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Impact of gender on benefits of exercise training on sympathetic nerve activity and muscle blood flow in heart failure

ANTUNES-CORREA, Ligia M.; MELO, Ruth C.; NOBRE, Thais S.; UENO, Linda M.; FRANCO, Fabio G. M.; BRAGA, Ana M. W.; RONDON, Maria U. P. B.; BRUM, Patricia C.; BARRETTO, Antonio C. P.; MIDDLEKAUFF, Holly R.; NEGRAO, Carlos E.
Fonte: OXFORD UNIV PRESS Publicador: OXFORD UNIV PRESS
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
75.97%
We compared the effects of exercise training on neurovascular control and functional capacity in men and women with chronic heart failure (HF). Forty consecutive HF outpatients from the Heart Institute, University of Sao Paulo, Brazil were divided into the following four groups matched by age: men exercise-trained (n = 12), men untrained (n = 10), women exercise-trained (n = 9), women untrained (n = 9). Maximal exercise capacity was determined from a maximal progressive exercise test on a cycle ergometer. Forearm blood flow was measured by venous occlusion plethysmography. Muscle sympathetic nerve activity (MSNA) was recorded directly using the technique of microneurography. There were no differences between groups in any baseline parameters. Exercise training produced a similar reduction in resting MSNA (P = 0.000002) and forearm vascular resistance (P = 0.0003), in men and women with HF. Peak VO(2) was similarly increased in men and women with HF (P = 0.0003) and VE/VCO(2) slope was significantly decreased in men and women with HF (P = 0.0007). There were no significant changes in left-ventricular ejection fraction in men and women with HF. The benefits of exercise training on neurovascular control and functional capacity in patients with HF are independent of gender.; Fundacao de Amparo a Pesquisa do Estado de Sao Paulo[FAPESP 2005/59740-7]; Fundacao Zerbini; CNPq Conselho Nacional de Pesquisa[302146/2007-5]; CNPq Conselho Nacional de Pesquisa[303518/2008-1]; CNPq Conselho Nacional de Pesquisa[301519/2008-0]; CNPq Conselho Nacional de Pesquisa[142366/2009-9]; CNPq Conselho Nacional de Pesquisa[142367/2009-5]; NIH[RO1-HL084525]

Vias centrais purinérgicas envolvidas na regulação do fluxo sangüíneo muscular durante os comportamentos de alerta e defesa; Purinergic central pathways involved in the muscle blood flow regulation during alerting defense behaviours.

Korim, Willian Seiji
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 15/12/2006 Português
Relevância na Pesquisa
76.01%
As reações de alerta e defesa compreendem ajustes cardiovasculares proporcionando um fluxo sangüíneo muscular adequado nas situações de "luta ou fuga". As vias centrais e os possíveis neurotransmissores envolvidos nestes ajustes permanecem ainda, em grande parte, desconhecidas. Neste estudo buscamos analisar a participação da neurotransmissão purinérgica e glutamatérgica no núcleo do trato solitário (NTS) na gênese da vasodilatação muscular durante reações de defesa e o papel das vias glutamatérgicas do NTS para o núcleo rostroventrolateral (RVL) nestas respostas. Ratos Wistar machos (250-350 g) foram anestesiados (uretana 600 mg/kg + alpha-chloralose 50 mg/kg, i.v.), paralisados (d-Tubocurarina, 0,5 mg/kg, i.v.) e ventilados artificialmente. Registramos a pressão arterial média (PAM), a freqüência cardíaca (FC) e o fluxo sangüíneo dos membros posteriores (FSMP). A condutância vascular dos membros posteriores (CVMP) foi determinada como a razão FSMP/PAM e expressa como percentagem do valor basal. A estimulação elétrica (EE; 150 MuA; 0,6 ms; 100 Hz; 6 s) do hipotálamo lateral provocou hipertensão, taquicardia e vasodilatação nos membros posteriores. A microinjeção bilateral de suramin (100 pmol/50 nl)...

Intact insulin stimulation of skeletal muscle blood flow, its heterogeneity and redistribution, but not of glucose uptake in non-insulin-dependent diabetes mellitus.

Utriainen, T; Nuutila, P; Takala, T; Vicini, P; Ruotsalainen, U; Rönnemaa, T; Tolvanen, T; Raitakari, M; Haaparanta, M; Kirvelä, O; Cobelli, C; Yki-Järvinen, H
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em 15/08/1997 Português
Relevância na Pesquisa
66.16%
We tested the hypothesis that defects in insulin stimulation of skeletal muscle blood flow, flow dispersion, and coupling between flow and glucose uptake contribute to insulin resistance of glucose uptake in non-insulin-dependent diabetes mellitus (NIDDM). We used positron emission tomography combined with [15O]H2O and [18F]-2-deoxy--glucose and a Bayesian iterative reconstruction algorithm to quantitate mean muscle blood flow, flow heterogeneity, and their relationship to glucose uptake under normoglycemic hyperinsulinemic conditions in 10 men with NIDDM (HbA1c 8.1+/-0.5%, age 43+/-2 yr, BMI 27.3+/-0.7 kg/m2) and in 7 matched normal men. In patients with NIDDM, rates of whole body (35+/-3 vs. 44+/-3 micromol/kg body weight.min, P < 0.05) and femoral muscle (71+/-6 vs. 96+/-7 micromol/kg muscle.min, P < 0.02) glucose uptake were significantly decreased. Insulin increased mean muscle blood flow similarly in both groups, from 1.9+/-0.3 to 2.8+/-0.4 ml/100 g muscle.min in the patients with NIDDM, P < 0.01, and from 2.3+/-0.3 to 3.0+/-0.3 ml/100 g muscle.min in the normal subjects, P < 0.02. Pixel-by-pixel analysis of flow images revealed marked spatial heterogeneity of blood flow. In both groups, insulin increased absolute but not relative dispersion of flow...

Relationship between limb and muscle blood flow in man.

Raitakari, M; Nuutila, P; Ruotsalainen, U; Teräs, M; Eronen, E; Laine, H; Raitakari, O T; Iida, H; Knuuti, M J; Yki-Järvinen, H
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em 15/10/1996 Português
Relevância na Pesquisa
66.22%
1. Since direct measurement of muscle blood flow in humans has been difficult, estimations of muscle flow have been made from measured total limb blood flow using a classic equation that predicts that the fraction of resting blood flow through muscle tissue decreases as total limb flow increases. 2. We used positron emission tomography and 15O-labelled water to directly quantify resting muscle and total limb blood flow in cross-sections of the femoral region in twenty-eight normal subjects (age, 30 +/- 8 years; body mass index, 24.1 +/- 3.3 Kg m-2) under conditions of constant environmental temperature of 22-23 degrees C. 3. Muscle blood flow averaged 3.1 +/- 1.7 ml (100 ml muscle)-1 min-1 (range, 1.1-7.5 ml (100 ml muscle)-1 min-1 and cross-sectional limb blood flow averaged 2.5 +/- 1.1 ml (100 ml limb)-1 min-1) (range, 1.0-4.8 ml (100 ml limb)-1 min-1). A linear relationship was observed between limb and muscle blood flow, and a regression equation was calculated for estimation of muscle blood flow bases on limb flow: muscle flow = (1.41 +/- 0.10) limb flow - (0.43 +/- 0.28). The slope of this equation was significantly greater than 1 (P < 0.001) indicating that the fraction of blood flow perfusing muscle tissue increases as a function of total limb flow. 4. These data provide a new equation for estimation of resting muscle blood flow in normal subjects...

Sodium nitroprusside increases human skeletal muscle blood flow, but does not change flow distribution or glucose uptake

Pitkänen, Olli-Pekka; Laine, Hanna; Kemppainen, Jukka; Eronen, Esa; Alanen, Anu; Raitakari, Maria; Kirvelä, Olli; Ruotsalainen, Ulla; Knuuti, Juhani; Koivisto, Veikko A; Nuutila, Pirjo
Fonte: Blackwell Science Inc Publicador: Blackwell Science Inc
Tipo: Artigo de Revista Científica
Publicado em 15/12/1999 Português
Relevância na Pesquisa
66.16%
The role of blood flow as a determinant of skeletal muscle glucose uptake is at present controversial and results of previous studies are confounded by possible direct effects of vasoactive agents on glucose uptake. Since increase in muscle blood flow can be due to increased flow velocity or recruitment of new capillaries, or both, it would be ideal to determine whether the vasoactive agent affects flow distribution or only increases the mean flow.In the present study blood flow, flow distribution and glucose uptake were measured simultaneously in both legs of 10 healthy men (aged 29 ± 1 years, body mass index 24 ± 1 kg m−2) using positron emission tomography (PET) combined with [15O]H2O and [18F]fluoro-2-deoxy-D-glucose (FDG). The role of blood flow in muscle glucose uptake was studied by increasing blood flow in one leg with sodium nitroprusside (SNP) and measuring glucose uptake simultaneously in both legs during euglycaemic hyperinsulinaemia (insulin infusion 6 pmol kg−1 min−1).SNP infusion increased skeletal muscle blood flow by 86 % (P < 0·01), but skeletal muscle flow distribution and insulin-stimulated glucose uptake (61·4 ± 7·5 vs. 67·0 ± 7·5 μmol kg−1 min−1, control vs. SNP infused leg, not significant)...

Contribution of respiratory muscle blood flow to exercise-induced diaphragmatic fatigue in trained cyclists

Vogiatzis, Ioannis; Athanasopoulos, Dimitris; Boushel, Robert; Guenette, Jordan A; Koskolou, Maria; Vasilopoulou, Maroula; Wagner, Harrieth; Roussos, Charis; Wagner, Peter D; Zakynthinos, Spyros
Fonte: Blackwell Science Inc Publicador: Blackwell Science Inc
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
76.06%
We investigated whether the greater degree of exercise-induced diaphragmatic fatigue previously reported in highly trained athletes in hypoxia (compared with normoxia) could have a contribution from limited respiratory muscle blood flow. Seven trained cyclists completed three constant load 5 min exercise tests at inspired O2 fractions () of 0.13, 0.21 and 1.00 in balanced order. Work rates were selected to produce the same tidal volume, breathing frequency and respiratory muscle load at each (63 ± 1, 78 ± 1 and 87 ± 1% of normoxic maximal work rate, respectively). Intercostals and quadriceps muscle blood flow (IMBF and QMBF, respectively) were measured by near-infrared spectroscopy over the left 7th intercostal space and the left vastus lateralis muscle, respectively, using indocyanine green dye. The mean pressure time product of the diaphragm and the work of breathing did not differ across the three exercise tests. After hypoxic exercise, twitch transdiaphragmatic pressure fell by 33.3 ± 4.8%, significantly (P < 0.05) more than after both normoxic (25.6 ± 3.5% reduction) and hyperoxic (26.6 ± 3.3% reduction) exercise, confirming greater fatigue in hypoxia. Despite lower leg power output in hypoxia, neither cardiac output nor QMBF (27.6 ± 1.2 l min−1 and 100.4 ± 8.7 ml (100 ml)−1 min−1...

Intercostal muscle blood flow limitation in athletes during maximal exercise

Vogiatzis, Ioannis; Athanasopoulos, Dimitris; Habazettl, Helmut; Kuebler, Wolfgang M; Wagner, Harrieth; Roussos, Charis; Wagner, Peter D; Zakynthinos, Spyros
Fonte: Blackwell Science Inc Publicador: Blackwell Science Inc
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
76.13%
We investigated whether, during maximal exercise, intercostal muscle blood flow is as high as during resting hyperpnoea at the same work of breathing. We hypothesized that during exercise, intercostal muscle blood flow would be limited by competition from the locomotor muscles. Intercostal (probe over the 7th intercostal space) and vastus lateralis muscle perfusion were measured simultaneously in ten trained cyclists by near-infrared spectroscopy using indocyanine green dye. Measurements were made at several exercise intensities up to maximal (WRmax) and subsequently during resting isocapnic hyperpnoea at minute ventilation levels up to those at WRmax. During resting hyperpnoea, intercostal muscle blood flow increased linearly with the work of breathing (R2= 0.94) to 73.0 ± 8.8 ml min−1 (100 g)−1 at the ventilation seen at WRmax (work of breathing ∼550–600 J min−1), but during exercise it peaked at 80% WRmax (53.4 ± 10.3 ml min−1 (100 g)−1), significantly falling to 24.7 ± 5.3 ml min−1 (100 g)−1 at WRmax. At maximal ventilation intercostal muscle vascular conductance was significantly lower during exercise (0.22 ± 0.05 ml min−1 (100 g)−1 mmHg−1) compared to isocapnic hyperpnoea (0.77 ± 0.13 ml min−1 (100 g)−1 mmHg−1). During exercise...

Effects of neuronal nitric oxide synthase inhibition on resting and exercising hindlimb muscle blood flow in the rat

Copp, Steven W; Hirai, Daniel M; Schwagerl, Peter J; Musch, Timothy I; Poole, David C
Fonte: Blackwell Science Inc Publicador: Blackwell Science Inc
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
76.13%
Nitric oxide (NO) derived from endothelial NO synthase (eNOS) is an integral mediator of vascular control during muscle contractions. However, it is not known whether neuronal NOS (nNOS)-derived NO regulates tissue hyperaemia in healthy subjects, particularly during exercise. We tested the hypothesis that selective nNOS inhibition would reduce blood flow and vascular conductance (VC) in rat hindlimb locomotor muscle(s), kidneys and splanchnic organs at rest and during dynamic treadmill exercise (20 m min−1, 10% grade). Nineteen male Sprague–Dawley rats (555 ± 23 g) were assigned to either rest (n= 9) or exercise (n= 10) groups. Blood flow and VC were determined via radiolabelled microspheres before and after the intra-arterial administration of the selective nNOS inhibitor S-methyl-l-thiocitrulline (SMTC, 2.1 ± 0.1 μmol kg−1). Total hindlimb muscle blood flow (control: 20 ± 2 ml min−1 100g−1, SMTC: 12 ± 2 ml min−1 100g−1, P < 0.05) and VC (control: 0.16 ± 0.02 ml min−1 100 g−1 mmHg−1, SMTC: 0.09 ± 0.01 ml min−1 100 g−1 mmHg−1, P < 0.05) were reduced substantially at rest. Moreover, the magnitude of the absolute reduction in blood flow and VC correlated (P < 0.05) with the proportion of oxidative muscle fibres found in the individual muscles or muscle parts of the hindlimb. During exercise...

Expiratory muscle loading increases intercostal muscle blood flow during leg exercise in healthy humans

Athanasopoulos, Dimitris; Louvaris, Zafeiris; Cherouveim, Evgenia; Andrianopoulos, Vasilis; Roussos, Charis; Zakynthinos, Spyros; Vogiatzis, Ioannis
Fonte: American Physiological Society Publicador: American Physiological Society
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
66.17%
We investigated whether expiratory muscle loading induced by the application of expiratory flow limitation (EFL) during exercise in healthy subjects causes a reduction in quadriceps muscle blood flow in favor of the blood flow to the intercostal muscles. We hypothesized that, during exercise with EFL quadriceps muscle blood flow would be reduced, whereas intercostal muscle blood flow would be increased compared with exercise without EFL. We initially performed an incremental exercise test on eight healthy male subjects with a Starling resistor in the expiratory line limiting expiratory flow to ∼ 1 l/s to determine peak EFL exercise workload. On a different day, two constant-load exercise trials were performed in a balanced ordering sequence, during which subjects exercised with or without EFL at peak EFL exercise workload for 6 min. Intercostal (probe over the 7th intercostal space) and vastus lateralis muscle blood flow index (BFI) was calculated by near-infrared spectroscopy using indocyanine green, whereas cardiac output (CO) was measured by an impedance cardiography technique. At exercise termination, CO and stroke volume were not significantly different during exercise, with or without EFL (CO: 16.5 vs. 15.2 l/min, stroke volume: 104 vs. 107 ml/beat). Quadriceps muscle BFI during exercise with EFL (5.4 nM/s) was significantly (P = 0.043) lower compared with exercise without EFL (7.6 nM/s)...

Critical speed in the rat: implications for hindlimb muscle blood flow distribution and fibre recruitment

Copp, Steven W; Hirai, Daniel M; Musch, Timothy I; Poole, David C
Fonte: Blackwell Science Inc Publicador: Blackwell Science Inc
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
76.14%
Critical speed (CS) constitutes an important metabolic and performance demarcator. However, active skeletal muscle blood flow distribution specifically surrounding CS remains unknown. We tested the hypotheses that CS could be accurately determined in the running rat and that measurement of hindlimb inter- and intramuscular blood flow below and above CS would support that the greatest muscle fibre recruitment above, relative to below, CS occurs in the predominantly glycolytic muscles. Seven male Sprague–Dawley rats performed five constant-speed tests to exhaustion at speeds between 95 and 115% of the speed that elicited to determine CS. Subsequent constant-speed tests were performed at speeds incrementally surrounding CS to determine time to exhaustion, , and hindlimb muscle blood flow distribution. Speed and time to exhaustion conformed to a hyperbolic relationship (r2= 0.92 ± 0.03) which corresponded to a linear 1/time function (r2= 0.93 ± 0.02) with a CS of 48.6 ± 1.0 m min−1. Time to exhaustion below CS was ∼5× greater (P < 0.01) than that above. Below CS stabilized at a submaximal value (58.5 ± 2.5 ml kg−1 min−1) whereas above CS (81.7 ± 2.5 ml kg−1 min−1) increased to (84.0 ± 1.8 ml kg−1 min−1, P > 0.05 vs. above CS). The 11 individual muscles or muscle parts that evidenced the greatest blood flow increases above...

Local heating, but not indirect whole body heating, increases human skeletal muscle blood flow

Heinonen, Ilkka; Brothers, R. Matthew; Kemppainen, Jukka; Knuuti, Juhani; Kalliokoski, Kari K.; Crandall, Craig G.
Fonte: American Physiological Society Publicador: American Physiological Society
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
66.17%
For decades it was believed that direct and indirect heating (the latter of which elevates blood and core temperatures without directly heating the area being evaluated) increases skin but not skeletal muscle blood flow. Recent results, however, suggest that passive heating of the leg may increase muscle blood flow. Using the technique of positron-emission tomography, the present study tested the hypothesis that both direct and indirect heating increases muscle blood flow. Calf muscle and skin blood flows were evaluated from eight subjects during normothermic baseline, during local heating of the right calf [only the right calf was exposed to the heating source (water-perfused suit)], and during indirect whole body heat stress in which the left calf was not exposed to the heating source. Local heating increased intramuscular temperature of the right calf from 33.4 ± 1.0°C to 37.4 ± 0.8°C, without changing intestinal temperature. This stimulus increased muscle blood flow from 1.4 ± 0.5 to 2.3 ± 1.2 ml·100 g−1·min−1 (P < 0.05), whereas skin blood flow under the heating source increased from 0.7 ± 0.3 to 5.5 ± 1.5 ml·100 g−1·min−1 (P < 0.01). While whole body heat stress increased intestinal temperature by ∼1°C...

Influence of exercise intensity on skeletal muscle blood flow, O2 extraction and O2 uptake on-kinetics

Jones, Andrew M; Krustrup, Peter; Wilkerson, Daryl P; Berger, Nicolas J; Calbet, José A; Bangsbo, Jens
Fonte: Blackwell Science Inc Publicador: Blackwell Science Inc
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
75.94%
Following the start of low-intensity exercise in healthy humans, it has been established that the kinetics of skeletal muscle O2 delivery is faster than, and does not limit, the kinetics of muscle O2 uptake (). Direct data are lacking, however, on the question of whether O2 delivery might limit kinetics during high-intensity exercise. Using multiple exercise transitions to enhance confidence in parameter estimation, we therefore investigated the kinetics of, and inter-relationships between, muscle blood flow (), a– difference and following the onset of low-intensity (LI) and high-intensity (HI) exercise. Seven healthy males completed four 6 min bouts of LI and four 6 min bouts of HI single-legged knee-extension exercise. Blood was frequently drawn from the femoral artery and vein during exercise and , a– difference and were calculated and subsequently modelled using non-linear regression techniques. For LI, the fundamental component mean response time (MRTp) for kinetics was significantly shorter than kinetics (mean ± SEM, 18 ± 4 vs. 30 ± 4 s; P < 0.05), whereas for HI, the MRTp for and was not significantly different (27 ± 5 vs. 29 ± 4 s, respectively). There was no difference in the MRTp for either or between the two exercise intensities; however...

ATP as a mediator of erythrocyte-dependent regulation of skeletal muscle blood flow and oxygen delivery in humans

González-Alonso, José
Fonte: Blackwell Science Inc Publicador: Blackwell Science Inc
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
86.16%
In healthy human beings, blood flow to dynamically contracting skeletal muscle is regulated primarily to match oxygen (O2) delivery closely with utilisation. This occurs across a wide range of exercise intensities, as well as when exercise is combined with conditions that modify blood O2 content. The red blood cells (RBCs), the primary O2 carriers in the blood, contribute to the regulation of the local processes matching O2 supply and demand. This is made possible by the ability of RBCs to release the vasoactive substance adenosine triphosphate (ATP) in response to reductions in erythrocyte and plasma O2, as well as to other adjuvant metabolic and mechanical stimuli. The regulatory role of RBCs in human beings is supported by the observations that, i) exercising skeletal muscle blood flow responds primarily to changes in the amount of O2 bound to the erythrocyte haemoglobin molecules, rather than the amount of O2 in plasma, and ii) exercising muscle blood flow can almost double (from 260 to 460 ml min−1 100 g−1) with alterations in blood O2 content, such that O2 delivery and are kept constant. Besides falling blood O2 content, RBCs release ATP when exposed to increased temperature, reduced pH, hypercapnia, elevated shear stress and augmented mechanical deformation...

Spreading the signal for vasodilatation: implications for skeletal muscle blood flow control and the effects of ageing

Behringer, Erik J; Segal, Steven S
Fonte: Blackwell Science Inc Publicador: Blackwell Science Inc
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
75.97%
Blood flow control requires coordinated contraction and relaxation of smooth muscle cells (SMCs) along and among the arterioles and feed arteries that comprise vascular resistance networks. Whereas smooth muscle contraction of resistance vessels is enhanced by noradrenaline release along perivascular sympathetic nerves, the endothelium is integral to coordinating smooth muscle relaxation. Beyond producing nitric oxide in response to agonists and shear stress, endothelial cells (ECs) provide an effective conduit for conducting hyperpolarization along vessel branches and into surrounding SMCs through myoendothelial coupling. In turn, bidirectional signalling from SMCs into ECs enables the endothelium to moderate adrenergic vasoconstriction in response to sympathetic nerve activity. This review focuses on the endothelium as the cellular pathway that coordinates spreading vasodilatation. We discuss the nature and regulation of cell-to-cell coupling through gap junctions, bidirectional signalling between ECs and SMCs, and how oxidative stress during ageing may influence respective signalling pathways. Our recent findings illustrate the role of small (SKCa) and intermediate (IKCa) Ca2+ activated K+ channels as modulators of electrical conduction along the endothelium. Gaps in current understanding indicate the need to determine mechanisms that regulate intracellular Ca2+ homeostasis and ion channel activation in the resistance vasculature with advancing age.

Vasodilator interactions in skeletal muscle blood flow regulation

Hellsten, Y; Nyberg, M; Jensen, L G; Mortensen, S P
Fonte: Blackwell Science Inc Publicador: Blackwell Science Inc
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
86.1%
During exercise, oxygen delivery to skeletal muscle is elevated to meet the increased oxygen demand. The increase in blood flow to skeletal muscle is achieved by vasodilators formed locally in the muscle tissue, either on the intraluminal or on the extraluminal side of the blood vessels. A number of vasodilators have been shown to bring about this increase in blood flow and, importantly, interactions between these compounds seem to be essential for the precise regulation of blood flow. Two compounds stand out as central in these vasodilator interactions: nitric oxide (NO) and prostacyclin. These two vasodilators are both stimulated by several compounds, e.g. adenosine, ATP, acetylcholine and bradykinin, and are affected by mechanically induced signals, such as shear stress. NO and prostacyclin have also been shown to interact in a redundant manner where one system can take over when formation of the other is compromised. Although numerous studies have examined the role of single and multiple pharmacological inhibition of different vasodilator systems, and important vasodilators and interactions have been identified, a large part of the exercise hyperaemic response remains unexplained. It is plausible that this remaining hyperaemia may be explained by cAMP- and cGMP-independent smooth muscle relaxation...

Positron emission tomography detects greater blood flow and less blood flow heterogeneity in the exercising skeletal muscles of old compared with young men during fatiguing contractions

Rudroff, Thorsten; Weissman, Jessica A; Bucci, Marco; Seppänen, Marko; Kaskinoro, Kimmo; Heinonen, Ilkka; Kalliokoski, Kari K
Fonte: Blackwell publishing Ltd Publicador: Blackwell publishing Ltd
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
66.14%
The purpose of this study was to investigate blood flow and its heterogeneity within and among the knee muscles in five young (26 ± 6 years) and five old (77 ± 6 years) healthy men with similar levels of physical activity while they performed two types of submaximal fatiguing isometric contraction that required either force or position control. Positron emission tomography (PET) and [15O]-H2O were used to determine blood flow at 2 min (beginning) and 12 min (end) after the start of the tasks. Young and old men had similar maximal forces and endurance times for the fatiguing tasks. Although muscle volumes were lower in the older subjects, total muscle blood flow was similar in both groups (young men: 25.8 ± 12.6 ml min−1; old men: 25.1 ± 15.4 ml min−1; age main effect, P = 0.77) as blood flow per unit mass of muscle in the exercising knee extensors was greater in the older (12.5 ± 6.2 ml min−1 (100 g)−1) than the younger (8.6 ± 3.6 ml min−1 (100 g)−1) men (age main effect, P = 0.001). Further, blood flow heterogeneity in the exercising knee extensors was significantly lower in the older (56 ± 27%) than the younger (67 ± 34%) men. Together, these data show that although skeletal muscles are smaller in older subjects...

The influence of muscle blood flow on fatigue during intermittent human hand-grip exercise and recovery

Pitcher, J.; Miles, T.
Fonte: BLACKWELL SCIENCE Publicador: BLACKWELL SCIENCE
Tipo: Artigo de Revista Científica
Publicado em //1997 Português
Relevância na Pesquisa
86.13%
1. The influence of muscle blood flow on fatigue and recovery was studied in the forearm muscles of eight male subject performing a powerful isometric hand-grip exercise. The exercise was performed with the exercising forearm normally perfused and, on a separate occasion, with its blood flow occluded with a sphygmomanometer cuff. 2. In the no cuff condition, peak force declined to an initial plateau at 40-50% of the maximal voluntary grip force (MVC). When perfusion was occluded, the force decline was similar during the first minute of exercise, then force fell rapidly to exhaustion. 3. In a separate experiment to investigate the mechanisms underlying the plateau in force loss, occlusion of blood flow during the force plateau phase resulted in a rapid decline in force to exhaustion. 4. Recovery of peak force after the cuff exercise was significantly greater during the initial 3.5 min of recovery than after no-cuff exercise. After this time, recovery was similar for both conditions. 5. Muscle blood flow occlusion during intermittent exercise profoundly reduces endurance without prolonging recovery. Recovery time may depend on the duration and energy cost of the exercise rather than on the degree of force loss. 6. The present study suggests that the fall in muscle force induced by a continuous MVC is a combination of profound short-term fatigue in anaerobic muscle fibres due to the consumption of their short-term energy supplies...

The Assessment of Functional Sympatholysis Post-Exercise in the Human Skeletal Muscle

MOYNES, JACLYN
Fonte: Quens University Publicador: Quens University
Tipo: Tese de Doutorado
Português
Relevância na Pesquisa
76.01%
To optimize muscle blood flow to the skeletal muscle during exercise, the vascular bed of the muscle is partially protected from sympathetic nervous activity (SNA) vasoconstriction via a phenomenon termed functional sympatholysis. Functional sympatholysis has been documented during exercise periods in human skeletal muscle. However, it remains unknown whether functional sympatholysis is specific to the exercising period, or if it may persist for a period of time following skeletal muscle exercise. Through this study, we aimed to confirm the presence and duration of post-exercise functional sympatholysis in the human skeletal muscle. The cold pressor test (CPT) was administered to 9 male (mean age = 21.1 ± 0.8 years) participants at various time points during four different experimental trials (Rest, Exercise, Recovery 1 and Recovery 2). Exercise consisted of 7 minutes of moderate isometric handgrip exercise (15% below critical power). Heart rate (HR) and mean arterial pressure (MAP) were recorded continuously throughout each trial. Brachial artery mean blood velocity measurements as well as brachial artery diameter measurements were recorded on each participant’s exercising arm throughout each trial. Deep venous blood samples were drawn pre- and post-CPT administration from a catheter inserted into an antecubital vein of each participant’s non-experimental arm. The cardiovascular response to the CPT was repeatable across experimental days as it consistently resulted in MAP elevations regardless of the experimental time point of administration. The CPT also resulted in a significant elevation in plasma norepinephrine concentration from 0.49 ± 0.04 ng/mL at “pre-CPT” measurement to 0.66 ± 0.05 ng/mL at the end of the CPT in the Rest trial (P < 0.05). The percentage reduction in forearm vascular conductance (FVC) due to CPT administration during Exercise (4.5 ± 6.6%) and Recovery 1 (4 minutes post-exercise; -11.6 ± 8.8%) was significantly blunted in comparison to that measured during Rest (-34.8 ± 7.4%) (P < 0.05). The percentage change in FVC during the Recovery 2 trial (10 minutes post-exercise; -20.1 ± 7.1%) was not significantly different from that measured at Rest. These findings support the concept of a lingering presence of functional sympatholysis 4 minutes...

Influence of Caffeine on Exercising Muscle Blood Flow and Exercise Tolerance in Type II Diabetes

POITRAS, VERONICA
Fonte: Quens University Publicador: Quens University
Tipo: Tese de Doutorado Formato: 3530486 bytes; application/pdf
Português
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BACKGROUND: Exercise is a critical treatment modality in persons with Type II Diabetes Mellitus (T2DM), however people with this disease experience chronic fatigue and a decreased exercise capacity, which affects their ability or willingness to participate in physical activity. Studies suggest that this exercise intolerance may be partly due to a reduced exercising muscle blood flow (MBF), and in particular to a reduced ability of red blood cells (RBCs) to evoke ATP-mediated vasodilation and an increase in MBF as they traverse areas of high O2 demand. Additional evidence suggests that caffeine may attenuate this impairment by enhancing the release of ATP from RBCs. HYPOTHESIS: Persons with T2DM would have reduced Forearm Blood Flow (FBF), oxygen consumption (VO2), and exercise tolerance responses to exercise compared to control (CON) subjects, and caffeine would attenuate these impairments. METHODS: T2DM (n = 4) and CON (n = 4) participants performed rhythmic forearm handgrip exercise at an intensity equivalent to 17.5 kg until “task failure” or 20 minutes of exercise was reached, after having consumed either a caffeine (5mg/kg; Caff) or placebo (Pl) capsule. FBF (Doppler and Echo ultrasound of the brachial artery), VO2 and lactate efflux (deep venous blood sampling)...

Dysfunctional Muscle Blood Flow Regulation During Exercise in Type 2 Diabetes

Pak, MELISSA
Fonte: Quens University Publicador: Quens University
Tipo: Tese de Doutorado Formato: 2803383 bytes; application/pdf
Português
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There is some evidence to suggest that oxygen consumption (VO2) and oxygen delivery to muscle are reduced at exercise onset and steady state in individuals with type 2 diabetes (T2D), although no studies have combined measurements of both muscle blood flow and VO2 during exercise in this population. OBJECTIVES: 1) To determine whether a reduction in VO2 during exercise would be accompanied by reduced leg blood flow (LBF). 2) To examine the dynamic response characteristics of LBF to determine whether feedforward and/or feedback control systems of blood flow regulation are impaired. METHODS: Four men with T2D and six healthy, activity matched controls (CON) performed supine, two-leg knee extension/flexion exercise tests involving progressive increase in exercise intensity to exhaustion and step increases to a low intensity equivalent to lifting 7.5 kg (LO7.5kg), and a moderate intensity equivalent to 90% of ventilatory threshold (VT90%). MEASUREMENTS: LBF, VO2, mean arterial pressure, heart rate, and stroke volume were measured continuously. RESULTS: Means ± SE, CON vs. T2D. 1) ∆VO2 was not different between groups during the incremental test (P= 0.264), ∆LBF in T2D tended to be lower (P = 0.098). 2) ∆VO2 was not different between groups at any time during LO7.5kg (P = 0.351). Individuals with T2D demonstrated a lower ∆LBF at time = 15 s (3435.6 ± 275.0 vs. 2120.4 ± 218.4 ml/min...