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

• Main Author: Quitério,RJ
• Publication Date: 2007
• Other Authors: Moraes,FR, Oliveira,L, Teixeira,LC, Gallo Jr,L, Catai,AM, Silva,E
• Format: Article
• Language: eng
• Source: Brazilian Journal of Physical Therapy
• Download full: http://old.scielo.br/scielo.php?script=sci_arttext&pid=S1413-35552007000300003
• topic: heart rate; torque; isometric exercise; knee flexion and extension

OBJECTIVE: To evaluate the influence of joint angle on heart rate (HR) responses induced by isometric exercise. METHODS: 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 60º and 90º and knee flexion at angles of 30º and 90º 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 (deltaHR) were analyzed using the Friedman test with the Dunn post-hoc test, and their correlation was analyzed using the Spearman test (alpha= 0.05). RESULTS: 1) MMT was significantly higher at 60º and 90º knee extension than at 30º and 90º knee flexion (p< 0.05), while no significant differences were found between the two extension angles or between the two flexion angles; 2) deltaHR was similar under all the experimental conditions; 3) No correlation was found between MMT and deltaHR. 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.