Efeitos do treinamento de força na susceptibilidade às arritmias ventriculares

• Autor(a) principal: Santos, Rodrigo Miguel dos
• Data de Publicação: 2020
• Tipo de documento: Tese
• Idioma: por
• Título da fonte: Repositório Institucional da UFS
• Texto Completo: http://ri.ufs.br/jspui/handle/riufs/15832
• topic: Ciências fisiológicas; Arritmia cardíaca; Exercícios físicos; Stress oxidativo; Coração - Doenças; Cardiac arrhythmia; Resistance training; Training intensity; Physical exercise; Oxidative stress; CIENCIAS BIOLOGICAS::FISIOLOGIA

Effects of strength training on ventricular arrhythmias susceptibility, Rodrigo Miguel dos Santos, São Cristóvão-SE, 2020. Physical training is an essential tool for disease prevention and has been used as treatment of diseases, especially for cardiovascular diseases. However, recent evidence suggests a potential negative effect when exercise is performed at excessive amount. It thus becomes important to investigate dose-response exercise protocols, aiming to define the limiting doses, particularly at which the cardiac effects become deleterious. Therefore, the present study aimed to evaluate the effects of strength training on cardiac arrhythmias in healthy rats. Male Wistar rats were trained for six weeks in a squat-mimicking strength training protocol. The animals were randomly allocated to control, low-, moderate- or high-intensity groups, trained three times a week; or control, low-, moderate-, and highintensity, trained five times a week. After the training period, animals were subjected to in vivo arrhythmias susceptibility assessments, under caffeine and epinephrine stimulation, and were monitored with electrocardiogram examinations. Our findings revealed that animals trained five times a week on high intensity protocols were more susceptible to ventricular arrhythmias than all other groups. Further, electrical and contractile cardiac properties were investigated in animals trained with high intensity and high frequency, where we found strength training caused QT interval prolongation. We also used RT-PCR to assess expression of key genes involved in cardiac repolarization, which revealed an increase in Kcnj2 and Kcne2 and reduced Kcnd3 expression. In addition, we observed an increase in triadin, calmodulin and calcium-dependent protein kinase/calmodulin type II delta expression, along with a reduction in the calcium ATPase of the sarcoplasmic reticulum and the sodium/calcium exchanger. Although strength training did not cause cardiac hypertrophy or fibrosis, it increased mRNA abundance of atrial natriuretic peptide, actin alfa 1 and myosin heavy chains – all biomarkers of pathological cardiac phenotypes. In order to better understand the changes caused by strenuous strength training, production of reactive oxygen species was assessed in cardiac tissue, and its increase was verified due to the increased expression of NADPH oxidase 4. These changes were followed by increased oxidative damage in left ventricles and reduced gene expression of the antioxidant enzymes superoxide dismutase and glutathione peroxidase. Altogether, our findings show that strength training induces a condition favorable to ventricular arrhythmias appearance, with an effect that is dependent on exercise intensity and frequency.