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An age‐associated increase in arterial blood pressure is evident for apparently healthy humans. This is frequently attributed to stiffening of the central arteries and a concurrent increase in sympathetic outflow, potentially mediated by a reduced ability of the baroreceptive vessels to distend. This is supported, in part, by a reduced mechanical component of the vascular sympathetic baroreflex (i.e., a reduction in distension for a given pressure). Previous characterization of the mechanical component has assessed only carotid artery distension; however, evidence suggests that both the aortic and carotid baroreflexes are integral to blood pressure regulation. In addition, given that baroreceptors are located in the vessel wall, the change in wall tension, comprising diameter, pressure and vessel wall thickness, and the mechanics of this change might provide a better index of the baroreceptor stimulus than the previous method used to characterize the mechanical component that relies on diameter alone. This brief review summarizes the data using this new method of assessing barosensory vessel mechanics and their influence on the vascular sympathetic baroreflex across the lifespan. What is the topic of this review? We review barosensory vessel mechanics and their role in blood pressure regulation across the lifespan. What advances does it highlight? In young normotensive men, aortic unloading mechanics contribute to the resting operating point of the vascular sympathetic baroreflex; however, with advancing age, this contribution is removed. This suggests that barosensory vessel unloading mechanics are not driving the well‐documented age‐related increase in resting muscle sympathetic nerve activity.

ObjectivesWe aimed to identify exercise tests that have been validated to support a safe discharge to home in patients with or without COVID-19.Study designScoping review, using PRISMA-ScR reporting standards. Medline, PubMed, AMED, Embase, CINAHL and LitCovid databases were searched between 16 and 22 February 2021, with studies included from any publication date up to and including the search date.InterventionShort exercise tests.Primary outcome measuresSafe discharge from hospital, readmission rate, length of hospital stay, mortality. Secondary outcomes measures: safety, feasibility and reliability.ResultsOf 1612 original records screened, 19 studies were included in the analysis. These used a variety of exercise tests in patients with chronic obstructive pulmonary disease, suspected pulmonary embolism and pneumocystis carinii pneumonia, heart failure or critical illness. Only six studies had examined patients with COVID-19, of these two were still recruiting to evaluate the 1 min sit-to-stand test and the 40-steps test. There was heterogeneity in patient populations, tests used and outcome measures. Few exercise tests have been validated to support discharge decisions. There is currently no support for short exercise tests for triage of care in patients with COVID-19.ConclusionsFurther research is needed to aid clinical decision-making at discharge from hospital.

Cardio-respiratory fitness (CRF) is a widespread essential indicator in Sports Science as well as in Sports Medicine. This study aimed to develop and validate a prediction model for CRF based on a 45 second self-test, which can be conducted anywhere. Criterion validity, test re-test study was set up to accomplish our objectives. Data from 81 healthy volunteers (age: 29 ± 8 years, BMI: 24.0 ± 2.9), 18 of whom females, were used to validate this test against gold standard. Nineteen volunteers repeated this test twice in order to evaluate its repeatability. CRF estimation models were developed using heart rate (HR) features extracted from the resting, exercise, and the recovery phase. The most predictive HR feature was the intercept of the linear equation fitting the HR values during the recovery phase normalized for the height2 (r2 = 0.30). The Ruffier-Dickson Index (RDI), which was originally developed for this squat test, showed a negative significant correlation with CRF (r = -0.40), but explained only 15% of the variability in CRF. A multivariate model based on RDI and sex, age and height increased the explained variability up to 53% with a cross validation (CV) error of 0.532 L ∙ min-1 and substantial repeatability (ICC = 0.91). The best predictive multivariate model made use of the linear intercept of HR at the beginning of the recovery normalized for height2 and age2; this had an adjusted r2 = 0. 59, a CV error of 0.495 L·min-1 and substantial repeatability (ICC = 0.93). It also had a higher agreement in classifying CRF levels (κ = 0.42) than RDI-based model (κ = 0.29). In conclusion, this simple 45 s self-test can be used to estimate and classify CRF in healthy individuals with moderate accuracy and large repeatability when HR recovery features are included.

Developing an exercise model that resembles a traditional form of aerobic exercise and facilitates a complete simultaneous assessment of multiple parameters within the oxygen cascade is critically for understanding exercise intolerances in diseased populations. Measurement of muscle blood flow is a crucial component of such a model and previous studies have used invasive procedures to determine blood flow kinetics; however, this may not be appropriate in certain populations. Furthermore, current models utilizing Doppler ultrasound use isolated limb exercise and while these studies have provided useful data, the exercise model does not mimic the whole‐body physiological response to continuous dynamic exercise. Therefore, we aimed to measure common femoral artery blood flow using Doppler ultrasound during continuous dynamic stepping exercise performed at three independent workloads to assess the within day and between‐day reliability for such an exercise modality. We report a within‐session coefficient of variation of 5.8% from three combined workloads and a between‐day coefficient of variation of 12.7%. These values demonstrate acceptable measurement accuracy and support our intention of utilizing this noninvasive exercise model for an integrative assessment of the whole‐body physiological response to exercise in a range of populations. We demonstrated that muscle blood flow could be reliably measured within and between days to acceptable standards using Doppler ultrasound at three different workloads during continuous dynamic stepping exercise. Such a model, combined with assessment of multiple parameters within the oxygen cascade facilitates a complete integrative approach for determining exercise intolerance in multiple populations.

To test the hypothesis that hot water immersion (HWI) improves cerebrovascular function via shear‐mediated mechanisms, this study determined cerebrovascular reactivity to carbon dioxide () before and after 60 min of 39°C HWI and a 21°C air control (CON) in 15 healthy participants. Thermal and haemodynamic variables were assessed throughout the trials, and was determined by a 4‐min inhalation of hypercapnic gas (6% CO 2 , 21% O 2 , N 2 balance) and the assessment of internal carotid artery (ICA) blood flow by duplex ultrasound before and 45 min after HWI and CON. At 60 min of the interventions, core body temperature (CON, 36.9 ± 0.3°C; HWI, 38.1 ± 0.3°C, P  < 0.01), heart rate ( P  < 0.01) and ICA conductance ( P  < 0.01) were higher in HWI than CON, while, mean arterial blood pressure was lower (CON, 82 ± 9 mmHg; HWI 65 ± 8 mmHg, P  < 0.01). No differences were observed for ICA diameter, ICA blood velocity, ICA shear rate and ICA blood flow between HWI and CON (all P  > 0.05). ICA did not change after either CON (pre: 13.9 ± 9.2 to post: 11.3 ± 6.1 mL min −1  mmHg −1 ) or HWI (pre: 14.6 ± 7.9 to post: 10.9 ± 5.4 mL min −1  mmHg −1 ; Interaction P  = 0.65). In conclusion, HWI reduced blood pressure and increased ICA conductance (i.e. autoregulation) to maintain blood flow to the brain; however, HWI did not influence subsequent cerebrovascular function, as assessed by . What is the central question of this study? Does a single session of whole‐body hot water immersion increase internal carotid artery blood flow and shear rate, and transiently increase subsequent cerebrovascular function, assessed by volumetric cerebrovascular reactivity to hypercapnia? What is the main finding and its importance? Whole‐body hot water immersion decreased blood pressure and increased internal carotid artery cerebrovascular conductance but not volumetric blood flow or shear rate. Subsequent cerebrovascular reactivity remained unaltered following hot water immersion, indicating no acute influence of heating on volumetrically assessed cerebrovascular function.

Relationships between demographic, anthropometric, inflammatory, lipid and glucose tolerance markers in connection with the fat but fit paradigm were investigated by supervised and unsupervised learning. Data from 81 apparently healthy participants (87% females) were used to generate four classes of fatness and fitness. Principal Component Analysis (PCA) revealed that the principal component was preponderantly composed of glucose tolerance parameters. IL-10 and high-density lipoprotein, low-density lipoprotein (LDL), and total cholesterol, along with body mass index (BMI), were the most important features according to Random Forest based recursive feature elimination. Decision Tree classification showed that these play a key role into assigning each individual in one of the four classes, with 70% accuracy, and acceptable classification agreement, κ = 0.54. However, the best classifier with 88% accuracy and κ = 0.79 was the Naïve Bayes. LDL and BMI partially mediated the relationship between fitness and fatness. Although unsupervised learning showed that the glucose tolerance cluster explains the highest quote of the variance, supervised learning revealed that the importance of IL-10, cholesterol levels and BMI was greater than the glucose tolerance PCA cluster. These results suggest that fitness and fatness may be interconnected by anti-inflammatory responses and cholesterol levels. Randomized controlled trials are needed to confirm these preliminary outcomes.

Hot‐water immersion (HWI) has been shown to reduce 24 h ambulatory systolic blood pressure in hypertensive adults and might represent a preventative strategy for maintaining cardiovascular health in normotensive adults. The purpose of this study was to determine the time course of post‐HWI hypotension and test the hypothesis that a single HWI reduces subsequent 24 h ambulatory blood pressure (ABP) in healthy adults. In a randomized, crossover design, 23 participants [7 female and 16 male; 26 (4) years of age] underwent blood pressure assessments before, during, immediately after and for 24 h following 60 min of immersion in 40.4°C hot water (HWI) and a thermoneutral (24.7°C) air control (CON). Thermal and cardiovascular variables were assessed during and for 60 min after the intervention, after which the participants were instrumented with an ABP monitor for 24 h. At min 60 of the interventions, body core temperature was higher [CON, 36.93 (0.28)°C; HWI, 38.83 (0.19)°C; P  < 0.001] and diastolic ( P  < 0.001) and mean ( P  < 0.001) arterial blood pressure lower in HWI than CON. HWI increased the diastolic blood pressure nocturnal dip compared with CON [CON, 15.4 (7.2)%; HWI, 19.1 (7.4)%; P  = 0.022]. No differences in ABP were observed for 24 h, daytime or nighttime systolic, diastolic or mean arterial blood pressures (all P  > 0.05). In conclusion, HWI transiently decreased mean arterial blood pressure and diastolic blood pressure for ≤20 min post‐heating and increased the subsequent nocturnal diastolic blood pressure dip in healthy adults. What is the central question of this study? Is arterial blood pressure reduced in the 24 h following a single morning session of hot‐water immersion, when assessed by ambulatory blood pressure monitoring in healthy adults? What is the main finding and its importance? Morning hot water‐immersion lowered mean arterial and diastolic blood pressure during and immediately after the hot‐water immersion and increased the nocturnal diastolic blood pressure dip in healthy adults. Hot‐water immersion causes a hypotensive effect that influences nighttime blood pressure.

Sympathetic nervous system activation is a hallmark of high‐altitude hypoxia, yet the afferent mechanisms remain incompletely defined. We examined the relative contributions of pulmonary arterial mechanoreceptors and carotid chemoreceptors – two excitatory pathways co‐activated by hypoxia – to sustained sympathoexcitation at altitude. Nine healthy lowlanders (27 ±  7 years, three female) were studied after 6–9 days at 3800 m under four conditions: (1) control, (2) inhaled nitric oxide (iNO, 40 ppm) to reduce pulmonary arterial pressure, (3) low‐dose dopamine infusion (2 µg kg − 1  min − 1 ) to suppress the carotid chemoreflex, and (4) combined iNO and dopamine. End‐tidal oxygen and carbon dioxide were kept constant throughout. We assessed muscle sympathetic nerve activity (MSNA), systemic haemodynamics, ventilation and pulmonary arterial systolic pressure. iNO reduced pulmonary arterial pressure and significantly decreased MSNA (condition 1: 25 ± 8 bursts min −1 vs. condition 2: 21 ± 7 bursts min −1 ; P  = 0.0415), whereas dopamine infusion reduced ventilation ( P  < 0.001) without a consistent effect on MSNA (condition 1: 25 ± 8 bursts min −1 vs. condition 3: 28 ± 13 bursts min −1 ; P  = 0.112). Combined intervention produced a small reduction in sympathetic nerve activity (condition 3: 28 ± 13 bursts min −1 vs. condition 4: 26 ± 13 bursts min −1 ; P  = 0.0643), likely due to baroreflex engagement. These findings confirm that unloading pulmonary arterial pressure attenuates MSNA, reinforcing the role of pulmonary mechanoreceptors in high altitude sympathoexcitation. Attempts to isolate a carotid chemoreflex contribution were likely confounded by dopamine's haemodynamic effect, which introduced variability and limited the specificity of this intervention. Thus, interpretation of this component remains exploratory, highlighting the integrative complexity of reflex control of high altitude sympathoexcitation in humans. What is the central question of this study? Does high altitude sympathoexcitation arise from distinct contributions by pulmonary arterial mechanoreceptors and the carotid chemoreflex? What is the main finding and its importance? Reducing pulmonary arterial pressure with inhaled nitric oxide lowered sympathetic nerve activity and reset baroreflex control, confirming that pulmonary mechanoreceptors are key drivers of sympathetic activation at altitude. This insight could inform treatments for conditions with elevated pulmonary pressures. In contrast, attempt to suppress the carotid chemoreflex via systemic dopamine infusion did not alter sympathetic vasomotor outflow, highlighting the need for better methods to isolate its role.

PurposeTo investigate the association between age, physical activity, femoral trochlear cartilage thickness and biomarkers of tissue metabolism in a cross-sectional sample of adult males. This study utilizes several emerging biomarkers that have been associated with early joint degenerative changes; serum COMP (cartilage oligomeric matrix protein), HA (hyaluronan) and lubricin.MethodsEighty-one males (age: mean (range): 43(18–70) years; body mass index: 25.2 (21.0–30.6) kg/m2) volunteered. Resting serum COMP, HA and lubricin concentrations were determined via commercially available enzyme-linked immunosorbent assay (ELISA) and femoral trochlear cartilage thickness via supra-patellar ultrasound imaging. Physical activity levels were assessed using questionnaires. Statistical analyses were performed using correlation and regression analyses.ResultsAge was correlated with lateral trochlear cartilage thickness (r = − 0.372; p < 0.01) and serum COMP (r = 0.342; p < 0.01). 7-day physical activity was correlated with serum COMP (r = 0.357, p < 0.01), and 12-month physical activity with both lateral trochlear cartilage thickness (r = 0.340, p = 0.01) and serum HA (r = 0.296, p < 0.05). Regression analyses revealed that age significantly accounted for the variability in lateral cartilage thickness and serum COMP, following the adjustment for potential cofounders. However, the association between age and lateral trochlear cartilage thickness was not moderated by physical activity levels (all p > 0.05).ConclusionThis study indicates that older age may be associated with thinner lateral trochlear cartilage and higher cartilage turnover. Being physically active may also be positive for lateral trochlear cartilage thickness. However, overall, both age and physical activity level only account for a small amount of the variability in cartilage thickness and serum biomarkers.

PurposeThere is considerable interindividual variability in the perception of pain. Given that pain management is a major public health problem, gaining insight into the underlying physiology of these perceptual differences is important. We tested the hypothesis that when interindividual variability in initial muscle sympathetic nerve activity (MSNA) responses to a cold pressor test (CPT) is identified, the divergent responses will be linked to differences in pain perception in healthy young men and women.MethodsIn the supine position, blood pressure (BP) and MSNA were measured at baseline and during a 2-min CPT. Immediately following the CPT, pain was rated (range 0–10).ResultsTwo groups were established: positive responders (Pos, n = 12) and negative responders (Neg, n = 12) based on the initial (first 30 s) MSNA response profiles (Pos: 12 ± 9, Neg: −3 ± 3 bursts/min, P < 0.0001). MSNA response profiles throughout the CPT were different between groups (P < 0.0001). Peak MSNA increases were different (Pos: 27 ± 11, Neg: 9 ± 5 bursts/min, P < 0.0001) and corresponded with initial MSNA responses (R2 = 0.6881, P < 0.0001). Blood pressure responses were also different throughout the CPT (P < 0.0001). Most importantly, the perception of pain induced by the CPT was different between the two groups (Pos: 8 ± 1, Neg: 4 ± 1, P < 0.0001).ConclusionsThe results indicate that in healthy young men and women, there are divergent initial sympathetic neural responses to a given painful stimulus that are linked to the magnitude of pain perception. These findings highlight the distinctive sympathetic patterns that may contribute to the considerable interindividual variability in the perception of pain.