Sympathetically mediated cardiac responses to isolated muscle metaboreflex activation following exercise are modulated by body position in humans.
Am J Physiol Heart Circ Physiol
; 314(3): H593-H602, 2018 03 01.
Article
em En
| MEDLINE
| ID: mdl-29351473
Isolated muscle metaboreflex activation with posthandgrip 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. Beat-to-beat HR (electrocardiography) and blood pressure (finger photoplethysmography) were continuously measured, and cardiac function was assessed by echocardiography in 13 healthy men (21 ± 3 yr). After a 15-min rest period, 90-s static handgrip at 40% maximum voluntary contraction was performed followed by 3 min of PEI. Four trials were randomly conducted during either seated or supine position with and without ß1-adrenergic blockade (25 mg atenolol). During PEI under control conditions, HR remained elevated from baseline in the seated [change (Δ): 4 ± 1 beats/min] but not in the supine (change: -1 ± 1 beats/min) position. Similarly, stroke volume and cardiac output were increased from baseline in the seated (∆13.0 ± 2.4 ml and ∆1.1 ± 0.2 l/min, respectively) but not in the supine (∆2.5 ± 2.9 ml and ∆0.13 ± 0.20 l/min, respectively) position. During ß1-adrenergic blockade, HR, stroke volume, and cardiac output remained unchanged in both conditions. We conclude that sympathetically mediated cardiac responses to PEI are influenced by changes in body position. These findings indicated that muscle metaboreflex and cardiopulmonary baroreflex have an interactive influence on the neural control of cardiovascular function in humans. NEW & NOTEWORTHY In the present study, we demonstrated that muscle metaboreflex activation increases heart rate, stroke volume, and cardiac output in the seated position but not in the supine position and not after ß1-adrenergic blockade. These findings indicate that sympathetically mediated cardiac responses to isolated muscle metaboreflex activation after exercise are modulated by central blood volume mobilization.
Palavras-chave
Texto completo:
1
Coleções:
01-internacional
Base de dados:
MEDLINE
Assunto principal:
Postura
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Sistema Nervoso Simpático
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Exercício Físico
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Células Quimiorreceptoras
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Barorreflexo
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Músculo Esquelético
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Metabolismo Energético
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Coração
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Hemodinâmica
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Contração Muscular
Tipo de estudo:
Clinical_trials
Limite:
Adult
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Humans
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Male
Idioma:
En
Revista:
Am J Physiol Heart Circ Physiol
Assunto da revista:
CARDIOLOGIA
/
FISIOLOGIA
Ano de publicação:
2018
Tipo de documento:
Article
País de afiliação:
Brasil
País de publicação:
Estados Unidos