Comparison of functional changes in the heart and QTc intervals in a maximal and isotonic isometric exercise activity in active and inactive men

QTc distance fluctuations are related to resting and exercise with ventricular arrhythmias and sudden cardiac death. Therefore, the aim of the present study was to investigate the changes of functional parameters of the heart and QTc interval in active and inactive men in one of the most isometric and isotonic exercise activities.

An experimental study was conducted at Shahid Rajaee Teacher Training University in 2018 with a pre-test and post-test. A total of 20 healthy active and inactive volunteers (n = 10) were randomly selected and hand-grip exercise protocol with maximal intentional contraction was performed as isometric with a longer stroke in the Fullext elbow mode by pressing the dynamometer knob for 30 seconds. After 60 minutes of rest, the isotonic protocol was run at the 90 degree Flex elbow angle of 15 sts. The change in QTc interval was corrected using the Bazett formula for heart rate. Systolic and diastolic blood pressures were recorded using a gyro barometer. Data were analyzed using repeated measures analysis (P≤0.05) in  SPSS, version 21.

The statistical findings showed a significant increase in cardiac performance indices of systolic blood pressure (1166.±6.74), heart rate (112.60±10.81), and the result of a doubling of pulse-pressure (RPP)(13.53±1.31) after isometric activity in active and inactive patients. But QTc (420.3± 36) distance and R-Rdistance (512.20± 64.36) after isotonic activity increased significantly. There was a significant difference in QTc changes, heart rate, R-Rspacing, and RPP between the three stages (p<0.05); however, there was no significant difference between the diastolic and diastolic blood pressure variables.

It seems that QTc after isotonic exercises can be screened for cardiovascular disease and assessing the cardiovascular status. It is also useful in predicting cardiovascular events.