Sitting decreases endothelial microparticles but not circulating angiogenic cells irrespective of lower leg exercises: a randomized cross-over trial.

NEW FINDINGS: What is the central question of this study? What are the cellular and molecular determinants of increased risk for cardiovascular disease from prolonged sitting? What is the main finding and its importance? Prolonged sitting, independent of calf raise interruption strategies, decreases microparticle counts linked to endothelial activation and apoptosis. An acute bout of prolonged sitting appears to promote paradoxical decreases in microparticle counts, but the implications are not yet clear. ABSTRACT: Repeated exposure to prolonged sitting increases the risk for cardiovascular disease. However, the cellular links by which repeated exposure to prolonged sitting lead to increased cardiovascular risk have not been fully elucidated, with markers of vascular damage and repair such as microparticles (MPs) and circulating angiogenic cell (CACs) being promising targets. The objective of the study was to examine the effects of 3 h of sitting with or without intermittent calf raises on annexin V+ /CD34+ , annexin V+ /CD62E+ , and annexin V+ /CD31+ /42b- MP populations linked to CAC paracrine activity, endothelial activation and apoptosis, respectively, as well as CD14+ /31+ , CD3+ /31+ , and CD34+ CACs, which are linked to endothelial repair. In a random order, 20 sedentary participants (14 females, 22 ± 3 years) remained seated for 180 min with or without performing 10 calf raises every 10 min. Blood samples were obtained after 20 min of quiet rest in the supine position before and after sitting. Overall, sitting decreased annexin V+ /CD34+ MPs (-12 ± 5 events µl-1 , P < 0.01), annexin V+ /CD62E+ MPs (-17 ± 4 events µl-1 , P < 0.001), and annexin V+ /CD31+ /42b- MPs (-22 ± 6 events µl-1 , P < 0.001) regardless of condition. There were no differences in endothelin-1 plasma concentration, CD14+ /31+ , CD34+ or CD3+ /31+ CAC frequencies. Sitting did not alter CAC number, but decreased MPs linked to endothelial activation, apoptosis and CAC paracrine activity in a manner that was independent of muscle contraction. These findings support changes in markers of endothelial activation and apoptosis with sedentary behaviour and provide new insights into altered intercellular communication with physical inactivity such as prolonged sitting.

Local exercise does not prevent the aortic stiffening response to acute prolonged sitting: a randomized crossover trial.

Prolonged sitting has been shown to promote endothelial dysfunction in the lower legs. Furthermore, it has been reported that simple sitting-interruption strategies, including calf raises, prevent leg endothelial dysfunction. However, it is unclear whether prolonged sitting affects central cardiovascular health, or whether simple sitting-interruption strategies prevent impaired central cardiovascular health. This study sought to answer two questions: in young, healthy adults 1) does prolonged sitting (3 h) lead to increased aortic stiffness, and 2) do intermittent calf raise exercises to prevent pooling prevent aortic stiffening. Twenty young, healthy participants (21.7 ± 2.5 yr, 70% female, 25.5 ± 6.1 kg/m2) were randomized to 3 h of sitting with (CALF) or without (CON) 10 calf raises every 10 min. Aortic stiffening [carotid-femoral pulse wave velocity (PWV)] was measured in the supine position pre- and post-sitting. Venous pooling during sitting was estimated with total hemoglobin (tHB) concentration using near-infrared spectroscopy. There were no condition × time interactions. Following 3 h of sitting, PWV significantly increased (0.30 ± 0.46 m/s, P < 0.001). There was no condition effect for PWV (P = 0.694), indicating the intermittent calf rises did not preserve central cardiovascular health. tHb was not significantly affected by sitting (P = 0.446) but was 1.9 µM higher for CON versus CALF (P = 0.106). Sitting increases aortic stiffness in young, healthy individuals, a process that may be influenced by lower extremity blood pooling. Calf raises, which have been reported to preserve vascular function in the legs, do not appear to provide sufficient stimulus for maintaining central cardiovascular health.NEW & NOTEWORTHY Although simple strategies, such as fidgeting or calf raises, are sufficient for preserving vascular function in the legs, data from the current study indicate that such strategies are not sufficient for maintaining central cardiovascular health, which is linked to cardiovascular disease.

Effects of acute prolonged sitting on cerebral perfusion and executive function in young adults: A randomized cross-over trial.

Exposure to acute prolonged sitting reportedly leads to decreased cerebral blood flow. However, it is unclear whether this exposure translates to decreased cerebral perfusion and executive function or whether simple strategies to break up sitting can maintain cerebral perfusion and executive function. This study sought to answer two questions: in young, healthy adults, (a) does prolonged (3 hr) sitting lead to decreased cerebral perfusion and executive function? and (b) does breaking up prolonged sitting, using intermittent calf raise exercises, prevent changes in cerebral perfusion and executive function? Twenty young, healthy participants (21.7 [2.5] years, 70% female, 25.5 [6.1] kg/m2 ) were randomized to 3 hr sitting with 10 calf raises every 10 min (CALF) and 3 hr sitting without intermittent calf raises (CON). Prefrontal cortex perfusion was assessed using near-infrared spectroscopy to monitor total hemoglobin (tHB) concentration and tissue saturation index (TSI, oxygenated hemoglobin). Executive function was assessed using the Stroop word and color tasks. Following 3 hr sitting, tHb was significantly lower in CALF versus CON (-2.1 µM, 95% CI [-3.1, -1.1]). TSI was not significantly different between conditions (p = .667). Word (1.6 ms, 95% CI [0.7, 2.5]) and color (1.3 ms, 95% CI [-0.2, 2.8]) completion times were longer (worse) for CALF compared to CON. In conclusion, calf raises decreased both cerebral perfusion and executive function. Simple strategies, such as fidgeting or calf raises, which have been reported to preserve vascular function in the legs, appear not to be sufficient to benefit cerebral perfusion or executive function.

Effects of Resistance Training on Arterial Stiffness in Persons at Risk for Cardiovascular Disease: A Meta-analysis.

BACKGROUND: Arterial stiffness (AS) is a key measure in predicting risk for cardiovascular disease (CVD) and related events, independent of other risk factors. Resistance training (RT) has been shown to increase AS in young healthy subjects. However, the effects of RT on AS in persons with or at risk for CVD remain unclear; this uncertainty is a barrier to RT prescription in this population. Considering RT may be as effective as or superior to aerobic exercise prescription in treating some co-morbidities associated with CVD, it would be helpful to clarify whether RT does lead to clinically meaningful increases (detrimental) in AS in those with CVD or CVD risk factors. OBJECTIVES: The aim of this study was to (1) assess the effects of RT on measures of AS in at-risk populations, and (2) discuss the implications of the findings for clinical exercise physiologists. DATA SOURCES: The electronic databases PubMed, Web of Science, SPORTDiscus, and Google Scholar were searched from inception to February 2018. The reference lists of eligible articles and reviews were also checked. STUDY SELECTION: Inclusion criteria were: (1) the trial was a randomized controlled trial; (2) exercise prescription of RT or a combination of resistance and aerobic exercise for at least 8 weeks; (3) control group characteristics allowed for comparison of the main effects of the exercise prescription; (4) subjects had known CVD or a risk factor associated with CVD according to the American College of Sports Medicine (ACSM) guidelines; (5) article measured at least carotid to femoral pulse wave velocity (PWV) or augmentation index (AIx). APPRAISAL AND SYNTHESIS METHODS: Initially, 1427 articles were identified. After evaluation of study characteristics, quality and validity data from 12 articles and 13 cohorts involving 651 participants (223 women, 338 men, 90 unknown) were extracted for the meta-analysis. To enable comparisons between assessments, and to infer clinical significance, standardized mean differences (SMD) were calculated. When data were not available, values were estimated according to Cochrane guidelines. RESULTS: According to the JADAD scale, the mean quality of studies was 3 out of 5. The duration of the included studies ranged from 8 weeks to 24 months. RT trended towards decreasing (improving) PWV (SMD = - 0.168, 95% CI - 0.854 to 0.152, p = 0.057). There were no significant differences in AIx (SMD = - 0.286), diastolic blood pressure (SMD = - 0.147), systolic blood pressure (SMD = - 0.126), or central systolic blood pressure (SMD = - 0.405). CONCLUSION: The available evidence suggests that RT does not increase (worsen) AS in patients who have or are at risk for CVD. Considering RT may be as effective as or superior to aerobic exercise prescription in treating some co-morbidities associated with CVD, these findings suggest that RT is a suitable exercise prescription in primary and secondary prevention settings.