Heart Frequency Patterns Due to 30% and 50% Maximal Isometric Contraction (MIC) in Adolescents

¹ Faculty of Medicine and Health Sciences, Muhammadiyah University of Yogyakarta, Yogyakarta, Indonesia
² Faculty of Medicine, Public Health, and Nursing, Gadjah Mada University/ Dr. Sardjito General Hospital, Yogyakarta, Indonesia

^* Corresponding author: ratna.indriawati@umy.ac.id

Abstract

We often do isometric contractions. Isometric contractions cause cardiovascular responses, including changes in heart rate. The aim of this study was to examine the effect of isometric contraction intensity equivalent to 30% MIC and 50% MIC with handgrip and backlift on increased heart rate. This research is a quasi-experimental, pretest, and post-test design. The subjects were 60 men aged 17-24 years who met the inclusion criteria and were divided into 2 groups, the group with a handgrip dynamometer and the treatment group with a backlift dynamometer. Heart rate frequency measurements were carried out before, during, and after isometric contraction with handgrip and backlift dynamometers, which were equivalent to 30% and 50% MIC. The results showed that there was a significant difference (p <0.05) between heart rate frequencies, before, during, and after isometric contractions. Increasing the intensity of isometric contraction from 30% to 50% MIC, both with handgrip and backlift dynamometer increased heart rate significantly (p <0.05). There was a significant increase (p <0.05) in the pulse frequency between isometric contraction and handgrip dynamometer with backlift. The conclusion of this study is that the magnitude of the increase in heart rate due to isometric contraction is 50% MIC equivalent to 30% MIC.