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1.
Exp Physiol ; 108(9): 1203-1214, 2023 09.
Artigo em Inglês | MEDLINE | ID: mdl-37548581

RESUMO

The purpose of this study was to examine how two common methods of continuous hypoxaemia impact the activity of intracortical circuits responsible for inhibition and facilitation of motor output, and spinal excitability. Ten participants were exposed to 2 h of hypoxaemia at 0.13 fraction of inspired oxygen ( F I O 2 ${F_{{\mathrm{I}}{{\mathrm{O}}_{\mathrm{2}}}}}$ clamping protocol) and 80% of peripheral capillary oxygen saturation ( S p O 2 ${S_{{\mathrm{p}}{{\mathrm{O}}_{\mathrm{2}}}}}$ clamping protocol) using a simulating altitude device on two visits separated by a week. Using transcranial magnetic and peripheral nerve stimulation, unconditioned motor evoked potential (MEP) area, short-interval intracortical inhibition (SICI) and intracortical facilitation (ICF), and F-wave persistence and area were assessed in the first dorsal interosseous (FDI) muscle before titration, after 1 and 2 h of hypoxic exposure, and at reoxygenation. The clamping protocols resulted in differing reductions in S p O 2 ${S_{{\mathrm{p}}{{\mathrm{O}}_{\mathrm{2}}}}}$ by 2 h ( S p O 2 ${S_{{\mathrm{p}}{{\mathrm{O}}_{\mathrm{2}}}}}$ clamping protocol: 81.9 ± 1.3%, F I O 2 ${F_{{\mathrm{I}}{{\mathrm{O}}_{\mathrm{2}}}}}$ clamping protocol: 90.6 ± 2.5%). Although unconditioned MEP peak to peak amplitude and area did not differ between the protocols, SICI during F I O 2 ${F_{{\mathrm{I}}{{\mathrm{O}}_{\mathrm{2}}}}}$ clamping was significantly lower at 2 h compared to S p O 2 ${S_{{\mathrm{p}}{{\mathrm{O}}_{\mathrm{2}}}}}$ clamping (P = 0.011) and baseline (P < 0.001), whereas ICF was higher throughout the F I O 2 ${F_{{\mathrm{I}}{{\mathrm{O}}_{\mathrm{2}}}}}$ clamping compared to S p O 2 ${S_{{\mathrm{p}}{{\mathrm{O}}_{\mathrm{2}}}}}$ clamping (P = 0.005). Furthermore, a negative correlation between SICI and S p O 2 ${S_{{\mathrm{p}}{{\mathrm{O}}_{\mathrm{2}}}}}$ (rrm  = -0.56, P = 0.002) and a positive correlation between ICF and S p O 2 ${S_{{\mathrm{p}}{{\mathrm{O}}_{\mathrm{2}}}}}$ (rrm  = 0.69, P = 0.001) were determined, where greater reductions in S p O 2 ${S_{{\mathrm{p}}{{\mathrm{O}}_{\mathrm{2}}}}}$ correlated with less inhibition and less facilitation of MEP responses. Although F-wave area progressively increased similarly throughout the protocols (P = 0.037), persistence of responses was reduced at 2 h and reoxygenation (P < 0.01) during the S p O 2 ${S_{{\mathrm{p}}{{\mathrm{O}}_{\mathrm{2}}}}}$ clamping protocol compared to the F I O 2 ${F_{{\mathrm{I}}{{\mathrm{O}}_{\mathrm{2}}}}}$ clamping protocol. After 2 h of hypoxic exposure, there is a reduction in the activity of intracortical circuits responsible for inhibiting motor output, as well as excitability of spinal motoneurones. However, these effects can be influenced by other physiological responses to hypoxia (i.e., hyperventilation and hypocapnia). NEW FINDINGS: What is the central question of this study? How do two common methods of acute hypoxic exposure influence the excitability of intracortical networks and spinal circuits responsible for motor output? What is the main finding and its importance? The excitability of spinal circuits and intracortical networks responsible for inhibition of motor output was reduced during severe acute exposure to hypoxia at 2 h, but this was not seen during less severe exposure. This provides insight into the potential cause of variance seen in motor evoked potential responses to transcranial magnetic stimulation (corticospinal excitability measures) when exposed to hypoxia.


Assuntos
Córtex Motor , Estimulação Elétrica Nervosa Transcutânea , Humanos , Estimulação Magnética Transcraniana/métodos , Potencial Evocado Motor/fisiologia , Córtex Motor/fisiologia , Hipóxia , Eletromiografia , Músculo Esquelético/fisiologia
2.
Am J Physiol Heart Circ Physiol ; 320(1): H159-H168, 2021 01 01.
Artigo em Inglês | MEDLINE | ID: mdl-33124881

RESUMO

Strenuous exercise elicits transient functional and biochemical cardiac imbalances. Yet, the extent to which these responses are altered owing to aging is unclear. Accordingly, echocardiograph-derived left ventricular (LV) and right ventricular (RV) global longitudinal strain (GLS) and high-sensitivity cardiac troponin I (hs-cTnI) were assessed before (pre) and after (post) a 60-min high-intensity cycling race intervention (CRIT60) in 11 young (18-30 yr) and 11 middle-aged (40-65 yr) highly trained male cyclists, matched for cardiorespiratory fitness. LV and RV GLS were measured at rest and during a semirecumbent exercise challenge performed at the same intensity (young: 93 ± 10; middle-aged: 85 ± 11 W, P = 0.60) pre- and post-CRIT60. Augmentation (change from rest-to-exercise challenge) of LV GLS (pre: -2.97 ± 0.65; post: -0.82 ± 0.48%, P = 0.02) and RV GLS (pre: -2.08 ± 1.28; post: 3.08 ± 2.02%, P = 0.01) was attenuated and completely abolished, in the young following CRIT60, while augmentation of LV GLS (pre: -3.21 ± 0.41; post: -3.99 ± 0.55%, P = 0.22) and RV GLS (pre: -3.47 ± 1.44; post: -1.26 ± 1.00%, P = 0.27) was preserved in middle-aged following CRIT60. While serum hs-cTnI concentration increased followingCRIT60 in the young (pre: 7.3 ± 1.6; post: 17.7 ± 1.6 ng/L, P < 0.01) and middle-aged (pre: 4.5 ± 0.6; post: 10.7 ± 2.0 ng/L, P < 0.01), serum hs-cTnI concentration increased to a greater extent in the young than in the middle-aged following CRIT60 (P < 0.01). These findings suggest that functional and biochemical cardiac perturbations induced by high-intensity exercise are attenuated in middle-aged relative to young individuals. Further study is warranted to determine whether acute exercise-induced cardiac perturbations alter the adaptive myocardial remodeling response.NEW & NOTEWORTHY High-intensity endurance exercise elicits acute cardiac imbalances that may be an important stimulus for adaptive cardiac remodeling. This study highlights that following a bout of high-intensity exercise that is typical of routine day-to-day cycling training, exercise-induced autonomic, biochemical, and functional cardiac imbalances are attenuated in middle-aged relative to young well-trained cyclists. These findings suggest that aging may alter exercise-induced stress stimulus response that initiates cardiac remodeling in athlete's heart.


Assuntos
Atletas , Cardiomegalia Induzida por Exercícios , Ventrículos do Coração/metabolismo , Resistência Física , Troponina I/sangue , Função Ventricular Esquerda , Função Ventricular Direita , Adaptação Fisiológica , Adolescente , Adulto , Fatores Etários , Idoso , Ciclismo , Biomarcadores/sangue , Ecocardiografia Doppler de Pulso , Frequência Cardíaca , Ventrículos do Coração/diagnóstico por imagem , Humanos , Masculino , Pessoa de Meia-Idade , Fatores de Tempo , Adulto Jovem
3.
J Card Fail ; 27(12): 1313-1320, 2021 12.
Artigo em Inglês | MEDLINE | ID: mdl-33974969

RESUMO

BACKGROUND: A warmup period of priming exercise has been shown to improve peripheral oxygen transport in older adults. We sought to determine the acute effects of priming exercise on central hemodynamics at rest and during a repeat exercise in heart failure with preserved ejection fraction (HFpEF). METHODS AND RESULTS: This is a post hoc analysis from 3 studies. Patients with HFpEF (n = 42) underwent cardiac catheterization with simultaneous expired gas analysis at rest and during exercise (20 W for 5 minutes, priming exercise). Measurements were then repeated at rest and during a second bout of exercise at a 20-W workload (second exercise). During the priming exercise, patients with HFpEF displayed dramatic increases in biventricular filling pressures and exercise-induced pulmonary hypertension. After the priming exercise at rest, biventricular filling pressures and pulmonary artery (PA) pressures were lower and lung tidal volume was increased. During the second bout of exercise, biventricular filling (PA wedge pressure, 29 ± 8 mm Hg at second exercise vs 32 ± 7 mm Hg at first exercise, P = .0003) and PA pressures were lower, and PA compliance increased. CONCLUSIONS: This study shows that short duration, submaximal priming exercise attenuates the pathologic increases in filling pressures, improving pulmonary vascular hemodynamics at rest and during repeat exercise in patients with HFpEF.


Assuntos
Insuficiência Cardíaca , Idoso , Teste de Esforço , Tolerância ao Exercício , Insuficiência Cardíaca/terapia , Hemodinâmica , Humanos , Volume Sistólico , Função Ventricular Esquerda
4.
Am J Physiol Regul Integr Comp Physiol ; 319(5): R602-R609, 2020 11 01.
Artigo em Inglês | MEDLINE | ID: mdl-32936678

RESUMO

Patients with heart failure with preserved ejection fraction (HFpEF) experience symptoms of exertional dyspnea that may be related to lung fluid accumulation during exercise. A computed tomography (CT)-based method was used to measure exercise-induced changes in extravascular lung fluid content and thoracic blood volumes and to determine the effect of lung fluid on lung diffusing capacity for carbon monoxide (DLCO) in stable subjects with HFpEF and healthy controls. Nine subjects with HFpEF (age = 68 ± 8 yr; body mass index = 32.1 ± 2.6 kg/m2) and eight healthy controls (62 ± 9 yr, 23.8 ± 2.4 kg/m2) performed triplicate rebreathe DLCO/DLNO (lung diffusing capacity for nitric oxide) tests in a supine position at rest and duplicate measurements during two 5-min submaximal exercise stages (15W and 35W) and recovery. Subjects subsequently performed a 5-min exercise bout (35W) inside a CT scanner, and extravascular lung fluid content and thoracic blood volumes were quantified at rest and immediately following exercise from thoracic and contrast perfusion scans, respectively. Subjects with HFpEF had a higher lung fluid content at rest compared with controls (means ± SD, HFpEF: 14.4 ± 1.7%, control: 12.8 ± 1.7%, P = 0.043) and a higher lung fluid content following exercise (15.2 ± 2.0% vs. 12.6 ± 1.5%, P = 0.009). Higher lung fluid content was associated with a lower DLCO and alveolar-capillary membrane conductance (Dm) in subjects with HFpEF (DLCO: R = -0.57, P = 0.022, Dm: R = -0.61, P = 0.012) but not in controls. Pulmonary blood volume was not altered by exercise and was similar between groups. Submaximal exercise elicited a greater accumulation of lung fluid in subjects with HFpEF compared with in controls, and lung fluid content was negatively correlated with lung diffusing capacity and alveolar-capillary membrane conductance in subjects with HFpEF.


Assuntos
Exercício Físico , Insuficiência Cardíaca/diagnóstico por imagem , Insuficiência Cardíaca/fisiopatologia , Pulmão/patologia , Volume Sistólico/fisiologia , Tomografia Computadorizada por Raios X , Idoso , Volume Sanguíneo/fisiologia , Feminino , Insuficiência Cardíaca/classificação , Hemodinâmica/fisiologia , Humanos , Masculino , Pessoa de Meia-Idade , Capacidade de Difusão Pulmonar/fisiologia , Troca Gasosa Pulmonar/fisiologia
5.
J Card Fail ; 26(11): 1011-1015, 2020 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-32750488

RESUMO

Elevated left ventricular filling pressure (measured as mean pulmonary capillary wedge pressure) at rest or with exercise is diagnostic of heart failure with preserved ejection fraction. However, the capacity of the right ventricle to compensate for a high mean pulmonary capillary wedge pressure and thus maintain an appropriate transpulmonary gradient (TPG) and perfusion of the pulmonary capillaries is likely an important contributor to gas exchange efficiency and exercise capacity. Therefore, this study aimed to determine whether a higher TPG at peak exercise is associated with superior exercise capacity and gas exchange. Gas exchange data from dyspneic patients referred for exercise right heart catheterization were retrospectively analyzed and patients were split into two groups based on TPG. Patients with a higher TPG at peak exercise had a higher peak VO2 (1025 ± 227 vs 823 ± 276, P = .038), end-tidal partial pressure of carbon dioxide (42.2 ± 7.9 vs 38.0 ± 4.7, P = .044), and gas exchange estimates of pulmonary vascular capacitance (408 ± 90 vs 268 ± 108, P = .001). A higher TPG at peak exercise correlated with a higher peak oxygen uptake, O2 pulse, and stroke volume (R = 0.42, 0.44 and 0.42, respectively, all P < 0.05). These findings indicate that a greater TPG with exercise might be important for improving exercise capacity in heart failure with preserved ejection fraction.


Assuntos
Insuficiência Cardíaca , Teste de Esforço , Tolerância ao Exercício , Insuficiência Cardíaca/diagnóstico , Humanos , Consumo de Oxigênio , Troca Gasosa Pulmonar , Estudos Retrospectivos , Volume Sistólico
6.
Eur J Appl Physiol ; 120(4): 799-809, 2020 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-32076831

RESUMO

INTRODUCTION: High-altitude ascent induces left (LV) and right (RV) ventricular adaptations secondary to hypoxia-related hemodynamic and myocardial alterations. Since cardiopulmonary decrements observed with aging (e.g., decreased LV compliance and increased pulmonary vascular resistance) may limit cardiac plasticity, this study examined myocardial adaptability throughout an 11 day sojourn to 5893 m in young and older-aged trekkers. METHODS AND RESULTS: Echocardiography was performed on 14 young (8 men; 32 ± 5 years) and 13 older-aged (8 men; 59 ± 5 years) subjects on non-trekking days (Day 0: 880 m; Day 3: 3100 m; Day 8: 4800 m; Day 12/post-climb: 880 m). RV systolic pressure (mmHg) was systematically higher in older-aged subjects (p < 0.01) with similar progressive increases observed during ascent for young and older subjects, respectively (Day 0: 18 ± 1 vs 20 ± 2; Day 3: 25 ± 2 vs 29 ± 3; Day 8: 30 ± 2 vs 35 ± 2). Estimates of LV filling pressure (E/E') were systematically higher in older subjects (p < 0.01) with similar progressive decreases observed during ascent for young and older-aged subjects, respectively (Day 0: 5.6 ± 0.3 vs 6.7 ± 0.5; Day 3: 5.1 ± 0.2 vs 6.1 ± 0.3; Day 8: 4.7 ± 0.3 vs 5.4 ± 0.3). Overall, RV end-diastolic and end-systolic area increased at altitude (p < 0.01), while LV end-diastolic and end-systolic volume decreased (p < 0.01). However, all RV and LV morphological measures were similar on Day 3 and Day 8 (p > 0.05), and returned to baseline post-climb (p > 0.05). Excluding mild LV dilatation in some older-aged trekkers on Day 8/Day 12 (p < 0.01), altitude-induced morphological and functional adaptations were similar for all trekkers (p > 0.05). CONCLUSION: Altitude-induced myocardial adaptations are chamber specific, secondary to RV and LV hemodynamic alterations. Despite progressive hemodynamic alterations during ascent, morphological and functional cardiac perturbations plateaued, suggesting rapid myocardial adaptation which was mostly comparable in young and older-aged individuals.


Assuntos
Aclimatação , Envelhecimento/fisiologia , Coração/fisiologia , Montanhismo/fisiologia , Circulação Pulmonar , Adulto , Idoso , Altitude , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Adulto Jovem
7.
Blood Press ; 29(1): 47-54, 2020 02.
Artigo em Inglês | MEDLINE | ID: mdl-31394939

RESUMO

Purpose: Regulation of blood pressure (BP) is important in reducing the risk for cardiovascular disease. There is growing interest in non-pharmacological methods to treat BP including a novel approach using pulsed electromagnetic field therapy (PEMF). PEMF therapy has been proposed to impact physiological function at the cellular and tissue level and one possible mechanism is through an impact on endothelial function and nitric oxide (NO) related pathways. The focus of the present study was to evaluate the effect of PEMF on BP and NO in subjects with mild to moderate metabolic syndrome.Materials and methods: For 12 weeks, 23 subjects underwent PEMF therapy and 21 subjects underwent sham therapy. BP was measured at rest and near the end of submaximal exercise pre- and 12 week post-therapy. Additionally, plasma NO was measured at similar time points.Results: The PEMF demonstrated an increase in NO after therapy (p = .04) but SHAM did not (p = .37). For resting BP, there were no differences in systolic BP (SBP), diastolic BP (DBP) or mean arterial pressure (MAP) between groups (p > .05). During exercise, PEMF had a reduction in peak SBP (p = .04), but not SHAM (p = .57). PEMF demonstrated significant relationships between baseline SBP and change in SBP following therapy (r = -0.71, p < .01) and between MAP and change in MAP following therapy (r = -0.60, p < .01), but no such relationships were found in SHAM. Subjects with resting hypertension (SBP ≥140 mmHg) in PEMF (n = 11) had significant reductions in SBP, DBP and MAP when compared to SHAM with hypertension (n = 9) (p < .05). In this sub-group analysis, PEMF demonstrated lowered peak SBP (p = .04) at a given exercise load (p = .40) but SHAM did not (p > .05).Conclusion: PEMF may increase plasma NO availability and improve BP at rest and during exercise. However, this beneficial effect appears to be more pronounced in subjects with existing hypertension.


Assuntos
Pressão Sanguínea , Magnetoterapia/métodos , Síndrome Metabólica/terapia , Óxido Nítrico/sangue , Adulto , Método Duplo-Cego , Feminino , Humanos , Hipertensão/fisiopatologia , Hipertensão/terapia , Masculino , Síndrome Metabólica/fisiopatologia , Pessoa de Meia-Idade
8.
Curr Sports Med Rep ; 19(8): 290-297, 2020 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-32769665

RESUMO

Regular physical activity decreases the risk of cardiovascular disease, type II diabetes, obesity, certain cancers, and all-cause mortality. Nevertheless, there is mounting evidence that extreme exercise behaviors may be detrimental to human health. This review collates several decades of literature on the physiology and pathophysiology of ultra-marathon running, with emphasis on the cardiorespiratory implications. Herein, we discuss the prevalence and clinical significance of postrace decreases in lung function and diffusing capacity, respiratory muscle fatigue, pulmonary edema, biomarkers of cardiac injury, left/right ventricular dysfunction, and chronic myocardial remodeling. The aim of this article is to inform risk stratification for ultra-marathon and to edify best practice for personnel overseeing the events (i.e., race directors and medics).


Assuntos
Sistema Cardiovascular/fisiopatologia , Corrida de Maratona/fisiologia , Sistema Respiratório/fisiopatologia , Biomarcadores/sangue , Humanos , Fatores de Risco
9.
Am J Physiol Regul Integr Comp Physiol ; 315(4): R810-R819, 2018 10 01.
Artigo em Inglês | MEDLINE | ID: mdl-29975566

RESUMO

Heart failure (HF) patients are susceptible to heat strain during exercise, secondary to blunted skin blood flow (SkBF) responses, which may be explained by impaired nitric oxide (NO)-dependent vasodilation. Folic acid improves vascular endothelial function and SkBF through NO-dependent mechanisms in healthy older individuals and patients with cardiovascular disease. We examined the effect of folic acid supplementation (5 mg/day for 6 wk) on vascular function [brachial artery flow-mediated dilation (FMD)] and SkBF responses [cutaneous vascular conductance (CVC)] during 60 min of exercise at a fixed metabolic heat production (300 WHprod) in a 30°C environment in 10 patients with HF (New York Heart Association Class I-II) and 10 healthy controls (CON). Serum folic acid concentration increased in HF [preintervention (pre): 1.4 ± 0.2; postintervention (post): 8.9 ± 6.7 ng/ml, P = 0.01] and CON (pre: 1.3 ± 0.6; post: 5.2 ± 4.9 ng/ml, P = 0.03). FMD improved by 2.1 ± 1.3% in HF ( P < 0.01), but no change was observed in CON postintervention ( P = 0.20). During exercise, the external workload performed on the cycle ergometer to attain the fixed level of heat production for exercise was similar between groups (HF: 60 ± 13; CON: 65 ± 20 external workload, P = 0.52). Increases in CVC during exercise were similar in HF (pre: 0.89 ± 0.43; post: 0.83 ± 0.45 au/mmHg, P = 0.80) and CON (pre: 2.01 ± 0.79; post: 2.03 ± 0.72 au/mmHg, P = 0.73), although the values were consistently lower in HF for both pre- and postintervention measurement intervals ( P < 0.05). These findings demonstrate that folic acid improves vascular endothelial function in patients with HF but does not enhance SkBF during exercise at a fixed metabolic heat production in a warm environment.


Assuntos
Artéria Braquial/efeitos dos fármacos , Suplementos Nutricionais , Endotélio Vascular/efeitos dos fármacos , Exercício Físico , Ácido Fólico/uso terapêutico , Insuficiência Cardíaca/tratamento farmacológico , Transtornos de Estresse por Calor/tratamento farmacológico , Temperatura Alta/efeitos adversos , Pele/irrigação sanguínea , Vasodilatação/efeitos dos fármacos , Idoso , Velocidade do Fluxo Sanguíneo , Regulação da Temperatura Corporal , Artéria Braquial/fisiopatologia , Suplementos Nutricionais/efeitos adversos , Endotélio Vascular/fisiopatologia , Ácido Fólico/efeitos adversos , Insuficiência Cardíaca/diagnóstico , Insuficiência Cardíaca/fisiopatologia , Transtornos de Estresse por Calor/diagnóstico , Transtornos de Estresse por Calor/fisiopatologia , Humanos , Masculino , Pessoa de Meia-Idade , Fluxo Sanguíneo Regional , Fatores de Tempo , Resultado do Tratamento
10.
J Card Fail ; 23(8): 621-627, 2017 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-28408306

RESUMO

Upon heat exposure, the thermoregulatory system evokes reflex increases in sweating and skin blood flow responses to facilitate heat dissipation and maintain heat balance to prevent the continuing rise in core temperature. These heat dissipating responses are mediated primarily by autonomic and cardiovascular adjustments; which, if attenuated, may compromise thermoregulatory control. In patients with heart failure (HF), the neurohumoral and cardiovascular dysfunction that underpins this condition may potentially impair thermoregulatory responses and, consequently, place these patients at a greater risk of heat-related illness. The aim of this review is to describe thermoregulatory mechanisms and the factors that may increase the risk of heat-related illness in patients with HF. An understanding of the mechanisms responsible for impaired thermoregulatory control in HF patients is of particular importance, given the current and projected increase in frequency and intensity of heat waves, as well as the promotion of regular exercise as a therapeutic modality. Furthermore, novel therapeutic strategies that may improve thermoregulatory control in HF, and the clinical relevance of this work in this population will be discussed.


Assuntos
Regulação da Temperatura Corporal/fisiologia , Insuficiência Cardíaca/fisiopatologia , Temperatura Alta/efeitos adversos , Sudorese/fisiologia , Exercício Físico/fisiologia , Insuficiência Cardíaca/diagnóstico , Humanos , Pele/irrigação sanguínea
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