Does a single oral administration of amiloride affect spontaneous arterial baroreflex sensitivity and blood pressure variability in healthy young adults?

Preclinical models indicate that amiloride (AMD) reduces baroreflex sensitivity and perturbs homeostatic blood pressure (BP) regulation. However, it remains unclear whether these findings translate to humans. This study investigated whether oral administration of AMD reduces spontaneous cardiac and sympathetic baroreflex sensitivity and perturbs BP regulation in healthy young humans. Heart rate (HR; electrocardiography), beat-to-beat BP (photoplethysmography), and muscle sympathetic activity (MSNA, microneurography) were continuously measured in 10 young subjects (4 females) during rest across two randomized experimental visits: 1) after 3 h of oral administration of placebo (PLA, 10 mg of methylcellulose within a gelatin capsule) and 2) after 3 h of oral administration of AMD (10 mg). Visits were separated for at least 48 h. We calculated the standard deviation and other indices of BP variability. Spontaneous cardiac baroreflex was assessed via the sequence technique and cardiac autonomic modulation through time- and frequency-domain HR variability. The sensitivity (gain) of the sympathetic baroreflex was determined via weighted linear regression analysis between MSNA and diastolic BP. AMD did not affect HR, BP, and MSNA compared with PLA. Indexes of cardiac autonomic modulation (time- and frequency-domain HR variability) and BP variability were also unchanged after AMD ingestion. Likewise, AMD did not modify the gain of both spontaneous cardiac and sympathetic arterial baroreflex. A single oral dose of AMD does not affect spontaneous arterial baroreflex sensitivity and BP variability in healthy young adults.NEW & NOTEWORTHY Preclinical models indicate that amiloride (AMD), a nonselective antagonist of the acid-sensing ion channels (ASICs), impairs baroreflex sensitivity and perturbs blood pressure regulation. We translated these findings into humans, investigating the impact of acute oral ingestion of AMD on blood pressure variability and spontaneous cardiac and sympathetic baroreflex sensitivity in healthy young humans. In contrast to preclinical evidence, AMD does not impair spontaneous arterial baroreflex sensitivity and blood pressure variability in healthy young adults.

Near-infrared reactance spectroscopy-derived visceral adipose tissue for the assessment of metabolic syndrome in a multi-ethnic sample of young adults.

OBJECTIVES: Visceral adipose tissue (VAT) is highly associated with metabolic syndrome (MetS), which is rapidly increasing in young adults. However, accessible VAT measurement methods are limited, restricting the use of VAT in early detection. This cross-sectional study sought to determine if near-infrared reactance spectroscopy (NIRS)-derived VAT (VATNIRS) was associated with MetS in a multi-ethnic sample of young adults. METHODS: A total of 107 male and female (F:62, M:45) participants (age: 23.0 ± 4.3y; BMI: 27.1 ± 6.6 kg/m2) completed measurements of fasting blood pressure, blood glucose (FBG), blood lipids, and anthropometric assessments including waist circumference and VATNIRS. MetS severity (MetSindex) was calculated from the aforementioned risk factors using sex and race-specific equations. RESULTS: VATNIRS was higher in participants with, and at risk for, MetS compared to those with lower risks (all p < .001). VATNIRS was positively associated with MetSindex for all groups (all p < .001). VATNIRS showed positive associations with systolic (SBP), diastolic (DBP), and mean arterial pressure (MAP), LDL-C and LDL-C-related biomarkers, and FBG; and negative associations with HDL-C and HDL-C-to-total cholesterol ratio (all p < .050). Associations between VATNIRS and blood pressure for females, and LDL-C and LDL-C-related biomarkers for males, were nonsignificant (all p > .050). VATNIRS was positively associated with DBP in African-American participants, and SBP in White participants, resulting in positive associations with MAP for both groups (all p < .050). CONCLUSIONS: VATNIRS is associated with MetS and individual MetS risks factors in a multi-ethnic sample of young adults; providing a noninvasive, cost-effective, portable, and accessible method that may assist in the early detection of MetS and other cardiometabolic abnormalities.

Exercise pressor responses are exaggerated relative to force production during, but not following, thirty-minutes of rhythmic handgrip exercise.

PURPOSE: This study tested the hypothesis that blood pressure responses would increase relative to force production in response to prolonged bouts of muscular work. METHODS: Fifteen individuals performed two minutes of static handgrip (SHG; 35% MVC), followed by three minutes of post-exercise-cuff-occlusion (PECO), before and after thirty minutes of rest (control), or rhythmic handgrip exercise (RHG) of the contralateral and ipsilateral forearms. Beat-by-beat recordings of mean arterial pressure (MAP), heart rate (HR), and handgrip force (kg) were averaged across one-minute periods at baseline, and minutes 5, 10, 15, 20, 25, and 30 of RHG. MAP was also normalized to handgrip force, providing a relative measure of exercise pressor responses (mmHg/kg). Hemodynamic responses to SHG and PECO were also compared before and after contralateral RHG, ipsilateral RHG, and control, respectively. Similar to the RHG trial, areas under the curve were calculated for MAP (blood pressure index; BPI) and normalized to the time tension index (BPInorm). RESULTS: HR and MAP significantly increased during RHG (15.3 ± 1.4% and 20.4 ± 3.2%, respectively, both p < 0.01), while force output decreased by up to 36.6 ± 8.0% (p < 0.01). This resulted in a 51.6 ± 9.4% increase in BPInorm during 30 min of RHG (p < 0.01). In contrast, blood pressure responses to SHG and PECO were unchanged following RHG (all p ≥ 0.07), and only the mean HR (4.2 ± 1.5%, p = 0.01) and ΔHR (67.2 ± 18.1%, p < 0.01) response to SHG were exaggerated following ipsilateral RHG. CONCLUSIONS: The magnitude of exercise pressor responses relative to force production progressively increases during, but not following, prolonged bouts of muscular work.

Associations between visceral adipose tissue estimates produced by near-infrared spectroscopy, mobile anthropometrics, and traditional body composition assessments and estimates derived from dual-energy X-ray absorptiometry.

Assessments of visceral adipose tissue (VAT) are critical in preventing metabolic disorders; however, there are limited measurement methods that are accurate and accessible for VAT. The purpose of this cross-sectional study was to evaluate the association between VAT estimates from consumer-grade devices and traditional anthropometrics and VAT and subcutaneous adipose tissue (SAT) from dual-energy X-ray absorptiometry (DXA). Data were collected from 182 participants (female = 114; White = 127; Black/African-American (BAA) = 48) which included anthropometrics and indices of VAT produced by near-infrared reactance spectroscopy (NIRS), visual body composition (VBC) and multifrequency BIA (MFBIA). VAT and SAT were collected using DXA. Bivariate and partial correlations were calculated between DXAVAT and DXASAT and other VAT estimates. All VAT indices had positive moderate-strong correlations with VAT (all P < 0·001) and SAT (all P < 0·001). Only waist:hip (r = 0·69), VATVBC (r = 0·84), and VATMFBIA (r = 0·86) had stronger associations with VAT than SAT (P < 0·001). Partial associations between VATVBC and VATMFBIA were only stronger for VAT than SAT in White participants (r = 0·67, P < 0·001) but not female, male, or BAA participants individually. Partial correlations for waist:hip were stronger for VAT than SAT, but only for male (r = 0·40, P < 0·010) or White participants (r = 0·48, P < 0·001). NIRS was amongst the weakest predictors of VAT which was highest in male participants (r = 0·39, P < 0·010) but non-existent in BAA participants (r = -0·02, P > 0·050) after adjusting for SAT. Both anthropometric and consumer-grade VAT indices are consistently better predictors of SAT than VAT. These data highlight the need for a standardised, but convenient, VAT estimation protocol that can account for the relationship between SAT and VAT that differs by sex/race.

Aortic stiffness increases during prolonged sitting independent of intermittent standing or prior exercise.

INTRODUCTION: Adverse vascular responses can occur during prolonged sitting, including stiffening of the aortic artery which may contribute to cardiovascular disease. Few studies have investigated the impact of intermittent standing and/or prior exercise as strategies to attenuate these potentially deleterious vascular changes. PURPOSE: To investigate central vascular health responses during prolonged sitting, with and without intermittent standing and/or prior exercise. METHODS: Fifteen males aged 18 to 31 years were recruited. Subjects completed a control condition [Sitting Only (SO)], and three randomized strategy conditions [Sitting Plus Standing (SSt), Exercise Plus Sitting (ES), Exercise Plus Sitting Plus Standing (ESSt)]. For all conditions, measurements of carotid-femoral pulse wave velocity (cfPWV) were taken at pre- and post-intervention, and brachial and central blood pressure (BP) at pre-, 1-h, 2-h, and 3-h intervention. RESULTS: cfPWV significantly increased from pre- to post-intervention for all conditions (all p ≤ 0.043), as did brachial mean arterial pressure (MAP) and diastolic BP, and central MAP and diastolic BP for the control condition (all p ≤ 0.022). Brachial and central systolic BP were significantly higher during SO compared to ESSt at 1 h, and compared to ES for central systolic BP (all p ≤ 0.036). CONCLUSIONS: Strategies of intermittent standing and/or prior exercise may not prevent aortic stiffening during sitting but may attenuate BP elevations in the brachial and aortic arteries. Future research should investigate causal mechanistic links between sitting and aortic stiffening, and other attenuation strategies.

Increased hip flexion gait as an exercise modality for individuals with obesity.

PURPOSE: Exercise is a critical element for the management of body weight and improvement of quality of life of individuals with obesity. Due to its convenience and accessibility, running is a commonly used exercise modality to meet exercise guidelines. However, the weight-bearing component during high impacts of this exercise modality might limit the participation in exercise and reduce the effectiveness of running-based exercise interventions in individuals with obesity. The hip flexion feedback system (HFFS) assists participants in meeting specific exercise intensities by giving the participant specific increased hip flexion targets while walking on a treadmill. The resulting activity involves walking with increased hip flexion which removes the high impacts of running. The purpose of this study was to compare physiological and biomechanical parameters during an HFFS session and an independent treadmill walking/running session (IND). METHODS: Heart rate, oxygen consumption (VO2), heart rate error, and tibia peak positive accelerations (PPA) were investigated for each condition at 40% and 60% of heart rate reserve exercise intensities. RESULTS: VO2 was higher for IND despite no differences in heart rate. Tibia PPAs were reduced during the HFFS session. Heart rate error was reduced for HFFS during non-steady state exercise. CONCLUSION: While demanding lower energy consumption compared to running, HFFS exercise results in lower tibia PPAs and more accurate monitoring of exercise intensity. HFFS might be a valid exercise alternative for individuals with obesity or individuals that require low-impact forces at the lower limbs.

Additive influence of exercise pressor reflex activation on Valsalva responses in white and black adults.

AIM: This study aimed to determine if activation of the exercise pressor reflex exerts additive or redundant influences on the autonomic responses to the Valsalva maneuver (VL), and if these responses differ between White and Black or African American (B/AA) individuals. METHODS: Twenty participants (B/AA n = 10, White n = 10) performed three separate experimental trials. In the first trial, participants performed two VLs in a resting condition. In a second trial, participants performed 5 min of continuous handgrip (HG) exercise at 35% of the predetermined maximal voluntary contraction. In a third and final trial, participants repeated the 5-min bout of HG while also performing two VLs during the 4th and 5th minutes. Beat by beat blood pressure and heart rate (HR) were recorded continuously and the absolute systolic blood pressure (SBP), diastolic blood pressure (DBP), mean arterial pressure (MAP), pulse pressure (PP), and heart rate (HR) responses were reported for phases I-IV of each VL. RESULTS: No significant group by trial interactions or main effects of group were observed for any phase of the VL (all p ≥ 0.36). However, significant main effects of time were observed for blood pressure and heart rate during phases IIa-IV (all p ≤ 0.02). Specifically, the addition of HG exercise exaggerated the hypertensive responses during phases IIb and IV (all p ≤ 0.04) and blunted the hypotensive responses during phases IIa and III (all p ≤ 0.01). CONCLUSIONS: These results suggest that activation of the exercise pressor reflex exerts an additive influence on autonomic responses to the VL maneuver in both White and B/AA adults.

A 10-mg dose of amiloride increases time to failure during blood-flow-restricted plantar flexion in healthy adults without influencing blood pressure.

Amiloride has been shown to inhibit acid-sensing ion channels (ASICs), which contribute to ischemia-related muscle pain during exercise. The purpose of this study was to determine if a single oral dose of amiloride would improve exercise tolerance and attenuate blood pressure during blood-flow-restricted (BFR) exercise in healthy adults. Ten subjects (4 females) performed isometric plantar flexion exercise with BFR (30% maximal voluntary contraction) after ingesting either a 10-mg dose of amiloride or a volume-matched placebo (random order). Time to failure, time-tension index (TTI), and perceived pain (visual analog scale) were compared between the amiloride and placebo trials. Mean blood pressure, heart rate, blood pressure index (BPI), and BPI normalized to TTI (BPInorm) were also compared between trials using both time-matched (TM50 and TM100) and effort-matched (T50 and T100) comparisons. Time to failure (+69.4 ± 63.2 s, P < 0.01) and TTI (+1,441 ± 633 kg·s, P = 0.02) were both significantly increased in the amiloride trial compared with placebo, despite no increase in pain (+0.4 ± 1.7 cm, P = 0.46). In contrast, amiloride had no significant influence on the mean blood pressure or heart rate responses, nor were there any significant differences in BPI or BPInorm between trials when matched for time (all P ≥ 0.13). When matched for effort, BPI was significantly greater in the amiloride trial (+5,300 ± 1,798 mmHg·s, P = 0.01), likely owing to an increase in total exercise duration. In conclusion, a 10-mg oral dose of amiloride appears to significantly improve the tolerance to BFR exercise in healthy adults without influencing blood pressure responses.

Diffusion tensor imaging indices of acute muscle damage are augmented after exercise in peripheral arterial disease.

PURPOSE: Although it is known that peripheral arterial disease (PAD) is associated with chronic myopathies, the acute muscular responses to exercise in this population are less clear. This study used diffusion tensor imaging (DTI) to compare acute exercise-related muscle damage between PAD patients and healthy controls. METHODS: Eight PAD patients and seven healthy controls performed graded plantar flexion in the bore of a 3T MRI scanner. Exercise began at 2 kg and increased by 2 kg every 2 min until failure, or completion of 10 min of exercise. DTI images were acquired from the lower leg pre- and post-exercise, and were analyzed for mean diffusivity, fractional anisotropy (FA), and eigenvalues 1-3 (λ1-3) of the medial gastrocnemius (MG) and tibialis anterior (TA). RESULTS: Results indicated a significant leg by time interaction for mean diffusivity, explained by a significantly greater increase in diffusivity of the MG in the most affected legs of PAD patients (11.1 × 10-4 ± 0.5 × 10-4 mm2/s vs. 12.7 × 10-4 ± 1.2 × 10-4 mm2/s at pre and post, respectively, P = 0.02) compared to healthy control subjects (10.8 × 10-4 ± 0.3 × 10-4 mm2/s vs. 11.2 × 10-4 ± 0.5 × 10-4 mm2/s at pre and post, respectively, P = 1.0). No significant differences were observed for the TA, or λ1-3 (all P ≥ 0.06). Moreover, no reciprocal changes were observed for FA in either group (all P ≥ 0.29). CONCLUSION: These data suggest that calf muscle diffusivity increases more in PAD patients compared to controls after exercise. These findings are consistent with the notion that acute exercise results in increased muscle damage in PAD.

Central and peripheral modulation of exercise pressor reflex sensitivity after nonfatiguing work.

Autonomic blood pressure control is fundamentally altered during a single bout of exercise, as evidenced by the downward resetting of the baroreflex following exercise (postexercise hypotension). However, it is unclear if an acute bout of exercise is also associated with a change in the sensitivity of the exercise pressor response to a controlled stimulus, such as a static contraction. This study tested the hypothesis that the blood pressure response to a controlled static contraction would be attenuated after unilateral cycling of the contralateral (opposite) leg, but preserved after cycling of the ipsilateral (same) leg. To test this, the blood pressure response to 90 s of isometric plantar flexion [50% maximal voluntary contraction (MVC)] was compared before and after 20 min of contralateral and ipsilateral single-leg cycling at 20% peak oxygen consumption and rest (control) in 10 healthy subjects (three males and seven females). The mean arterial pressure response was significantly attenuated after contralateral single-leg cycling (+9.8 ± 7.5% ∆mmHg vs. +6.7 ± 6.6% ∆mmHg pre and postexercise, respectively, P = 0.04) and rest (+9.0 ± 7.5% ∆mmHg vs. +6.6 ± 5.2% ∆mmHg pre and postexercise, respectively, P = 0.03). In contrast, the pressor response nonsignificantly increased following ipsilateral single-leg cycling (+5.5 ± 5.2% ∆mmHg vs. +8.9 ± 7.2% ∆mmHg pre and postexercise, respectively, P = 0.08). The heart rate, leg blood flow, and leg conductance responses to plantar flexion were not affected by any condition (P ≥ 0.12). These results are consistent with the notion that peripheral, but not central mechanisms promote exercise pressor reflex sensitivity after exercise.

Knee extension with blood flow restriction: Impact of cuff pressure on hemodynamics.

INTRODUCTION: Blood flow restriction (BFR) exercise has emerged as a method of increasing muscle size and strength with low intensity resistance training. While the cuff pressures used during BFR are typically a percentage of resting arterial occlusion pressure (AOP), the impact these cuff pressures have on blood flow during lower body exercise is unknown. PURPOSE: To determine how various cuff pressures impact blood flow and tissue perfusion during exercise. METHODS: Eleven healthy male participants completed four sets of knee extension (30 reps per set at 30% max torque) with 0%, 60%, 80%, and 100% of arterial occlusion pressure (AOP) was applied to the proximal portion of the thigh. Femoral artery blood flow, tissue oxygenation, and central hemodynamics were continuously recorded before, during, and after exercise. Electromyography (EMG) amplitude was recorded from the vastus lateralis during exercise. RESULTS: Blood flow increased during exercise compared to rest across all cuff pressures (p < 0.001), however compared to 0%, the absolute blood flow was reduced by 34 ± 17%, 45 ± 22%, and 72 ± 19% for 60, 80, and 100% AOP, respectively. Furthermore, each cuff pressure resulted in similar relative changes in blood flow before, during, and after exercise. During exercise, tissue saturation index (TSI) decreased as cuff pressure increased (p ≤ 0.005) with the exception of 80 to 100% AOP. Deoxyhemoglobin increased (p ≤ 0.001) with cuff pressure. CONCLUSION: Our data indicate that while BFR knee extension elicits an absolute hyperemic response at cuff pressures up to 100% resting AOP, the relative reductions in blood flow are consistent across rest, exercise and recovery.

Limb blood flow and tissue perfusion during exercise with blood flow restriction.

INTRODUCTION: Exercise with blood flow restriction (BFR) is emerging as an effective modality for improving muscular function in clinical and athletic populations. Selection of cuff pressure is critical because it should maximize metabolic stress without completely occluding blood flow or compromising user safety. It is unknown how cuff pressures determined at rest influence blood flow hemodynamics during exercise. PURPOSE: We evaluated changes in blood flow and tissue perfusion before, during, and after exercise with BFR. METHODS: Ten males performed rhythmic handgrip exercise (30 contractions, 30% MVC) at 0%, 60%, 80%, 100%, and 120% of limb occlusion pressure (LOP). Brachial artery blood flow and tissue saturation were assessed using Doppler ultrasound and near-infrared spectroscopy, respectively. RESULTS: At rest blood flow generally decreased with increased pressure (0% > 60% ≈ 80% > 100% ≈ 120% LOP). During 60% and 80% LOP conditions, blood flow increased during exercise from rest and decreased after exercise (all P < 0.05). Compared to 0% LOP, relative blood flow at 60% and 80% LOP decreased by 22-47% at rest, 22-48% during exercise, and 52-71% after exercise (all P < 0.05). Increased LOP decreased tissue saturation during exercise with BFR (P < 0.05). Heart rate, mean arterial pressure, and cardiac output did not differ across LOP. CONCLUSION: At pressures below LOP the cardiovascular system overcame the external pressure and increased blood flow to exercising muscles. Relative reductions in blood flow at rest were similar to those during exercise. Thus, the relative occlusion measured at rest approximated the degree of occlusion during exercise. Moderate cuff pressures increased metabolic stress without completely occluding blood flow.

Passive limb movement intervals results in repeated hyperemic responses in those with paraplegia.

STUDY DESIGN: Repeated measures. OBJECTIVES: Reports suggest passive limb movement (PLM) could be used as a therapy to increase blood flow and tissue perfusion in the paralyzed lower limbs of those with spinal cord injuries. However, the hyperemic response to PLM appears to be transient, lasting only 30-45 s despite continued limb movement. The purpose of this investigation was to determine whether the hyperemic response is repeatable across multiple short bouts of passive limb movement. SETTING: Cleveland Veterans Affairs Medical Center. METHODS: Nine individuals with paraplegia 46 ± 6 years of age, 17 ± 12 years post injury (range: 3-33 years) with complete T3-T11 injuries were subject to 5 × 1 min bouts of passive knee extension/flexion at 1 Hz with a 1 min recovery period between each bout. Heart rate (HR), mean arterial pressure (MAP), femoral artery blood flow (FABF), skin blood flow (SBF), and tissue perfusion in the lower limb were recorded during baseline and throughout each bout of PLM. RESULTS: Despite no increase in HR (p ≥ 0.8) or MAP (p ≥ 0.40) across all four bouts of PLM, the average increase in FABF during each bout ranged from 71 ± 87% to 88 ± 93% greater than baseline (p ≤ 0.043). SBF also increased between 465 ± 302% and 582 ± 309% across the five bouts of PLM (p ≤ 0.005). CONCLUSIONS: Repeated bouts of PLM in those with SCI while in an upright position resulted in a robust and steady increase in FABF and SBF which could have implications for improving vascular health and tissue perfusion in the lower limbs of those with paraplegia.

Conflicting Associations among Bioelectrical Impedance and Cardiometabolic Health Parameters in Young White and Black Adults.

PURPOSE: The purpose of this cross-sectional evaluation was to determine the associations between raw bioelectrical impedance and cardiometabolic health parameters in a sample of young non-Hispanic White and African American adults. METHODS: A total of 96 (female: 52, male: 44) non-Hispanic White ( n = 45) and African American adults ( n = 51) between the ages of 19 and 37 yr (22.7 ± 3.83 yr) completed several fasted assessments including resting systolic blood pressure (rSBP), blood glucose (FBG), blood lipids, and bioelectrical impedance spectroscopy. Bioelectrical impedance spectroscopy-derived measurements included phase angle, bioimpedance index (BI), impedance ratio (IR), reactance index (XCi), fat-free mass (FFM), FFM index (FFMi), and absolute (a) and relative (%) total body water (TBW) and extracellular (ECF) and intracellular fluid (ICF). All bioelectric variables were collected at 50 kHz other than IR (250 kHz/5 kHz). Multiple regressions were conducted and adjusted for sex, age, and body mass index. RESULTS: rSBP was positively, and HDL was inversely, associated with all bioelectrical impedance and absolute hydration variables (all P ≤ 0.050) other than XCi for rSBP and XCi and FFMi for HDL. rSBP ( P < 0.001) was inversely, and HDL ( P = 0.034) was positively, associated with IR. FBG was positively associated with BI, XCi, FFM, TBWa, and ECFa (all P < 0.050). Metabolic syndrome severity was positively associated with BI, FFM, TBWa, and ECFa for women (all P ≤ 0.050) and with ICFa for African American women ( P = 0.016). CONCLUSIONS: Given the rapid increase in the prevalence of cardiometabolic health risks among young adults and the broad use of bioelectrical impedance in practice, the conflicting associations we observed in this age group suggest that bioelectrical impedance parameters should be used with caution in the context of cardiometabolic health risks and age.

Exploring gait velocity as a predictor of cardiometabolic disease risk in young adults.

Background: The association between poor gait and functional movement ability and metabolic syndrome (MetS) has been well established in older adults. A continuous cardiometabolic risk score, MetSindex, may more easily identify individuals at risk for cardiometabolic disease who do not yet meet the stringent criteria for a formal MetS diagnosis. Although the association between MetS and gait velocity is well established in older adults, no such relationship has been identified in younger adults; a group experiencing a rapid increase in the development of MetS. Methods: MetSindex was determined for 21 young adults using standard procedures. Gait velocity was measured as participants completed a ten-meter walk test. Spatiotemporal parameters of gait were also derived using a motion capture system. Simple linear regression was used to determine the relationship between MetSindex and gait velocity, as well as MetSindex and spatiotemporal parameters of gait. Results: There was a large inverse relationship between MetSindex and gait velocity. A large inverse relationship was also observed between MetSindex and cadence, and a large positive relationship was observed between stance time and double limb support time. Conclusions: Gait velocity slows in young adults who do not necessarily meet the criterion for positive diagnosis of MetS-but demonstrate an increased risk for MetS and cardiovascular disease through higher MetSindex scores. The mechanism underlying reduced gait velocity may be fewer, but not shorter steps. Determining easy-to-use surrogates of MetS (e.g., gait velocity) may help combat the growing prevalence of MetS by increasing access to preventative approaches.

Altered Autonomic Function in Metabolic Syndrome: Interactive Effects of Multiple Components.

Metabolic syndrome (MetS) describes a set of disorders that collectively influence cardiovascular health, and includes hypertension, obesity, insulin resistance, diabetes, and dyslipidemia. All these components (hypertension, obesity, dyslipidemia, and prediabetes/diabetes) have been shown to modify autonomic function. The major autonomic dysfunction that has been documented with each of these components is in the control of sympathetic outflow to the heart and periphery at rest and during exercise through modulation of the arterial baroreflex and the muscle metaboreflex. Many studies have described MetS components in singularity or in combination with the other major components of metabolic syndrome. However, many studies lack the capability to study all the factors of metabolic syndrome in one model or have not focused on studying the effects of how each component as it arises influences overall autonomic function. The goal of this review is to describe the current understanding of major aspects of metabolic syndrome that most likely contribute to the consequent/associated autonomic alterations during exercise and discuss their effects, as well as bring light to alternative mechanisms of study.

Measurements of Abdominal Obesity are Associated with Metabolic Syndrome Severity Independent of Hypertensive Phenotype in White but not Black Young Adults.

PURPOSE: This study sought to determine if metabolic syndrome severity (MetSindex) was differentially associated with abdominal obesity based on waist circumference (WC) site and the presentation of hypertensive phenotypes in a group of young White and Black adults. METHODS: A total of 139 young adult (22.5 ± 3.3 years) non-Hispanic White (n = 73) and non-Hispanic Black (n = 66) males and females (M 53, 86 F) completed this cross-sectional evaluation. Participants had their WC measured at three distinct locations along the abdomen which were used to calculate waist-to-hip and waist-to-height ratios. Systolic (SBP) and diastolic blood pressure (DBP) were collected and used to calculate mean arterial pressure (MAP). In addition to traditional metabolic syndrome (MetS) risk factors, BP values were individually used to produce three separate MetSindex scores representing three specific hypertensive phenotypes (MetSSBP, MetSDBP, MetSMAP), and each of these were evaluated against each abdominal obesity estimate. RESULTS: MetSDBP and MetSSBP were significantly higher than all other indices for females (all p ≤ 0.002) and males (all p < 0.001), respectively. MetSDBP was significantly higher than MetSMAP for White females (p = 0.039), and MetSSBP was significantly higher than MetSDBP and MetSMAP (both p < 0.001) for Black males. Standalone and joint estimates of abdominal obesity were uniquely associated with MetSindex across hypertensive phenotypes for White, but not Black males and females. CONCLUSIONS: Specific hypertensive phenotypes may differentially determine MetSindex, but these estimates are not associated with abdominal obesity in young Black adults regardless of measurement location. Healthcare professionals should address this disparity by providing more comprehensive MetS screening procedures for young Black adults. CLINICAL TRIALS REGISTRATION: NCT05885672.

Fat-free mass is associated with exercise pressor responses, but not cold pressor responses, in humans: influence of maximal voluntary contraction.

Objective: This study examined the contributions of fat mass (FM) and fat-free mass (FFM) to the magnitude of exercise pressor responses in humans. Methods: The cumulative blood pressure responses (blood pressure index; BPI) to handgrip exercise (BPIhg), post-exercise-circulatory-occlusion (BPIpeco), and cold-pressor activation (BPIcpt) were collected from 67 individuals grouped by BMI (27.8 ± 7.3 kg/m2), FFM index (FFMi, 29.1 ± 3.8 kg/m2), and FM index (FMi 12.5 ± 4.8 kg/m2) quartiles. BPI responses to HG were also normalized to the time-tension index of HG, providing a relative index of exercise pressor response magnitude (BPInorm). Results: BPIhg and BPIpeco were significantly elevated in the third FFMi quartile (p ≤ 0.034), while BPInorm significantly decreased in the second and fourth quartiles (p ≤ 0.029). In contrast, no differences in BPIcpt were observed across any FFMi, BMI, or FMi quartiles (p ≥ 0.268). FFM was independently associated with BPIhg, BPI-peco, and BPInorm (all p ≤ 0.049), however, FFM was eliminated as an independent predictor when maximal voluntary contraction (MVC) was included in these regression models (all p ≥ 0.495). Neither FFM nor MVC was associated with BPIcpt (p ≥ 0.229). Conclusions: These findings indicate that exercise pressor responses, but not cold-pressor responses, are significantly associated with FFM in humans, and that this association is driven by FFM related differences in MVC.

Smartphone derived anthropometrics: Agreement between a commercially available smartphone application and its parent application intended for use at point-of-care.

BACKGROUND & AIMS: Smartphone applications can now automate body composition and anthropometric measurements remotely, prompting applications intended for use at point-of-care to provide commercially available smartphone applications intended for personal use. However, the agreement between such anthropometrics remain unclear. METHODS: A total of 123 apparently healthy participants (F: 69; M: 54; age: 28.1 ± 11.3; BMI: 26.9 ± 5.9) completed consecutive body composition scans using a 3D smartphone application intended for personal use (MeThreeSixty; MTS) and it stationary counterpart intended for use in practice (Mobile Fit Booth; MFB). Agreement between devices were evaluated using root mean square error (RMSE), Bland-Altman analyses, and linear regression for all measurements, and additional equivalence testing was conducted for all circumference and limb length comparisons. RESULTS: When evaluated against the MFB, MTS significantly overestimated all measurements other than waist circumference (p = 0.670) using paired t-tests. RMSE was 2.5 % for body fat percentage (BF%), 0.64-3.74 cm for all body circumferences, 0.71-2.3 kg for all lean mass estimates, and 126-659 cm2 and 608-4672 cm3 across all body surface area and body volume estimates, respectively. BF% was the only body composition estimate that did not demonstrate proportional bias (p = 0.221). Circumferences of the chest, shoulder, biceps, forearm, and ankle all demonstrated proportional bias (all coefficients: p < 0.050), but only chest, shoulder, and arm circumferences did not demonstrate equivalence. Arm surface area (p < 0.001) and arm (p = 0.002) and leg volumes (p = 0.004) were the only body surface area and volume estimates to reveal proportional biases. CONCLUSIONS: These findings demonstrate the agreement between 3D anthropometric applications intended for clinical and personal use, particularly for whole-body composition estimates and clinically meaningful body circumferences. Given the advantages of commercially available remote applications, practitioners and consumers may consider using this method in place of those intended for clinical practice, but should express caution when overestimation is a concern.

Hemodynamic responses to the cold pressor test in individuals with metabolic syndrome: a case-control study in a multiracial sample of adults.

Previous research shows that exercise pressor and metaboreflex responses are significantly exaggerated in individuals with metabolic syndrome, but it is unclear if these exaggerated responses extend to the cold pressor test (CPT). This study tested the hypothesis that, contrary to previously reported exaggerated responses during exercise, CPT responses would not be significantly exaggerated in individuals with MetS compared to matched controls. Eleven individuals with MetS and eleven control participants matched by age, race, sex, and ethnicity completed a cardiometabolic prescreening and a CPT. Each CPT required participants to immerse their hand in ice water for two minutes while beat-by-beat blood pressure, heart rate (HR), and leg blood flow (LBF) were continuously measured. Leg vascular conductance (LVC) was calculated as LBF divided by mean arterial pressure (MAP). The precent changes in MAP, systolic blood pressure (SBP), diastolic blood pressure (DBP), HR, LBF, and LVC were compared across time (BL vs. Minutes 1 and 2 of CPT) and between groups (MetS vs. Control) using repeated measures analyses of variance. As expected, MAP (f = 32.11, p < 0.001), SBP (f = 23.18, p < 0.001), DBP (f = 40.39, p < 0.001), and HR (f = 31.81, p < 0.001) increased during the CPT, and LBF (f = 4.75, p = 0.014) and LVC (f = 13.88, p < 0.001) decreased. However, no significant main effects of group or group by time interactions were observed (f ≤ 0.391, p ≥ 0.539). These findings indicate that the hemodynamic responses to the CPT are not significantly exaggerated in MetS, and therefore, previous reports of exaggerated exercise pressor and metaboreflex responses in MetS cannot be attributed to generalized sympathetic overexcitability.