Influences of torque and joint angle on heart rate responses during isometric exercise in young men

Abstract

Objective: To evaluate the influence of joint angle on heart rate (HR) responses induced by isometric exercise. Method: Ten healthy men (23.8 ± 2.5 years old) underwent isometric maximum voluntary contraction (MVC) tests lasting 10 sec using an electronic dynamometer under the following experimental conditions: knee extension at angles of 60° and 90° and knee flexion at angles of 30° and 90° angles. Their HR was recorded at rest (65 sec), during MVC (10 sec) and during the recovery period (120 sec). The data on mean maximum torque (MMT) and HR variation (ΔHR) were analyzed using the Friedman test with the Dunn post-hoc test, and their correlation was analyzed using the Spearman test (α= 0.05). Results: 1) MMT was significantly higher at 60° and 90° knee extension than at 30° and 90° knee flexion (p< 0.05), while no significant differences were found between the two extension angles or between the two flexion angles; 2) ΔHR was similar under all the experimental conditions; 3) No correlation was found between MMT and ΔHR. Conclusion: The data suggest that the rapid increase in HR during the 10 sec of isometric MVC does not depend on the joint angle or the morphofunctional differences between the two muscle groups studied.

Respostas Da Frequência Cardíaca Ao Exercício Resistido E Sua Relação Com a Variabilidade Da Frequência Cardíaca Em Indivíduos Com Fatores De Risco Para Doenças Cardiovasculares

“…Para avaliação das respostas da FC ao esforço máximo, utilizamos o teste de 1RM, que teve um esforço com duração média de oito segundos, caracterizando um estímulo dependente essencialmente da inibição do sistema parassimpático sobre o nodo sinusal 2,11,41,42 . A variação da FC repouso-exercício obtida neste estudo (21,1 bat/min) apresenta semelhança aos achados do estudo de Farinatti e Assis 37 , que, ao avaliar jovens de ambos os sexos, encontraram uma variação de 22,1 bat/min, sendo que a FC variou de 74,9 bat/min na condição de repouso para 97 bat/min no pico do esforço.…”