The effect of acute magnesium loading on the maximal exercise performance of stable chronic obstructive pulmonary disease patients

OBJECTIVE: The potential influence of magnesium on exercise performance is a subject of increasing interest. Magnesium has been shown to have bronchodilatatory properties in asthma and chronic obstructive pulmonary disease patients. The aim of this study was to investigate the effects of acute magnesium IV loading on the aerobic exercise performance of stable chronic obstructive pulmonary disease patients. METHODS: Twenty male chronic obstructive pulmonary disease patients (66.2 + 8.3 years old, FEV1: 49.3+19.8%) received an IV infusion of 2 g of either magnesium sulfate or saline on two randomly assigned occasions approximately two days apart. Spirometry was performed both before and 45 minutes after the infusions. A symptom-limited incremental maximal cardiopulmonary test was performed on a cycle ergometer at approximately 100 minutes after the end of the infusion. ClinicalTrials.gov: NCT00500864 RESULTS: Magnesium infusion was associated with significant reductions in the functional residual capacity (-0.41 l) and residual volume (-0.47 l), the mean arterial blood pressure (-5.6 mmHg) and the cardiac double product (734.8 mmHg.bpm) at rest. Magnesium treatment led to significant increases in the maximal load reached (+8 w) and the respiratory exchange ratio (0.06) at peak exercise. The subgroup of patients who showed increases in the work load equal to or greater than 5 w also exhibited significantly greater improvements in inspiratory capacity (0.29 l). CONCLUSIONS: The acute IV loading of magnesium promotes a reduction in static lung hyperinflation and improves the exercise performance in stable chronic obstructive pulmonary disease patients. Improvements in respiratory mechanics appear to be responsible for the latter finding

Heart rate variability under resting conditions in postmenopausal and young women

The aim of the present study was to compare the modulation of heart rate in a group of postmenopausal women to that of a group of young women under resting conditions on the basis of R-R interval variability. Ten healthy postmenopausal women (mean ± SD, 58.3 ± 6.8 years) and 10 healthy young women (mean ± SD, 21.6 ± 0.82 years) were submitted to a control resting electrocardiogram (ECG) in the supine and sitting positions over a period of 6 min. The ECG was obtained from a one-channel heart monitor at the CM5 lead and processed and stored using an analog to digital converter connected to a microcomputer. R-R intervals were calculated on a beat-to-beat basis from the ECG recording in real time using a signal-processing software. Heart rate variability (HRV) was expressed as standard deviation (RMSM) and mean square root (RMSSD). In the supine position, the postmenopausal group showed significantly lower (P<0.05) median values of RMSM (34.9) and RMSSD (22.32) than the young group (RMSM: 62.11 and RMSSD: 49.1). The same occurred in the sitting position (RMSM: 33.0 and RMSSD: 18.9 compared to RMSM: 57.6 and RMSSD: 42.8 for the young group). These results indicate a decrease in parasympathetic modulation in postmenopausal women compared to young women which was possibly due both to the influence of age and hormonal factors. Thus, time domain HRV proved to be a noninvasive and sensitive method for the identification of changes in autonomic modulation of the sinus node in postmenopausal women

Investigating autonomic nervous system dysfunction among patients with post-COVID condition and prolonged cardiovascular symptoms

Heart Rate Variability (HRV) and arterial pressure (AP) variability and their responses to head-up tilt test (HUTT) were investigated in Post-COVID-19 syndrome (PCS) patients reporting tachycardia and/or postural hypotension. Besides tachycardia, PCS patients also showed attenuation of the following HRV parameters: RMSSD [square root of the mean of the sum of the squares of differences between adjacent normal-to-normal (NN) intervals] from statistical measures; the power of RR (beat-to-beat interval) spectra at HF (high frequency) from the linear method spectral analysis; occurrence of 2UV (two unlike variation) pattern of RR from the nonlinear method symbolic analysis; and the new family of statistics named sample entropy, when compared to control subjects. Basal AP and LF (low frequency) power of systolic AP were similar between PCS patients and control subjects, while 0 V (zero variation) patterns of AP from the nonlinear method symbolic analysis were exacerbated in PCS patients. Despite tachycardia and a decrease in RMSSD, no parameter of HRV changed during HUTT in PCS patients compared to control subjects. PCS patients reassessed after 6 months showed higher HF power of RR spectra and a higher percentage of 2UV pattern of RR. Moreover, the reassessed PCS patients showed a lower occurrence of 0 V patterns of AP, while the HUTT elicited HR (heart rate) and AP responses identical to control subjects. The HRV and AP variability suggest an autonomic dysfunction with sympathetic predominance in PCS patients. In contrast, the lack of responses of HRV and AP variability indices during HUTT indicates a marked impairment of autonomic control. Of note, the reassessment of PCS patients showed that the noxious effect of COVID-19 on autonomic control tended to fade over time

Relação entre os caracteres determinantes das eficiências no uso de nitrogênio e fósforo em milho

O melhoramento genético das eficiências no uso de N (EUN) e P (EUP) é um dos meios para se obterem produtividades de grãos satisfatórias, com menores custos e de modo sustentável. Todavia, pouco se sabe a respeito da relação entre os caracteres determinantes dessas eficiências, o que tem dificultado o uso da seleção precoce e indireta. Portanto, objetivou-se, com este trabalho, identificar a relação entre os caracteres determinantes das eficiências no uso de nitrogênio e fósforo, em milho. Para isso, avaliaram-se 14 linhagens e 39 híbridos simples, em dois experimentos, em baixa e alta disponibilidade de N e P, em delineamento inteiramente ao acaso, com duas repetições, em esquema fatorial simples. Os experimentos foram conduzidos em telado. Foram utilizados tubos cilíndricos de PVC, com 4 dm³ de capacidade, preenchidos com dois tipos de substrato, de acordo com o experimento. As soluções nutritivas foram fornecidas a partir do sétimo dia após o transplantio, aplicando-se 250 ml tubo-1, a cada dois dias. As plantas foram colhidas em estádio de seis folhas completamente expandidas (V6) e os caracteres avaliados foram: massa da parte aérea seca (MPS), área de raiz específica (ARE), comprimento de raízes laterais (CRLat) e axiais (CRAxi) e os dois componentes da EUN e EUP, as eficiências de utilização (EUt) e a de absorção (EAb). Foram realizadas análises de variância e de trilha dos dados coletados. Os caracteres de raiz não apresentaram efeitos significativos sobre as EUN e EUP. A MPS é o principal determinante das EUN e EUP, independentemente da disponibilidade nutricional

Physical Training as Non-Pharmacological Treatment of Neurocardiogenic Syncope

Fundamento: Caracterizada por perda súbita e transitória da consciência e do tônus postural, com recuperação rápida e espontânea, a síncope é causada por uma redução aguda da pressão arterial sistêmica e, por conseguinte, do fluxo sanguíneo cerebral. Os resultados insatisfatórios com o uso de fármacos permitiu que o tratamento não farmacológico da síncope neurocardiogênica fosse contemplado como primeira opção terapêutica. Objetivos: Comparar, em pacientes com síncope neurocardiogênica, o impacto do Treinamento Físico Aeróbico (TFA) de moderada intensidade e de uma intervenção controle, na positividade do Teste de Inclinação Passiva (TIP) e no tempo de tolerância ortostática. Métodos: Foram estudados 21 pacientes com história de síncope neurocardiogênica recorrente e TIP positivo. Esses foram aleatorizados em: Grupo Treinado (GT), n = 11, e Grupo Controle (GC), n = 10. O GT foi submetido a 12 semanas de TFA supervisionado, em cicloergômetro, e o GC, a um procedimento controle que consistia na realização de 15 minutos de alongamentos e 15 minutos de caminhada leve. Resultados: O GT apresentou efeito positivo ao treinamento físico, com aumento significativo do consumo de oxigênio-pico. Já o GC não apresentou nenhuma mudança estatisticamente significante, antes e após a intervenção. Após o período de intervenção, 72,7% da amostra do GT apresentou resultado negativo ao TIP, não apresentando síncope na reavaliação. Conclusão: O programa de treinamento físico aeróbico supervisionado por 12 semanas foi capaz de reduzir o número de TIP positivos, assim como foi capaz de aumentar o tempo de tolerância na posição ortostática durante o teste após o período de intervenção

Influence of Aerobic Training on The Mechanics of Ventricular Contraction After Acute Myocardial Infarction: A Pilot Study

Abstract The study of myocardial contractility, based on the new anatomical concepts that govern cardiac mechanics, represents a promising strategy of analysis of myocardial adaptations related to physical training in the context of post-infarction. We investigated the influence of aerobic training on physical capacity and on the evaluation parameters of left ventricular contraction mechanics in patients with myocardial infarction. Thirty-one patients (55.1 ± 8.9 years) who had myocardial infarction in the anterior wall were prospectively investigated in three groups: interval training group (ITG) (n = 10), moderate training group (MTG) n = 10) and control group (CG) (n = 10). Before and after 12 weeks of clinical follow-up, patients underwent cardiopulmonary exercise testing and cardiac magnetic resonance imaging. The trained groups performed supervised aerobic training on treadmill, in two different intensities. A statistically significant increase in peak oxygen uptake (VO2) was observed in the ITG (19.2 ± 5.1 at 21.9 ± 5.6 ml/kg/min, p < 0.01) and in the MTG 18.8 ± 3.7 to 21.6 ± 4.5 ml/kg/min, p < 0.01). The GC did not present a statistically significant change in peak VO2. A statistically significant increase in radial strain (STRAD) was observed in the CG: basal STRAD (57.4 ± 16.6 to 84.1 ± 30.9%, p < 0.05), medial STRAD (57.8 ± 27, 9 to 74.3 ± 36.1%, p < 0.05) and apical STRAD (38.2 ± 26.0 to 52.4 ± 29.8%, p < 0.01). The trained groups did not present a statistically significant change of the radial strain. The present study points to a potential clinical application of the parameters of ventricular contraction mechanics analysis, especially radial strain, to discriminate post-infarction myocardial adaptations between patients submitted or not to aerobic training programs

Aerobic Training after Myocardial Infarction: Remodeling Evaluated by Cardiac Magnetic Resonance

Abstract Background: Numerous studies show the benefits of exercise training after myocardial infarction (MI). Nevertheless, the effects on function and remodeling are still controversial. Objectives: To evaluate, in patients after (MI), the effects of aerobic exercise of moderate intensity on ventricular remodeling by cardiac magnetic resonance imaging (CMR). Methods: 26 male patients, 52.9 ± 7.9 years, after a first MI, were assigned to groups: trained group (TG), 18; and control group (CG), 8. The TG performed supervised aerobic exercise on treadmill twice a week, and unsupervised sessions on 2 additional days per week, for at least 3 months. Laboratory tests, anthropometric measurements, resting heart rate (HR), exercise test, and CMR were conducted at baseline and follow-up. Results: The TG showed a 10.8% reduction in fasting blood glucose (p = 0.01), and a 7.3-bpm reduction in resting HR in both sitting and supine positions (p < 0.0001). There was an increase in oxygen uptake only in the TG (35.4 ± 8.1 to 49.1 ± 9.6 mL/kg/min, p < 0.0001). There was a statistically significant decrease in the TG left ventricular mass (LVmass) (128.7 ± 38.9 to 117.2 ± 27.2 g, p = 0.0032). There were no statistically significant changes in the values of left ventricular end-diastolic volume (LVEDV) and ejection fraction in the groups. The LVmass/EDV ratio demonstrated a statistically significant positive remodeling in the TG (p = 0.015). Conclusions: Aerobic exercise of moderate intensity improved physical capacity and other cardiovascular variables. A positive remodeling was identified in the TG, where a left ventricular diastolic dimension increase was associated with LVmass reduction

Influence of Aerobic Training on The Mechanics of Ventricular Contraction After Acute Myocardial Infarction: A Pilot Study

<div><p>Abstract The study of myocardial contractility, based on the new anatomical concepts that govern cardiac mechanics, represents a promising strategy of analysis of myocardial adaptations related to physical training in the context of post-infarction. We investigated the influence of aerobic training on physical capacity and on the evaluation parameters of left ventricular contraction mechanics in patients with myocardial infarction. Thirty-one patients (55.1 ± 8.9 years) who had myocardial infarction in the anterior wall were prospectively investigated in three groups: interval training group (ITG) (n = 10), moderate training group (MTG) n = 10) and control group (CG) (n = 10). Before and after 12 weeks of clinical follow-up, patients underwent cardiopulmonary exercise testing and cardiac magnetic resonance imaging. The trained groups performed supervised aerobic training on treadmill, in two different intensities. A statistically significant increase in peak oxygen uptake (VO2) was observed in the ITG (19.2 ± 5.1 at 21.9 ± 5.6 ml/kg/min, p < 0.01) and in the MTG 18.8 ± 3.7 to 21.6 ± 4.5 ml/kg/min, p < 0.01). The GC did not present a statistically significant change in peak VO2. A statistically significant increase in radial strain (STRAD) was observed in the CG: basal STRAD (57.4 ± 16.6 to 84.1 ± 30.9%, p < 0.05), medial STRAD (57.8 ± 27, 9 to 74.3 ± 36.1%, p < 0.05) and apical STRAD (38.2 ± 26.0 to 52.4 ± 29.8%, p < 0.01). The trained groups did not present a statistically significant change of the radial strain. The present study points to a potential clinical application of the parameters of ventricular contraction mechanics analysis, especially radial strain, to discriminate post-infarction myocardial adaptations between patients submitted or not to aerobic training programs.</p></div

Insuficiencia cardíaca: comparación entre el test de esfuerzo de seis minutos y el test cardiopulmonar

FUNDAMENTO: A insuficiência cardíaca crônica (IC) é uma síndrome complexa caracterizada pela redução do débito cardíaco em relação às necessidades metabólicas do organismo, bem como alterações metabólicas e do eixo neuro-hormonal. Sintomas como fadiga muscular e dispneia são notórios e os testes de esforço são amplamente utilizados para a avaliação da capacidade funcional, prognóstico e eficácia das intervenções terapêuticas nessa síndrome. OBJETIVO: Avaliar a reprodutibilidade do teste de caminhada de seis minutos (TC6') em pacientes com IC e correlacionar a magnitude das variáveis atingidas no pico do esforço do TC6' com as de um teste cardiopulmonar (TCP). MÉTODOS: Foram estudados 16 pacientes (12 homens e 4 mulheres) com diagnóstico de IC CF I-II (NYHA). Os voluntários foram submetidos a dois testes TC6' (TC6'1 e TC6'2) com intervalo de 30 minutos entre eles; posteriormente realizaram um TCP máximo. RESULTADOS: Todas as variáveis obtidas nos dois TC6' mostraram-se significantes, com altas correlações: distância percorrida (DP) (r = 0,93; p < 0,0001), frequência cardíaca (FC) (r = 0,89; p < 0,0001), consumo de oxigênio (VO2) (r = 0,93; p < 0,0001) e escala de percepção de esforço (r = 0,85; p < 0,0001). Por sua vez, todas as variáveis analisadas no TC6' mostraram correlações moderadas e significantes com as variáveis obtidas no TCP, a saber: FC pico (r = 0,66; p = 0,005); VO2 (r = 0,57; p = 0,02) e VO2 no TCP e DP no TC6'2 (r = 0,70; p = 0,002). CONCLUSÃO: O TC6' foi reprodutível nesse grupo de pacientes com IC (NYHA - I-II) e se correlacionou com o TCP. Sendo assim, apresenta-se como ferramenta de avaliação fidedigna, constituindo-se numa alternativa adequada, segura e de baixo custo para a prescrição de exercícios físicos aeróbicos em pacientes com IC.BACKGROUND: Chronic heart failure (HF) is a syndrome characterized by reduced cardiac output in relation to the metabolic needs of the organism, as well as metabolic and neurohormonal axis abnormalities. Symptoms such as fatigue and dyspnoea are notorious and stress tests are widely used to assess functional capacity, prognosis and effectiveness of therapeutic interventions in this syndrome. OBJECTIVE: To evaluate the reproducibility of the six-minute walk test (6MW) in patients with HF and correlate the magnitude of the variables reached at peak exercise of the 6MWT with a cardiopulmonary exercise test (CPET). METHODS: We studied 16 patients (12 men and 4 women) diagnosed with HF FC I-II (NYHA). The volunteers underwent two 6MWT (6MWT'1 and 6MWT'2) with 30-minute interval between them; then, they underwent a maximum CPET. RESULTS: All variables obtained in the two 6MWT' proved to be significant with high correlations: distance walked (DW) (r = 0.93, p < 0.0001), heart rate (HR) (r = 0.89, p < 0.0001), oxygen consumption (VO2) (r = 0.93, p < 0.0001) and scale of perceived exertion (r = 0.85, p < 0.0001). In turn, all variables analyzed in the 6MWT' showed significant and moderate correlations with the variables obtained from the CPET, namely: peak HR (r = 0.66; p = 0.005); VO2 (r = 0.57; p = 0.02) and VO2 in the CPET and DT in the 6MWT'2 (r = 0.70; p = 0.002). CONCLUSION: The 6MWT was reproducible in this group of patients with HF (NYHA - I-II) and correlated with the CPET. Therefore, it is a tool for reliable evaluation, and a suitable, safe and low-cost alternative for the prescription of aerobic exercise in patients with HF.FUNDAMENTO: La insuficiencia cardíaca crónica (IC), es un síndrome complejo que se caracteriza por la reducción del débito cardíaco con relación a las necesidades metabólicas del organismo, como también por las alteraciones metabólicas y del eje neuro hormonal. Los síntomas como el cansancio muscular y la disnea son notables y los test de esfuerzo son ampliamente utilizados para la evaluación de la capacidad funcional, pronóstico y eficacia de las intervenciones terapéuticas en ese síndrome. OBJETIVO: Evaluar la reproductibilidad del test de esfuerzo de seis minutos (TE6') en pacientes con IC y correlacionar la magnitud de las variables alcanzadas en el pico del esfuerzo del TE6' con las de un test cardiopulmonar (TECP). MÉTODOS: Se estudiaron 16 pacientes (12 hombres y 4 mujeres) con un diagnóstico de IC CF I-II (NYHA). Los voluntarios se sometieron a dos test TE6' (TC6'1 y TC6'2), con un intervalo de 30 minutos entre ellos. Posteriormente realizaron un TECP máximo. RESULTADOS: Todas las variables obtenidas en los dos TE6' fueron significativas, y con altas correlaciones: distancia recorrida (DR) (r = 0,93; p < 0,0001), frecuencia cardíaca (FC) (r = 0,89; p < 0,0001), consumo de oxígeno (VO2) (r = 0,93; p < 0,0001) y escala de percepción de esfuerzo (r = 0,85; p < 0,0001). A su vez, todas las variables analizadas en el TE6' mostraron correlaciones moderadas y significativas con las variables obtenidas en el TECP, a saber: FC pico (r = 0,66; p = 0,005); VO2 (r = 0,57; p = 0,02) y VO2 en el TECP y DR en el TE6'2 (r = 0,70; p = 0,002). CONCLUSIÓN: El TE6' se pudo reproducir en ese grupo de pacientes con IC (NYHA - I-II) y se correlacionó con el TECP. Por lo tanto, se presenta como una herramienta de evaluación fidedigna y constituye una alternativa adecuada, segura y de bajo coste para la prescripción de ejercicios físicos aeróbicos en pacientes con IC.FAEPACoordenacao de Aperfeicoamento de Pessoal de Nivel Superior (CAPES)CNPqFAPES