Cardiorespiratory responses to high-intensity skeletal muscle metaboreflex activation in chronic obstructive pulmonary disease.

Background: Augmented skeletal muscle metaboreflex activation may accompany chronic obstructive pulmonary disease (COPD). The maintained metaboreflex control of mean arterial pressure (MAP) that has been reported may reflect limited evaluation using only one moderate bout of static handgrip (HG) and following postexercise ischaemia (PEI).

Objective: We tested the hypothesis that cardiovascular and respiratory responses to high-intensity static HG and isolated metaboreflex activation during PEI are augmented in COPD patients.

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.

Functional sympatholysis is preserved in healthy young Black men during rhythmic handgrip exercise.

Black men have attenuated increases in forearm vascular conductance (FVC) and forearm blood flow (FBF) during moderate- and high-intensity rhythmic handgrip exercise compared with White men, but the underlying mechanisms are unclear. Here, we tested for the first time the hypothesis that functional sympatholysis (i.e.

Augmented resting beat-to-beat blood pressure variability in young, healthy, non-Hispanic black men.

New Findings: What is the central question of this study? The prevalence of hypertension in black individuals exceeds that in other racial groups. Despite this well-known heightened risk, the underlying contributory factors remain incompletely understood. We hypothesized that young black men would exhibit augmented beat-to-beat blood pressure variability compared with white men and that black men would exhibit augmented total peripheral resistance variability.

Muscle pump-induced inhibition of sympathetic vasomotor outflow during low-intensity leg cycling is attenuated by muscle metaboreflex activation.

Muscle sympathetic nerve activity (MSNA) decreases during leg cycling at low intensity because of muscle pump-induced increases in venous return and loading of the cardiopulmonary baroreceptors. However, MSNA increases during leg cycling when exercise is above moderate intensity or for a long duration, suggesting that the sympathoinhibitory effect of the cardiopulmonary baroreflex can be overridden by a powerful sympathoexcitatory drive, such as the skeletal muscle metaboreflex. Therefore, we tested the hypothesis that high-intensity muscle metaboreflex activation attenuates muscle pump-induced inhibition of MSNA during leg cycling.

Effect of acute high-phosphate intake on muscle metaboreflex activation and vascular function.

Increased consumption of inorganic phosphate (Pi), an abundant ingredient in processed foods, has been associated with elevated cardiovascular disease risk; however, studies investigating underlying mechanisms are limited. Recently, high dietary Pi was shown to exaggerate the pressor response to static muscle contraction in rodents in part because of overactivation of metabolically sensitive skeletal muscle afferents. Whether acute high Pi consumption affects muscle metaboreflex activation in humans remains unknown.

Sex differences in the contribution of blood pressure to acute changes in aortic augmentation index.

Augmentation index (AIx), derived from aortic pulse waveform, is related to arterial stiffness and increased cardiac workload. Sex differences were observed in the relationship between blood pressure (BP) and AIx at rest. In addition, positive correlation between BP and AIx in men during a pressor stimulus was observed previously.

Regulation of regional cerebral blood flow during graded reflex-mediated sympathetic activation via lower body negative pressure.

The role of the sympathetic nervous system in cerebral blood flow (CBF) regulation remains unclear. Previous studies have primarily measured middle cerebral artery blood velocity to assess CBF. Recently, there has been a transition toward measuring internal carotid artery (ICA) and vertebral artery (VA) blood flow using duplex Doppler ultrasound.

Attenuated forearm vascular conductance responses to rhythmic handgrip in young African-American compared with Caucasian-American men.

Previous studies have demonstrated that African-American (AA) individuals have heightened vasoconstrictor and reduced vasodilator responses under resting conditions compared with Caucasian-American (CA) individuals. However, potential differences in vascular responses to exercise remain unclear. Therefore, we tested the hypothesis that, compared with CA subjects, AA subjects would present an attenuated increase in forearm vascular conductance (FVC) during rhythmic handgrip exercise.

Absent increase in vertebral artery blood flow during l-arginine infusion in hypertensive men.

Endothelial dysfunction is observed in the peripheral vasculature of hypertensive patients, but it is unclear how the cerebral circulation is affected. More specifically, little is known about the impact of human hypertension on vertebral artery (VA) endothelial function. This study evaluated whether the endothelial function of the VA is impaired in hypertensive men.

Capsaicin-based analgesic balm attenuates the skeletal muscle metaboreflex in healthy humans.

The exercise pressor reflex (EPR) is comprised of group III and IV skeletal muscle afferents and is one of the principal mediators of the cardiovascular response to exercise. In animals, capsaicin-based analgesic balm (CAP) attenuates the pressor response to muscle contraction, indicating the transient receptor potential vanilloid 1 (TRPv1) receptor (localized on the group IV afferent neuron) as an important mediator of the EPR. However, whether these findings can be extrapolated to humans remains unknown.

High-intensity muscle metaboreflex activation attenuates cardiopulmonary baroreflex-mediated inhibition of muscle sympathetic nerve activity.

Previous studies have shown that muscle sympathetic nerve activity (MSNA) is reduced during low- and mild-intensity dynamic leg exercise. It has been suggested that such inhibition is mediated by loading of the cardiopulmonary baroreceptors and that this effect is overridden by muscle metaboreflex activation with higher-intensity exercise. However, limited data are available regarding the interaction between the cardiopulmonary baroreflex and the muscle metaboreflex.

Insulin increases ventilation during euglycemia in humans.

Evidence from animal studies indicates that hyperinsulinemia, without changes in glucose, increases ventilation via a carotid body-mediated mechanism. However, whether insulin elevates ventilation in humans independently of changes in glucose remains unclear. Therefore, we tested the hypothesis that insulin increases ventilation in humans during a hyperinsulinemic-euglycemic clamp in which insulin was elevated to postprandial concentrations while glucose was maintained at fasting concentrations.

Cardiovascular response to trigeminal nerve stimulation at rest and during exercise in humans: does sex matter?

We sought to investigate the possibility that there are sex differences in the cardiovascular responses to trigeminal nerve stimulation (TGS) with cold exposure to the face at rest and during dynamic exercise. In 9 healthy men (age: 28 ± 3 yr; height: 178 ± 1 cm; weight: 77 ± 8 kg) and 13 women (age 26 ± 5 yr; height 164 ± 3 cm; weight 63 ± 7 kg) beat-to-beat heart rate (HR) and blood pressure were recorded. Mean arterial pressure (MAP), stroke volume (SV), cardiac index (CI), and total vascular resistance index (TVRI) were calculated.

Exaggerated Vasoconstriction to Spontaneous Bursts of Muscle Sympathetic Nerve Activity in Healthy Young Black Men.

Blacks have the highest prevalence of hypertension, putting them at greater risk of cardiovascular disease and death. Previous studies have reported that, relative to whites, healthy black men have augmented pressor responses to sympathoexcitatory stressors. Although important, these studies do not inform about the resting state and the influence of spontaneous changes in resting muscle sympathetic nerve activity (MSNA).

Adults with initial metabolic syndrome have altered muscle deoxygenation during incremental exercise.

Objective: Reduced aerobic power is independently associated with metabolic syndrome (MetS) incidence and prevalence in adults. This study investigated whether muscle deoxygenation (proxy of microvascular O extraction) during incremental exercise is altered in MetS and associated with reduced oxygen consumption ( V˙O ).

Methods: Twelve men with initial MetS (no overt diseases and medication-naive; mean ± SD, age 38 ± 7 years) and 12 healthy controls (HCs) (34 ± 7 years) completed an incremental cycling test to exhaustion, in which pulmonary ventilation and gas exchange (metabolic analyzer), as well as vastus lateralis deoxygenation (near infrared spectroscopy), were measured.

Effects of face cooling on pulse waveform and sympathetic activity in hypertensive subjects.

Adverse cardiovascular events occur more frequently during cold weather. To test the hypothesis that cold exposure would lead to increased sympathetic activity and impaired hemodynamic control, we measured muscle sympathetic nerve activity and hemodynamic parameters in nine men with hypertension before and during trigeminal stimulation and facial cooling. The procedure increased blood pressure (p < 0.

Carotid baroreflex function at the onset of cycling in men.

Arterial baroreflex function is important for blood pressure control during exercise, but its contribution to cardiovascular adjustments at the onset of cycling exercise remains unclear. Fifteen healthy male subjects (24 ± 1 yr) performed 45-s trials of low- and moderate-intensity cycling, with carotid baroreceptor stimulation by neck suction at -60 Torr applied 0-5, 10-15, and 30-35 s after the onset of exercise. Cardiovascular responses to neck suction during cycling were compared with those obtained at rest.

Relationship between aortic augmentation index and blood pressure during metaboreflex activation in healthy young men.

Background: Heightened aortic augmentation index (AIx; surrogate of arterial stiffness) is associated with an elevated risk of cardiovascular events; however, it is currently unclear whether peripheral blood pressure (BP) modulates AIx.

Aim: Given this, we studied the relationship between AIx and BP under resting conditions as well as during skeletal muscle metaboreflex activation, which is a maneuver that generates steady elevations in BP.

Methods: In nine healthy male participants (23±2 years), the graded activation of the muscle metaboreflex was achieved by postexercise ischemia (PEI) following moderate and high-intensity static handgrip performed at 30 and 40% maximum voluntary contraction.

Intrathecal fentanyl abolishes the exaggerated blood pressure response to cycling in hypertensive men.

The increase in blood pressure observed during physical activities is exaggerated in patients with hypertension, exposing them to a higher cardiovascular risk. Neural signals from the skeletal muscles appear to be overactive, resulting in this abnormal response in hypertensive patients. In the present study, we tested whether the attenuation of these neural signals in hypertensive patients could normalize their abnormal increase in blood pressure during physical activity.

Oscillatory blood pressure response to the onset of cycling exercise in men: role of group III/IV muscle afferents.

What is the central question of this study? Neural feedback from group III/IV muscle afferents has a key role in regulation of cardiovascular responses to exercise. Blood pressure oscillates in the first seconds of dynamic exercise, but the contribution of muscle afferent feedback to this pattern is unclear. What is the main finding and its importance? We demonstrate that attenuation of group III/IV muscle afferent feedback by spinal fentanyl impairs the pressor response after 10 s of moderate leg cycling exercise, but this afferent feedback does not appear to be necessary for induction of the oscillatory pattern of blood pressure at the onset of exercise.

Diving and exercise: the interaction of trigeminal receptors and muscle metaboreceptors on muscle sympathetic nerve activity in humans.

Swimming involves muscular activity and submersion, creating a conflict of autonomic reflexes elicited by the trigeminal receptors and skeletal muscle afferents. We sought to determine the autonomic cardiovascular responses to separate and concurrent stimulation of the trigeminal cutaneous receptors and metabolically sensitive skeletal muscle afferents (muscle metaboreflex). In eight healthy men (30 ± 2 yr) muscle sympathetic nerve activity (MSNA; microneurography), mean arterial pressure (MAP; Finometer), femoral artery blood flow (duplex Doppler ultrasonography), and femoral vascular conductance (femoral artery blood flow/MAP) were assessed during the following three experimental conditions: 1) facial cooling (trigeminal nerve stimulation), 2) postexercise ischemia (PEI; muscle metaboreflex activation) following isometric handgrip, and 3) trigeminal nerve stimulation with concurrent PEI.