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Effect of Prolonged Sitting and Breaks in Sitting Time on Endothelial Function
Abstract
Unlabelled:
Sitting time (ST) is associated with cardiovascular disease risk factors, whereas breaking ST has been reported to be beneficial for reducing cardiovascular risk.
Purpose:
The objective of this study is to examine the effects of breaking ST on superficial femoral artery (SFA) endothelial function.
Hypotheses:
1) Prolonged sitting would induce endothelial dysfunction and changes in shear forces, and 2) breaking ST with brief periods of activity would prevent attenuation in endothelial function.
Methods:
Twelve nonobese men (24.2 ± 4.2 yr) participated in two randomized 3-h sitting trials. In the sitting (SIT) trial, subjects were seated on a firmly cushioned chair for 3 h without moving their lower extremities. In the breaking ST trial (ACT), subjects sat similar to the SIT trial but walked on a treadmill for 5 min at 2 mph at 30 min, 1 h 30 min, and 2 h 30 min during the sitting interval. SFA flow-mediated dilation (FMD) was assessed at baseline, 1 h, 2 h, and 3 h in each trial. Statistical analyses were performed using dependent variables SFA FMD and shear rates. Significance was set at P ≤ 0.05.
Results:
In the SIT trial, there was a significant decline in SFA FMD from baseline to 3 h (baseline, 4.72% ± 3.78%; 1 h, 0.52% ± 0.85%; 2 h, 1.66% ± 1.11%; 3 h, 2.2% ± 2.15; P < 0.05 by ANOVA) accompanied by a decline in mean shear rate and antegrade shear rate but no difference in shear rate (area under the curve). By two-way repeated-measures ANOVA, ACT prevented the sitting-induced decline in FMD (baseline, 4.5% ± 2.3%; 1 h, 5.04% ± 2.85%; 2 h, 5.28% ± 5.05%; 3 h, 6.9% ± 4.5%) along with no decline in shear rates.
Conclusion:
Three hours of sitting resulted in a significant impairment in shear rate and SFA FMD. When light activity breaks were introduced hourly during sitting, the decline in FMD was prevented.
... There is epidemiological research connecting sedentary behavior and prolonged sitting with impaired physiological outcomes and chronic disease, e.g., [2,3,[21][22][23][24][25][26][27][28][29][30]. Acute experimental research has shown that breaking periods of prolonged sitting prevents declines in vascular function, glucose response, and insulin response e.g., [31][32][33][34]. Free-living sedentary behavior interventions have found small effects on biomarkers of cardiometabolic risk [35]. ...
... Freedson Adult (1998) criteria were used to determine physical activity and sedentary behavior. To analyze uninterrupted bouts of sitting, we operationally defined a sedentary bout as 20 or more minutes of consecutive sitting, based on results from physiological laboratory studies [31][32][33][34]. Accelerometer data were also used to compare sitting time, standing time, pedaling time, and frequency and duration of bouts of uninterrupted sitting between conditions. ...
... This method has demonstrated 80% sensitivity and 85% specificity in identifying coronary endothelial dysfunction [54]. Vascular function was measured because laboratory-based studies have shown that prolonged sitting causes acute detriments in vascular functioning, and largescale studies have linked sedentary behavior with cardiovascular disease [2,3,[21][22][23][24][25][26][27][28][29][30][31][32][33][34]. To our knowledge, this is the first workplace sedentary behavior intervention to measure vascular function. ...
We used the Total Worker Health® approach to develop a multi-component workplace sedentary behavior intervention and tested intervention effectiveness in a cluster randomized trial. Participants (n = 198; 75% female) were recruited from three call-centers (two intervention and one usual practice control). All worksites received pedal stand active workstations. The usual practice site received no additional support, while the intervention group completed a six-month program of activities including computer-based training, behavioral self-monitoring, health and safety discussions, and pedaling competitions. Data collection included a survey, a physical health assessment, and accelerometer measures of sedentary behavior, physical activity, and sitting/standing time. Primary analyses were generalized estimating equations comparing changes between intervention and usual practice conditions over time, along with analyses of changes in both groups combined over time. Six-month results revealed less prolonged sitting and reductions in musculoskeletal pain in both groups (all p < 0.05), while the intervention group showed additional improvements in moderate physical activity (p < 0.001) and use of pedal stands (p < 0.01). At 12-months, the additional physical activity and pedal stand use in the intervention group regressed to baseline levels, while reductions in prolonged sitting in both groups were durable (p < 0.01). This study adds to previous research showing the effectiveness of the Total Worker Health® approach for workplace health and safety. Results also show that, while providing employees with health and safety resources is beneficial, providing ongoing support for the adoption and use of resources is more effective.
... Prolonged sitting compromised shear in SFA and popliteal artery, alleviated by PA breaks. Low-intensity PA breaks increased cerebral blood flow velocities [47,51,52] but high-intensity breaks require further exploration for their potential endothelial alterations. [21,25,53] Flow velocity PA breaks significantly impacted cardiometabolic diseases of vascular origin. ...
... [54] Yet, studies focused primarily on break frequency and duration, overlooking the intensity's pivotal role. [23,26,47] ...
... PRISMA flowchart demonstrating the inclusion and exclusion of the studies in the review in office settings, indicating positive impacts on cardiovascular health, metabolic rates, and overall well-being across diverse populations. Studies emphasized the value of incorporating breaks, even low-intensity ones, in prolonged sitting, shedding light on various aspects of vascular function and responses under different conditions and interventions[11][12][13][14][16][17][18][19][20][21][22][23][24][26][27][28][29][30][31][32][33]39,[45][46][47][48] ...
Emerging evidence claims the vascular benefits of varied frequency and duration of physical activity (PA) breaks, whereas the efficacy of varied intensity remains unexplored. We aimed to collate and summate the studies investigating the PA breaks at various intensities on vascular protection. Seven electronic databases were searched for potential studies till Jan 31, 2022. The eligible studies should have administered PA breaks of differing intensities in prolonged sitting postures and explored regional vascular changes [flow mediated dilation (FMD), shear stress, diameter, and blood flow] using ultrasound and novel outcome markers. Two independent reviewers assessed the studies for eligibility after abstract and full-text screen, and appropriate data were extracted to summarise vascular protective effects with PA breaks. Our findings reveal adverse regional vascular outcomes with prolonged sitting (FMD ≈-1.5%, diameter ≈-0.06 mm), whereas PA breaks of any intensity were found to improve endothelial functions (FMD ≈ +0.5%, diameter ≈ +0.1 mm, shear ≈ +13 s-1) and mitigate the adverse effects associated with prolonged sitting. Compared with high-intensity activity, low-intensity PA breaks alleviate arterial stiffness and endothelial dysfunction risks.
... Participants were randomly assigned to experimental conditions to eliminate the influence of the order of the experiments. A one-week washout period was allowed to exclude any hemodynamic effects of previous experimental conditions [25]. ...
... The vessel diameter and mean blood flow velocity in the shallow femoral artery (SFA) were measured using a general-purpose ultrasound imaging system (ACUSON Juniper; Tokyo, Japan: SIEMENS Healthineers). Furthermore, a 13.3 MHz linear array probe (12L3, ACUSON Juniper; Tokyo, Japan: SIEMENS Healthineers) was placed on the skin 10 cm below the inguinal line [25]. The SFA was selected because it is an easily accessible artery [25]. ...
... Furthermore, a 13.3 MHz linear array probe (12L3, ACUSON Juniper; Tokyo, Japan: SIEMENS Healthineers) was placed on the skin 10 cm below the inguinal line [25]. The SFA was selected because it is an easily accessible artery [25]. The angle of incidence of the ultrasound beam was automatically adjusted to 60° and measurements were made using the pulsed Doppler method. ...
Introduction: Belt electrode-skeletal muscle electrical stimulation (B-SES) is a treatment prescribed for individuals with difficulty performing exercise therapy that improves muscle strength, exercise tolerance, and glucose metabolism. However, the effects of B-SES on the hemodynamics of the central and lower extremity conduit arteries have not been studied. Therefore, this study compared the acute effects of B-SES on the central and lower extremity conduit arteries in healthy young males.
Methods: This randomized crossover study included nine healthy young males (mean age: 21.0±1.1 years). Participants were assigned to the following experimental conditions, with a washout period of one week: condition 1 included 20 min of electrical stimulation of the lower extremity at the participant’s sensation threshold intensity (Sham, n=9) and condition 2 included 20 min of electrical stimulation of the lower extremity at the maximum intensity the participant can tolerate (B-SES, n=9). The heart rate (HR), stroke volume (SV), cardiac output (CO), mean arterial pressure (MAP), and total peripheral vascular resistance (TPR) were measured as central hemodynamics. The hemodynamics of the lower extremity conduit arteries were measured and calculated for the shallow femoral artery (SFA), including vessel diameter, mean blood flow velocity (MBFV), shear rate (SR), and mean blood flow (MBF) rate. These indices were measured before stimulation (Pre), 10 min after the start of stimulation (Stimulating), and immediately after the end of stimulation (Post). These indices were compared using a repeated two-way analysis of variance.
Results: In B-SES, HR (Pre: 63.2±8.6; Stimulating: 73.7±6.9; Post: 70.0±4.2 bpm, p<0.01), CO (Pre: 5.1±1.0; Stimulating: 6.5±1.5, p<0.01; Post: 6.3±1.2 L/min, p=0.02), and MAP (Pre: 104.0±11.5; Stimulating: 116.4±10.8, p<0.01; Post: 109.6±9.7 mmHg, p=0.02) increased significantly. In addition, B-SES significantly increased MBFV (Pre: 19.2±4.0; Stimulating: 50.5±14.9; Post: 30.1±4.0 cm/s, p<0.01), SR (Pre: 118.9±28.8; Stimulating: 302.7±91. 2, p<0.01; Post: 182.1±70.1/s, p=0.02), and MBF (Pre: 382.0±61.5; Stimulating: 1009.6±321.4; Post: 626.8±176.6 mL/min, p<0.01). However, there were no significant changes in SV and TPR.
Conclusions: The findings of this study indicate that B-SES in healthy young males increases CO without increasing SV or TPR and improves the MBFV and SR in the SFA.
... However, because of the recent surge in popularity of esports and video game play, the health risks associated with prolonged sitting affect a wider and younger demographic beyond just office workers. Several studies have shown that short, frequent breaks improve blood flow (3,(14)(15)(16)(17). Individuals can enhance blood circulation, and possibly mitigate the potential risks associated with extended periods of sedentary behavior, by engaging in regular breaks (3,(15)(16)(17). ...
... Several studies have shown that short, frequent breaks improve blood flow (3,(14)(15)(16)(17). Individuals can enhance blood circulation, and possibly mitigate the potential risks associated with extended periods of sedentary behavior, by engaging in regular breaks (3,(15)(16)(17). ...
... The determination of the sample size for this study was influenced by findings from a previous study conducted by Thosar et al. (17). Based on these results, and aiming for an 80% statistical power and a significance level set at P ¼ 0.05, we calculated that a total of 10 subjects would be sufficient for our randomized, crossover design study (17). Twelve healthy men and women first-person shooter gamers between the ages of 18 and 22 yr old participated in this study; two subjects withdrew because of personal reasons (Fig. 1). ...
With the growing popularity of video gaming, deep vein thromboses are increasingly being reported in gamers. This study aimed to compare lower leg graduated compression sleeves and a 6-minute walking break during prolonged gaming on blood flow and hemodynamics in competitive esport players to help mitigate this risk. Ten healthy gamers (19.6 ±1.2y, 9 men) consented to participate in this mixed-model cross-over design study that consisted of three visits: Visit 1: participants engaged in continuous 2-hour video game play wearing no compression (Continuous). Visit 2 and 3 involved 2-hour play wearing compression sleeves (Compression), and 2-hour game play interrupted at 1-hour by a 6-minute walk (Walk). Doppler ultrasound measurements of the left popliteal artery were taken at 30, 60, 90 120-minutes, 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 condition 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 to the Walk group at the 90-minute mark (p=0.04, p=0.01). No differences were found between the Compression and Walk group or the Continuous and Compression group (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-minute walk every 60 minutes during prolonged gaming is advisable to counteract the negative effects on blood flow hemodynamics.
... En esta línea, Restaino et al. (2015), reportó que 6 horas de sedentarismo prolongado provocan disfunción endotelial aguda de la extremidad inferior, representado por un menor %VMF, SS y FS. De manera similar, Thosar et al. (2015), encontró que tres horas de sedentarismo prolongado pueden alterar significativamente el SS y reducir consecuentemente el %VMF. Otros estudios refuerzan estos hallazgos, encontrando que el SS y el %VMF disminuyen de forma importante, incluso, en exposiciones cortas al sedentarismo, luego de trascurrida una hora en posición sedente (Cho et al., 2020;Climie et al., 2018;Morishima et al., 2016). ...
... Las estrategias de interrupción del sedentarismo prolongado para la prevención de la disfunción endotelial aguda (provocada por sedentarismo prolongado) han sido propuestas por diversos estudios. Estos utilizan programas de interrupción del sedentarismo a través de estrategias de cambio de posición (Tremblay et al., 2019), con ejercicio de ligera intensidad como pararse y caminar (Carter et al., 2019;Kruse et al., 2018;Peddie et al., 2021;Thosar et al., 2015), o bien con ejercicio de moderada intensidad siguiendo un programa de entrenamiento de resistencia (Cho et al., 2020;Climie et al., 2018), aplicados en intervalos y periodos de tiempo variables. Algunos de estos estudios han encontrado interesantes resultados y han demostrado que dichas estrategias podrían prevenir la disfunción endotelial aguda provocada por el prolongado tiempo sentado, al evitar la disminución o mejorar los valores del SS, el %VMF y FS. ...
... Cho et al. (2020), encontró que la interrupción del sedentarismo a través de ejercicio de moderada intensidad (66% de la frecuencia cardiaca máxima de reserva) mantiene constante los niveles de VMF, aumenta el SS y FS. En esta línea, estrategias de ejercicio de ligera intensidad como el movimiento repetido del tobillo y las caminatas también han mostrado efectos similares sobre dichas variables Thosar et al., 2015). Este efecto descrito permite concebir reflexiones sobre el posible efecto preventivo que pudiese tener la práctica regular de actividad física (o el nivel de actividad física previa de las personas) sobre la disfunción endotelial provocada por sedentarismo prolongado. ...
... A study by Thosar et al. (2015) involved 12 men participating in two randomized three-hour sitting trials. The first trial was a sitting trial where the subject was seated in one position without interruption The second trial was a sit-walk trial where the subjects walked on treadmills for five minutes at two mph for 30 minutes, 1.5-hour and 2.5-hour intervals during the sitting period. ...
... The sitwalk trial, however, showed a significant difference in the FMD and mean shear rate compared to the sit trial, indicating that walking during prolonged sitting may benefit arterial health. 23 As compared to our study, both CA and SFA are measured. In our study all interventionsaside from the prolonged sittingshowed a minor decrease in CA velocity over time. ...
Background The aim of this study was to observe and analyze vascular function in ‘prolonged sitting’, followed by a yoga asana routine and pranayama intervention. Participants in this study include those who work from desks in offices. The study required the participants to attend on three separate days at random, and they had to finish a computerized test on each day. On the first day, participants were required to complete a computer test while sitting still for four hours (with the exception of washroom breaks). The next day, they underwent a computerized test along with a pranayama intervention. Finally, on the last day, they underwent a computerized test along with a yoga asana intervention. At the start of the study and after two and four hours, we measured the diameter and velocity of the common carotid artery (CCA) and superficial femoral artery (SFA). Methods The study was a within-subjects prospective single-center trial conducted in the Department of Radio-Diagnosis and Imaging, Kasturba Medical Hospital, Manipal, India, between September 2022 and January 2023. Participants were asked to do one of the following ‘activities’ over successive weeks: Week 1 – Prolonged sitting; Week 2 – Pranayama intervention; and Week 3 – Yoga asana intervention during prolonged sitting. The baseline and follow-up variables of pulse velocity, endothelial thickness, and shear rate were assessed for normality through a Shapiro-Wilk Test. Results Our sample included 11 participants with moderate physical activity, five with high physical activity and one with low physical activity. Yoga asana intervention comprised participants sitting continuously for four hours, with a yoga asana intervention being provided every hour, lasting for 10 minutes. Conclusions Yoga asana improves vascular functions in prolonged sitting conditions. This routine can promote the concept of interrupted sitting and ways to reduce it with efficient yoga asana practice without changing the work culture and provide better physical relief. Trial registration Clinical Trials Registry – India ( CTRI/2022/09/045628), date of registration: 19/09/2022(CTRI/2022/9/045628)https://ctri.nic.in/Clinicaltrials/main1.php?EncHid=16349.27799
... The vascular functions using Doppler ultrasound was measured as stated and administered in the earlier studies. 9,[25][26][27][28][29][30] Dynamic central (right carotid artery) and peripheral vascular (Superficial Femoral Artery) functions [diameter, velocity] were measured using Duplex ultrasound (GE Voluson Swift, Germany) at a pulsed frequency of 50 MHz using the probe insonated at an angle of 60°were used. The diameter and the velocity were automatically measured using inbuilt edge-detection software, and the captured images were analysed using B Mode images and confirmed with the carotid artery's diameter and velocity. ...
... Altered central vascular hemodynamic, especially carotid artery stiffness and sclerosis, is a long recognised risk for cognitive decline in the elderly. (26,27) Is the work clearly and accurately presented and does it cite the current literature? Yes ...
Background Alteration in the central vascular hemodynamics is speculated to influence cognitive functions, including executive functions in young adults. Prolonged sitting is associated with compromised central vascular functions, which activity micro-breaks could mitigate. However, the association between the carotid vascular hemodynamic alteration and the executive functions is yet to be explored. Methods We administered a randomised controlled trial investigating the effects of various intensities' micro-breaks on central vascular and cognitive functions during simulated work conditions for four hours. The carotid artery hemodynamics and cognitive functions were measured by Duplex ultrasound at 0 th , 2 nd and 4 th hour and computer-based Flanker tests at 0 th , 1 st , 2 nd , 3 rd and 4 th hour of visit days, respectively. From the randomised controlled trial, we extracted the secondary data of carotid artery hemodynamics and cognitive functions change at the 4 th hour from the baseline and analysed for any relation. Results Though we observed linear relation between the carotid artery hemodynamics and the executive functions, the relation was not statistically significant. we found a significant reduction in carotid artery diameter during prolonged sitting (0.03 cm [95%CI 0.01, 0.05]), velocity (10.35 cm/s [95%CI -2.85, 17.86]) and shear rate during interrupted sitting (174.39 [95%CI 65.67, 283.11]) We found increased accuracy during prolonged sitting (12.7% [95%CI 0.66, 24.81]) and sitting with light-intensity activity breaks (6.92% [95%CI 1.39, 12.44]). We did not find any significant relation between the change in central vascular functions (carotid artery diameter, velocity, shear rate and blood flow) and the cognitive functions during three different work conditions. Conclusion Though a significant relation between carotid artery function and cognitive function could not be established, microbreaks can mitigate the vascular and cognitive risks associated with prolonged sitting.
... As a result, extensive sitting time is associated with and physiologically involved in cardiometabolic disease development. Rising to stand from a seated position immediately raises circulation and enhances nutrient, insulin, and oxygen delivery to the lower extremities [17][18][19]. Acute standing breaks during prolonged sitting bouts improve vascular function and glycemic control [17,20,21]. Replacing sitting with standing is a practical and feasible long-term behavior change that may improve health outcomes in individuals who sit for prolonged periods. ...
... The practical method of replacing sitting with standing is a long-term behavior change that may improve health outcomes in those who sit for prolonged periods. Standing from a seated position immediately increases circulation in the lower extremities and raises shear stress on vascular endothelial cells, which improves intracellular signaling and reduces oxidative stress [18,19]. The increased blood flow from standing also enhances oxygen, nutrient, and insulin delivery to the lower limbs [17]. ...
Background: Incidence of cardiometabolic disease among U.S. Hispanics/Latinos is higher than in non-Hispanic Whites. Prolonged sitting duration is prevalent in older adults, and compounded with menopause, greatly increases cardiometabolic risk in postmenopausal women. Metabolomic analyses of interventions to reduce sitting are lacking and mechanistic understanding of health-promoting behavior change in postmenopausal Latinas is needed. Methods: To address this knowledge gap, an exploratory analysis investigated the plasma metabolome impact of a 12-week increased standing intervention among sedentary postmenopausal Latinas with overweight or obesity. From a parent-randomized controlled trial, a subset of Best Responders (n = 43) was selected using parameters of highest mean change in sitting bout duration and total sitting time; baseline variable-Matched Controls (n = 43) were selected using random forest modeling. Targeted LC-MS/MS analysis of archived baseline and 12-week plasma samples was conducted. Metabolite change was determined using a covariate-controlled general linear model and multivariate testing was performed. A false discovery rate correction was applied to all analyses. Results: Best Responders significantly changed time sitting (−110.0 ± 11.0 min; −21%), standing (104.6 ± 10.1 min; 40%), and sitting in bouts >30 min (−102.3 ± 13.9 min; −35%) compared to Matched Controls (7.1 ± 9.8 min, −7.8 ± 9.0 min, and −4.6 ± 12.7 min, respectively; all p < 0.001). Twelve-week metabolite change was significantly different between the two groups for 24 metabolites (FDR < 0.05). These were primarily related to amino acid metabolism, improved blood flow, and ATP production. Enzyme enrichment analysis predicted significant changes regulating glutamate, histidine, phenylalanine, and mitochondrial short-chain fatty acid catabolism. Pathway analysis showed significant intervention effects on glutamate metabolism and phenylalanine, tyrosine, and tryptophan biosynthesis, potentially indicating reduced cardiometabolic disease risk. Conclusions: Replacing nearly two hours of daily sitting time with standing and reduced prolonged sitting bouts significantly improved metabolomic profiles associated with cardiometabolic risk among postmenopausal Latinas.
... Feasible and effective methods to reduce periods of prolonged sitting and associated cardiometabolic incidence are needed to improve postmenopausal health. Rising to stand immediately increases lower extremity circulation and shear stress on vascular endothelial cells that improves intercellular and intracellular signaling and lowers oxidative stress [15,16]. Enhanced blood flow associated with postural change from sitting to standing also increases delivery of oxygen, nutrients, and hormones, including insulin, to lower extremity tissues [17]. ...
... The similarity of our STS postprandial metabolome with these MVPA results may potentially be due to the relative energy expenditure increase for our overweight/obese postmenopausal sample. The cardiometabolic benefits of merely rising to stand improve blood flow and oxygen and nutrient delivery to the digestive tract, peripheral tissues, and skeletal muscle [15][16][17]. Regular postural changes also require large muscle contractions and increase energy expenditure to rise and stay in a standing position [18,19]. Interestingly, circulating cholesterol was slightly reduced after the controlled sit but nearly unchanged after the STS visit, a difference between conditions that was statistically significant. ...
Older adults sit during most hours of the day; more than 30% are considered physically inactive. The accumulation of prolonged sitting time is an exercise-independent risk factor for aging-related conditions such as cardiometabolic disease and cancer. Archival plasma samples from a randomized controlled, four-condition crossover study conducted in 10 postmenopausal women with overweight or obesity were analyzed. During 5-hour conditions completed on separate days, the trial tested three interruption modalities: two-minute stands each 20 min (STS), hourly ten-minute standing breaks (Stand), hourly two-minute walks (Walk), and a controlled sit. Fasting baseline and 5-hour end point (2 h postprandial) samples were used for targeted metabolomic profiling. Condition-associated metabolome changes were compared using paired t-tests. STS eliminated the postprandial elevation of amino acid metabolites that was observed in the control. A norvaline derivative shown to have anti-hypertensive and -hyperglycemic effects was significantly increased during Stand and STS. Post-hoc testing identified 19 significantly different metabolites across the interventions. Tight metabolite clustering by condition was driven by amino acid, vasoactive, and sugar metabolites, as demonstrated by partial least squares-discriminant analyses. This exploratory study suggests that brief, low-intensity modalities of interrupting prolonged sitting can acutely elucidate beneficial cardiometabolic changes in postmenopausal women with cardiometabolic risk.
... G/I/TG/CP/NEFA+iAUC ↓/→/→/→/→ G/I/TG/CP/NEFA+iAUC ↓/→/→/→/→ 抗阻和自重抗阻；负荷量为 2~10 min；强度为低~中；频率为 20~60 min。结果显示，>2 min 低、中强度 运动以 20~60 min/次间断可降低收缩压[53,[75][76][77][78][79] 、舒张压[75,80,77,79] 和平均动脉压[75,79] 。也有研究发现，收缩 压[63,58,81] 、舒张压[63,58,76,78] 和平均动脉压[58] 无改善。 共有 9 项研究报告了久坐间断对健康人群血流动力学指标的影响(表 3) 。方式为步行、单关节抗 阻、爬楼和自重抗阻；负荷量为 15 s~5 min；强度为低~中；频率为 20~60 min。结果显示，>5 min 低、 中强度全身运动以 20~60 min/次间断可能改善血流介导的血管扩张功能[82,70] 和大脑中动脉血流速度[71] ； 15 s~5 min 低、中强度全身运动间断可改善血流量[66,70,83] 、血管剪切应力[66,82,70,83] 和大脑中动脉血流速度[71] 。也有研究发现，血流介导的血管扩张功能[66,74,83] 、血流量/血管剪切应力[74] 和脉搏波传导速度[73,84] 无 改善。共有 6 项研究报告了久坐间断对临床人群血流动力学指标的影响。方式为步行、单关节抗阻和自 重抗阻；负荷量为 2~10 min，均为强度低；频率为 30 min/60 min。结果显示，3~6 min 低、中强度全身运 动以 30~60 min/次间断可改善血流介导的血管扩张功能[85,86] 、血流量/血管剪切应力[85,87,86] 和大脑中动脉血 流速度[88] 。也有研究发现，血流介导的血管扩张功能[77,87] 、血流量/血管剪切应力[77] 和脉搏波传导速度[63] ...
... G/I/TG/CP/NEFA+iAUC ↓/→/→/→/→ G/I/TG/CP/NEFA+iAUC ↓/→/→/→/→ 抗阻和自重抗阻；负荷量为 2~10 min；强度为低~中；频率为 20~60 min。结果显示，>2 min 低、中强度 运动以 20~60 min/次间断可降低收缩压[53,[75][76][77][78][79] 、舒张压[75,80,77,79] 和平均动脉压[75,79] 。也有研究发现，收缩 压[63,58,81] 、舒张压[63,58,76,78] 和平均动脉压[58] 无改善。 共有 9 项研究报告了久坐间断对健康人群血流动力学指标的影响(表 3) 。方式为步行、单关节抗 阻、爬楼和自重抗阻；负荷量为 15 s~5 min；强度为低~中；频率为 20~60 min。结果显示，>5 min 低、 中强度全身运动以 20~60 min/次间断可能改善血流介导的血管扩张功能[82,70] 和大脑中动脉血流速度[71] ； 15 s~5 min 低、中强度全身运动间断可改善血流量[66,70,83] 、血管剪切应力[66,82,70,83] 和大脑中动脉血流速度[71] 。也有研究发现，血流介导的血管扩张功能[66,74,83] 、血流量/血管剪切应力[74] 和脉搏波传导速度[73,84] 无 改善。共有 6 项研究报告了久坐间断对临床人群血流动力学指标的影响。方式为步行、单关节抗阻和自 重抗阻；负荷量为 2~10 min，均为强度低；频率为 30 min/60 min。结果显示，3~6 min 低、中强度全身运 动以 30~60 min/次间断可改善血流介导的血管扩张功能[85,86] 、血流量/血管剪切应力[85,87,86] 和大脑中动脉血 流速度[88] 。也有研究发现，血流介导的血管扩张功能[77,87] 、血流量/血管剪切应力[77] 和脉搏波传导速度[63] ...
目的：系统综述运动间断久坐对糖、脂代谢与血管功能的急性影响，并梳理其科学机理，提供循证应用建议。方法：检索Pubmed等四个数据库，使用Cochrane工具评估偏倚风险，审查纳入文献的方法学质量。由于纳入文献在受试者、结局指标与干预方案存在高度异质性，因此未使用荟萃分析定量合成证据。结果：共纳入59篇随机交叉试验文献，受试者共1214人。偏倚风险主要为实施与测量偏倚，部分研究在受试者纳入与方案设计上存在方法学问题。健康人群中，多数研究支持运动间断久坐能降低餐后血糖、胰岛素与血脂，并改善收缩压、舒张压、血流量与剪切应力。临床人群中，多数研究支持运动间断久坐有效降低餐后血糖、胰岛素，也能够降低收缩压、舒张压、平均动脉压、血流量与剪切应力，但难以改善血脂。涉及血流介导的血管舒张功能的研究极少且结果不一致，难以得出具体结论。结果差异主要源自受试者与干预方案差异。运动间断久坐相关科学机理可能与蛋白质转运、调节激素分泌和动作力学模式相关。结论：运动间断久坐能抵消久坐的不利影响，并急性改善糖、脂代谢与血管功能。未来应考虑更多元应用情景、人群与结局，探究间断的量-效关系并整合电子提醒等环境干预策略，方法设计需基于循证且亟待规范，确定核心测量指标及工具以降低测量结果异质性，检测更直接的生物标记物及其信号通路变化，通过效应-多组学-分子-功能等整合范式以识别心血管代谢潜在风险因素间的协同联系。
... The sample size required for statistical power (G*Power 3.1.9.4) was calculated based on a previous study 25 that observed an effect size of 0.33 (for interaction) for FMD. Thus, considering F test (analysis of variance [ANOVA] repeated measures, within-between interaction) with an α of .05 and β of .20, 2 groups, 3 measurements, correlation among repeated measures of 0.5, and nonsphericity correction ε of 1, the minimum required number was 18. ...
... Notably, it led to an increase in popliteal FMD response up to 30 min after the intervention in these participants. In agreement with our findings, previous studies that examined different break strategies such as walking 25,26 or dynamic resistance exercises 28 reported improvements in FMD verified an impairment after prolonged uninterrupted sitting. ...
Purpose
The World Health Organization has recommended breaking up sitting time to improve cardiovascular health. However, whether isometric exercise can be effectively used as a strategy to break up sitting time remains unclear. Thus, the aim of this study was to analyze the acute effects of breaking up prolonged sitting with isometric wall squat exercise (IWSE) on vascular function and blood pressure (BP) in sedentary adults.
Methods
This randomized crossover trial included 17 adults (53% male, 26 ± 6 yr, 22.4 ± 3.6 kg/m ² ) with high sedentary behavior (≥ 6 hr/d). The participants completed 2 experimental sessions in a randomized order, both sharing a common sitting period of 180 min: Breaks (2-min breaks were incorporated into the IWSE, with participants maintaining their knees at the angle determined by the incremental test, which occurred every 30 min) and Control (sitting for 180 min continuously). Popliteal artery flow-mediated dilation (FMD) and brachial BP were measured before and at 10 and 30 min after the experimental sessions.
Results
The results did not indicate significant session vs time interaction effects on popliteal FMD and brachial BP ( P > .05). A subanalysis including only participants with popliteal FMD reduction after the Control session (n = 11) revealed that Breaks enhanced popliteal FMD after 10 min (1.38 ± 6.45% vs −4.87 ± 2.95%, P = .002) and 30 min (−0.43 ± 2.48% vs −2.11 ± 5.22%, P = .047).
Conclusion
Breaking up prolonged sitting with IWSE mitigates impaired vascular function resulting from prolonged sitting but has no effect on BP in sedentary adults.
... A study by Thosar et al. (2015) involved 12 men participating in two randomized three-hour sitting trials. The first trial was a sitting trial where the subject was seated in one position without interruption The second trial was a sit-walk trial where the subjects walked on treadmills for five minutes at two mph for 30 minutes, 1.5-hour and 2.5-hour intervals during the sitting period. ...
... The sitwalk trial, however, showed a significant difference in the FMD and mean shear rate compared to the sit trial, indicating that walking during prolonged sitting may benefit arterial health. 23 As compared to our study, both CA and SFA are measured. In our study all interventionsaside from the prolonged sittingshowed a minor decrease in CA velocity over time. ...
Background The aim of this study was to observe and analyze vascular function in ‘prolonged sitting’, followed by a yoga asana routine and pranayama intervention. Participants in this study include those who work from desks in offices. The study required the participants to attend on three separate days at random, and they had to finish a computerized test on each day. On the first day, participants were required to complete a computer test while sitting still for four hours (with the exception of washroom breaks). The next day, they underwent a computerized test along with a pranayama intervention. Finally, on the last day, they underwent a computerized test along with a yoga asana intervention. At the start of the study and after two and four hours, we measured the diameter and velocity of the common carotid artery (CCA) and superficial femoral artery (SFA). Methods The study was a within-subjects prospective single-center trial conducted in the Department of Radio-Diagnosis and Imaging, Kasturba Medical Hospital, Manipal, India, between September 2022 and January 2023. Participants were asked to do one of the following ‘activities’ over successive weeks: Week 1 – Prolonged sitting; Week 2 – Pranayama intervention; and Week 3 – Yoga asana intervention during prolonged sitting. The baseline and follow-up variables of pulse velocity, endothelial thickness, and shear rate were assessed for normality through a Shapiro-Wilk Test. Results Our sample included 11 participants with moderate physical activity, five with high physical activity and one with low physical activity. Yoga asana intervention comprised participants sitting continuously for four hours, with a yoga asana intervention being provided every hour, lasting for 10 minutes. Conclusions Yoga asana improves vascular functions in prolonged sitting conditions. This routine can promote the concept of interrupted sitting and ways to reduce it with efficient yoga asana practice without changing the work culture and provide better physical relief. Trial registration Clinical Trials Registry – India ( CTRI/2022/09/045628), date of registration: 19/09/2022(CTRI/2022/9/045628)https://ctri.nic.in/Clinicaltrials/main1.php?EncHid=16349.27799
... A study by Thosar et al. (2015) involved 12 men participating in two randomized three-hour sitting trials. The first trial was a sitting trial where the subject was seated in one position without interruption The second trial was a sit-walk trial where the subjects walked on treadmills for five minutes at two mph for 30 minutes, 1.5-hour and 2.5-hour intervals during the sitting period. ...
... The sitwalk trial, however, showed a significant difference in the FMD and mean shear rate compared to the sit trial, indicating that walking during prolonged sitting may benefit arterial health. 23 As compared to our study, both CA and SFA are measured. In our study all interventionsaside from the prolonged sittingshowed a minor decrease in CA velocity over time. ...
Background
The aim of this study was to observe and analyze vascular function in ‘prolonged sitting’, followed by a yoga routine and pranayama intervention. Participants in this study include those who work from desks in offices. The study required the participants to attend on three separate days at random, and they had to finish a computerized test on each day. On the first day, participants were required to complete a computer test while sitting still for four hours (with the exception of washroom breaks). The next day, they underwent a computerized test along with a pranayama intervention. Finally, on the last day, they underwent a computerized test along with a yoga intervention. At the start of the study and after two and four hours, we measured the diameter and velocity of the common carotid artery (CCA) and superficial femoral artery (SFA).
Methods
The study was a within-subjects prospective single-center trial conducted in the Department of Radio-Diagnosis and Imaging, Kasturba Medical Hospital, Manipal, India, between September 2022 and January 2023. Participants were asked to do one of the following ‘activities’ over successive weeks: Week 1 – Prolonged sitting; Week 2 – Pranayama intervention; and Week 3 – Yoga intervention during prolonged sitting. The baseline and follow-up variables of pulse velocity, endothelial thickness, and shear rate were assessed for normality through a Shapiro-Wilk Test.
Results
Our sample included 11 participants with moderate physical activity, five with high physical activity and one with low physical activity. Yoga intervention comprised participants sitting continuously for four hours, with a yoga session intervention being provided every hour, lasting for 10 minutes.
Conclusions
Yoga improves vascular functions in prolonged sitting conditions. This routine can promote the concept of interrupted sitting and ways to reduce it with efficient yoga practice without changing the work culture and provide better physical relief.
Trial registration
Clinical Trials Registry – India ( CTRI/2022/09/045628), date of registration: 19/09/2022(CTRI/2022/9/045628)https://ctri.nic.in/Clinicaltrials/main1.php?EncHid=16349.27799
... In short, the sitting posture could have established a physiological environment distinct from that established in the body inactivity model (defined as less than 150 minutes of moderate to vigorous physical activity per week) and other experimental inactivity models [5], and numerous experimental studies conducted worldwide have sought to identify the underlying mechanism. A meta-analysis of such experimental studies revealed that prolonged sitting decreases the endothelial function of lower extremity vessels by 2.12% [6], which was associated with decreased arterial shear stress [7]. Such findings have been suggested as the mechanisms driving the increased risk of CVD and all-cause mortality. ...
... Therefore, we set the experimental condition to three hours. The washout period was determined according to previous studies [7]. ...
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.
... This has led to a considerable body of literature focused on exploring the adverse implications of habitual prolonged sitting and a lack of physical activity [13,17,[24][25][26][27][28]. The predominant physiological markers investigated thus far indicative of the negative impacts of prolonged sitting include observational and experimental studies that have identified acute and chronic effects concerning high plasma glucose [9], endothelial dysfunction [29], high levels of low-density lipoprotein (LDL) and total cholesterol [18,30], suppression of high-density lipoprotein (HDL) [31,32], elevated plasma triglycerides, decreased insulin sensitivity [33], heightened C-reactive protein (CRP) [34][35][36][37], fibrinogen [38][39][40], and white blood cell (WBC) count [39,41]. ...
... This heightened understanding is crucial since extended time to recovery can decrease exercise tolerance, therefore likely affecting adherence to an exercise training program [44,76] and difficulty in upholding the WHO physical activity recommendations [22]. Recent literature suggests that breaking up prolonged sitting time with light physical activity has the potential to minimize systemic inflammation [17,27,29]. However, there is an absence of research examining the impact of prolonged sitting on recovery. ...
(1) There is growing concern surrounding the adverse effects of prolonged sitting on health, yet its impact on post-exercise recovery remains relatively unexplored. This study aimed to better understand the potential influence of habitual prolonged sitting on recovery time and the unfavorable impact prolonged sitting may have on time to recovery, as assessed by muscle damage and inflammatory markers and an isokinetic dynamometer. (2) Nine college-age men (mean age ± SD = 22.1 ± 3.1 years, body mass = 80.9 ± 15.7 kg, height = 171 ± 9.0 cm, Body Mass Index (BMI) = 27.6 ± 4.9 kg·m2) participated in an exhaustive exercise protocol. Creatine Kinase (CK), Myoglobin (Mb), C-Reactive Protein (CRP), White Blood Cell Count (WBC), Peak Torque (PT), and muscle soreness were measured at baseline and 0, 24, 48, and 72 h post-exercise. Dietary and exercise logs were maintained during the 5-day testing procedure. (3) No significant differences were observed in muscle damage markers (CK [p = 0.068] and Mb [p = 0.128]), inflammatory markers (CRP [p = 0.814] and WBC [p = 0.140]), or PT [p = 0.255]) at any time point. However, a significant positive correlation was found between daily sitting time and the percent increase in CK concentration from 0 h to 72 h (r = 0.738, p = 0.023). Strong correlations were also noted between prolonged sitting and percent change in Mb concentration at 48 h (r = 0.71, p = 0.033) and 72 h (r = 0.889, p = 0.001). There was a significant two-way interaction for time × velocity (p = 0.043) for PT with a simple main effect for time at 60°·s−1 (p = 0.038). No significant associations were detected between daily carbohydrate or protein intake and recovery markers (p > 0.05). (4) The findings suggest minimizing daily sitting time may expedite and potentially aid muscle recovery after an intense exercise bout, although further research is warranted to validate these findings.
... The muscular inactivity that accompanies excessive sedentary time, time largely spent seated, results in well-documented deleterious outcomes, including detrimental shifts in metabolic processes, particularly glucose metabolism, and alterations in cardiovascular function (Hamilton, 2018). In various models of enforced sitting, evidence indicates that acute bouts of sitting contribute to peripheral vascular deconditioning in adults and children (McManus et al., 2015;Taylor et al., 2022;Thosar et al., 2015). In adults these reductions are related to reduced shear stress, which decreases the availability of nitric oxide and increases the production of vasoconstrictors (Thosar et al., 2012), suggesting sitting alters endothelial integrity (Thosar et al., 2015). ...
... In various models of enforced sitting, evidence indicates that acute bouts of sitting contribute to peripheral vascular deconditioning in adults and children (McManus et al., 2015;Taylor et al., 2022;Thosar et al., 2015). In adults these reductions are related to reduced shear stress, which decreases the availability of nitric oxide and increases the production of vasoconstrictors (Thosar et al., 2012), suggesting sitting alters endothelial integrity (Thosar et al., 2015). Far less is understood about the cerebrovascular changes that accompany bouts of prolonged sitting; however, reductions in middle cerebral artery (MCA) blood velocity of 2.5-5.5% have been documented in adults following an acute bout of enforced sitting (Carter et al., 2018;Wheeler et al., 2019). ...
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 (Q̇), 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 ICA Q̇/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.
... Nowadays, there is growing evidence that appropriate exercise can prevent or treat endothelial dysfunction associated with SB, [9][10] However, the effect is inconsistent among different exercise modalities. While moderate-intensity continuous exercise (MICE) is a well-known exercise regime for improving endothelial function, 11 it can be time-consuming and monotonous. ...
Abstracts
Objectives
Our study investigated the effects of acute high-intensity interval exercise (HIIE) and moderate-intensity continuous exercise (MICE) on endothelial function and its associated biomarkers in sedentary young individuals.
Methods
Fifteen subjects (10M / 5F; 22 ± 2 years; BMI: 23.07 ± 4.12 kg/m²) participated in a crossover trial including three experimental conditions: HIIE, MICE, and a control session of rest (CON) in random order separated by a 7-day washout period. Endothelial function was assessed using flow-mediated dilation (FMD), mean shear rate (MSR), and circulating levels of blood lactate, VEGF, IGF-1, and irisin.
Results
Both HIIE and MICE significantly enhanced FMD% (both P < 0.001 and P < 0.01, respectively), lactate (both P < 0.001), VEGF (P < 0.001 and P < 0.01, respectively), IGF-1 (both P < 0.001), and irisin (P < 0.001 and P < 0.05, respectively), with a greater extent after HIIE compared to MICE in FMD% (P < 0.001), MSR (P < 0.05), lactate (P < 0.001), VEGF (P < 0.05), and IGF-1 (P < 0.05). Additionally, change (post-pre) in FMD% was positively correlated with changes in MSR, lactate, and VEGF in both HIIE and MICE conditions. Change in MSR was positively associated with changes in lactate and VEGF in both HIIE and MICE conditions. Furthermore, enhancement in lactate was correlated with enhancements in VEGF in both HIIE and MICE conditions.
Conclusions
Acute HIIE is a more effective method than MICE at improving endothelial function in sedentary young individuals and increases in lactate and its mediated VEGF release, attributed to increase in shear rate after exercise, are involved in regulatory mechanisms.
... Laboratory studies in adults and older adults have shown that breaking up prolonged periods of sedentary behavior with short bouts of physical activity can positively impact markers of health. For instance, randomized trials using cross-over study designs have demonstrated that short (2-3 min), but frequent (every 20-30 min) disruptions of sedentary time that involve either light-or moderate-intensity aerobic or resistance activity can have an acute positive impact on glucose metabolism (Dunstan et al., 2012;Duvivier et al., 2013;Peddie et al., 2013;Yates et al., 2020), blood pressure Larsen et al., 2014;Yates et al., 2020;Zeigler et al., 2016), lipid metabolism (Dempsey, Larsen, Winkler, et al., 2018;Duvivier et al., 2013), and endothelial function (Restaino et al., 2016;Thosar et al., 2015). While these studies have shown promise in the laboratory, some researchers have applied similar interventions in the field. ...
Background/Objectives : The aim of this systematic review was to evaluate the available evidence regarding the impact of breaks in sedentary time on cardiovascular, metabolic, functional, and psychosocial health of adults aged 60 years and older. Methods : A systematic search of databases was performed in May 2024. This review was registered with PROSPERO (#374311) and has been reported using the Preferred Reporting Items for Systematic reviews and Meta-Analyses (PRISMA) guidelines. Results : A total of seven articles (five unique studies) were included. The available evidence suggests minimal changes in health-related variables. Specifically, changes to cardio-metabolic and psychosocial variables were limited. Changes to physical function appear to show the most promise. While only one of the studies included focused solely on reducing sedentary behavior, all others focused on reducing sedentary behavior by increasing physical activity. Two of the seven articles showed significant changes compared with the control group to sedentary time ranging from 32 to 58 min. Mean sedentary bout time and number of sedentary bouts longer than 30 min were reduced in two of the seven articles. No changes in sit-to-stand transitions were reported. Conclusion : There is limited evidence focusing on the impact of breaks or interruptions to sedentary time on the physical and mental health of community-dwelling adults 60+ years. Significance/Implications : This systematic review examines recent research aimed to disrupt sedentary behavior and positively impact health in community-dwelling older adults. Results show the difficulty of increasing sit-to-stand transitions/breaks in sedentary behavior, and highlight the challenge of disentangling the effects of sedentary behavior, and physical activity on health.
... Both physical activity and physical inactivity can trigger significant and contrasting alterations in vascular function (66)(67)(68). For instance, do Amaral et al found that older adults who were previously hospitalized with COVID-19 experienced significant improvements in carotid-femoral pulse wave velocity, a prognostic marker of cardiovascular function, after undergoing HBET (69). ...
Purpose: This study assessed the impact of a 12-week, home-based exercise training (HBET) program on health-related quality of life (HRQOL, primary outcome), cardiovascular and metabolic parameters in pediatric COVID-19 patients.
Methods: In this single-center, randomized controlled trial conducted in Sao Paulo (Brazil) from October 2020 to January 2022, 32 patients (mean age 12 ± 3.3 years; median 4 months [range: 0.7–6.6] between COVID-19 diagnosis [n = 25 mild, n = 4 moderate, n = 3 severe illness] and study entry) from a tertiary hospital were randomly assigned to either HBET or standard of care (CONTROL) in a 2:1 ratio. The HBET group underwent supervised and unsupervised sessions 3 times/week for 12 weeks emphasizing aerobic and bodyweight exercises and the CONTROL group received standard care which included general advice for a healthy lifestyle with no prescribed exercise intervention. HRQOL (Pediatric Quality of Life Inventory [PedsQL], cardiopulmonary exercise test (CPET), brachial flow-mediated dilation (b-FMD) and echocardiography assessments were conducted in both groups. Statistical analysis was performed using an intention-to-treat approach (ITT) for the primary analysis and complete-case (per-protocol) as sensitivity analysis and significance was set at P ≤ 0.05 (P ≤ 0.10 were considered as trend).
Results: There was no difference in HRQOL between groups. Intention-to-treat analysis showed a trend toward increased VO 2 at anaerobic threshold at post-intervention for the HBET group. Additionally, a sensitivity analysis showed significant changes in peak HR, HRR 1min, RER and chronotropic response and tendency towards significance in VE/MVV and chronotropic response for the HBET group. No other between-group differences were detected for CPET, b-FMD and echocardiography variables (all p > 0.05).
Conclusions: In this RCT, a 12-week HBET intervention did not impact HRQOL in pediatric COVID-19 patients. However, HBET led to greater improvements in VO 2 VAT, heart rate peak and one-minute recovery and in chronotropic response with no changes in other cardiovascular parameters. Further studies are needed to explore the effects of exercise on the recovery of pediatric COVID-19 patients with persistent COVID-19 symptoms.
... Various strategies have emerged to reduce the time spent sitting at work, such as active workstations, [28][29][30] with promising results. [31][32][33][34] Nevertheless, the use of sit-andstand desk or cycle ergometer may differ in benefits between some working conditions. 35 Hence, interventions ought to be tailored to the specific context and working environment of the populations they aim to reach. ...
Introduction
Sedentary behaviour is a public health problem. We mainly have sedentary behaviour at work, transforming them into occupational risk. To our knowledge, there is no intervention study on the reduction of occupational sedentary behaviour in a real work situation and its impact on health and biomarkers of stress. The main objective is to study changes in sedentary behaviour following a behavioural intervention (sit-and-stand desk and cycle ergometer).
Methods and analysis
This is a randomised controlled trial in cross-over design conducted in a single centre. The study will be proposed to emergency medical dispatchers of Clermont-Ferrand. Each volunteer will be followed during three cycles of 1 week (3 weeks in total). Each 1-week cycle is made up of 12 hours of work (three conditions: a control and two interventions), 12 hours of successive rest and 6 days of follow-up. For each condition, the measurements will be identical: questionnaire, measure of heart rate variability, electrodermal activity and level of physical activity, saliva and blood sampling. The primary outcome is sedentary behaviour at work (ie, number of minutes per day standing/active). Data will be analysed with both intention-to-treat and per protocol analysis. A p<0.05 will be considered as indicating statistical significance.
Ethics and dissemination
The study protocol has been approved by the Ethics Committee Ouest IV, FRANCE. The study is registered in ClinicalTrials.gov. All patients will be informed about the details of the study and sign written informed consent before enrolment in the study. Results from this study will be published in a peer-reviewed journal. This study involves human participants and was approved by Comité de protection des personnes Ouest IVCPP reference: 23/132-2National number: 2022-A02730-43.
Trial registration number
NCT05931406 .
... In addition, evidence is emerging that inactivity results in physiological mechanisms, termed inactive physiology, that may eventually lead to a reduced quality and quantity of life (10). The sit-stand desk has been solidified as an effective tool to reduce total sedentary time throughout the day (11) and although an optimal sit-stand ratio has not yet been determined (13), light activity breaks from sitting have been shown to reduce impairments to the superficial femoral artery (27). Sedentary behavior researchers continue to make important contributions to the growing knowledge base of sedentary behavior. ...
... Sin embargo, también podrían ofrecer una explicación empírica de los efectos sobre la función cognitiva. Investigaciones recientes han evidenciado que pasar largos periodos sentado provoca disfunción endotelial aguda, una fase precursora en la patogénesis de la ateroesclerosis (Restaino et al., 2016;Thosar, Bielko, Mather, Johnston, y Wallace, 2015). Este proceso disfuncional es provocado por la reducción en las fuerzas de cizallamiento sobre el endotelio vascular, disminuyendo la síntesis y disponibilidad del óxido nítrico, lo que, a su vez, conlleva una disminución en la capacidad vasodilatadora arterial (Thosar, Johnson, Johnston y Wallace, 2012). ...
... 9,10 Additionally, prolonged periods of sitting can result in reduced blood flow to the lower extremities, thereby increasing the risk of blood clots. 11,12 These multifaceted health concerns underscore the critical importance of promoting physical activity among working pregnant women. They face the dual demands of work and pregnancy, often with limited social support and time for prenatal care may require a specific solution to encounter this issue. ...
This review explores the benefits of yoga during pregnancy and considers its implications for working pregnant women, focusing on safety, future directions, and limitations. The physical and psychological changes experienced during pregnancy can lead to increased stress and discomfort, impacting both maternal and fetal health, which may be further augmented by work stress during pregnancy. To address these challenges, various interventions such as yoga, relaxation techniques, and meditation have been proposed. Although there is evidence to support the benefits of yoga at both physical and psychological levels, there is a lack of proper strategies and guidelines for the implications of these interventions among working pregnant women. Incorporating yoga as a safe and cost‐effective intervention for managing work‐related distress during pregnancy can have significant benefits for both maternal and fetal health. However, careful consideration of safety guidelines, further research on working pregnant women, and exploring optimal implementation strategies are essential to fully harness the potential of yoga in this context. This review aims to provide a comprehensive overview of the current evidence for the benefits and safety of yoga during pregnancy, with a specific focus on working pregnant women. To ensure the scientific rigor of this review, we conducted a systematic search of the PubMed database for high‐quality research studies published in peer‐reviewed journals.
... Therefore, occupational interventions that seek to decrease sedentary time and increase physical activity would likely be a great benefit to workers. The literature shows that breaking up a 3 h sitting segment with 5 min of light physical activity protects cardiovascular function, which could easily be implemented in a work-from-home environment [44]. Workplace supports to increase PA and decrease SB include treadmill desks [45], sit-and-stand stations, and pedal machines [46]. ...
At the start of the COVID-19 pandemic, many workplaces transitioned to remote work, which altered lifestyle behaviors. We conducted a meta-analysis to understand if the transition to working from home due to the pandemic affected workers’ physical activity and sedentary behavior worldwide. We reviewed articles published between November 2019 and May 2022. Of an initial 3485 articles, a total of 17 were included, 15 of 17 were included for their physical activity (PA) comparisons (n = 36,650), and 12 of 17 (n = 57,254) were included for their sedentary behavior (SB) comparisons (10 studies have data for both PA and SB). This work is registered through PROSPERO (CRD42022356000). Working from home resulted in a significant decrease in PA (Hedge’s g = −0.29, 95% CI [−0.41, −0.18]) and an increase in SB (Hedge’s g = +0.36, 95% CI [0.20, 0.52]). Working from home impaired preventative activity behaviors, and these results are relevant to worker health as the future of work evolves beyond the pandemic.
... Recent studies have demonstrated that engaging in exercise can counteract the effects of SB on endothelial function [30][31][32][33][34]. Along these lines, strategies to interrupt prolonged sitting through activities such as walking or stair climbing [24,35,36] or simple resistance exercises (i.e., body weight-resisted exercises) [25] have been found to prevent the reduction in %FMD, SS, and BF. Furthermore, recent trials have investigated the potential preventive effect of performing exercise prior to a session of SB (e.g., prior exercise to prolonged sitting) on endothelial dysfunction. ...
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.
... 3 Experimental studies have shown that endothelial function is acutely altered by very small physical movements such as fidgeting, 4 or by small breaks in sedentary time. 5 It is therefore possible that the influence of a given volume of PA on vascular health may not be uniform, rather it may depend on different patterns of rest and PA. To date, research investigating differences in patterns of habitual PA accumulation and associations with vascular health is sparse. ...
While physical activity (PA) is understood to promote vascular health, little is known about whether the daily and weekly patterns of PA accumulation associate with vascular health. Accelerometer‐derived (activPAL3) 6‐ or 7‐day stepping was analyzed for 6430 participants in The Maastricht Study (50.4% women; 22.4% Type 2 diabetes mellitus (T2DM)). Multivariable regression models examined associations between stepping metrics (average step count, and time spent slower and faster paced stepping) with arterial stiffness (measured as carotid–femoral pulse wave velocity (cfPWV)), and several indices of microvascular health (heat‐induced skin hyperemia, retinal vessel reactivity and diameter), adjusting for confounders and moderators. PA pattern metrics were added to the regression models to identify associations with vascular health beyond that of stepping metrics. Analyses were stratified by T2DM status if an interaction effect was present. Average step count and time spent faster paced stepping was associated with better vascular health, and the association was stronger in those with compared to those without T2DM. In fully adjusted models a higher step count inter‐daily stability was associated with a higher (worse) cfPWV in those without T2DM (std β = 0.04, p = 0.007) and retinal venular diameter in the whole cohort (std β = 0.07, p = 0.002). A higher within‐day variability in faster paced stepping was associated with a lower (worse) heat‐induced skin hyperemia in those with T2DM (std β = −0.31, p = 0.008). Above and beyond PA volume, the daily and weekly patterns in which PA was accumulated were additionally associated with improved macro‐ and microvascular health, which may have implications for the prevention of vascular disease.
... Reducing sedentary time with frequent bouts of standing or walking is safe and feasible for patients with chronic diseases [8,21,22]. Emerging evidence from meta-analyses and intervention studies conducted in free-living environments indicate significant beneficial relationships of sedentary breaks with BMI, waist circumference, and C-reactive protein (CRP) [23], as well as average glucose levels, insulin and blood pressure (BP) [23][24][25]. Therefore, frequent sedentary breaks can not only reduce the total sedentary time and increase total standing and walking time, but also break prolonged sitting time, bringing additional cardiometabolic benefits and possibly overcoming common barriers to moderate-to-vigorous PA. ...
Sedentary behavior, a key modifiable risk factor for cardiovascular disease, is prevalent among cardiovascular disease patients. However, few interventions target sedentary behavior in this group. This paper describes the protocol of a parallel two-group randomized controlled trial for a novel multi-technology sedentary behavior reduction intervention for cardiovascular disease patients (registered at Clinicaltrial.gov, NCT05534256). The pilot trial (n = 70) will test a 12-week “Sit Less” program, based on Habit Formation theory. The 35 participants in the intervention group will receive an instructional goal-setting session, a Fitbit for movement prompts, a smart water bottle (HidrateSpark) to promote hydration and encourage restroom breaks, and weekly personalized text messages. A control group of 35 will receive the American Heart Association’s “Answers by Heart” fact sheets. This trial will assess the feasibility and acceptability of implementing the “Sit Less” program with cardiovascular disease patients and the program’s primary efficacy in changing sedentary behavior, measured by the activPAL activity tracker. Secondary outcomes include physical activity levels, cardiometabolic biomarkers, and patient-centered outcomes (i.e. sedentary behavior self-efficacy, habit strength, and fear of movement). This study leverages commonly used mobile and wearable technologies to address sedentary behavior in cardiovascular disease patients, a high-risk group. Its findings on the feasibility, acceptability and primary efficacy of the intervention hold promise for broad dissemination.
... Here, we attached the stimulators exclusively to the lower body, and particularly the part of tissue involved in sitting. Prolonged sitting is a known cause of cardiovascular diseases, diabetes, muscle deterioration, an increased enveloping fat layer, and other chronic diseases [14][15][16]. Sustained pressure and tissue load can have an accumulative effect on the seated buttocks, causing pressure ulcers to occur. Areas near bony prominences, namely the ischial tuberosity, are especially susceptible [14]. ...
Background: The perception of tactile-stimulation locations is an important function of the human somatosensory system during body movements and its interactions with the surroundings. Previous psychophysical and neurophysiological studies have focused on spatial location perception of the upper body. In this study, we recorded single-trial electroencephalography (EEG) responses evoked by four vibrotactile stimulators placed on the buttocks and thighs while the human subject was sitting in a chair with a cushion. Methods: Briefly, 14 human subjects were instructed to sit in a chair for a duration of 1 h or 1 h and 45 min. Two types of cushions were tested with each subject: a foam cushion and an air-cell-based cushion dedicated for wheelchair users to alleviate tissue stress. Vibrotactile stimulations were applied to the sitting interface at the beginning and end of the sitting period. Somatosensory-evoked potentials were obtained using a 32-channel EEG. An artificial neural net was used to predict the tactile locations based on the evoked EEG power. Results: We found that single-trial beta (13–30 Hz) and gamma (30–50 Hz) waves can best predict the tactor locations with an accuracy of up to 65%. Female subjects showed the highest performances, while males’ sensitivity tended to degrade after the sitting period. A three-way ANOVA analysis indicated that the air-cell cushion maintained location sensitivity better than the foam cushion. Conclusion: Our finding shows that tactile location information is encoded in EEG responses and provides insights on the fundamental mechanisms of the tactile system, as well as applications in brain–computer interfaces that rely on tactile stimulation.
... To date, strategies, such as walking (Thosar et al., 2015), leg fidgeting (Morishima et al., 2016), and cycling (Garten et al., 2019;Park et al., 2022), have been shown to successfully protect against vascular dysfunction in the context of prolonged sitting. Short resistance exercise breaks (REB), which include performing body weight squats, high knees, and calf raises periodically throughout the day, have also been shown to mitigate aberrant cardiometabolic responses to prolonged sitting. ...
We investigated the acceptability of bodyweight resistance exercise breaks (REB) to disrupt prolonged sedentary behavior in the workplace. Twenty-nine individuals completed a REB, where they performed 3-min REB 4, 8, and 16 times on days 1–2, 3–4, and 5 of the workweek, respectively, and a control condition (i.e., SIT). Productivity was assessed on days 1 and 5 each week. The acceptability of each REB frequency was assessed. When asked to complete 4, 8, and 16 REB, participants completed (mean values) 3.2, 6.2, and 9.2 REB/day, respectively. Moreover, 88%, 40%, and 9% of participants expressed that the 4-, 8-, and 16-REB frequencies were acceptable, respectively. Decision-making ability and concentration levels increased from day 1–5 of the REB week (p=0.048) but were stable during SIT. REB (4/day) are highly acceptable and could be a promising intervention strategy for reducing occupational sitting, thus decreasing sedentary-behavior-induced risk.
... Evidence suggests that increased sedentary time (independent of physical activity levels) is associated with increased CVD risk [40,41]. Long periods of sitting reduces endothelial shear stress [42], decreasing endothelial nitric oxide synthase activity [43]. In older females, increased physical activity is associated with improvements in self-efficacy as well as physical fitness and function [44]. ...
Background
Obesity (OB) is highly prevalent in females after menopause, especially visceral adipose tissue (VAT) accumulation which contributes to endothelial dysfunction. The endothelium assists in regulating blood flow (BF) during exercise and is attenuated in females with OB. The purpose of this study was to examine upper and lower limb flow-mediated dilation (FMD) and BF regulation during graded low-intensity submaximal exercises in postmenopausal females with BMI in the lean (LN), overweight (OW) and OB categories.
Methods
Participants were grouped by body mass index (BMI) into LN (BMI 18.5–24.9 kg/m²; n = 11), OW (BMI 25.0–29.9 kg/m²; n = 15), and OB (BMI 30.0–39.9 kg/m²; n = 13). FMD of the brachial (BA-FMD) and superficial femoral arteries (FA-FMD) were assessed. Subsequently, BF and vascular conductance (VC) in the upper (BA-BF and BA-VC) and lower limbs (FA-BF and FA-VC) were measured during separate 3-stage incremental rhythmic handgrip and plantarflexion exercises.
Results
Significantly lower FA-FMD (P < 0.05) were seen in OB than LN and OW groups with no differences in BA-FMD. Increases in FA-BF and FA-VC were attenuated during the last stage of plantarflexion exercise at 30% of 1RM in OB (both P < 0.001) compared to LN and OW, while upper-body exercise vasodilation was unchanged. FA-BF and FA-VC during plantarflexion exercise were correlated to FA-FMD (FA-BF: r = 0.423, P = 0.007, FA-VC: r = 0.367, P = 0.021) and BMI (FA-BF: r = −0.386, P = 0.015, FA-VC: r = −0.456, P = 0.004).
Conclusion
Postmenopausal females with OB have reduced lower-limb endothelial and exercise vasodilator function during submaximal dynamic plantarflexion exercise compared to LN and OW. Our findings indicate that obesity may predict diminished leg endothelial function, BF and VC during exercise in postmenopausal females.
... The results from the meta-analysis, showed a decrease in this biomarker after the exposure. The changes of this biomarker are associated with possible vascular dysfunctionalities of lower extremities, because of the decrease in the blood flow and %FMD (Thosar et al. 2015). ...
... [14,15] Moreover, repeated bouts of prolonged sitting leads to endothelial dysfunction, which has been linked to vascular mortality. [16] Therefore, increased ST during the CBMR period could have increased the risk of adverse physiological and metabolic outcomes. Increased sedentariness is apparently a common outcome of movement restrictions or home confinements, as recent studies also report a significant increase in daily sedentary minutes in the respective populations. ...
Introduction
Social lockdowns and quarantines have been enforced in various populations to mitigate the spread of coronavirus disease 2019 (COVID-19) in the community. This study investigated the impact of COVID-19 lockdown, known as circuit breaker movement restrictions (CBMR), on physical activity (PA) and sedentary time (ST) distribution patterns among Singapore residents aged 21–65 years.
Methods
This was a cross-sectional retrospective study that utilised a 44-item questionnaire that included sections to determine PA and ST distribution patterns before and during CBMR. It also included information on sleep duration, PA preference and routine, awareness of local initiatives and perceptions on barriers towards PA during the CBMR period.
Results
There was an overall decrease in PA and a significant increase in physical inactivity and ST during the CBMR period. A greater proportion of participants reported sleeping for longer hours, suggesting positive adaptations in sleep habits during CBMR. Majority were unaware of online exercise initiatives and programmes offered during the CBMR period, and >50% of the respondents never used an online resource for exercise. Singapore residents seemed to prefer outdoor and facility-based venues for exercise and PA, and closure of facilities was the primary barrier for PA during the CBMR period.
Conclusion
Reduced PA and increased ST during CBMR reflect negative lifestyle adaptations and may have adverse public health implications. Increased sleep duration suggests successful coping, which may consequently lead to physical and mental health benefits. While Singapore adult residents may be flexible with certain aspects of being physically active, they seemed less adaptive to changes in type of exercise, facility and environment.
... Prolonged sitting also correlates with a detrimental cardiometabolic profile, such as obesity and type 2 diabetes, which can alter the volume of blood and the elasticity of vessels [45]. Additionally, it can adversely impact endothelial function, a critical determinant of vascular tone and BP regulation [46]. Finally, the entwinement of diabetes and cardiovascular disease with extended periods of sitting can potentially exacerbate OH due to induced alterations in blood vessel function and nerve damage [47]. ...
Orthostatic hypotension (OH) is frequently observed in benign prostatic hyperplasia (BPH) patients undergoing alpha-1 adrenergic antagonist (A1AA) therapy. While previous studies have acknowledged the prevalence of OH in BPH patients on A1AAs, limited data exist on ranking the safety of different A1AAs. This comprehensive review explores the underlying mechanisms of OH, examines numerous factors influencing its development, and provides insights into effective treatment strategies such as hydration, gradual postural changes, leg exercises, compression stockings, and tilt-table training for BPH management. The review highlights the significance of individualized care, interdisciplinary collaboration, and further research to optimize A1AA treatment, improve patient outcomes, and enhance quality of life.
... Os níveis de atividade física atuais são os menores de toda a história da humanidade e devem-se a fatores como a urbanização, automação, melhoria dos sistemas de transporte e aumento dos comportamentos sedentários em frente à TV, computador e videogame (ARCHER; BLAIR, 2011;O'KEEFE et al., 2011;NG;POPKIN, 2012). Várias doenças não comunicáveis são atribuídas justamente aos menores níveis de atividade física observados na atualidade (LENZ, 2014;REZENDE et al., 2014;STEINBERG et al., 2015;THOSAR et al., 2015). Desta forma, o educador físico possui um papel educativo importante informando e contribuindo para a maior adesão a hábitos de vida saudáveis. ...
Educadores físicos e outros profissionais de saúde fazem-se cada vez mais presentes nas redes sociais brasileiras. Este ensaio faz um apanhado sobre a importância da comunicação em saúde e o papel das emoções para a adoção de comportamentos mais saudáveis. A forma como as informações em saúde são veiculadas influencia m escolhas, afetam a compreensão de termos e conceitos, assim como a aceitação das prescrições feitas. Este texto foca na importância da comunicação como ferramenta facilitadora da tomada de decisões promotoras da saúde.
The present study aims to examine the effect of 4 h of continuous sitting on cerebral endothelial function, which is a crucial component of cerebral blood flow regulation. We hypothesized that 4 h of sitting may impair cerebral endothelial function similarly to how it affects lower limb vasculature. Thirteen young, healthy participants were instructed to remain seated for 4 h without moving their lower limbs. The blood flow and shear rate (SR) in the popliteal and internal carotid artery (ICA) were measured using duplex Doppler ultrasound. During the 4‐h sitting, peripheral (popliteal artery) and cerebral (ICA) endothelial function were assessed every hour. We induced peripheral and cerebral flow‐mediated dilation (pFMD and ICA FMD) using hyperemia (5 min of cuff inflation on lower limb, then deflation) or hypercapnia (30s of hypercapnia, end‐tidal partial pressure of CO2 + 9 mmHg), respectively. We then calculated each relative peak dilation from the baseline diameter to identify both pFMD and ICA FMD. We observed a significant decrease in pFMD starting at 2 h from the onset of sitting, and this reduction persisted throughout the 4‐h sitting [Base (6.8 ± 4.2%) vs. 2‐h (3.9 ± 2.0%), p = 0.044; vs. 3‐h (3.2 ± 1.8%), p = 0.016; vs. 4‐h (3.2 ± 1.9%), p = 0.005]. In contrast, during the 4‐h sitting, ICA blood flow, SR, and ICA FMD remained unchanged (p = 0.062, p = 0.068, and p = 0.203, respectively). Unlike peripheral endothelial function, cerebral endothelial function remained stable during 4‐h sitting. This suggests that the acute effect of prolonged sitting on cerebral vasculature differs from that of lower limb vasculature.
Objectives
This study aimed to compare the effectiveness of different wearable intervention strategies in reducing sedentary time (ST) and prolonged sitting (PS) on healthy adults.
Design
A network meta-analysis (NMA).
Data sources
PubMed, Web of Science, SPORTDiscus, ProQuest, Opengrey, Medline and Cochrane Central Register of Controlled Trials were searched up to 1 June 2024.
Eligibility criteria for selecting studies
Randomised controlled trials (RCTs) that examined the effect of wearable device interventions on ST and PS among healthy adults were included.
Data extraction and synthesis
Two independent reviewers used standardised methods to search, screen and code included studies. Bias risks were assessed using Cochrane tools (Risk of Bias 2.0). Data were analysed using a frequentist framework NMA to directly and indirectly compare the effects of the five different intervention strategies (comparators). The results were reported as standardised mean differences (SMDs) with 95% CI and surface under cumulative ranking curve (SUCRA) was used to rank the best interventions. The five comparators were as follows: (1) wearable-only intervention (only using wearable devices for self-monitoring); (2) wearable combined with online intervention (ie, online coaching and social media support); (3) wearable combined with offline intervention (ie, face-to-face seminars and courses); (4) comparison group (ie, traditional, non-wearable interventions); (5) control group (ie, maintaining daily routine, waitlist).
Results
12 RCTs with a total of 2957 participants were included. Results of NMA showed that the ‘wearable+online’ has significantly better effects in reducing ST compared with control group, comparison group and ‘wearable only’, with moderate to large effect sizes (SMD=0.96, 95% CI 0.65 to 1.27; SMD=0.87, 95% CI 0.21 to 1.53; SMD=0.78, 95% CI 0.14 to 1.42, respectively). However, no significant differences were identified between the groups in reducing PS. The SUCRA values were ranked as wearable+online (98.1%), wearable+offline (64.4%,), ‘wearable only’ (40.5%), comparison group (25.9%) and control group (21.1%) for ST reduction. Similar rankings were observed for PS reduction, with probabilities of 69.9%, 61.1%, 59.7%, 37.1% and 22.1%, respectively.
Conclusions
Wearable+online is the best intervention strategy for reducing ST in healthy adults. Additionally, none of the wearable-based interventions effectively reduced PS in healthy adults, but as there is little research on PS, it should receive more attention in the future.
PROSPERO registration number: CRD42021290017.
Rheumatoid arthritis (RA) is characterized by deteriorated vascular health and increased cardiovascular risk. Physical activity (PA) is recommended for cardiovascular management in RA, but evidence on the associations between objectively-measured PA and vascular health markers in RA is limited. In this cross-sectional study, eighty-two post-menopausal women with RA (62±7 years) undertook ultrasound assessments of vascular function and structure, including brachial and superficial femoral artery (BA and SFA) flow-mediated dilation; baseline and post-hyperemia peak diameters; and carotid intima-media thickness. Participants also performed a 7-day accelerometer-based assessment of PA and sedentary behavior (SB). Fitted regression models controlled for age, body mass index and disease activity were conducted to examine associations between vascular and PA outcomes. Regression analyses revealed that prolonged SB (bouts>60min) and total sedentary time were inversely associated with both baseline and peak BA diameters, with each additional hour of SB resulting in decreases of 0.08-0.1mm in these diameters (p≤0.01). Total sedentary time also showed similar negative associations with peak SFA diameters (β=-0.14[-0.24-0.05], p<0.01). Conversely, light-intensity PA and stepping time were positively associated with both baseline and peak BA diameters, with each additional hour increasing these diameters by 0.10-0.24mm (p≤0.02). Finally, standing time was positively associated with SFA peak diameter (β=0.11[0.01-0.20], p=0.02). No associations were found between moderate-to-vigorous PA and vascular outcomes. In conclusion, in patients with RA, SB was negatively, while light PA was positively, associated with BA and SFA diameters. These findings suggest that reducing SB and increasing PA, even at light intensities, may improve vascular health in RA.
Background/Aims
The growing prevalence of sedentary behaviour across the life course is linked to an increased risk of chronic venous disease and related mortality, warranting the need for non-invasive interventions to improve blood flow and lower extremity function. The aim of this study was to investigate the change in venous blood flow, heart rate and blood pressure after 8 minutes of using the Leeper device, Circulation Booster and light intensity walking.
Methods
A quasi-experimental crossover study involving 11 participants (eight women, three men, mean age 23.91 years, standard deviation 1.04 years) was conducted using Leeper and Circulation Booster devices and light intensity walking. During each intervention, participants exercised for 8 minutes, and blood flow was recorded at 0, 4 and 8 minutes. Heart rate and blood pressure were recorded at 0 and 8 minutes. Blood flow was the primary outcome measure, and heart rate and blood pressure were secondary outcomes. Participants rested for 10 minutes between exercise. A two-way repeated measures analysis of variance was used to analyse the effect of intervention and time on blood flow, blood pressure and heart rate.
Results
There was no significant interaction between intervention and time on blood flow (P=0.180) indicating that blood flow did not change over time depending on intervention. There was no significant main effect of time on blood flow (P=0.206), indicating that no intervention caused a significant increase or decrease in blood flow after 8 minutes of exercise.
Conclusions
The interventions involving the Leeper and Circulation Booster devices and light intensity walking did not appear to significantly increase blood flow in young adults. Further studies involving participants from older age groups and those with pathological interventions are warranted to examine the potential effectiveness of these interventions.
Implications for practice
The findings may assist with the advice that allied health professionals provide regarding the use of seated exercise trainers and EMS devices and their ability to influence changes in blood flow.
Purpose
Oxygen extraction in skeletal muscle is an important determinant of exercise tolerance. Prolonged sitting decreases oxygen extraction in the gastrocnemius muscle. However, the underlying mechanism remains unknown, and preventive measures are yet to be established. Therefore, we aimed to elucidate the mechanism by which prolonged sitting decreased muscle oxygen extraction and investigate preventive measures.
Methods
Ten healthy young males (age 21.2 ± 0.4 years; body mass index, 20.5 ± 1.3 kg/m²) were randomly assigned to each of the following conditions: 3-h supine (CON), 3-h sitting (SIT), and 3-h fidgeting of one lower leg during sitting (FID). Oxygen extraction from the gastrocnemius muscle was measured using near-infrared spectroscopy and the vascular occlusion test under each condition. The rate of change in total Hb + Mb (THb) was measured as an indicator of venous stasis and interstitial fluid accumulation in the lower leg.
Results
Muscle oxygen extraction was significantly lower at 180 min for SIT and FID than for CON (4384.2 ± 1426.8; 5281.5 ± 1823.7; 6517.4 ± 1390.8 a.u., respectively) and significantly higher for FID than for SIT (5281.5 ± 1823.7 vs. 4384.2 ± 1426.8 a.u., respectively). The rate of THb change was significantly higher at 180 min for SIT than for CON and FID (12.9 ± 15.1; −2.3 ± 5.7; 2.2 ± 11.6%, respectively). However, no significant difference was observed between CON and FID.
Conclusion
We found that 3-h prolonged sitting reduced oxygen extraction in the gastrocnemius muscles due to reduced oxygen supply to capillaries and increased distance between capillaries and myocytes. However, leg fidgeting alleviated this effect in healthy young males.
Trial registration number
UMIN000050531 (March 8, 2023).
Graphical abstract
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.
Background/Aims
The growing prevalence of sedentary behaviour across the life course is linked to an increased risk of chronic venous disease and related mortality, warranting the need for non-invasive interventions to improve blood flow and lower extremity function. The aim of this study was to investigate the change in venous blood flow, heart rate and blood pressure after 8 minutes of using the Leeper device, Circulation Booster and light intensity walking.
Methods
A quasi-experimental crossover study involving 11 participants (eight women, three men, mean age 23.91 years, standard deviation 1.04 years) was conducted using Leeper and Circulation Booster devices and light intensity walking. During each intervention, participants exercised for 8 minutes, and blood flow was recorded at 0, 4 and 8 minutes. Heart rate and blood pressure were recorded at 0 and 8 minutes. Blood flow was the primary outcome measure, and heart rate and blood pressure were secondary outcomes. Participants rested for 10 minutes between exercise. A two-way repeated measures analysis of variance was used to analyse the effect of intervention and time on blood flow, blood pressure and heart rate.
Results
There was no significant interaction between intervention and time on blood flow (P=0.180) indicating that blood flow did not change over time depending on intervention. There was no significant main effect of time on blood flow (P=0.206), indicating that no intervention caused a significant increase or decrease in blood flow after 8 minutes of exercise.
Conclusions
The interventions involving the Leeper and Circulation Booster devices and light intensity walking did not appear to significantly increase blood flow in young adults. Further studies involving participants from older age groups and those with pathological interventions are warranted to examine the potential effectiveness of these interventions.
Implications for practice
The findings may assist with the advice that allied health professionals provide regarding the use of seated exercise trainers and EMS devices and their ability to influence changes in blood flow.
Endothelial dysfunction is an early predictor of atherosclerosis and cardiovascular disease. Flow-mediated dilation (FMD) is the gold standard to assess endothelial function in humans. FMD reproducibility has been mainly assessed in the brachial artery (BA) with limited research in lower limb arteries. The purpose of this study was to compare FMD reproducibility in the upper limb BA and lower limb superficial femoral artery (SFA) in young healthy adults.
Fifteen young healthy adults (nine males; six females) underwent FMD, resting diameter, velocity, and shear rate measurements on three occasions to determine intra-and inter-day reproducibility in both BA and SFA, assessed by coefficient of variation (CV), intraclass correlation coefficient (ICC), and Bland–Altman plots.
BA FMD CVs (intra-day: 4.2%; inter-day: 8.7%) and ICCs (intra-day: 0.967; inter-day: 0.903) indicated excellent reproducibility and reliability, while for SFA FMD, both CVs (intra-day: 11.6%; inter-day: 26.7%) and ICCs (intra-day: 0.898; inter-day: 0.651) showed good/moderate reproducibility and reliability. BA FMD was significantly more reproducible than SFA FMD (p < 0.05). Diameter reproducibility was excellent and similar between arteries, while resting velocity and shear rate have lower reproducibility in the BA compared to SFA. Bland–Altman plots displayed no proportional and fixed bias between measurements.
In summary, SFA FMD is less reproducible than BA FMD, with identical volume of ultrasound training. Given the increasing interest in using SFA FMD to test the efficacy of interventions targeting lower limb’s vascular health and as a potential biomarker for peripheral arterial disease risk, future studies should ensure higher levels of training for adequate reproducibility.
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.
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, causes endothelial dysfunction. This conclusion has been mainly supported by studies using flow-mediated dilation in the lower extremities as the measured outcome. In this mini-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 (VSMC). 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 VSMC and inward remodeling, and that these changes manifest in a timeframe 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.
Purpose
Sedentary behaviour 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 females, 25 ± 3 years) completed three 3-hour 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 following 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 following sitting (both p < 0.01) and periodic standing (both p < 0.01) but were unchanged following elliptical activity. Lower limb pulse wave velocity did not change following sitting (p = 0.73) or standing (p = 0.21) but did decrease following elliptical activity (p = 0.03).
Conclusions
Prolonged sitting without interruptions increased central wave reflection while 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 behaviours.
Sedentary behaviours—i.e. ‘too much sitting as distinct from too little exercise’—are ubiquitous in modern societies. Accumulating epidemiological evidence indicates that higher volumes of sedentary behaviour are associated with elevated risks for all-cause mortality, cardiovascular disease incidence and mortality, type 2 diabetes incidence and some cancers, particularly among those who are not achieving recommended amounts of moderate-to-vigorous intensity physical activity. Based on these observations, and in part on a growing body of experimental research, it has been proposed that sedentary behaviour influences health risk through some mechanisms that act similarly or independently of physical inactivity. However, the observational evidence is well ahead of evidence on the physiological responses to sedentary behaviour, leaving uncertainties around the potential biological mechanisms that may explain the observed associations. Here, we summarise and discuss experimental evidence to date on the physiological effects of sedentary behaviours, including potential solutions-oriented research aiming to address sedentary behaviour as a health risk. We also highlight future research that is needed to fully ascertain the specific impact of sedentary behaviour on altering human physiology.
Background
Individuals with chronic kidney disease tend to have sedentary behavior and decreased physical activity, both are independent predictors of mortality in general population. While physical inactivity correlates to adverse health outcomes in patients with reduced kidney function, it is unclear whether this relationship remains significant for sedentary behavior. Our study purpose is to evaluate the association of sedentary lifestyle with mortality risk in individuals with renal insufficiency.
Methods
The study population were adult participants of 2007-2016 National Health and Nutrition Examination Survey (NHANES) with estimated glomerular filtration rate (eGFR) < 60 ml/min/1.73 m ² or self-reporting receiving dialysis (N=1419). Sedentary lifestyle was defined as sedentary time > 6 hours per day. Outcome of interest was all-cause and cardiovascular disease (CVD)- or cancer-related mortality.
Results
We observed that non-Hispanic Whites, and individuals with younger age and higher educational level were more likely to have sedentary lifestyle. During a median follow-up of 99 (interquartile range 70 to 128) months, a total of 458 participants died (3.98 deaths per 1000 person-months); 120 died from CVD and 92 from cancer, respectively. The crude analysis showed that individuals with sedentary lifestyle have higher risk of all-cause and CVD-related but not cancer-related mortality compared with the non-sedentary population. After adjusting for potential confounders, we showed that all-cause mortality and CVD-related mortality were 1.64-fold (95% CI 1.26-2.12) and 1.66-fold (95% CI 1.03-2.67) higher, respectively, in the sedentary population compared with the non-sedentary population. Similar results were observed in the sensitive analyses, in which we excluded individuals with dialysis, eGFR < 15 ml/min/1.73 m ² , or mobility disability.
Conclusions
Our findings suggest that sedentary lifestyle correlated to greater risk of all-cause and CVD-related mortality among individuals with reduced kidney function. Interventions targeting the individuals with risky behaviors may have practical importance for public health.
Emerging evidence indicates that acute bouts of uninterrupted prolonged sitting decrease cerebral blood flow and impair executive function. Few studies have investigated the use of feasible sedentary behavior interruptions to attenuate these effects. This study aimed to investigate effects of intermittent half-squat exercises during prolonged sitting on executive function. Twenty participants (45% women, 21±1 years) were randomized to sit for 3 h (i) without any interruptions (control) or (ii) with 1 min half-squats every 20 min (exercise). Executive function was determined using the Color Word Stroop Test (CWST) and Trail Making Test-B (TMT-B). Subjective feelings of arousal and measures of fatigue, concentration, and motivation were evaluated. Internal carotid artery (ICA) blood flow was measured using Doppler ultrasound. There was a significant interaction effect for correct response times with the incongruent CWST ( P<0.01), which were 3.5% faster in the exercise and 4.2% slower in the control over 3 hours of sitting. There was also a significant interaction effect for TMT-B completion times ( P<0.01) which were 10.0% faster in the exercise and 8.8% slower in the control. Exercise suppressed decreases in concentration with a significant interaction effect (-28.7% vs. -9.2% for control vs. exercise, P=0.048), and increases in mental fatigue with a significant interaction effect (285% vs. 157% for control vs. exercise, P<0.04). These changes may have been related to changes in ICA blood flow, which had a significant interaction effect ( P=0.087). These results suggest that a simple strategy like intermittent squat exercises could help to maintain executive function during prolonged sitting.
Atherosclerosis, the leading cause of death in the developed world and
nearly the leading cause in the developing world, is associated with systemic
risk factors including hypertension, smoking, hyperlipidemia, and diabetes
mellitus, among others. Nonetheless, atherosclerosis remains a geometrically
focal disease, preferentially affecting the outer edges of vessel bifurcations.
In these predisposed areas, hemodynamic shear stress, the frictional force
acting on the endothelial cell surface as a result of blood flow, is weaker
than in protected regions. Studies have identified hemodynamic shear stress
as an important determinant of endothelial function and phenotype. Arterial-level
shear stress (>15 dyne/cm2) induces endothelial quiescence and
an atheroprotective gene expression profile, while low shear stress (<4
dyne/cm2), which is prevalent at atherosclerosis-prone sites, stimulates
an atherogenic phenotype. The functional regulation of the endothelium by
local hemodynamic shear stress provides a model for understanding the focal
propensity of atherosclerosis in the setting of systemic factors and may help
guide future therapeutic strategies.
Sedentary behavior, as distinct from a lack of moderate-to-vigorous physical activity, is an emerging health risk behavior for the development of chronic diseases. Examples of sedentary behavior include sitting, watching television, using a computer, and driving a car. In this article, we define sedentary behavior; outline key concepts related to the physiology of sedentary behavior, review the recent evidence on the effects of prolonged sedentary behavior (or sitting) on the risk of cardio-metabolic disease and all cause mortality, and discuss the implications for current clinical practice. We found that most large scale studies on sedentary behavior were published in the last 5 years. There is moderately consistent evidence for an association between total sitting time and all-cause mortality, even when adjusted for or stratified by leisure time physical activity. Overall, we identified a compelling case for sitting reduction to be included in clinical preventive advice as a key component of ‘active living,’ where adults and children are encouraged to ‘move more and sit less’ across different settings and locations throughout the day.
Oscillatory and retrograde shear rate (SR) impairs endothelial function, potentially through shear-induced oxidative stress. We tested the hypothesis that acute vitamin C supplementation would prevent the attenuation of brachial artery flow-mediated dilation (FMD) after a period of augmented oscillatory and retrograde SR. Twelve healthy men (aged 26 ± 3 years) participated in two 30-min study visits in which one arm was subjected to increased oscillatory and retrograde SR, using 60 mm Hg of forearm cuff compression, and the contralateral arm served as the control. Subjects ingested capsules containing either placebo (sucrose) or vitamin C at 90 and 120 min (1000 mg total vitamin C) prior to cuff compression periods in a randomized placebo-controlled double-blind crossover study. Oscillatory and retrograde SR in the cuffed arms increased during the compression periods in the placebo and vitamin C study visits (p < 0.01 for both), with no difference between studies (p > 0.05). Antegrade SR remained unchanged throughout the compression periods (p > 0.05), and mean SR was lower in the cuffed arm than in the control arm for both study visits (p < 0.05). FMD decreased after cuff compression in the placebo cuffed arm (precompression vs. postcompression, 5.2% ± 1.4% vs. 3.5% ± 1.4%; p < 0.05), but remained unchanged after vitamin C therapy in the cuffed arm (precompression vs. postcompression, 5.3% ± 2.4% vs. 5.7% ± 2.6%; p > 0.05). No FMD changes were observed in the control arm for either study visit (p > 0.05). These data demonstrate that acute vitamin C supplementation prevents the attenuation of FMD due to altered SR patterns, suggesting that oxidative stress contributes to the oscillatory and retrograde SR-induced impairment of FMD.
Epidemiological studies suggest that excessive sitting time is associated with increased health risk, independent of the performance of exercise. We hypothesized that a daily bout of exercise cannot compensate the negative effects of inactivity during the rest of the day on insulin sensitivity and plasma lipids.
Eighteen healthy subjects, age 21±2 year, BMI 22.6±2.6 kgm(-2) followed randomly three physical activity regimes for four days. Participants were instructed to sit 14 hr/day (sitting regime); to sit 13 hr/day and to substitute 1 hr of sitting with vigorous exercise 1 hr (exercise regime); to substitute 6 hrs sitting with 4 hr walking and 2 hr standing (minimal intensity physical activity (PA) regime). The sitting and exercise regime had comparable numbers of sitting hours; the exercise and minimal intensity PA regime had the same daily energy expenditure. PA was assessed continuously by an activity monitor (ActivPAL) and a diary. Measurements of insulin sensitivity (oral glucose tolerance test, OGTT) and plasma lipids were performed in the fasting state, the morning after the 4 days of each regime. In the sitting regime, daily energy expenditure was about 500 kcal lower than in both other regimes. Area under the curve for insulin during OGTT was significantly lower after the minimal intensity PA regime compared to both sitting and exercise regimes 6727.3±4329.4 vs 7752.0±3014.4 and 8320.4±5383.7 mU•min/ml, respectively. Triglycerides, non-HDL cholesterol and apolipoprotein B plasma levels improved significantly in the minimal intensity PA regime compared to sitting and showed non-significant trends for improvement compared to exercise.
One hour of daily physical exercise cannot compensate the negative effects of inactivity on insulin level and plasma lipids if the rest of the day is spent sitting. Reducing inactivity by increasing the time spent walking/standing is more effective than one hour of physical exercise, when energy expenditure is kept constant.
Sedentary activity is a modifiable life-style behavior and a key component in the etiology of atherosclerotic cardiovascular disease (ACVD). US adults and children spend more than half their waking time in sedentary pursuits. Sedentary activity has been shown to result in impaired insulin sensitivity, impaired metabolic function and attenuated endothelial function, which are classic markers of ACVD. Sedentary activity is defined as 'sitting without otherwise being active.' This behavior promotes reduced muscular activity of the lower extremities which decreases leg blood flow, increases blood pooling in the calf, augments mean arterial pressure, and deforms arterial segments resulting in low mean shear stress (SS). SS activates distinct physiological mechanisms which have been proposed to be protective against ACVD; specifically through a SS-induced endothelium-derived nitric oxide mechanism. Reduced bioavailability of nitric oxide creates a pro-oxidant milieu resulting in increased oxidative stress. There is sufficient evidence which demonstrates that endothelial function is attenuated in the presence of oxidative stress. Sedentary activity results in low SS in the lower extremities which may result in increased oxidative stress and impaired endothelial function. This review furthers the use of sitting as model to study the effects of inactivity, discusses possible physiological mechanisms and suggests future directions.
Observational studies show breaking up prolonged sitting has beneficial associations with cardiometabolic risk markers, but intervention studies are required to investigate causality. We examined the acute effects on postprandial glucose and insulin levels of uninterrupted sitting compared with sitting interrupted by brief bouts of light- or moderate-intensity walking.
Overweight/obese adults (n = 19), aged 45-65 years, were recruited for a randomized three-period, three-treatment acute crossover trial: 1) uninterrupted sitting; 2) seated with 2-min bouts of light-intensity walking every 20 min; and 3) seated with 2-min bouts of moderate-intensity walking every 20 min. A standardized test drink was provided after an initial 2-h period of uninterrupted sitting. The positive incremental area under curves (iAUC) for glucose and insulin (mean [95% CI]) for the 5 h after the test drink (75 g glucose, 50 g fat) were calculated for the respective treatments.
The glucose iAUC (mmol/L) · h after both activity-break conditions was reduced (light: 5.2 [4.1-6.6]; moderate: 4.9 [3.8-6.1]; both P < 0.01) compared with uninterrupted sitting (6.9 [5.5-8.7]). Insulin iAUC (pmol/L) · h was also reduced with both activity-break conditions (light: 633.6 [552.4-727.1]; moderate: 637.6 [555.5-731.9], P < 0.0001) compared with uninterrupted sitting (828.6 [722.0-950.9]).
Interrupting sitting time with short bouts of light- or moderate-intensity walking lowers postprandial glucose and insulin levels in overweight/obese adults. This may improve glucose metabolism and potentially be an important public health and clinical intervention strategy for reducing cardiovascular risk.
Knowledge of sedentary behaviour associations with health has relied mainly on television-viewing as a proxy and studies with other measures are less common. To clarify whether sedentary behaviour is associated with disease-risk, we examined associations for television-viewing and sitting at work.
Using the 1958 British birth cohort (n = 7660), we analysed cross-sectional associations between television-viewing and work sitting (four categories, 0-1 to ≥ 3 h/d) with total, high-density lipoprotein (HDL) and low-density lipoprotein (LDL)-cholesterol, triglycerides, blood pressure, glycated haemoglobin, fibrinogen, C-reactive protein, hypertension and metabolic syndrome at 45 y. We adjusted for lifestyle and socio-demographic factors and assessed mediation of associations by body mass index (BMI) and diet. We also assessed whether the sedentary indicators are related similarly to factors linked to disease-risk.
There was a general trend of adverse socio-demographic and lifestyle characteristics with higher h/d television-viewing, but trends in the opposite direction for work sitting. Television-viewing was associated with most biomarkers and associations were mediated by BMI: e.g. for each category increase in television-viewing, HDL-cholesterol in men was lower by 2.3% (95% CI: 1.5%, 3.2%) and, in BMI and diet adjusted analyses, by 1.6% (0.8%, 2.4%); for women, by 2.0% (1.2%, 2.9%) and 0.9% (0.1%, 1.6%) respectively. Few, weaker associations for work sitting were found, in men only: e.g. corresponding values for HDL-cholesterol were 1.2% (0.5%, 1.9%) and 0.9% (0.3%, 1.5%). Odds for metabolic syndrome were elevated by 82% and 33% respectively for men watching television or work sitting for ≥ 3 vs. 0-1 h/d.
Associations with cardiovascular disease and diabetes biomarkers in mid-adulthood differed for television-viewing and work sitting. The role of sedentary behaviour may vary by leisure and work domains or the two indicators reflect differing associations with other disease-related influences.
Aim:
To explore the association between sedentary leisure time behavior (SLTB) and cardiovascular biomarkers, taking into account snacking habits, alcohol intake and physical activity level.
Design:
Cross-sectional.
Methods:
Study participants were recruited from the 5-year follow-up of a population-based intervention study, The Inter99 Study (1999-2006, Copenhagen, Denmark). A group of 6536 men and women, aged 35-65, was invited to attend a health examination and fill in a self-report questionnaire. Multiple linear regression analysis was applied.
Results:
Response rate was 69% (N = 4511), with equal gender distribution and mean age of 52. SLTB (hours per day) was significantly positively associated with triglyceride in men (β = 1.030, [1.013; 1.047]) and women (β = 1.036, [1.022; 1.050]), non-HDL cholesterol in men (β = 0.044, [0.012; 0.076]) and women (β = 0.064, [0.035; 0.094]), waist circumference in men (β = 0.835, [0.517; 1.153]) and women (β = 1.234, [0.087; 1.598]), and with waist/hip ratio (WHR) in men (β = 0.0054, [0.0036; 0.0073]) and women (β = 0.0040, [0.0019; 0.0060]). The associations persisted after adjustment for relevant confounders, except in HDL, where the association became non-significant in men (β = 0.9924, [0.9839; 1.0011]) and women (β = 0.9932, [0.8605; 1.0014]).
Conclusion:
SLTB appears to be an independent CVD risk factor, regardless of snacking habits and physical activity.
Escalating evidence indicates that disturbed flow patterns, characterized by the presence of retrograde and oscillatory shear stress, induce a proatherogenic endothelial cell phenotype; however, the mechanisms underlying oscillatory shear profiles in peripheral conduit arteries are not fully understood. We tested the hypothesis that acute elevations in muscle sympathetic nerve activity (MSNA) are accompanied by increases in conduit artery retrograde and oscillatory shear. Fourteen healthy men (25 +/- 1 yr) performed three sympathoexcitatory maneuvers: graded lower body negative pressure (LBNP) from 0 to -40 Torr, cold pressor test (CPT), and 35% maximal voluntary contraction handgrip followed by postexercise ischemia (PEI). MSNA (microneurography; peroneal nerve), arterial blood pressure (finger photoplethysmography), and brachial artery velocity and diameter (duplex Doppler ultrasound) in the contralateral arm were recorded continuously. All maneuvers elicited significant increases in MSNA total activity from baseline (P < 0.05). Retrograde shear (-3.96 +/- 1.2 baseline vs. -8.15 +/- 1.8 s(-1), -40 LBNP, P < 0.05) and oscillatory shear index (0.09 +/- 0.02 baseline vs. 0.20 +/- 0.02 arbitrary units, -40 LBNP, P < 0.05) were progressively augmented during graded LBNP. In contrast, during CPT and PEI, in which MSNA and blood pressure were concomitantly increased (P < 0.05), minimal or no changes in retrograde and oscillatory shear were noted. These data suggest that acute elevations in MSNA are associated with an increase in conduit artery retrograde and oscillatory shear, an effect that may be influenced by concurrent increases in arterial blood pressure. Future studies should examine the complex interaction between MSNA, arterial blood pressure, and other potential modulatory factors of shear rate patterns.
Endothelial dysfunction is now considered an important early event in the development of atherosclerosis, which precedes gross morphological signs and clinical symptoms. The assessment of flow-mediated dilation (FMD) was introduced almost 20 years ago as a noninvasive approach to examine vasodilator function in vivo. FMD is widely believed to reflect endothelium-dependent and largely nitric oxide-mediated arterial function and has been used as a surrogate marker of vascular health. This noninvasive technique has been used to compare groups of subjects and to evaluate the impact of interventions within individuals. Despite its widespread adoption, there is considerable variability between studies with respect to the protocols applied, methods of analysis, and interpretation of results. Moreover, differences in methodological approaches have important impacts on the response magnitude, can result in spurious data interpretation, and limit the comparability of outcomes between studies. This review results from a collegial discussion between physiologists with the purpose of developing considered guidelines. The contributors represent several distinct research groups that have independently worked to advance the evidence base for improvement of the technical approaches to FMD measurement and analysis. The outcome is a series of recommendations on the basis of review and critical appraisal of recent physiological studies, pertaining to the most appropriate methods to assess FMD in humans.
Recommendations for the measurement of brachial flow-mediated dilation (FMD) typically suggest images be obtained at identical times in the cardiac cycle, usually end diastole (QRS complex onset). This recommendation presumes that inter-individual differences in arterial compliance are minimized. However, published evidence is conflicting. Furthermore, ECG gating is not available on many ultrasound systems; it requires an expensive software upgrade or increased image processing time. We tested whether analysis of images acquired with QRS gating or with the more simplified method of image averaging would yield similar results. We analyzed FMD and nitroglycerin-mediated dilation (NMD) in 29 adults with type 2 diabetes mellitus and in 31 older adults and 12 young adults without diabetes, yielding a range of brachial artery distensibility. FMD and NMD were measured using recommended QRS-gated brachial artery diameter measurements and, alternatively, the average brachial diameters over the entire R-R interval. We found strong agreement between both methods for FMD and NMD (intraclass correlation coefficients = 0.88-0.99). Measuring FMD and NMD using average diameter measurements significantly reduced post-image-processing time (658.9 ± 71.6 vs. 1,024.1 ± 167.6 s for QRS-gated analysis, P < 0.001). FMD and NMD measurements based on average diameter measurements can be performed without reducing accuracy. This finding may allow for simplification of FMD measurement and aid in the development of FMD as a potentially useful clinical tool.
Objective:
Total sedentary (absence of whole-body movement) time is associated with obesity, abnormal glucose metabolism, and the metabolic syndrome. In addition to the effects of total sedentary time, the manner in which it is accumulated may also be important. We examined the association of breaks in objectively measured sedentary time with biological markers of metabolic risk.
Research design and methods:
Participants (n = 168, mean age 53.4 years) for this cross-sectional study were recruited from the 2004-2005 Australian Diabetes, Obesity and Lifestyle study. Sedentary time was measured by an accelerometer (counts/minute(-1) < 100) worn during waking hours for seven consecutive days. Each interruption in sedentary time (counts/min > or = 100) was considered a break. Fasting plasma glucose, 2-h plasma glucose, serum triglycerides, HDL cholesterol, weight, height, waist circumference, and resting blood pressure were measured. MatLab was used to derive the breaks variable; SPSS was used for the statistical analysis.
Results:
Independent of total sedentary time and moderate-to-vigorous intensity activity time, increased breaks in sedentary time were beneficially associated with waist circumference (standardized beta = -0.16, 95% CI -0.31 to -0.02, P = 0.026), BMI (beta = -0.19, -0.35 to -0.02, P = 0.026), triglycerides (beta = -0.18, -0.34 to -0.02, P = 0.029), and 2-h plasma glucose (beta = -0.18, -0.34 to -0.02, P = 0.025).
Conclusions:
This study provides evidence of the importance of avoiding prolonged uninterrupted periods of sedentary (primarily sitting) time. These findings suggest new public health recommendations regarding breaking up sedentary time that are complementary to those for physical activity.
Unlike quadrupeds, humans exhibit a larger hydrostatic pressure in the lower limbs compared with the upper limbs during a major part of the day. It is plausible that repeated episodes of elevated pressure in the legs may negatively impact the endothelium, hence contributing to the greater predisposition of atherosclerosis in the legs. We tested the hypothesis that an acute exposure to increased hydrostatic pressure would induce conduit artery endothelial dysfunction. In protocol 1, to mimic the hemodynamic environment of the leg, we subjected the brachial artery to a hydrostatic pressure gradient ( approximately 15 mmHg) by vertically hanging the arm for 3 h. Brachial artery flow-mediated dilation (FMD) was assessed in both arms before and following the intervention. In protocol 2, we directly evaluated popliteal artery FMD before and after a 3-h upright sitting (pressure gradient approximately 48 mmHg) and control (supine position) intervention. Our arm-hanging model effectively resembled the hemodynamic milieu (high pressure and low shear rate) present in the lower limbs during the seated position. Endothelium-dependent vasodilation at the brachial artery was attenuated following arm hanging (P < 0.05); however, contrary to our hypothesis, upright sitting did not have an impact on popliteal artery endothelial function (P > 0.05). These data suggest an intriguing vascular-specific response to increased hydrostatic pressure and reduced shear rate. Further efforts are needed to determine if this apparent protection of the leg vasculature against an acute hydrostatic challenge is attributable to posture-induced chronic adaptations.
Background
Normalization of brachial artery flow-mediated dilation (FMD) to individual shear stress area under the curve (peak FMD:SSAUC ratio) has recently been proposed as an approach to control for the large inter-subject variability in reactive hyperemia-induced shear stress; however, the adoption of this approach among researchers has been slow. The present study was designed to further examine the efficacy of FMD normalization to shear stress in reducing measurement variability.
Methods
Five different magnitudes of reactive hyperemia-induced shear stress were applied to 20 healthy, physically active young adults (25.3 ± 0. 6 yrs; 10 men, 10 women) by manipulating forearm cuff occlusion duration: 1, 2, 3, 4, and 5 min, in a randomized order. A venous blood draw was performed for determination of baseline whole blood viscosity and hematocrit. The magnitude of occlusion-induced forearm ischemia was quantified by dual-wavelength near-infrared spectrometry (NIRS). Brachial artery diameters and velocities were obtained via high-resolution ultrasound. The SSAUC was individually calculated for the duration of time-to-peak dilation.
Results
One-way repeated measures ANOVA demonstrated distinct magnitudes of occlusion-induced ischemia (volume and peak), hyperemic shear stress, and peak FMD responses (all p < 0.0001) across forearm occlusion durations. Differences in peak FMD were abolished when normalizing FMD to SSAUC (p = 0.785).
Conclusion
Our data confirm that normalization of FMD to SSAUC eliminates the influences of variable shear stress and solidifies the utility of FMD:SSAUC ratio as an index of endothelial function.
Spaceflight studies have demonstrated that adaptation to increased gravitational stress after prolonged microgravity includes sympathetic activation, water retention, and arterial pressure increase, i.e. is very similar to essential hypertension, which looks like an advanced stage of adaptation to a further increase in gravitational stress.
Theoretical analysis and literature review were performed to develop an hypothesis of essential hypertension as adaptation to increased gravitational stress associated with prolonged sitting.
Gravitation shifts blood downwards, and gravitational stress (GS) on the cardiovascular system in an upright position may be defined as the amount of work necessary to return the blood upwards and maintain adequate upper-body circulation calculated as the product of the gravitational potential (Ugr=g*h) and the mass of blood moved: GS =Ugr*Mshift. In a complex vascular network, this blood shift is actually a function of time, estimated in a first approximation as Mshift(t)=(Ugr*t)/Rd (Rd: the resistance to downward blood flow). Thus, gravitational stress is proportional to the time spent upright GS=Ugr*Mshift(t)=(Ugr2*t)/Rd=(g2*h2*t)/Rd. From this analysis, regular, prolonged sitting typical of modern life should cause a significant increase in gravitational stress on the cardiovascular system, requiring advanced antigravitational response with sympathetic hyperactivity, vasoconstriction, volume overload, and arterial hypertension. The hypertensive effect of prolonged sitting has been demonstrated in clinical studies.
Essential hypertension may be explained as adaptation to increased gravitational stress caused by regular, prolonged sitting. This gravitational hypothesis of essential hypertension, supported by clinical data, offers a way to its complete healing through elimination of the primary factor of prolonged sitting.
Blood flow in arteries is dominated by unsteady flow phenomena. The
cardiovascular system is an internal flow loop with multiple branches in
which a complex liquid circulates. A nondimensional frequency parameter,
the Womersley number, governs the relationship between the unsteady and
viscous forces. Normal arterial flow is laminar with secondary flows
generated at curves and branches. The arteries are living organs that
can adapt to and change with the varying hemodynamic conditions. In
certain circumstances, unusual hemodynamic conditions create an abnormal
biological response. Velocity profile skewing can create pockets in
which the direction of the wall shear stress oscillates. Atherosclerotic
disease tends to be localized in these sites and results in a narrowing
of the artery lumena stenosis. The stenosis can cause turbulence and
reduce flow by means of viscous head losses and flow choking. Very high
shear stresses near the throat of the stenosis can activate platelets
and thereby induce thrombosis, which can totally block blood flow to the
heart or brain. Detection and quantification of stenosis serve as the
basis for surgical intervention. In the future, the study of arterial
blood flow will lead to the prediction of individual hemodynamic flows
in any patient, the development of diagnostic tools to quantify disease,
and the design of devices that mimic or alter blood flow. This field is
rich with challenging problems in fluid mechanics involving
three-dimensional, pulsatile flows at the edge of turbulence.
Using NHANES 2009/2010, to describe the amount of time a representative sample of the U.S. population spends sitting by age, sex, ethnicity, education, and body mass index.
Cross-sectional analysis.
Participants (n=5911, ≥20 years) self-reported demographic variables and the amount of time they spend sitting on a typical day. Body mass index was calculated from measured height and weight.
Mean self-reported sitting time was 285min/day for males and 281min/day for females. Mexican-Americans reported sitting less than both non-Hispanic Whites and non-Hispanic Blacks (all p<0.0001). Non-Hispanic White males reported sitting more than non-Hispanic Black males, while Non-Hispanic White females reported sitting more than Other Hispanic females (both p<0.0001). No significant differences were found between sexes in any age group. There was a trend for increased sitting time with increasing age for females (p for trend=0.0045), for all Mexican-American and Hispanic participants and non-Hispanic Black males (all p≤0.006) and with increasing education (p for trend <0.0001). At the College Graduate level, females reported sitting less than males (p<0.0001). Obese females reported sitting more than normal weight and overweight females (p=0.0008). There were no significant differences in sitting time by body mass index for males.
Self-reported sitting time differed by ethnicity, age group, education and body mass index but there was no overall difference by sex. These results represent the most up to date prevalence of self-reported sitting for the US adult population. Certain groups should be targeted to reduce sitting time, for example those with higher educational attainment and obese females.
Prolonged periods of limited muscle activity can reduce insulin action. Acute changes in low muscle activity (ie, sitting) have not been assessed. In addition, unless energy intake is reduced during sitting to match low expenditure, the concurrent energy surplus may explain lower insulin action. The objective of the study was to evaluate the acute effect of sitting, with and without energy surplus, on insulin action. Fourteen young (26.1 ± 4.5 years, mean ± SD), nonobese (23.7% ± 7.1% fat), fit (peak oxygen consumption = 49.1 ± 3.3 mL·kg(-1)·min(-1)) men (n = 7) and women (n = 7) completed three 24-hour conditions: (1) an active, no-sitting condition (high energy expenditure of 2944 ± 124 kcal with energy intake matched to expenditure) = NO-SIT; (2) low energy expenditure (sitting) of 2195 ± 121 kcal with no reduction in energy intake (energy surplus) = SIT; and (3) sitting with energy intake reduced to 2139 ± 118 kcal to match low expenditure (energy balance) = SIT-BAL. Insulin action was measured the following morning during a continuous infusion of [6,6-(2)H]-glucose. Data were analyzed using linear mixed-effects models with planned contrasts. Compared with NO-SIT, insulin action, defined as whole-body rate of glucose disappearance normalized to mean plasma insulin, was reduced by 39% in SIT (P < .001) and by 18% in SIT-BAL (P = .07). Insulin action was higher in SIT-BAL compared with SIT (P = .04). One day of sitting considerably reduced insulin action; this effect was minimized, but not prevented, when energy intake was reduced to match expenditure. Strategies to limit daily sitting may reduce metabolic disease risk.
Whole blood viscosity is affected by a number of factors, among which plasma proteins are a major component. They exert their effects either directly or through their influence on red cell aggregation. Changes in fibrinogen and in immunoglobulins, under both physiologic and pathologic conditions can increase whole blood viscosity. Blood flow through the microvasculature is impaired when viscosity increases, leading to tissue ischemia and a syndrome complex usually referred to as the hyperviscosity syndrome. Abnormalities of fibrinogen greatly increase its ability to cause red cell aggregation, and is a contributory pathogenic factor in ischemic heart disease and stroke. Immunoglobulins may affect blood viscosity directly, or by increasing the red cell aggregation. Changes are seen in many clinical disorders, ranging from inflammatory diseases to plasma cell dyscrasias. The clinical manifestations may be mild and often unnoticed, or they may be life threatening requiring emergency plasmapheresis. Proper management requires a clear understanding of the underlying pathology. When the symptom complex indicates a high probability of the hyperviscosity syndrome, it should lead to early diagnosis and treatment. Therapeutic approaches should include both removing the abnormal plasma protein and treating the primary cause.
Endothelial dysfunction refers to impairment of endothelium-dependent vasodilatation and implies widespread abnormalities in endothelial integrity and homeostasis. The ability to assess endothelial function has been critical to advancing our understanding of the significance of this complex monolayer to cardiovascular (CV) disease. Early human translational approaches required invasive assessments in the coronary and brachial circulatory beds but had limited utility. Popularization of brachial reactivity testing using ultrasound by Celermajer et al,1 better known as flow-mediated dilatation (FMD), allowed more widespread clinical application by providing an estimate of conductance vessel NO bioactivity in response to a fixed hyperemic stimulus.
Although the link between endothelial dysfunction and adverse CV events was first described in studies performed in the human coronary circulation,2 the development of this noninvasive method led to widespread expectations that FMD could be used as a risk prediction tool and as a surrogate end point for novel therapies. Numerous studies demonstrated significant association between impaired FMD and CV risk factors. Although studies in those with CV disease have shown prognostic association with lower FMD predicting worse long-term outcomes,2 the real promise of FMD as a noninvasive tool was in demonstrating predictive use in community-based population cohorts.
In the largest of just 3 studies addressing this question, Yeboah et al3 examined 3026 subjects free of CV disease from the Multi-Ethnic Study of Atherosclerosis (MESA) cohort. They demonstrated that, at 5 years, after multivariate analysis, each SD increase in FMD conferred a hazard ratio of 0.84 for incident CV events. Importantly, FMD also improved net reclassification of risk when compared with the Framingham risk score. Two further studies in more selected populations, including the Cardiovascular Health Study of elderly subjects and a study by Rossi et al4 on >2000 postmenopausal women, support these findings by demonstrating significant association …
Shear stress is an important stimulus to arterial adaptation in response to exercise and training in humans. We recently observed significant reverse arterial flow and shear during exercise and different antegrade/retrograde patterns of shear and flow in response to different types of exercise. The purpose of this study was to simultaneously examine flow-mediated dilation, a largely NO-mediated vasodilator response, in both brachial arteries of healthy young men before and after 30-minute interventions consisting of bilateral forearm heating, recumbent leg cycling, and bilateral handgrip exercise. During each intervention, a cuff inflated to 60 mm Hg was placed on 1 arm to unilaterally manipulate the shear rate stimulus. In the noncuffed arm, antegrade flow and shear increased similarly in response to each intervention (ANOVA; P<0.001, no interaction between interventions; P=0.71). Baseline flow-mediated dilation (4.6%, 6.9%, and 6.7%) increased similarly in response to heating, handgrip, and cycling (8.1%, 10.4%, and 8.9%, ANOVA; P<0.001, no interaction; P=0.89). In contrast, cuffed arm antegrade shear rate was lower than in the noncuffed arm for all of the conditions (P<0.05), and the increase in flow-mediated dilation was abolished in this arm (4.7%, 6.7%, and 6.1%; 2-way ANOVA: all conditions interacted P<0.05). These results suggest that differences in the magnitude of antegrade shear rate transduce differences in endothelial vasodilator function in humans, a finding that may have relevance for the impact of different exercise interventions on vascular adaptation in humans.
Cycling is associated with a reproducible systolic anterograde and diastolic retrograde flow pattern in the brachial artery (BA) of the inactive upper limb, which results in endothelial nitric oxide (NO) release. The purpose of this study was to examine the impact of different types and intensities of lower limb exercise on the BA flow pattern.
We examined BA blood flow and shear rate patterns during cycling, leg kicking, and walking exercise in 12 young subjects (24 +/- 3 yr). BA diameter, blood flow, and shear rate were assessed at baseline (1 min) and at three incremental intensity levels of cycling (60, 80, and 120 W), bilateral leg kicking (5, 7.5, and 10 kg), and walking (3, 4, and 5 km x h(-1)), performed for 3 min each. Edge detection and wall tracking of high-resolution B-mode arterial ultrasound images, combined with synchronized Doppler waveform envelope analysis, were used to calculate conduit artery diameter and anterograde/retrograde blood flow and shear rate continuously across the cardiac cycle.
BA mean blood flow and shear rate increased significantly throughout each exercise protocol (P < 0.001), and BA anterograde blood flow and shear rate showed comparable increases throughout each protocol (P < 0.001). Retrograde blood flow and shear rate, however, demonstrated a significant increase during cycling and walking (P < 0.001) but not during leg kicking.
Rhythmic lower limb exercise (cycling and walking) results in an increase in BA systolic anterograde blood flow and shear rate, directly followed by a large retrograde flow and shear rate. This typical pattern, previously linked with endothelial NO release, is not present during a different type of exercise such as leg kicking.
This study represents a systematic analysis of the fine-structural characteristics of atherosclerotic lesions of the superficial femoral artery in man together with the growth characteristics in culture of the smooth muscle cells derived from these lesions. Occlusive fibrous atherosclerotic plaques were obtained from 29 male patients at the time of bypass surgery for occlusion of the superficial femoral artery and were studied by light and transmission electron microscopy. The occluded segment of each artery was obtained immediately after removal from the patient and examined with sterile techniques, and representative segments were fixed for light- and electron-microscopic study. Adjacent segments were used for dissection of the lesion away from the underlying media, and smooth muscle cells were cultured from lesion and nonlesion areas and compared in terms of their growth responses to increasing concentrations of a pool of human whole blood serum. The majority of the lesions were fibroproliferative and contained relatively little lipid. The fibrous cap that covered each lesion consisted of a special form of dense connective tissue that contained flat, pancake-shaped smooth muscle cells in a lacunalike space. This space consisted of concentric layers of basement membrane, collagen fibrils, and proteoglycan. The majority of the cells beneath the fibrous cap were smooth muscle cells mixed with small but varying numbers of macrophages. Most of the lesions were occluded by a thrombus, which had undergone organization and recanalization. A small number of the lesions had deep lipid deposits together with foci of degeneration and calcification. The occluded thrombi contained smooth muscle cells and a larger proportion of macrophages than the lesions themselves. The in vitro growth properties of the smooth muscle cells isolated from the lesion and the underlying media suggested that the lesion cells had senesced, compared with the medial smooth muscle cells derived from the same artery.