Nadir blood pressure responses to longer consecutive cardiac cycle sequences absent of sympathetic bursts are associated with popliteal endothelial-dependent dilation.

PURPOSE: The nadir pressure responses to cardiac cycles absent of muscle sympathetic nerve activity (MSNA) bursts (or non-bursts) are typically reported in studies quantifying sympathetic transduction, but the information gained by studying non-bursts is unclear. We tested the hypothesis that longer sequences of non-bursts (≥8 cardiac cycles) would be associated with a greater nadir diastolic blood pressure (DBP) and that better popliteal artery function would be associated with an augmented reduction in DBP. METHODS: Resting beat-by-beat DBP (via finger photoplethysmography) and common peroneal nerve MSNA (via microneurography) were recorded in 39 healthy, adults (age 23.4 ± 5.3 years; 19 females). For each cardiac cycle absent of MSNA bursts, the mean nadir DBP (ΔDBP) during the 12 cardiac cycles following were determined, and separate analyses were conducted for ≥8 or < 8 cardiac cycle sequences. Popliteal artery endothelial-dependent (via flow-mediated dilation; FMD) and endothelial-independent vasodilation (via nitroglycerin-mediated dilation; NMD) were determined. RESULTS: The nadir DBP responses to sequences ≥8 cardiac cycles were larger (-1.40 ± 1.27 mmHg) than sequences <8 (-0.38 ± 0.46 mmHg; p < 0.001). In adjusting for sex and burst frequency (14 ± 8 bursts/min), larger absolute or relative FMD (p < 0.01), but not NMD (p > 0.53) was associated with an augmented nadir DBP. This overall DBP-FMD relationship was similar in sequences ≥8 (p = 0.04-0.05), but not <8 (p > 0.72). CONCLUSION: The DBP responses to non-bursts, particularly longer sequences, were inversely associated with popliteal endothelial function, but not vascular smooth muscle sensitivity. This study provides insight into the information gained by quantifying the DBP responses to cardiac cycles absent of MSNA.

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

INTRODUCTION: Single bouts of prolonged bent-legged sitting attenuate popliteal endothelial-dependent vasodilation (as assessed via flow-mediated dilation [FMD]), which is partially attributed to arterial 'kinking'. However, the impact of knee-flexion angle on sitting-induced popliteal FMD is unknown. The objective of this study was to perform separate laboratory and free-living studies to test the hypotheses that: (1) popliteal FMD impairments would be graded between knee flexions at 90° (bent-legged sitting) > 45° > 0° (straight-legged sitting) following a 3-hour bout of sitting; and (2) more habitual time spent bent-legged sitting (< 45°) would be associated with lower FMD. METHODS: The laboratory study included eight young, healthy adults (24 ± 2 years; four women) who underwent two sitting bouts over 2 days with one leg positioned at a knee-flexion angle of 0° or 90° and the opposite leg at 45° knee flexion. Popliteal FMD was assessed at pre- and postsitting timepoints. RESULTS: Sitting-induced reductions in FMD were similar between all knee-flexion angles (all, p > 0.674). The free-living study included 35 young, healthy adults (23 ± 3 years; 16 women) who wore three activPAL monitors (torso, thigh, shin) to determine detailed sedentary postures. Time spent sedentary (624 ± 127 min/day), straight-legged sitting (112 ± 98 min/day), and bent-legged sitting (442 ± 106 min/day) were not related to relative FMD (5.3 ± 1.8%; all, p > 0.240). CONCLUSION: These findings suggest that knee-flexion angle-mediated arterial 'kinking' during sitting is not a major contributor toward sitting-induced popliteal endothelial-dependent vasodilatory dysfunction.

Impact of exercise training on pulse wave velocity in healthy and clinical populations: a systematic review of systematic reviews.

Elevated pulse wave velocity (PWV) determined arterial stiffness is a prominent marker of cardiovascular disease (CVD) risk. Exercise training delays the progression of CVD, but existing reviews on the impact of training on PWV are conflicting. We synthesized the evidence on the effects of exercise training interventions on PWV. We searched Scopus, EMBASE, PubMed, CINAHL, and Academic Search Premier databases for systematic reviews including PWV, and examined the effects of exercise training on PWV. We screened 842 citations that resulted in 44 systematic reviews, including 22 meta-analyses [unique participants, n = 6,719 (3,390 females)]. Studies were conducted in general adults with/without disease(s) (n = 19, 8 meta-analyses), kidney disease (n = 9, 6 meta-analyses), increased CVD risk or CVD (n = 7, 5 meta-analyses), type 2 diabetes mellitus (n = 3, 2 meta-analyses), and other conditions (n = 6, 2 meta-analyses). In general adults, PWV was reduced by aerobic exercise (ß, -0.75 to -0.52 m/s) and low-to-moderate intensity resistance exercise training (ß, -0.34 m/s). Exercise training was beneficial for patients with kidney disease (ß, -1.13 to -0.56 m/s). Aerobic exercise improved PWV in adults with CVD or high CVD risk (ß, -0.70 to -0.42 m/s). Combined aerobic and resistance exercise training decreased carotid-femoral (CF) PWV in patients with CVD (ß, -1.15 m/s) and decreased brachial-ankle (BA) PWV in postmenopausal females (ß, -1.18 m/s). Neither aerobic nor combined training improved PWV in individuals with type 2 diabetes. The potential physiological mechanisms involved are discussed. Overall, the included systematic reviews and meta-analyses documented that exercise training was an effective strategy to improve PWV, but the optimal type of training varied between populations.

Binge drinking and smoking are associated with worse academic performance in Canadian undergraduate students.

OBJECTIVE: Test the hypothesis that smoking, fast-food consumption, and binge drinking were negatively associated with academic performance in Canadian undergraduate students. PARTICIPANTS: Undergraduate students across Canada [n = 411 (335♀) aged: 22 ± 4 years] completed a questionnaire regarding their lifestyle behaviors and academic grades. METHODS: Relationships between lifestyle behaviors and academic performance were assessed via covariate-adjusted multiple regressions. Mediation models were used to test whether significant relationships between smoking/fast-food and grades were explained by binge drinking. RESULTS: Smoking (ß= -4.00, p < .001) and binge drinking (ß= -1.98, p = .002) were independent predictors of grades (average: 84 ± 8%). Binge drinking partially mediated the relationships between smoking (indirect effect ß= -1.19, 95%CI [-2.49, -0.08] and fast-food consumption (indirect effect: ß= -.75, 95%CI [-1.20, -0.29]), with grades. CONCLUSIONS: These findings highlight the negative influence of binge drinking, smoking, and fast-food consumption on academic success, with binge drinking as a partial mediator of these relationships.

Higher habitual lying time is inversely associated with vagal-related heart rate variability outcomes in younger adults.

Heart rate variability (HRV) is a well-established noninvasive marker of autonomic cardiac control. We test whether time spent sitting (negatively) versus lying (positively) influences vagal HRV outcomes. HRV (10 min supine electrocardiogram) and free-living postures (dual-accelerometer configuration, 7 days) were measured in 31 young healthy adults (15♀, age: 23 ± 3 years). Habitual lying (66 ± 61 min/day), but not sitting time (558 ± 109 min/day), total sedentary time (623 ± 132 min/day), nor step counts (10 752 ± 3200 steps/day; all, p > 0.090), was associated with root mean square of successive cardiac interval differences (ρ = -0.409, p = 0.022) and normalized high-frequency HRV (ρ = -0.361, p = 0.046). These findings document a paradoxical negative impact of waking lying time on cardioautonomic function. Take home message Using a multi-accelerometer configuration, we demonstrated that more habitual waking time lying, but not sitting or total sedentary time, was associated with worse vagally mediated cardiac control.

Validity of ActivPAL CREA software detection of sitting and lying during free-living conditions.

Objective. Approaches to differentiate sitting and lying are available within the default activPAL software from a single thigh-worn monitor. Dual-monitor methods use multiple monitors positioned on the thigh and torso to characterize sitting versus lying. We evaluated the validity between these two methods to measure waking, sitting, and lying time in free-living conditions. We also examined if the degree-threshold distinguishing sitting/lying for the dual-monitor (<30° and <45°) impacted results.Approach. Thirty-five young adults (24 ± 3 years, 16 females) wore an activPAL 24 h per day on their thigh and torso during free-living conditions (average: 6.8 ± 1.0 d, 239 total). Data were processed using the default activPAL software (thigh-only) or a custom MATLAB program (dual-monitor).Main results. The single-monitor recorded less lying time (59 ± 99 min d-1) and more sitting time (514 ± 203 min d-1) than the dual-monitor method regardless of 30° (lying: 85 ± 94 min d-1; sitting: 488 ± 166 min d-1) or 45° lying threshold (lying: 170 ± 142, sitting: 403 ± 164 min d-1; all,p< 0.001). The single monitor lying time was weakly correlated to the dual-monitor (30°:ρ= 0.25, 45°:ρ= 0.21; both,p< 0.001), whereas sitting was moderate-strong (30°:ρ= 0.76, 45°:ρ= 0.58; both,p< 0.001). However, the mean absolute error was 81 min d-1(30°) and 132 min d-1(45°) for both lying and sitting.Significance. The method of differentiating sitting/lying from a single thigh-worn activPAL records more sitting time and less lying time compared to a dual-monitor configuration (regardless of degree-threshold) that considered the position of the torso. A further refinement of algorithms or implementation of multiple-monitor methods may be needed for researchers to derive detailed sedentary positions.

More moderate-intensity physical activity and less prolonged sedentary time are associated with better very short-term systolic blood pressure variability in healthy adults.

Whole-day movement guidelines for improving health, recommend that adults engage in at least 150 min week-1 of moderate-to-vigorous aerobic physical activity and limit their sedentary time. In young adults, higher systolic blood pressure variability (BPV) is a precursor for the development of hypertension. The impact of habitual activity that comprises (inter)national guidelines on BPV is unclear. We tested the hypothesis that less habitual physical activity and greater sedentary time would be associated with larger BPV. Ninety-two normotensive participants [age: 19-38 years, body mass index (BMI): 23.6 ± 3.3 kg/m2, 44♀] wore an activPAL monitor on their thigh for 7.0 ± 0.3 days. Ten minutes of supine systolic arterial pressure was measured via finger photoplethysmography (115 ± 11 mmHg). Beat-by-beat systolic BPV was measured using the average real variability index (1.1 ± 0.6 mmHg). Relationships between habitual activity outcomes and BPV were assessed via multiple regressions adjusted for age, sex, and BMI. Moderate-intensity physical activity (average: 36 ± 19 min day-1; ß = -0.010, p = 0.02) and time spent in sedentary bouts >1-h (245 ± 134 min day-1; ß = 0.002, p < 0.001), but not light-intensity activity, vigorous-intensity activity, standing time, sedentary breaks, or time spent in sedentary bouts <1-h (all, p > 0.10) were predictors of systolic BPV. Higher moderate physical activity and lower prolonged sedentary time were associated with attenuated systolic BPV responses in young adults. These findings highlight the cardiovascular benefits of habitual activity among younger adults and suggest that simple strategies such as reducing long periods of uninterrupted sitting and increasing moderate-intensity physical activity may be efficacious for reducing the risk of developing or delaying the onset of hypertension.

Impact of Exercise Training Interventions on Flow-Mediated Dilation in Adults: An Umbrella Review.

BACKGROUND: Dysfunction of the endothelium is a key precursor of cardiovascular disease. Endothelial function, as assessed via the flow-mediated dilation test, is attenuated with chronic disease (e.g., type 2 diabetes mellitus, hypertension). Exercise training may mitigate this dysfunction and promote better vascular health. OBJECTIVE: The main objective of this umbrella review was to determine the impact of exercise training on flow-mediated dilation in healthy adults and those with chronic disease. METHODS: Studies were included if they conducted a systematic review and/or meta-analysis on flow-mediated dilation responses to exercise interventions in adults. Sources were searched in January 2022 and included Scopus, EMBASE, MEDLINE, CINAHL, and Academic Search Premier. National Institutes of Health quality assessment tools were used. The results were presented narratively. RESULTS: Twenty-seven systematic reviews, including 19 meta-analyses, (total: 5464 unique participants, 2181 reported unique female individuals) met the inclusion criteria. The average overall quality of included reviews was 8.8/11. The quality of studies within each included review varied from low to moderate using a variety of quality assessment scales. Reviews were conducted in healthy adults (n = 9, meta-analyses = 6), as well as those with type 2 diabetes (n = 5, meta-analyses = 4), cardiovascular conditions [i.e., conditions that impact the cardiovascular system, but excluding samples of only type 2 diabetes] (n = 11, meta-analyses = 7), and other chronic conditions (n = 2, meta-analyses = 2). Overall, the included reviews provided evidence that the type of training to optimally improve FMD may vary based on disease condition. Specifically, the evidence suggests that healthy adults benefitted most from higher intensity aerobic training and/or more frequent low-to-moderate resistance training. In addition, adults with type 2 diabetes benefitted most from low-intensity resistance or aerobic exercise training, whereas those with cardiovascular conditions should consider engaging in high-intensity aerobic training to improve endothelial function. CONCLUSIONS: This information may help guide the design of specific exercise programs or recommendations for adults with chronic conditions.

Characterization of Detailed Sedentary Postures Using a Tri-Monitor ActivPAL Configuration in Free-Living Conditions.

Objective monitors such as the activPAL characterize time when the thigh is horizontal as sedentary time. However, there are physiological differences between lying, bent-legged sitting, and straight-legged sitting. We introduce a three-monitor configuration to assess detailed sedentary postures and demonstrate its use in characterizing such positions in free-living conditions. We explored time spent in each sedentary posture between prolonged (>1 h) versus non-prolonged (<1 h) sedentary bouts. In total, 35 healthy adults (16♀, 24 ± 3 years; 24 h/day for 6.8 ± 1.0 days) wore an activPAL accelerometer on their thigh, torso, and shin. Hip and knee joint flexion angle estimates were determined during sedentary bouts using the dot-product method between the torso−thigh and thigh−shin, respectively. Compared to lying (69 ± 60 min/day) or straight-legged sitting (113 ± 100 min/day), most time was spent in bent-legged sitting (439 ± 101 min/day, p < 0.001). Most of the bent-legged sitting time was accumulated in non-prolonged bouts (328 ± 83 vs. 112 ± 63 min/day, p < 0.001). In contrast, similar time was spent in straight-legged sitting and lying between prolonged/non-prolonged bouts (both, p > 0.26). We document that a considerable amount of waking time is accumulated in lying or straight-legged sitting. This methodological approach equips researchers with a means of characterizing detailed sedentary postures in uncontrolled conditions and may help answer novel research questions on sedentariness.

Comparison of signal-averaging and regression approaches to analyzing sympathetic transduction.

PURPOSE: Spontaneous sympathetic transduction reflects the vascular and/or pressor responses to bursts of muscle sympathetic nerve activity (MSNA). Separately, signal-averaging and regression-based approaches have been implemented to quantify resting sympathetic transduction. It is unknown whether the outcomes of these analytical approaches provide (dis)similar information, which is imperative for between-study comparisons and the amalgamation of results for synthesis of multiple studies (i.e., meta-analyses). We explored the diastolic blood pressure (DBP) responses to spontaneous bursts of MSNA between these two methods of analysis. METHODS: Resting beat-by-beat DBP (via finger photoplethysmography) and common peroneal nerve MSNA (via microneurography) were recorded in 52 healthy, normotensive adults (age 38 ± 20 years; 19 females). For the signal-averaged method, transduction was quantified as the mean peak increase in DBP (ΔDBP) during the 12 cardiac cycles following each MSNA burst. In addition, DBP was regressed to a moving two-cardiac-cycle window of normalized relative burst height (mmHg/relative %) to provide the regression-based transduction outcome. RESULTS: The signal-averaged (1.2 ± 0.7 mmHg) and regression-based approaches (0.009 ± 0.016 mmHg/%) were unrelated (ρ = 0.03, p = 0.86). Adding to the discrepancy, only the signal-averaging approach demonstrated a lower transduction in middle-aged-older males versus younger males. CONCLUSIONS: The decision of which method to use when calculating sympathetic transduction influences study outcomes, with the two most common methods of determining transduction being unrelated. There are challenges of making sweeping conclusions across studies if different analysis strategies are implemented. An understanding of when to use each method is needed to adopt a harmonized approach to quantifying sympathetic transduction.