± 2.6% vs. 3.7 ± 2.9%; p < 0.001). NID was smaller in subjects with sitting time at non-working day of ≥ 8 h/day than in subjects with sitting time on a non-working day of < 8 h/day (10.1 ± 5.6% vs. 11.5 ± 5.0%; p = 0.01). After adjustment for confounding factors for vascular function, the odds of having the lowest tertile of FMD was significantly higher in subjects with sitting time on a non-working day of ≥6 h/day than in subjects with sitting time on a non-working day of <6 h/day. The odds of having the lowest tertile of NID was significant higher in subjects with sitting time on a non-working day of ≥ 8 h/day than in subjects with sitting time on a non-working day of < 8 h/day. These findings suggest that prolonged sitting time on a non-working day is associated with blunted FMD and blunted NID.

Monitoring calf circumference: changes during prolonged constrained sitting

Prolonged sitting has been associated with negative health effects; however, short-term time-varying exposure and response data is lacking. Twenty-two young and healthy participants were seated for 2 hours with the instruction to avoid the confounding effects of large leg movements while calf circumference, perceived discomfort, and lower limb muscle activity were collected. Calf circumference increased significantly (0.90 ± 0.32 cm) during sitting with no statistical differences between sexes. Perceived discomfort increased significantly over time in the low back and gluteal regions (p = 0.001-0.072, η_p²=0.080-0.360). On average, it took 20.31 ± 10.87 minutes of walking for calf measures to return to pre-sitting baseline. These results suggest that sitting for 2 hours without activity breaks may not be advisable and that recovery may take longer than expected. The exposure/response data from this study may be helpful in the design of future studies, with a larger and more general population, aiming to better define recommended duration/activity ratios for sitting-focused occupations. Practitioner summary: Leg swelling is a concern in prolonged sitting. In this study of young, healthy participants, we found a 2 hour constrained sitting exposure (controlling for large leg movements) induced significant increases in calf circumference that took an average of 20.31 ± 10.87 min of walking to return to baseline.Abbreviations: FMD: flow-mediated dilation, GSC: gastrocnemius; TA: tibialis anterior; EMG: electromyography; VAS: visual analog scale; MVC: maximum voluntary contractions.

Examination of Sex-Specific Participant Inclusion in Exercise Physiology Endothelial Function Research: A Systematic Review

Background

To combat historical underrepresentation of female participants in research, guidelines have been established to motivate equal participation by both sexes. However, the pervasiveness of female exclusion has not been examined in vascular exercise physiology research. The purpose of this study was to systematically quantify the sex-specific prevalence of human participants and identify the rationales for sex-specific inclusion/exclusion in research examining the impact of exercise on vascular endothelial function.

Methods

A systematic search was conducted examining exercise/physical activity and vascular endothelial function, assessed via flow mediated dilation. Studies were categorized by sex: male-only, female-only, or mixed sex, including examination of the sample size of males and females. Analysis was performed examining sex-inclusion criteria in study design and reporting and rationale for inclusion/exclusion of participants on the basis of sex. Changes in proportion of female participants included in studies were examined over time in 5 year cohorts.

Results

A total of 514 studies were identified, spanning 26 years (1996–2021). Of the total participants, 64% were male and 36% were female, and a male bias was identified (32% male-only vs. 12% female-only studies). Proportions of female participants in studies remained relatively constant in the last 20 years. Male-only studies were less likely to report sex in the title compared to female-only studies (27 vs. 78%, p < 0.001), report sex in the abstract (72 vs. 98%, p < 0.001) and justify exclusion on the basis of sex (15 vs. 55%, p < 0.001). Further, male-only studies were more likely to be conducted in healthy populations compared to female-only studies (p = 0.002). Qualitative analysis of justifications identified four themes: sex-specific rationale or gap in the literature, exclusion of females based on the hormonal cycle or sex-differences, maintaining congruence with the male norm, and challenges with recruitment, retention and resources.

Conclusions

This systematic review provides the first analysis of sex-based inclusion/exclusion and rationale for sex-based decisions in human vascular exercise physiology research. These findings contribute to identifying the impact of research guidelines regarding inclusion of males and females and the perceived barriers to designing studies with equal sex participation, in an effort to increase female representation in vascular exercise physiology research.

Systematic Review Registration:

CRD42022300388.

Impact of habitual sedentary patterns on popliteal artery endothelial-dependent vasodilation in healthy adults

Introduction:

Acute, laboratory-based bouts of prolonged sitting attenuate lower-limb arterial endothelial-dependent vasodilation. However, the impact of habitual sedentary patterns on popliteal artery endothelial health is unclear. We tested the hypothesis that greater habitual total sedentary time, more time spent in prolonged sedentary bouts, and fewer sedentary breaks would be associated with worse popliteal flow-mediated dilation (FMD) responses.

Methods:

This cross-sectional study used 98 healthy participants (19–77 years, 53 females) that wore an activPAL monitor on the thigh for 6.4 ± 0.8 days to objectively measure sedentary activity and completed a popliteal ultrasound assessment to determine FMD. Both relative (%baseline diameter) and absolute (mm) FMD were calculated. Using bivariate correlation and multiple regression analyses, we examined if there were relationships between sedentary outcomes and FMD while statistically controlling for any potential confounders.

Results:

In the multiple regression model, age (p = 0.006, β = −0.030, 95% CI = −0.051, −0.009) and total time in sedentary bouts > 1 hour (p = 0.031, β = −0.005, 95% CI = −0.009, −0.001) were independent predictors of relative FMD. Age (β = −0.002, 95% CI = −0.003, −0.001), mean blood flow (β = 0.013, 95% CI = 0.002, 0.024), moderate-intensity physical activity (β = 155.9E⁻⁵, 95% CI = 22.4E⁻⁵, 289.4E⁻⁵), sedentary breaks (β = 0.036, 95% CI = 0.007, 0.066), and total time spent in sedentary bouts > 1 hour (β = −25.02E⁻⁵, 95% CI = −47.67E⁻⁵, −2.378E⁻⁵) were predictors of absolute FMD (all, p < 0.047). All independent outcomes remained significant after partially controlling for all other predictor variables (all, p < 0.031).

Conclusions:

Habitual prolonged sedentary bouts and sedentary breaks, but not total sedentary time, were predictors of popliteal endothelial-dependent vasodilatory function. The patterns by which sedentary time is accumulated may be more important than the total sedentary time on lower-limb arterial health.

A Delphi Study to Identify Research Priorities Regarding Physical Activity, Sedentary Behavior and Sleep in Pregnancy

This study aimed to produce a list of the top 10 research priorities regarding physical activity, sedentary behavior, and sleep in pregnancy. Using the Delphi methodology, pregnant/postpartum individuals (N = 118), exercise professionals and healthcare providers (N = 55) listed up to 10 questions perceived as unanswered regarding physical activity, sedentary behavior, and sleep in pregnancy (Round 1). Respondents rated the proposed questions on a Likert importance scale (Round 2), and the sum of ratings received were totaled. Questions of priority regarding physical activity among pregnant/postpartum individuals (N = 67), healthcare providers and exercise professionals (N = 22) pertained to exercise prescription, impact of exercise on maternal and fetal outcomes and impact of exercise on pregnancy conditions, special population groups and clinical education and access to information. Sedentary behavior priorities included the impact of sedentary behavior on maternal and fetal outcomes, sedentary recommendations and exercise and sedentary positioning. Sleep research priorities included the impact of pregnancy on sleep, safety, sleeping aids and the effect of exercise on sleep. Pregnant/postpartum women, healthcare providers and exercise professionals prioritized questions that have in part been addressed by existing research, highlighting a need for improved knowledge translation from research to practice. They have also identified novel questions that warrant prioritization within future research.

Effects of passive and active leg movements to interrupt sitting in mild hypercapnia on cardiovascular function in healthy adults

Prolonged sitting in a mild hypercapnic environment impairs peripheral vascular function. The effects of sitting interruptions using passive or active skeletal muscle contractions are still unclear. Therefore, we sought to examine the vascular effects of brief periods (2 min every half hour) of passive and active lower limb movement to interrupt prolonged sitting with mild hypercapnia in adults. Fourteen healthy adults (24 ± 2 yr) participated in three experimental visits sitting for 2.5 h in a mild hypercapnic environment (CO₂ = 1,500 ppm): control (CON, no limb movement), passive lower limb movement (PASS), and active lower limb movement (ACT) during sitting. At all visits, brachial and popliteal artery flow-mediated dilation (FMD), microvascular function, plasmatic levels of nitrate/nitrite and endothelin-1, and heart rate variability were assessed before and after sitting. Brachial and popliteal artery FMDs were reduced in CON and PASS (P < 0.05) but were preserved (P > 0.05) in ACT. Microvascular function was blunted in CON (P < 0.05) but was preserved in PASS and ACT (P > 0.05). In addition, total plasma nitrate/nitrite was preserved in ACT (P > 0.05) but was reduced in CON and PASS (P < 0.05), and endothelin-1 levels were decreased in ACT (P < 0.05). Both passive and active movement induced a greater ratio between the low-frequency and high-frequency bands for heart rate variability (P < 0.05). For the first time, to our knowledge, we found that brief periods of passive leg movement can preserve microvascular function, but that an intervention that elicits larger increases in shear rate, such as low-intensity exercise, is required to fully protect both macrovascular and microvascular function and circulating vasoactive substance balance.NEW & NOTEWORTHY Passive leg movement could not preserve macrovascular endothelial function, whereas active leg movement could protect endothelial function. Attenuated microvascular function can be salvaged by passive movement and active movement. Preservation of macrovascular hemodynamics and plasma total nitrate/nitrite and endothelin-1 during prolonged sitting requires active movement. These findings dissociate the impacts induced by mechanical stress (passive movement) from the change in metabolism (active movement) on the vasculature during prolonged sitting in a mild hypercapnic environment.

Cardiovasomobility: an integrative understanding of how disuse impacts cardiovascular and skeletal muscle health

Cardiovasomobility is a novel concept that encompasses the integration of cardiovascular and skeletal muscle function in health and disease with critical modification by physical activity, or lack thereof. Compelling evidence indicates that physical activity improves health while a sedentary, or inactive, lifestyle accelerates cardiovascular and skeletal muscle dysfunction and hastens disease progression. Identifying causative factors for vascular and skeletal muscle dysfunction, especially in humans, has proven difficult due to the limitations associated with cross-sectional investigations. Therefore, experimental models of physical inactivity and disuse, which mimic hospitalization, injury, and illness, provide important insight into the mechanisms and consequences of vascular and skeletal muscle dysfunction. This review provides an overview of the experimental models of disuse and inactivity and focuses on the integrated responses of the vasculature and skeletal muscle in response to disuse/inactivity. The time course and magnitude of dysfunction evoked by various models of disuse/inactivity are discussed in detail, and evidence in support of the critical roles of mitochondrial function and oxidative stress are presented. Lastly, strategies aimed at preserving vascular and skeletal muscle dysfunction during disuse/inactivity are reviewed. Within the context of cardiovasomobility, experimental manipulation of physical activity provides valuable insight into the mechanisms responsible for vascular and skeletal muscle dysfunction that limit mobility, degrade quality of life, and hasten the onset of disease.

Is Sedentary Behavior a Novel Risk Factor for Cardiovascular Disease?

PURPOSE OF REVIEW

Review the most recent evidence on the role of sedentary behavior in the prevention of cardiovascular disease (CVD).

RECENT FINDINGS

Prospective cohort studies continue to suggest a relationship between sedentary behavior and CVD, but the dose-response association, and the implications of sedentary pattern (vs. total volume) and context on CVD risk require further investigation. Most recent evidence suggests that physical activity influences the association between sedentary time and CVD risk, and that replacing sedentary time with other movement behaviors yields cardiometabolic benefits. Short-term intervention studies have further demonstrated that interrupting prolonged sitting with bouts of physical activity can elicit acute improvements on cardiometabolic biomarkers and vascular function relative to prolonged, uninterrupted sitting, albeit limited evidence exists on the long-term effects. More conclusive evidence regarding the implications of sedentary time on CVD risk is warranted before the optimal sedentary behavior reduction prescription for the prevention of CVD can be elucidated.

Effects of Breaking Up Prolonged Sitting on Cardiovascular Parameters: A systematic Review

The aim of this systematic review was to analyze the acute and chronic effects of sitting breaks on cardiovascular parameters. PubMed and Web of Science databases were searched by two independent researchers for relevant studies published until February 2020. Acute or chronic studies reporting the effects of sitting breaks or reduction in sitting time on cardiovascular parameters were examined. The eligibility criteria followed PICOS: Population - Humans ≥ 18 years old; Interventions - Sitting break strategies; Comparisons - Uninterrupted sitting; Outcomes - Cardiovascular parameters (blood pressure, heart rate, ambulatory blood pressure, vascular function, pulse-wave velocity, cerebral blood flow and biomarkers); Study design - Randomized controlled trials, non-randomized non-controlled trials and randomized crossover trials. Forty-five studies were included, where 35 investigated the acute and 10 the chronic effects of sitting breaks or reductions in sitting time. Walking was the main acute study strategy, used in different volumes (1 min 30 s to 30 min), intensities (light to vigorous) and frequencies (every 20 min to every 2 h). Acute studies found improvements on cardiovascular parameters, especially blood pressure, flow-mediated dilation, and biomarkers, whereas chronic studies found improvements mostly on blood pressure. Breaking up or reducing sitting time improves cardiovascular parameters, especially with walking.

An In Vivo Data-Based Computational Study on Sitting-Induced Hemodynamic Changes in the External Iliac Artery

Although sedentary behavior (characterized by prolonged sitting without otherwise being active in daily life) is widely regarded as a risk factor for peripheral artery disease (PAD), underlying biomechanical mechanisms remain insufficiently understood. In this study, geometrical models of ten external iliac arteries were reconstructed based on angiographic data acquired from five healthy young subjects resting in supine and sitting (mimicked by side lying with bent legs) positions, respectively, which were further combined with measured blood flow velocity waveforms in the common iliac arteries (with each body posture being maintained for 30 min) to build computational models for simulating intra-arterial hemodynamics. Morphological analyses showed that the external iliac arteries suffered from evident bending deformation upon the switch of body posture from supine to sitting. Measured blood flow velocity waveforms in the sitting position exhibited a marked decrease in mean flow velocity while increase in retrograde flow ratio compared with those in the supine position. Hemodynamic computations further revealed that sitting significantly altered blood flow patterns in the external iliac arteries, leading to a marked enlargement of atheroprone wall regions exposed to low and oscillatory wall shear stress (WSS), and enhanced multidirectional disturbance of WSS that may further impair endothelial function. In summary, our study demonstrates that prolonged sitting induces atheropromoting hemodynamic changes in the external iliac artery due to the combined effects of vascular bending deformation and changes in flow velocity waveform, which may provide important insights for understanding the involvement of biomechanical factors in sedentary behavior-related PAD.

Exercise Snacks: A Novel Strategy to Improve Cardiometabolic Health

We define exercise snacks as isolated ≤1-min bouts of vigorous exercise performed periodically throughout the day. We hypothesize that exercise snacks are a feasible, well-tolerated, and time-efficient approach to improve cardiorespiratory fitness and reduce the negative impact of sedentary behavior on cardiometabolic health. Efficacy has been demonstrated in small proof-of-concept studies. Additional research should investigate this novel physical activity strategy.

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

OBJECTIVE

This study aimed to determine the dose-response relationship between prolonged sitting and vascular function in healthy individuals and those with metabolic disturbances and to investigate the acute effects, on vascular function, of interventions that target interrupting prolonged sitting.

DESIGN

This is a systematic review with meta-analysis.

DATA SOURCES

Ovid Embase, Ovid Medline, PubMed, and CINAHL were searched from inception to 4 December 2020.

ELIGIBILITY CRITERIA

Randomized crossover trials, quasi-randomized trials, and parallel group trials where vascular function (flow-mediated dilation [FMD]) was assessed before and after an acute period of sedentary behavior was used in this study.

RESULTS

Prolonged sitting resulted in a significant decrease in the standardized mean change (SMC) for lower-limb FMD at the 120-min (SMC = -0.85, 95% confidence interval [CI] = -1.32 to -0.38) and 180-min (SMC = -1.18, 95% CI = -1.69 to -0.66) time points. A similar pattern was observed for lower-limb shear rate. No significant changes were observed for any outcomes in the upper limb. Subgroup analysis indicated that prolonged sitting decreased lower-limb FMD in healthy adults (SMC = -1.33, 95% CI = -1.89 to -0.78) who had higher a priori vascular endothelial function, but not in those with metabolic and vascular dysfunction (SMC = -0.51, 95% CI = -1.18 to 0.15). Interrupting sitting with active interruptions increased the standardized mean difference for FMD, relative to prolonged sitting, but it was not statistically significant (0.13, 95% CI = -0.20 to 0.45).

CONCLUSIONS

Lower-limb vascular function is progressively impaired as a consequence of prolonged sitting, up to 180 min. A similar trend was not observed in upper-limb vascular function. Subgroup analysis indicated that prolonged sitting negatively affects healthy populations, a finding not observed in those with metabolic disturbances. Regularly interrupting sitting with activity may be beneficial for those with metabolic disturbances.

The Effects of Acute Exposure to Prolonged Sitting, with and Without Interruption, on Peripheral Blood Pressure Among Adults: A Systematic Review and Meta-Analysis

BACKGROUND

Previous reviews have shown that exposure to acute prolonged sitting can have detrimental effects on several cardiovascular and cardiometabolic health markers. However, to date, there has been no synthesis of peripheral blood pressure data (including systolic blood pressure, diastolic blood pressure and mean arterial pressure), an important and translatable marker of cardiovascular health. Similarly, no previous study has consolidated the effects of sitting interruptions on peripheral blood pressure.

OBJECTIVES

We aimed to (1) assess the effect of exposure to acute prolonged sitting on peripheral blood pressure and (2) determine the efficacy of sitting interruption strategies as a means of offsetting any negative effects. Subgroup analyses by age and interruption modality were performed to explore heterogeneity.

DATA SOURCES

Electronic databases (PubMed, Web of Science and, SPORTDiscus) were searched from inception to March 2021. Reference lists of eligible studies and relevant reviews were also screened.

STUDY SELECTION

Inclusion criteria for objective (1) were: (i) peripheral blood pressure was assessed non-invasively in the upper limb pre-sitting and post-sitting; (ii) studies were either randomised controlled, randomised crossover or quasi-experimental pre-test vs post-test trials; (iii) the sitting period was ≥ 1 h; (iv) pre-sitting and post-sitting measures were performed in the same posture; and (v) participants were adults (aged ≥ 18 years), free of autonomic or neuromuscular dysfunction. Additional criteria for objective (2) were: (i) the interruption strategy was during the sitting period; (ii) there was an uninterrupted sitting control condition; and (iii) the interruption strategy must have involved participants actively moving their upper or lower limbs.

APPRAISAL AND SYNTHESIS METHODS

In total, 9763 articles were identified, of which 33 met inclusion criteria for objective (1). Of those articles, 22 met inclusion criteria for objective (2). Weighted mean difference (WMD), 95% confidence intervals (95% CI), and standardised mean difference (SMD) were calculated for all trials using inverse variance heterogeneity meta-analysis modelling. Standardised mean difference was used to determine the magnitude of effect, where < 0.2, 0.2, 0.5 and 0.8 were defined as trivial, small, moderate and large, respectively.

RESULTS

(1) Prolonged uninterrupted sitting resulted in trivial and small significant increases in systolic blood pressure (WMD = 3.2 mmHg, 95% CI 0.6 to 5.8, SMD = 0.14) and mean arterial pressure (WMD = 3.3 mmHg, 95% CI 2.2 to 4.4, SMD = 0.37), respectively, and a non-significant trivial increase in diastolic blood pressure. Subgroup analyses indicated that the increases in systolic blood pressure and mean arterial pressure were more pronounced in younger age groups. (2) Interrupting bouts of prolonged sitting resulted in significantly lower systolic blood pressure (WMD =  - 4.4 mmHg, 95% CI - 7.4 to - 1.5, SMD = 0.26) and diastolic blood pressure (WMD =  - 2.4 mmHg, 95% CI - 4.5 to - 0.3, SMD = 0.19) compared with control conditions, particularly when using aerobic interruption strategies.

CONCLUSIONS

Exposure to acute prolonged uninterrupted sitting results in significant increases in systolic blood pressure and mean arterial pressure, particularly in younger age groups. Regularly interrupting bouts of prolonged sitting, particularly with aerobic interruption strategies may reduce negative effects.

Macrovascular and microvascular responses to prolonged sitting with and without bodyweight exercise interruptions: A randomized cross-over trial

Exposure to uninterrupted prolonged sitting leads to macro- and microvascular complications, which can contribute to increased cardiovascular disease risk. This study investigated the macrovascular and microvascular responses to 3 h of sitting that was: (i) uninterrupted (CON); and (ii) interrupted every 20 min with 1 min light intensity half squats plus calf raises (EX). Twenty healthy participants (21 [SD: 2] years; 21.5 [SD: 1.6] kg/m²) were recruited to participate in this randomized cross-over trial. Macrovascular function was quantified using brachial-ankle pulse wave velocity (baPWV) and the lower- and upper-limb arterial stiffness index (ASI). Microvascular function was quantified as the medial gastrocnemius tissue oxygen saturation (StO₂) area under the curve (AUC) during reactive hyperemia. The baPWV did not significantly change with time (p = 0.594) or by condition (p = 0.772). The arm ASI increased by 3.6 (95% CI: 0.7 to 6.6, effect size [ES] = 0.27) with a nonsignificant condition effect (p = 0.219). There was a significant interaction effect for leg ASI (p = < 0.001), with ASI increasing (impairment) by 18.7 (95% CI: 12.1 to 25.3, ES = 0.63) for CON and decreasing (improvement) by -11.9 (95% CI: -18.5 to -5.3, ES = 0.40) for EX compared to presitting. Similarly, the AUC decreased (detrimental) by 18% (Δ = -321, 95% CI: -543 to -100, ES = 0.32) for CON and increased by 32% (Δ = 588, 95% CI: 366 to 809, ES = 0.59) for EX. The leg ASI was inversely associated with StO₂ AUC (interclass correlation coefficient: -0.66, 95% CI: -0.51 to -0.77). These preliminary findings suggest that regularly interrupting prolonged sitting with simple bodyweight exercises may help to preserve lower-limb vascular function.

Impact of a single bout of resistance exercise on serum Klotho in healthy young men

BACKGROUND

It has been shown that Klotho protects vascular endothelial function. Given that a single bout of resistance-exercise-induced hypertensive stimulus causes endothelial dysfunction, we postulated that acute resistance exercise would reduce serum Klotho levels. In this respect, the reduction in serum Klotho levels would be associated with the response of flow-mediated dilation (FMD). Therefore, the purpose of this study was to investigate the impact of acute resistance exercise on the Klotho response in serum. In addition, we examined the relationship between the serum Klotho and FMD responses following acute resistance exercise.

METHODS

Twelve untrained men participated in this study (20.4 ± 0.3 years). Following baseline measurements (blood pressure, blood collection, FMD), subjects performed leg extensions, which consisted of 10 repetitions for five sets at 70% of one-repetition maximum. After the exercise, measurement of blood pressure, blood collection, and FMD assessment were repeated for 60 min. We analyzed Klotho and endothelin-1 (ET-1) concentrations in blood serum.

RESULTS

As expected, the exercise significantly elevated blood pressure and led to decreased FMD (p < 0.05). However, Klotho concentrations were significantly increased following exercise (p < 0.05). No correlation was observed in Klotho and FMD responses following acute resistance exercise. However, there was a significant positive correlation between Klotho and ET-1 in response to resistance exercise (p < 0.05).

CONCLUSION

In conclusion, the present study reveals that serum Klotho significantly increased following a single bout of resistance exercise. However, the increase in Klotho may not associate with the acute reduction in endothelial function.

Effect of a dynamic seat pan design on spine biomechanics, calf circumference and perceived pain during prolonged sitting

This study investigates the effects of a dynamic seat pan design on sitting biomechanics, perceived pain and seat movement compared to a control. Thirty male participants were recruited for two experimental sessions consisting of a 2-h sitting exposure (standardized typing task). Spine angles, back muscle activity, perceived pain and calf circumference were measured pre and post exposure. Sitting in the dynamic condition resulted in lower pain ratings (p = 0.031), decreased calf circumference (p < 0.001), lower average seat pressure (p < 0.001), and greater seat contact area (p = 0.003) compared to the control. Spine angles and low back EMG for all 6 muscles showed no significant differences between chair conditions. These results suggest this dynamic seat pan design is effective at decreasing several negative components associated with sitting for the occupant. Future work should examine the longer-term effects of dynamic office chair features in the field setting with a more generalizable population.

Effects of Prolonged Sitting with or without Elastic Garments on Limb Volume, Arterial Blood Flow, and Muscle Oxygenation

Supplemental digital content is available in the text.

Purpose

The physiological response induced by acute prolonged sitting is not fully understood. Therefore, we examined the effects of 8-h constant sitting on microcirculation and associated factors in the lower extremity among healthy males. We also evaluated the protective effects of lower-pressure thigh-length elastic compression garments on these parameters.

Methods

Nine healthy males (age, 22.6 ± 1.4 yr; body mass index, 22.4 ± 1.8 kg·m⁻²) completed the 8-h constant sitting experiment. Following baseline measurements, each subject was randomized to wear a lower-pressure elastic garment on the right or left leg from the inguinal region to the ankle joint, with the noncompressed contralateral leg as a control. Circumferences of the calf and malleolus, extracellular water contents, blood flow and shear rate of the dorsal metatarsal artery, and oxygen dynamics in the gastrocnemius muscles were measured in both extremities before and during 8-h constant sitting.

Results

Compared with baseline values, 8-h constant sitting caused enlargement of circumferences (calf, 2.4% ± 0.7%; malleolus, 2.7% ± 1.4%), retention of extracellular water in lower extremity muscles (10.1% ± 1.78%), deterioration of the blood flow (61.4% ± 16.2% of baseline) and shear rate of the dorsal metatarsal artery, and decrease in oxygenated hemoglobin and total hemoglobin levels in the gastrocnemius muscle (P < 0.05, respectively). When subjects wore the lower-pressure thigh-length compression garment, a significant reduction of these effects was observed (P < 0.05, for all).

Conclusions

Prolonged sitting for 8 h induced edema, as well as deterioration of the arterial blood flow, shear rate, and microcirculation in lower limb muscles. Conversely, application of the lower-pressure elastic garment successfully prevented the pathophysiological deterioration associated with prolonged sitting.