Sympathetic transduction at rest and during cold pressor test in young healthy non-Hispanic Black and White women.

Non-Hispanic Black (BL) individuals have the highest prevalence of hypertension and cardiovascular disease (CVD) compared with all other racial/ethnic groups. Previous work focused on racial disparities in sympathetic control and blood pressure (BP) regulation between young BL and White (WH) adults, have mainly included men. Herein, we hypothesized that BL women would exhibit augmented resting sympathetic vascular transduction and greater sympathetic and BP reactivity to cold pressor test (CPT) compared with WH women. Twenty-eight young healthy women (BL: n = 14, 22 [Formula: see text] 4 yr; WH: n = 14, 22 [Formula: see text] 4 yr) participated. Beat-to-beat BP (Finometer), common femoral artery blood flow (duplex Doppler ultrasound), and muscle sympathetic nerve activity (MSNA; microneurography) were continuously recorded. In a subset (BL n = 10, WH n = 11), MSNA and BP were recorded at rest and during a 2-min CPT. Resting sympathetic vascular transduction was quantified as changes in leg vascular conductance (LVC) and mean arterial pressure (MAP) following spontaneous bursts of MSNA using signal averaging. Sympathetic and BP reactivity were quantified as changes in MSNA and MAP during the last minute of CPT. There were no differences in nadir LVC following resting MSNA bursts between BL (-8.70 ± 3.43%) and WH women (-7.30 ± 3.74%; P = 0.394). Likewise, peak increases in MAP following MSNA bursts were not different between groups (BL: +2.80 ± 1.42 mmHg; vs. WH: +2.99 ± 1.15 mmHg; P = 0.683). During CPT, increases in MSNA and MAP were also not different between BL and WH women, with similar transduction estimates between groups (ΔMAP/ΔMSNA; P = 0.182). These findings indicate that young, healthy BL women do not exhibit exaggerated sympathetic transduction or augmented sympathetic and BP reactivity during CPT.NEW & NOTEWORTHY This study was the first to comprehensively investigate sympathetic vascular transduction and sympathetic and BP reactivity during a cold pressor test in young, healthy BL women. We demonstrated that young BL women do not exhibit exaggerated resting sympathetic vascular transduction and do not have augmented sympathetic or BP reactivity during cold stress compared with their WH counterparts. Collectively, these findings suggest that alterations in sympathetic transduction and reactivity are not apparent in young, healthy BL women.

Peripheral and Cerebral Vasodilation in Black and White Women: Examining the Impact of Psychosocial Stress Exposure Versus Internalization and Coping.

BACKGROUND: Black women have among the highest rates of cardiovascular and cerebrovascular disease prevalence and mortality in part due to blunted vascular function. Psychosocial stress likely also contributes but its relationship to vascular function remains incompletely understood. Recent studies suggest that stress internalization and coping strategies are more important than stress exposures alone. We hypothesized that Black women would have blunted peripheral and cerebral vasodilation and that, among Black women, this would be inversely related with psychosocial stress internalization/coping but not stress exposures. METHODS: Healthy Black (n=21; 20±2 years) and White (n=16; 25±7 years) women underwent testing for forearm reactive hyperemia, brachial artery flow-mediated dilation (FMD), and cerebrovascular reactivity. Psychosocial stress exposures (adverse childhood experiences; past week discrimination) and internalization/coping techniques (John Henryism Active Coping Scale; Giscombe Superwoman Schema Questionnaire) were assessed. RESULTS: Reactive hyperemia and cerebrovascular reactivity were not different between groups (P>0.05), whereas FMD was lower in Black women (P=0.007). Neither adverse childhood experiences nor past week discrimination were associated with FMD in either group (P>0.05 for all). John Henryism Active Coping Scale scores were negatively associated with FMD in Black women (P=0.014) but positively associated with FMD in White women (P=0.042). Superwoman Schema-Succeed was negatively associated (P=0.044) and Superwoman Schema-Vulnerable tended to be negatively associated (P=0.057) with FMD in Black women. CONCLUSIONS: These findings indicate that blunted FMD in Black women may be due more to stress internalization and maladaptive coping than stress exposures alone.

Pod-based e-cigarettes versus combustible cigarettes: The impact on peripheral and cerebral vascular function and subjective experiences.

INTRODUCTION: The vaping epidemic in the US has been largely attributed to the emergence of pod-based e-cigarette devices. While these devices continue to be promoted as alternatives to cigarettes, their impact on cardiovascular and behavioral outcomes remains incompletely understood. This study assessed the impact of pod-based e-cigarettes on peripheral and cerebral vascular function, along with subjective experiences among adult cigarette smokers. METHODS: In a crossover laboratory design study, a total of 19 (e-cigarette naïve) cigarette smokers (aged 21-43 years) attended two lab sessions. In one session, participants smoked a cigarette and in the other, vaped a pod-based e-cigarette. Participants completed questions assessing subjective experiences. Peripheral macrovascular and microvascular function was assessed via brachial artery FMD and reactive hyperemia, while cerebral vascular function was assessed as the blood velocity response of the middle cerebral artery during hypercapnia. Measurements were taken before and after exposure. RESULTS: Compared with baseline, there was a reduction in peripheral macrovascular function (indexed by FMD), following e-cigarette (pre=9.3±4.3%; post=6.4±4.1%) and cigarette use (pre=10.2±3.7%; post=6.8±3.8%; main effect of time p<0.0001). Cerebral vascular function (indexed by cerebral vasodilatory response during hypercapnia) was also reduced following e-cigarette (pre=53±19%; post=44±15%) and cigarette use (pre=54±21%; post=44±17%; main effect of time p<0.01). The magnitude of reduction in peripheral and cerebral vascular function was similar between conditions (condition × time, p>0.05). Compared with vaping an e-cigarette, participants scored higher for measures of satisfaction, taste, puff liking, and suppression of craving following smoking (p>0.05). CONCLUSIONS: Similar to smoking, vaping a pod-based e-cigarette leads to an impairment in peripheral and cerebral vascular function while providing a reduced subjective experience compared with a cigarette among adult smokers. While these data challenge the notion that e-cigarette use is a safe and satisfactory alternative to cigarette use, large longitudinal studies are needed to assess the long-term impact of pod-based e-cigarette devices on cardiovascular and behavioral outcomes.

The acute effect of whole-body heat therapy on peripheral and cerebral vascular reactivity in Black and White females.

Among females in the U.S., Black females suffer the most from cardiovascular disease and stroke. While the reasons for this disparity are multifactorial, vascular dysfunction likely contributes. Chronic whole-body heat therapy (WBHT) improves vascular function, but few studies have examined its acute effect on peripheral or cerebral vascular function, which may help elucidate chronic adaptative mechanisms. Furthermore, no studies have investigated this effect in Black females. We hypothesized that Black females would have lower peripheral and cerebral vascular function relative to White females and that one session of WBHT would mitigate these differences. Eighteen young, healthy Black (n = 9; 21 ± 3 yr; BMI: 24.7 ± 4.5 kg/m2) and White (n = 9; 27 ± 3 yr; BMI: 24.8 ± 4.1 kg/m2) females underwent one 60 min session of WBHT (49 °C water via a tube-lined suit). Pre- and 45 min post-testing measures included post-occlusive forearm reactive hyperemia (peripheral microvascular function, RH), brachial artery flow-mediated dilation (peripheral macrovascular function, FMD), and cerebrovascular reactivity (CVR) to hypercapnia. Prior to WBHT, there were no differences in RH, FMD, or CVR (p > 0.05 for all). WBHT improved peak RH in both groups (main effect of WBHT: 79.6 ± 20.1 cm/s to 95.9 ± 30.0 cm/s; p = 0.004, g = 0.787) but not Δ blood velocity (p > 0.05 for both groups). WBHT improved FMD in both groups (6.2 ± 3.4 % to 8.8 ± 3.7 %; p = 0.016, g = 0.618) but had no effect on CVR in either group (p = 0.077). These data indicate that one session of WBHT acutely improves peripheral micro- and macrovascular but not cerebral vascular function in Black and White females.

Application of blood flow restriction in hypoxic environment augments muscle deoxygenation without compromising repeated sprint exercise performance.

NEW FINDINGS: What is the central question of this study? Does applying blood flow restriction during the rest periods of repeated sprint exercise in a hypoxic environment lead to greater local hypoxia within exercising muscles without compromising training workload? What is the main finding and its importance? Repeated sprint exercise with blood flow restriction administered during rest periods under systemic hypoxia led to severe local hypoxia within the exercised muscles without a reduction in power output. The maintained power output might be due to elevated neuromuscular activation. Accordingly, the proposed repeated sprint exercise in the current study may be an effective training modality. ABSTRACT: Repeated sprint exercise (RSE) is a popular training modality for a wide variety of athletic activities. The purpose of this study was to assess the combined effects of systemic hypoxia and blood flow restriction (BFR) on muscle deoxygenation and RSE performance. Twelve healthy young men performed a standard RSE training modality (five sets of 10 s maximal sprint with a 60 s rest) under four different conditions: (1) normoxic control (NC), normoxia (N, 20.9%) + control BFR (C, 0 mmHg); (2) normoxic BFR (NB), normoxia (N, 20.9%) + BFR (B, 140 mmHg); (3) hypoxic control (HC), hypoxia (H, 13.7%) + control BFR (C, 0 mmHg); and (4) hypoxic BFR (HB): hypoxia (H, 13.7%) + BFR (B, 140 mmHg). BFR was only administered during the rest period of the respective RSE trials. In the local exercising muscles, muscle oxygen saturation ( Sm O 2 $\textit{Sm}{O}_{2}$ ) and neuromuscular activity were measured using near-infrared spectroscopy and surface electromyography, respectively. SmO2 was lower in systemic hypoxia conditions relative to normoxia conditions (P < 0.05). A rther decrease in SmO2 was observed in HB relative to HC (Set 1: HC 70.0 ± 17.5 vs. HB 57.4 ± 11.3%, P = 0.001; Set 4: HC 67.5 ± 14.6 vs. HB 57.0 ± 12.0%, P = 0.013; Set 5: HC 61.0 ± 15.3 vs. HB 47.7 ± 11.9%, P < 0.001). No differences in RSE performance were observed between any of the conditions (P > 0.05). Interestingly, an elevated neuromuscular activity was seen in response to the BFR, particularly during conditions of systemic hypoxia (P < 0.05). Thus, RSE with BFR administered during rest periods under systemic hypoxia led to severe local hypoxia without compromising training workload.

Peripheral and Cerebral Vascular Reactivity in Black and White Women: Examining the Impact of Psychosocial Stress Exposure Versus Internalization and Coping.

Black women have the highest rates of cardiovascular and cerebrovascular disease prevalence and mortality in part due to blunted vascular function. Psychosocial stress likely also contributes but its relationship to vascular function remains incompletely understood. Recent studies suggest that internalization and coping strategies are more important than stress exposure alone. We hypothesized that Black women have blunted peripheral and cerebral vascular function and that, among Black women, this would be inversely related with psychosocial stress internalization/coping but not stress exposures. Healthy Black ( n = 21; 20 ± 2 yr) and White ( n = 16; 25 ± 7 yr) women underwent testing for forearm reactive hyperemia (RH), brachial artery flow-mediated dilation (FMD), and cerebrovascular reactivity (CVR). Psychosocial stress exposure (adverse childhood experiences, ACEs; past week discrimination, PWD) and internalization/coping techniques (John Henryism Active Coping Scale, JHAC12; Giscombe Superwoman Schema Questionnaire, G-SWS-Q) were assessed. RH and CVR ( p > 0.05) were not different between groups whereas FMD was lower in Black women ( p = 0.007). Neither ACEs nor PWD were associated with FMD in either group ( p > 0.05 for all). JHAC12 scores were negatively associated with FMD in Black women ( p = 0.014) but positively associated with FMD in White women ( p = 0.042). SWS-Succeed was negatively associated ( p = 0.044) and SWS-Vulnerable tended to be negatively associated ( p = 0.057) with FMD in Black women. These findings indicate that blunted FMD in Black women may be due more to internalization and maladaptive coping than stress exposure alone.

Epinephrine iontophoresis attenuates changes in skin blood flow and abolishes cutaneous contamination of near-infrared diffuse correlation spectroscopy estimations of muscle perfusion.

Near-infrared diffuse correlation spectroscopy (NIR-DCS) is an optical imaging technique for measuring relative changes in skeletal muscle microvascular perfusion (i.e., fold change above baseline) during reactive hyperemia testing and exercise and is reported as a blood flow index (BFI). Although it is generally accepted that changes in BFI are primarily driven by changes in muscle perfusion, it is well known that large, hyperthermia-induced changes in cutaneous blood flow can uncouple this relationship. What remains unknown, is how much of an impact that changes in cutaneous perfusion have on NIR-DCS BFI and estimates of skeletal muscle perfusion under thermoneutral conditions, where changes in cutaneous blood flow are assumed to be relatively low. We therefore used epinephrine iontophoresis to pharmacologically block changes in cutaneous perfusion throughout a battery of experimental procedures. The data show that 1) epinephrine iontophoresis attenuates changes in cutaneous perfusion for up to 4-h posttreatment, even in the face of significant neural and local stimuli, 2) under thermoneutral conditions, cutaneous perfusion does not significantly impact NIR-DCS BFI during reactive hyperemia testing or moderate-intensity exercise, and 3) during passive whole body heat stress, when cutaneous vasodilation is pronounced, epinephrine iontophoresis preserves NIR-DCS measures of skeletal muscle BFI during moderate-intensity exercise. Collectively, these data suggest that cutaneous perfusion is unlikely to have a major impact on NIR-DCS estimates of skeletal muscle BFI under thermoneutral conditions, but that epinephrine iontophoresis can be used to abolish cutaneous contamination of the NIR-DCS BFI signal during studies where skin blood flow may be elevated but skeletal muscle perfusion is of specific interest.

Exercise Leg Blood Flow Is Preserved in Long-term Breast Cancer Survivors Previously Treated With Anthracycline Chemotherapy.

PURPOSE: The objective of this investigation was to compare the acute hemodynamic responses during single-leg knee extension (SLKE) exercise between female breast cancer (BC) survivors previously treated with anthracycline chemotherapy and age- and sex-matched control (CON) subjects. METHODS: Fourteen BC survivors (age: 61 ± 7 yr; time post-anthracycline therapy: 12 ± 6 yr) and nine CON subjects (age: 59 ± 7 yr) performed SLKE exercise at 25%, 50%, and 75% of peak power output during which heart rate, blood pressure (BP), leg blood flow (Doppler ultrasonography), and vascular conductance (leg blood flow/mean BP) were measured. Quadriceps mass was estimated from thigh volume and skinfold measures. RESULTS: Breast cancer survivors had lower quadriceps mass compared with CON subjects (1803 ± 607 vs 2601 ± 1102 g, P = .04). No difference was found between groups for maximal SLKE power output (28 ± 11 vs 34 ± 17 W, P = .35), heart rate (109 ± 14 vs 103 ± 13 bpm, P = .36), or mean arterial BP (122 ± 18 vs 119 ± 26 mm Hg, P = .33). Rest and submaximal exercise mean arterial BP, leg blood flow (indexed to quadriceps muscle mass), and leg vascular conductance were not significantly different between BC survivors and CON subjects. CONCLUSION: Leg blood flow during submaximal SLKE exercise is preserved in long-term BC survivors previously treated with anthracycline chemotherapy.

On the use and misuse of cerebral hemodynamics terminology using transcranial Doppler ultrasound: a call for standardization.

Cerebral hemodynamics, e.g., cerebral blood flow, can be measured and quantified using many different methods, with transcranial Doppler ultrasound (TCD) being one of the most commonly used approaches. In human physiology, the terminology used to describe metrics of cerebral hemodynamics are inconsistent and in some instances technically inaccurate; this is especially true when evaluating, reporting, and interpreting measures from TCD. Therefore, this perspective article presents recommended terminology when reporting cerebral hemodynamic data. We discuss the current use and misuse of the terminology in the context of using TCD to measure and quantify cerebral hemodynamics and present our rationale and consensus on the terminology that we recommend moving forward. For example, one recommendation is to discontinue the use of the term "cerebral blood flow velocity" in favor of "cerebral blood velocity" with precise indication of the vessel of interest. We also recommend clarity when differentiating between discrete cerebrovascular regulatory mechanisms, namely, cerebral autoregulation, neurovascular coupling, and cerebrovascular reactivity. This will be a useful guide for investigators in the field of cerebral hemodynamics research.

The impact of a plant-based diet on indices of cardiovascular health in African Americans: a cross-sectional study.

African-American (AA) individuals are disproportionately affected by cardiovascular diseases. Plant-based diets (PBD) may be cardioprotective in part through their high antioxidant capacity and low inflammatory load. We tested the hypothesis that AA individuals adhering to a 100% PBD would have better vascular health than AA individuals following a typical American diet (TAD). Eighteen AA individuals participated; 9 (24 ± 4 years; 6 females) were following a PBD for 2.4 ± 0.8 years and 9 (21 ± 2 years; 5 females) were following a TAD. Blood lipids and C-reactive protein (CRP) were assessed. Peripheral and central blood pressure (BP) were measured, and vascular function tests included cerebrovascular reactivity to hypercapnia, brachial artery flow-mediated dilation and reactive hyperemia, and local heating-induced cutaneous hyperemia. Total (TC) and low-density lipoprotein (LDL-C) serum cholesterol was lower (TC: 142 ± 30 vs. 174 ± 36 mg/dL; LDL-C: 76 ± 17 vs. 106 ± 33 mg/dL; p < 0.05 and d > 0.80 for both) and serum CRP tended to be lower (0.38 ± 0.18 mg/L vs. 0.96 ± 0.89 mg/L; p = 0.05, d = 0.91) in the PBD cohort. Brachial (b) and central (c) mean arterial BP (MAP) were lower in the PBD cohort (bMAP: 86 ± 5 vs. 91 ± 7 mm Hg; cMAP: 81 ± 5 vs. 87 ± 7 mm Hg; p < 0.05 and d > 0.80 for both). All indices of vascular function were similar between groups (p > 0.05 for all). A PBD was associated with more optimal blood lipid concentrations and decreased peripheral and central BP in AA individuals, but this association was not present in the various indices of vascular function. Registered at ClinicalTrials.gov: NCT05344287.

Young, non-Hispanic Black men and women exhibit divergent peripheral and cerebral vascular reactivity.

NEW FINDINGS: What is the central question of the study? Do peripheral and cerebral vascular function differ between young non-Hispanic Black men and women? What is the main finding and its importance? The non-Hispanic Black women in this study presented greater peripheral conduit artery and cerebrovascular reactivity, yet similar peripheral microvascular function relative to the non-Hispanic Black men. These preliminary findings suggest that young Black women and men possess divergent vascular function, possibly contributing to the unique non-Hispanic Black sex differences in cardiovascular and cerebrovascular diseases. ABSTRACT: In the USA, cardiovascular and cerebrovascular diseases remain more prominent in the non-Hispanic Black (BL) population relative to other racial/ethnic groups. Typically, sex differences emerge in the manifestation of these diseases, though these differences may not fully materialize in the BL population. While numerous mechanisms are implicated, differences in vascular function likely contribute. Research has demonstrated blunted vasodilatation in several vascular regions in BL versus non-Hispanic White individuals, though much of this work did not assess sex differences. Therefore, this study aimed to ascertain if indices of vascular function are different between young BL women (BW) and men (BM). Eleven BW and 15 BM (22 (4) vs. 23 (3) years) participated in this study. Each participant underwent testing for brachial artery flow-mediated dilatation (FMD), post-occlusive reactive hyperaemia and cerebral vasomotor reactivity during rebreathing-induced hypercapnia. BW exhibited greater adjusted FMD than BM (P < 0.05 for all), but similar or lower reactive hyperaemia when assessed as blood velocity (P > 0.39 for all) or blood flow reactivity (P < 0.05 for all), respectively. Across a range of hypercapnia, BW had greater middle cerebral artery blood velocity and cerebrovascular conductance index than BM (P < 0.001 for both). These preliminary data suggest that young BW have greater vascular function relative to young BM, though this was inconsistent across different indices. These findings provide insight into the divergent epidemiological findings between BM and BW. Further research is needed to elucidate possible mechanisms and relate these physiological responses to epidemiological observations.

Validity of transcranial Doppler ultrasonography-determined dynamic cerebral autoregulation estimated using transfer function analysis.

Transcranial Doppler ultrasonography (TCD) is used widely to evaluate dynamic cerebral autoregulation (dCA). However, the validity of TCD-determined dCA remains unknown because TCD is only capable of measuring blood velocity and thus only provides an index as opposed to true blood flow. To test the validity of TCD-determined dCA, in nine healthy subjects, dCA was evaluated by transfer function analysis (TFA) using cerebral blood flow (CBF) or TCD-measured cerebral blood velocity during a perturbation that induces reductions in TCD-determined dCA, lower body negative pressure (LBNP) at two different stages: LBNP - 15 mmHg and - 50 mmHg. Internal carotid artery blood flow (ICA Q) was assessed as an index of CBF using duplex Doppler ultrasound. The TFA low frequency (LF) normalized gain (ngain) calculated using ICA Q increased during LBNP at - 50 mmHg (LBNP50) from rest (P = 0.005) and LBNP at - 15 mmHg (LBNP15) (P = 0.015), indicating an impaired dCA. These responses were the same as those obtained using TCD-measured cerebral blood velocity (from rest and LBNP15; P = 0.001 and P = 0.015). In addition, the ICA Q-determined TFA LF ngain from rest to LBNP50 was significantly correlated with TCD-determined TFA LF ngain (r = 0.460, P = 0.016) despite a low intraclass correlation coefficient. Moreover, in the Bland-Altman analysis, the difference in the TFA LF ngains determined by blood flow and velocity was within the margin of error, indicating that the two measurement methods can be interpreted as equivalent. These findings suggest that TCD-determined dCA can be representative of actual dCA evaluated with CBF.

Contributions of endothelin-1 and l-arginine to blunted cutaneous microvascular function in young, black women.

Non-Hispanic black (BL) individuals have the greatest prevalence of cardiovascular disease (CVD), relative to other racial/ethnic groups (e.g., non-Hispanic white population; WH), which may be secondary to blunted vascular function. Although women typically present with reduced CVD relative to men of the same racial/ethnic group, the prevalence is similar between BL women and men though the mechanisms differ. This study hypothesized that reduced microvascular function in young, BL women is associated with endothelin-1 (ET-1) overactivity or insufficient l-arginine bioavailability. Nine BL and nine WH women participated (age: 20 ± 2 vs. 22 ± 2 yr). Cutaneous microvascular function was assessed during 39°C local heating, whereas lactated Ringer's (control), BQ-123 (ET-1 receptor type A antagonist), BQ-788 (ET-1 receptor type B antagonist), or l-arginine were infused via intradermal microdialysis to modify cutaneous vascular conductance (CVC). Subsequent infusion of Nω-nitro-l-arginine methyl ester allowed for quantification of the nitric oxide (NO) contribution to vasodilation, whereas combined sodium nitroprusside and 43°C heating allowed for normalization to maximal CVC (%CVCmax). BL women had blunted %CVCmax and NO contribution to dilation during the 39°C plateau (P < 0.027 for both). BQ-123 improved this response through augmented NO-mediated dilation (P < 0.048 for both). BQ-788 and l-arginine did not alter the CVC responses (P > 0.835 for both) or the NO contribution (P > 0.371 for both). Cutaneous microvascular function is reduced in BL women, and ET-1 receptor type A may contribute to this reduced function. Further research is needed to better characterize these mechanisms in young, BL women.NEW & NOTEWORTHY Cardiovascular disease remains a burden in the United States non-Hispanic black (BL) population, although its manifestation through blunted vasodilation in this population is different between men and women. Accordingly, this study determined that reduced microvascular function in young, BL women may be partially controlled by endothelin-1 (ET-1) type A receptors, although neither type B receptors nor insufficient l-arginine bioavailability seems to contribute to this response. Accordingly, further research is needed to better characterize these ET-1 related mechanisms and illuminate other pathways that may contribute to this disparate vascular function in young, BL women.

Impact of cutaneous blood flow on NIR-DCS measures of skeletal muscle blood flow index.

Near-infrared diffuse correlation spectroscopy (NIR-DCS) is an optical technique for estimating relative changes in skeletal muscle perfusion during exercise but may be affected by changes in cutaneous blood flow, as photons emitted by the laser must first pass through the skin. Accordingly, the purpose of this investigation was to examine how increased cutaneous blood flow affects NIR-DCS blood flow index (BFI) at rest and during exercise using a passive whole body heating protocol that increases cutaneous, but not skeletal muscle, perfusion in the uncovered limb. BFI and cutaneous perfusion (laser-Doppler flowmetry) were assessed in 15 healthy young subjects before (e.g., rest) and during 5 min of moderate-intensity handgrip exercise in normothermic conditions and after cutaneous blood flow was elevated via whole body heating. Hyperthermia significantly increased both cutaneous perfusion (∼7.3-fold; P ≤ 0.001) and NIR-DCS BFI (∼4.5-fold; P ≤ 0.001). Although relative BFI (i.e., fold-change above baseline) exhibited a typical exponential increase in muscle perfusion during normothermic exercise (2.81 ± 0.95), there was almost no change in BFI during hyperthermic exercise (1.43 ± 0.44). A subset of eight subjects were subsequently treated with intradermal injection of botulinum toxin-A (Botox) to block heating-induced elevations in cutaneous blood flow, which 1) nearly abolished the hyperthermia-induced increase in BFI and 2) restored BFI kinetics during hyperthermic exercise to values that were not different from normothermic exercise (P = 0.091). Collectively, our results demonstrate that cutaneous blood flow can have a substantial, detrimental impact on NIR-DCS estimates of skeletal muscle perfusion and highlight the need for technical and/or pharmacological advancements to overcome this issue moving forward.NEW & NOTEWORTHY We used passive whole body heat stress, in combination with local intradermal botulinum toxin type A treatment, to experimentally manipulate cutaneous blood flow and investigate its impact on NIR-DCS measures of skeletal muscle BFI at rest and during exercise. Collectively, the results show that cutaneous blood flow, which was augmented in response to passive whole body heat stress, markedly affects NIR-DCS-derived BFI, such that the BFI signal becomes dominated by changes in cutaneous red blood cell flux.

Global Reach 2018: Nitric oxide-mediated cutaneous vasodilation is reduced in chronic, but not acute, hypoxia independently of enzymatic superoxide formation.

We tested the hypotheses that 1) cutaneous microvascular function is impaired by acute normobaric and chronic hypobaric hypoxia and 2) that the superoxide free radical (via NADPH oxidase or xanthine oxidase) contributes to this impairment via nitric oxide (NO) scavenging. Local heating-induced cutaneous hyperemia (39 °C) was measured in the forearm of 11 male lowlanders at sea level (SL) and following 14-18 days at high altitude (HA; 4340 m in Cerro de Pasco, Peru), and compared to 11 highlanders residing permanently at this elevation. Cutaneous vascular conductance (CVC; laser-Doppler flux/mean arterial pressure) was not different during 39 °C [control site: 73 (19) vs. 71 (18)%max; P = 0.68] between normoxia and acute normobaric hypoxia (FIO2 = 0.125; equivalent to HA), respectively. At HA, CVC was reduced during 39 °C in lowlanders compared to SL [control site: 54 (14) vs. 73 (19)%max; P < 0.01] and was lower in Andean highlanders compared to lowlanders at HA [control site: 50 (24) vs. 54 (14)%max; P = 0.02]. The NO contribution to vasodilation during 39 °C (i.e., effect of NO synthase inhibition) was reduced in lowlanders at HA compared to SL [control site: 41 (11) vs 49 (10)%max; P = 0.04] and in Andean highlanders compared to lowlanders at HA [control site: 32 (21) vs. 41 (11)%max; P = 0.01]. Intradermal administration (cutaneous microdialysis) of the superoxide mimetic Tempol, inhibition of xanthine oxidase (via allopurinol), or NADPH oxidase (via apocynin) had no influence on cutaneous endothelium-dependent dilation during any of the conditions (all main effects of drug P > 0.05). These results suggest that time at HA impairs NO-mediated cutaneous vasodilation independent of enzymatic superoxide formation.

Blunted hyperemic response to mental stress in young, non-Hispanic black men is not impacted by acute dietary nitrate supplementation.

Non-Hispanic black individuals suffer from an elevated prevalence of hypertension and cardiovascular disease (CVD) relative to other populations. This elevated disease risk is, in large part, related to impaired vascular function, secondary to reduced nitric oxide (NO) bioavailability. Emerging evidence suggests that dietary nitrate supplementation improves several cardiovascular parameters, including vascular function, in part by increased NO bioavailability. However, whether these findings extend to a population of black individuals is unknown. This study tested the hypothesis that forearm blood flow responses in young, non-Hispanic, black (BL) men during a mental stress challenge would be blunted relative to young, non-Hispanic, white (WH) men. We further hypothesized that acute dietary nitrate supplementation would improve this response in BL men. This study comprised two parts (phase 1 and phase 2). Phase 1 investigated the difference in blood flow responses between young, BL, and WH men. In contrast, phase 2 investigated the effect of acute nitrate supplementation on the responses in a subset of the BL men from phase 1. Eleven (nine for phase 2) BL and eight WH men (23 ± 3 vs. 24 ± 4 yr, respectively) participated in this double-blind, placebo-controlled, randomized, crossover study. During each visit, hemodynamic responses during 3 min of mental stress were assessed in the brachial artery using duplex Doppler ultrasound. Phase 1 was completed in one visit, whereas phase 2 was completed over two visits separated by ∼1 wk. During phase 2, data were collected before and 2-h postconsumption of a beverage either high in nitrate content or nitrate depleted. In phase 1, peak forearm blood flow (FBF; P < 0.001), total FBF (P < 0.01), and forearm vascular conductance (FVC; P < 0.001) were blunted in the BL. During phase 2, prebeverage responses were similar to phase 1 and were unaffected following beverage consumption (P > 0.05 vs. prebeverage for all variables). These data indicate that young, BL men have blunted microvascular vasodilatory responses to acute mental stress, which may not be altered following acute nitrate supplementation.NEW & NOTEWORTHY This study tested the hypothesis that non-Hispanic black (BL) men have a blunted forearm hyperemic response to mental stress, which would be augmented following acute nitrate supplementation. The increase in forearm blood flow during mental stress was attenuated in BL men and was not impacted by nitrate supplementation. This supports findings of altered vascular function in this population. This is especially important as BL experience a higher prevalence of stress, which contributes to CVD risk.

Effects of acute interval handgrip exercise on cognitive performance.

Previous studies have reported that even a single bout of dynamic exercise improves cognitive performance. However, the acute effect of the interval handgrip (HG) exercise protocol, which is effective in reducing resting blood pressure, on cognitive performance is poorly understood. Cognitive performance was assessed in 17 young healthy subjects before and after a resting control (e.g., time control) and the interval HG exercise (Exercise), which consisted of four trials of 2-min HG exercise at 25% of maximum voluntary contraction with 3-min recovery in between each trial. Mean arterial blood pressure (MAP) and middle cerebral artery blood velocity (MCA V) were measured continuously throughout the experiment. Memory recognition and executive function were assessed using memory recognition and Go/No-Go tasks, respectively. During interval HG exercise, MAP and mean MCA V increased from the resting baseline condition (both P < 0.049) and returned to the resting baseline levels during recovery after the interval HG exercise (both P = 1.000). The reaction time and performance accuracy of the memory recognition task did not change in either the time control condition or Exercise condition (P = 0.514 and P = 0.414 respectively). However, the changes in reaction time of Go/No-Go task from the baseline in Exercise condition was significantly shorter than that in time-control condition (P = 0.004) without affecting performance accuracy (P = 0.482). The results of the present study show that an acute interval HG exercise could improve the processing speed in executive function despite no post-exercise improvement in hemodynamic parameters in young healthy subjects. These findings suggest that the interval HG exercise is a useful exercise mode that can be expected to have a positive effect on the processing speed in executive function regardless of cardiovascular adaptation to exercise.

Attenuated Rapid-Onset Vasodilation to Forearm Muscle Contraction in Black Men.

PURPOSE: Non-Hispanic Black individuals have a blunted ability to vasodilate at rest compared with other racial groups. Limited studies have investigated blood flow responses to exercise in Black individuals. Recently, our laboratory demonstrated that Black men exhibit attenuated increases in forearm vascular conductance (FVC) during steady-state rhythmic handgrip. The mechanisms for this remain unknown. Herein, we used single muscle contractions, a modality that allows for assessment of rapid-onset vasodilation (ROV) independent of major elevations in shear stress, tissue metabolism, and systemic hemodynamics. METHODS: Ten young, healthy Black and White men performed single forearm contractions at 20%, 40%, and 60% maximal voluntary contraction (MVC). In addition, cuff inflations were performed on the forearm to examine the contribution of mechanical compression to ROV. Forearm blood flow (FBF; duplex Doppler ultrasound), heart rate (ECG), and mean arterial pressure (Finometer) were continuously measured. FVC was calculated as FBF/mean arterial pressure. RESULTS: Baseline FVC (White men vs Black men, 0.75 ± 0.11 vs 0.80 ± 0.09 mL·min-1·mm Hg-1; P = 0.73), FBF, and MVCs (White men vs Black men, 54 ± 2 vs 54 ± 2 kg; P = 0.95) were similar between the groups. After single contractions, both groups exhibited intensity-dependent FVC and FBF increases during ROV; however, these responses were attenuated in the Black group at all intensities (e.g., 60%MVC FVC: White men vs Black men, +371% ± 37% vs +220% ± 23% baseline; P = 0.001). FVC and FBF responses to cuff inflation alone were also attenuated in Black individuals (P < 0.001). CONCLUSIONS: Collectively, these data indicate that Black men have an overall blunted ability to rapidly vasodilate compared with young White men.

Influence of sex on heightened vasoconstrictor mechanisms in the non-Hispanic black population.

Cardiovascular disease (CVD) affects individuals of all races and ethnicities; however, its prevalence is highest in non-Hispanic black individuals (BL) relative to other populations. While previous research has provided valuable insight into elevated CVD risk in the BL population, this work has been almost exclusively conducted in men. This is alarming given that BL women suffer from CVD at an equivalent rate to BL men and each has a greater prevalence when compared to all other ethnicities, regardless of sex. The importance of investigating sex differences in mechanisms of cardiovascular function is highlighted by the National Institute of Health requiring sex to be considered as a biological variable in research studies to better our "understanding of key sex influences on health processes and outcomes." The mechanism(s) responsible for the elevated CVD risk in BL women remains unclear and is likely multifactorial. Limited studies in BL women suggest that, while impaired vasodilator capacity is involved, heightened vasoconstrictor tone and/or responsiveness may also contribute. Within this mini-review, we will discuss potential mechanisms of elevated rates of hypertension and other CVDs in BL individuals with a particular focus on young, otherwise healthy, college-aged women. To stimulate academic thought and future research, we will also discuss potential mechanisms for impaired vascular function in BL women, as well as possible divergent mechanisms between BL men and women based on either preliminary data or plausible speculation extending from findings in the existing literature. Last, we will conclude with potential future research directions aimed at better understanding the elevated risk for hypertension and CVD in BL women.