Volume 30, Issue 3 (5-2023)                   RJMS 2023, 30(3): 129-140 | Back to browse issues page

Research code: 0
Ethics code: IR.LUMS.REC.1398.254
Clinical trials code: IRCT20201022049111N1

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Delfani Z, Shahidi F, Kashef M, Namdari M. The Effect of A Period of Low-Volume and High-Intensity Aerobic Interval Training on the Response of Structural and Functional Indicators of the Heart in Patients with Myocardial Infarction. RJMS 2023; 30 (3) :129-140
URL: http://rjms.iums.ac.ir/article-1-7619-en.html
PhD Student, Department of Sport Physiology, Faculty of Physical Education and Sport Sciences, Shahid Rajaee Teacher Training University, Tehran, Iran , venus_delfani@yahoo.com
Abstract:   (431 Views)
Background & Aims: Myocardial infarction is one of the most important ischemic cardiopathies (1). Despite progressive improvement in medical therapy and standard care, Exercise-based rehabilitation programs have been shown to improve the exercise capacity of patients with myocardial infarction through a multifactorial effect (2). In this context, high-intensity interval exercise is a growing field of research (3). Many studies have shown that High-intensity interval training (HIIT) has more protective effects on myocardial tissue than aerobic exercise (6). Therefore, this study aimed to investigate the effect of a period of low-volume, high-intensity interval aerobic exercise on heart structural and functional indicators in patients with myocardial infarction.
Methods: In this semi-experimental study with pretest–A post testdesign,20 patients with documented MI (without regular exercise history) volunteered to participate in the research randomly in two control groups (n=10) and exercise group (n=10).The subjects trained for 3 d/week for 12 weeks (one session on a treadmill and another session on an exercise bike), under the supervision of an expert physician and exercise physiologistspecialists. We asked the control group patients not to engage in any other leisure exercise during the study.The rationale formixing bike and treadmill was to avoid the osteoarticular effects of two treadmill days by considering the HIIT program. We calculated the optimizedexercise zone using the Karvonen formula, which calculates the exercise heart rate as a percentage of the heart rate reserve, added to the resting heart rate (11).The training intensity was adjusted by constantly changing the treadmill's speed and incline or the bike's power and speed to ensure that we performed all training sessions with the target heart rate (HR)(9). Training intensity was controlled by monitoring participants’ heart rate (HR) using a Polar HR monitor (Polar Electro OY, Finland). Heart rate, blood pressure, and perceived exertion were evaluated using the Borg Scale (6 to 20 points) before, during, and after each session (12). We measured the structural and functional indices of the heart using an echocardiography device in baseline conditions and after 12 weeks of training. We performed all examinations at rest in the left lateral decubitus position according to the guidelines of the American Society of Echocardiography (16). We analyzed data using paired t-test and independent t-test.All statistical tests were performed with SPSS software version 28.0 (IBM SPSS, Inc, Armonk, NY). Values of p <0.05 were considered statistically significant.
Results: End-diastolic diameter, end-diastolic volume, injection fraction, left ventricular stroke volume, and peak oxygen consumption of the training group wassignificantly increased compared to the baseline conditions and compared to the control group (P<0.05) and Resting heart rate, systolic and diastolic blood pressure showed a significant decrease (P<0.05).But there was no significant change in the thickness of the posterior wall at the end of the diastoleof the left ventricle.
Conclusion: The main results of this study showed that the HIITtraining protocol withthe lowvolume produced positive and significant changes in systolic blood pressure, diastolic blood pressure, resting heart rate and VO2 peak, which shows a positive training response in these patients. But we found no improvement in the control group and only systolic and diastolic blood pressure remained unchanged. Also, in the parameters of resting heart rate, systolic and diastolic blood pressure and VO2 peak, a significant difference was found between the HIIT group and the control group, which is related to the improvement of physical activity level and functional capacity. These findings show the effectiveness of a low-volume HIIT program in improving clinically important parameters. The results of the present study showed that left ventricular end-diastolic volume, left ventricular ejection fraction (EF) and stroke volume (SV) increased significantly after HIIT exercises compared to the control group. Recent studies have shown that physiological adaptations of the left ventricle following exercise are divided into three general sections: 1) physiological hypertrophy of existing myocytes, which is associated with increased production of specific growth factors; 2) activation of cardiac stem cells, which increase the number and their differentiation leads to myocytes and vascular cells and 3) accumulation of new heart cells called new myocytes and vascular cells (32, 33). These cellular changes depend on the intensity and duration of exercise, which is associated with increased contractile muscle mass, cardiac function, and decreased wall tension. Therefore, since the results of the present study show an improvement in left ventricular function index  in patients with MI following low volumes of HIIT training, it is likely that low volume of HIIT volumes could be stimulated the above mechanisms and play an important role in improving cardiovascular function. The results of the present study showed that the end-diastolic diameter of the left ventricle increased significantly in the HIIT group compared to the control group. Therefore, it can be said that 12 weeks of low-volume HIIT training has led to an increase in blood volume and venous return (because of skeletal muscle pumping and venous contraction), which according to Frank-Starling's law, increases ventricular stretch and ventricular contractility. It has led to an increase in injection fraction, which ultimately causes an increase in stroke volume and a decrease in resting heart rate, and one reason for the significant increase in VO2 peak after 12 weeks of low-volume HIIT training may be the increase in blood volume and ventricular end-diastolic diameter. Be left, because these two mechanisms cause an increase in the number of mitochondria and their enzyme contents, capillary density and better blood flow in active muscles and heart muscles (38). Also, the results showed that the average thickness of the posterior wall of the left ventricle at the end of diastole in the HIIT group had a slight and non-significant increase. Reports show that aerobic activity causes a volume load on the heart, an increase in the heart chambers, especially the left ventricle, and a relative increase in the ventricular walls of the heart (39). Perhaps the reason for the non-significant changes in the thickness of the posterior wall at the end of left ventricular diastole in this study was the rapid filling of the left ventricle during ventricular diastole or the small volume of the exercise program, because the volume of the exercise program was not enough to cause obvious structural changes. In summary,interval aerobic training with low volume and high intensity improves the structure and function of the left ventricle, but we need more training volume to achieve more obvious structural changes in the left ventricle of patients with MI.

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Type of Study: Research | Subject: Exercise Physiology

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