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Clare Minahan, Hailey O'Neill, Nelie Sikkema, Sarah Joyce, Brianna Larsen, Surendran Sabapathy
We sought to determine whether oral contraception alters the gender-related differences observed in the exercise pressor reflex during isometric handgrip exercise. Fifteen men, fifteen normally menstruating women (WomenNM), and fifteen women taking monophasic oral contraceptives (WomenOC) completed two trials of a 3-min isometric handgrip exercise protocol performed at 30% of their maximal voluntary contraction: (1) where arterial occlusion was applied to the previously exercising arm during a 3-min recovery period (Occlusion trial); (2) where no arterial occlusion was applied during recovery (Control trial)...
March 2018: Physiological Reports
Ken D O'Halloran
Respiratory muscle metaboreflexes exert substantial influence over cardiorespiratory and autonomic control, exemplified during heavy dynamic exercise in health, and in obstructive airways disease even at rest. This article is protected by copyright. All rights reserved.
February 5, 2018: Experimental Physiology
André L Teixeira, Mauricio Daher, Mayara Souza, Plinio Santos Ramos, James P Fisher, Lauro C Vianna
Isolated muscle metaboreflex activation with post-handgrip exercise ischemia (PEI) increases sympathetic nerve activity and partially maintains the exercise-induced increase in blood pressure, but a smaller heart rate (HR) response occurs. The cardiopulmonary baroreceptors, mechanically sensitive receptors that respond to changes in central blood volume and pressure, are strongly associated with changes in body position and upon activation elicit reflex sympathoinhibition. Here, we tested the hypothesis that postural changes modulate the sympathetically-mediated cardiac response to PEI in humans...
December 15, 2017: American Journal of Physiology. Heart and Circulatory Physiology
Keisho Katayama, Joshua R Smith, Kanako Goto, Kaori Shimizu, Mitsuru Saito, Koji Ishida, Teruhiko Koike, Satoshi Iwase, Craig A Harms
We compared changes in muscle sympathetic nerve activity (MSNA) and cardiovascular variables during leg cycle exercise with increased inspiratory muscle resistance in men and women. We hypothesized that sympathetic vasomotor outflow during exercise with increased inspiratory resistance would be attenuated in young women compared with age-matched men. Eight women and seven men completed the study. The subjects performed two 10-min exercise bouts at 40% peak oxygen uptake using a cycle ergometer in a semirecumbent position [spontaneous breathing for 5 min and voluntary hyperventilation with or without inspiratory resistive breathing for 5 min (breathing frequency: 50 breaths min-1 with a 50% duty cycle, inspiratory resistance: 30% of maximal inspiratory pressure)]...
January 15, 2018: Experimental Physiology
Daniel Boulton, Chloe E Taylor, Simon Green, Vaughan G Macefield
Both central command and metaboreflex inputs from contracting muscles increase muscle sympathetic nerve activity (MSNA) to non-contracting muscle during sustained isometric exercise. We recently showed that MSNA to contracting muscle also increases in an intensity-dependent manner, but whether this can be sustained by the metaboreflex is unknown. MSNA was recorded from the left common peroneal nerve and spikes of MSNA extracted. Eleven subjects performed a series of four-minute dorsiflexions of the left ankle at 10% of maximum voluntary contraction under three conditions: without ischaemia, with 6 min of post-exercise ischaemia and with ischaemia during and after exercise; these were repeated in the right leg...
January 8, 2018: Journal of Physiology
Hanna R Parmar, Jasmin Sears, Yannick Molgat-Seon, Cara L McCulloch, Laura A McCracken, Courtney V Brown, Andrew William Sheel, Paolo B Dominelli
There are known sex-differences in blood pressure regulation. The differences are related to ovarian hormones that influence β-adrenergic receptors and the transduction of muscle sympathetic nerve activity. Oral contraceptives (OC) modulate the ovarian hormonal profile in women and therefore may alter the cardiovascular response. We questioned if OC would alter the absolute pressor response to static exercise and influence the day-to-day variability of the response. Healthy men (n=11) and women (n=19) completed a familiarization day and two experimental testing days...
December 5, 2017: Applied Physiology, Nutrition, and Metabolism, Physiologie Appliquée, Nutrition et Métabolisme
Sara Magnani, Silvana Roberto, Gianmarco Sainas, Raffaele Milia, Girolamo Palazzolo, Lucia Cugusi, Virginia Pinna, Azzurra Doneddu, Seyed Alireza Hosseini Kakhak, Filippo Tocco, Giuseppe Mercuro, Antonio Crisafulli
This study was devised to investigate the effect of coronary artery disease (CAD) without overt signs of heart failure on the cardiovascular responses to muscle metaboreflex activation. We hypothesized that any CAD-induced pre-clinical systolic and/or diastolic dysfunction could impair hemodynamic response to the metaboreflex test. Twelve males diagnosed with CAD without any sign or symptoms of heart failure and 11 age-matched healthy controls (CTL) participated in the study. Subjects performed a post-exercise muscle ischemia (PEMI) test to activate the metaboreflex...
November 10, 2017: American Journal of Physiology. Heart and Circulatory Physiology
Masashi Ichinose, Mayumi Matsumoto, Naoto Fujii, Narumi Yoshitake, Takeshi Nishiyasu
Voluntary apnea during dynamic exercise evokes marked bradycardia, peripheral vasoconstriction and pressor responses. However, the mechanism(s) underlying the cardiovascular responses seen during apnea in exercising humans is unknown. We therefore tested the hypothesis that the muscle metaboreflex contributes to the apnea-induced pressor response during dynamic exercise. Thirteen healthy subjects participated in apnea and control trials. In both trials, subjects performed a two-legged dynamic knee extension exercise at a workload that elicited heart rates around 100 beats/min...
November 3, 2017: American Journal of Physiology. Heart and Circulatory Physiology
Anthony V Incognito, Connor J Doherty, Jordan B Lee, Matthew J Burns, Philip J Millar
Negative and positive muscle sympathetic nerve activity (MSNA) responders have been observed during mental stress. We hypothesized that similar MSNA response patterns could be identified during the first minute of static handgrip and contribute to the inter-individual variability throughout exercise. Supine measurements of multi-unit MSNA (microneurography) and continuous blood pressure (Finometer) were recorded in 29 young healthy men during the first (HG1) and second (HG2) minute of static handgrip (30% maximal voluntary contraction) and subsequent post-exercise circulatory occlusion (PECO)...
October 25, 2017: American Journal of Physiology. Regulatory, Integrative and Comparative Physiology
Jasdeep Kaur, Danielle Senador, Abhinav C Krishnan, Hanna W Hanna, Alberto Alvarez, Tiago M Machado, Donal S O'Leary
When oxygen delivery to active muscle is insufficient to meet the metabolic demand during exercise, metabolites accumulate and stimulate skeletal muscle afferents inducing a reflex increase in blood pressure, termed the muscle metaboreflex. In healthy individuals, muscle metaboreflex activation (MMA) during submaximal exercise increases arterial pressure primarily via an increase in cardiac output (CO), as little peripheral vasoconstriction occurs. This increase in CO partially restores blood flow to ischemic muscle...
September 22, 2017: American Journal of Physiology. Heart and Circulatory Physiology
Pramita Dubey, Sunita Tiwari, Manish Bajpai, Kalpana Singh, Praveen Jha
INTRODUCTION: Metaboreflex is a reflex in which muscle receptors send signals regarding metabolic (metabolites accumulation like lactic acid, potassium, adenosine) conditions of the muscles to nucleus tractus solitarius via afferent III and IV fibres to cause haemodynamic adjustments in order to regulate blood flow on the basis of the status of contracting muscle. Dysregulation in its mechanism in metabolic syndrome is demonstrated. AIM: To study the effect of metaboreflex by both isometric and rhythmic handgrip exercise on CVS parameters {Blood Pressure (BP), Cardiac Output (CO) and Systemic Vascular Resistance (SVR)} in subjects of metabolic syndrome...
July 2017: Journal of Clinical and Diagnostic Research: JCDR
Antonio Crisafulli
Hemodynamics during dynamic exercise is finely regulated by some neural mechanisms. One of these mechanisms is the metabolic part of the exercise pressor reflex, i.e. the muscle metaboreflex. Hemodynamic response during the metaboreflex is characterised by the recruitment of the reserves in cardiac inotropism, pre-load, after-load and chronotropism. If one of these reserves is exhausted, then the cardiovascular response is achieved by recruiting one of the other reserves, thereby indicating a remarkable plasticity of the control of circulation...
August 4, 2017: Current Cardiology Reviews
Anthony V Incognito, Connor J Doherty, Jordan B Lee, Matthew J Burns, Philip J Millar
Ischemic preconditioning (IPC) has been hypothesized to elicit ergogenic effects by reducing feedback from metabolically sensitive group III/IV muscle afferents during exercise. If so, reflex efferent neural outflow should be attenuated. We investigated the effects of IPC on muscle sympathetic nerve activity (MSNA) during static handgrip (SHG) and used post-exercise circulatory occlusion (PECO) to isolate for the muscle metaboreflex. Thirty-seven healthy men (age: 24 ± 5 years [mean ± SD]) were randomized to receive sham (n = 16) or IPC (n = 21) interventions...
July 2017: Physiological Reports
Masashi Ichinose, Tomoko Ichinose-Kuwahara, Kazuhito Watanabe, Narihiko Kondo, Takeshi Nishiyasu
The purpose of the present study was to test our hypothesis that unloading the carotid baroreceptors alters the threshold and gain of the muscle metaboreflex in humans. Ten healthy subjects performed a static handgrip exercise at 50% of maximum voluntary contraction. Contraction was sustained for 15, 30, 45, and 60 s and was followed by 3 min of forearm circulatory arrest, during which forearm muscular pH is known to decrease linearly with increasing contraction time. The carotid baroreceptors were unloaded by applying 0...
September 1, 2017: American Journal of Physiology. Heart and Circulatory Physiology
Carli M Peters, Joseph F Welch, Paolo B Dominelli, Yannick Molgat-Seon, Lee M Romer, Donald C McKenzie, A William Sheel
What is the central question of this study? This study is the first to measure objectively both inspiratory and expiratory muscle fatigue after inspiratory resistive loading to determine whether the expiratory muscles are activated to the point of fatigue when specifically loading the inspiratory muscles. What is the main finding and its importance? The absence of abdominal muscle fatigue suggests that future studies attempting to understand the neural and circulatory consequences of diaphragm fatigue can use inspiratory resistive loading without considering the confounding effects of abdominal muscle fatigue...
June 24, 2017: Experimental Physiology
Bruno Archiza, Daniela Kuguimoto Andaku, Flávia Cristina Rossi Caruso, José Carlos Bonjorno, Cláudio Ricardo de Oliveira, Paula Angélica Ricci, André Capaldo do Amaral, Stela Márcia Mattiello, Cleiton Augusto Libardi, Shane A Phillips, Ross Arena, Audrey Borghi-Silva
This study was conducted to determine the effects of inspiratory muscle training (IMT) on respiratory and peripheral muscles oxygenation during a maximal exercise tolerance test and on repeated-sprint ability (RSA) performance in professional women football players. Eighteen athletes were randomly assigned to one of the following groups: SHAM (n = 8) or IMT (n = 10). After a maximal incremental exercise test, all participants performed (on a different day) a time-to-exhaustion (Tlim) test. Peripheral and respiratory muscles oxygenation by near-infrared spectroscopy, breath-by-breath ventilatory and metabolic variables, and blood lactate concentration were measured...
April 2018: Journal of Sports Sciences
Joshua R Smith, Kaylin D Didier, Shane M Hammer, Andrew M Alexander, Stephanie P Kurti, Steven W Copp, Thomas J Barstow, Craig A Harms
Inspiratory muscle metaboreflex activation increases mean arterial pressure (MAP) and limb vascular resistance (LVR) and decreases limb blood flow (Q̇L). Cyclooxygenase (COX) inhibition has been found to attenuate limb skeletal muscle metaboreflex-induced increases in muscle sympathetic nerve activity. We hypothesized that compared to placebo (PLA), COX inhibition would attenuate inspiratory muscle metaboreflex-induced 1) increases in MAP and LVR and 2) decreases in Q̇L Seven men (22±1 years) were recruited and orally consumed ibuprofen (IB, 10mg/kg) or PLA 90 min prior to performing the cold pressor test (CPT) for 2 min and inspiratory resistive breathing task (IRBT) for 14...
May 18, 2017: Journal of Applied Physiology
Adalgiza M Moreno, Alessandra C Toledo-Arruda, Jéssica S Lima, Carolina S Duarte, Humberto Villacorta, Antonio C L Nóbrega
BACKGROUND: The impact of inspiratory muscle training (IMT) on respiratory and peripheral muscle oxygenation and perfusion during inspiratory muscle fatigue in patients with chronic heart failure (HF) has not been established. METHODS AND RESULTS: Twenty-six patients with chronic HF were randomly assigned to either 8 weeks of IMT or a control group. Inspiratory fatigue was induced by means of a progressive inspiratory resistive loading protocol until there was an inability to sustain inspiratory pressure, when the inspiratory muscle metaboreflex should be activated...
May 9, 2017: Journal of Cardiac Failure
Danielle Senador, Jasdeep Kaur, Alberto Alvarez, Hanna W Hanna, Abhinav C Krishnan, Yasir H Altamimi, Donal S O'Leary
The muscle metaboreflex is a powerful pressor reflex induced by the activation of chemically sensitive muscle afferents as a result of metabolite accumulation. During submaximal dynamic exercise, the rise in arterial pressure is primarily due to increases in cardiac output, since there is little systemic vasoconstriction. Indeed, in normal animals, we have often shown a small, but significant, peripheral vasodilation during metaboreflex activation, which is mediated, at least in part, by release of epinephrine and activation of vascular β2-receptors...
July 1, 2017: American Journal of Physiology. Regulatory, Integrative and Comparative Physiology
James A Lang, Kevin A Smaller
What is the central question of this study? Ageing is associated with altered sympathetic responses to stress, which are explained in part by reduced noradrenergic function. The impact of supplementation with oral l-tyrosine, the amino acid precursor for catecholamine synthesis, on the effector responses to cold and exercise stress has yet to be examined. What is the main finding and its importance? Oral l-tyrosine ingestion augmented the sympathetically mediated vasoconstriction response to cold exposure in aged skin...
May 5, 2017: Experimental Physiology
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