Effects of Resistance Training on Ventricular Function and Hypertrophy in a Rat Model

Abstract

Objective: The purpose of this study was to follow the ventricular function and cardiac hypertrophy in rats undergoing a resistance-training program for a period of 3 months.Design: Forty animals were divided into two major groups: control (n=16) and resistance trained (n=24). From the resistance-trained group, 12 animals were resistance trained for 1 month and another 12 for 3 months.The resistance-training protocol was performed with 4 sets of 12 repetitions using 65% to 75% of one repetition maximum (maximum lifted weight with the exercise apparatus). Methods:Echocardiographic analysis was performed at the beginning of the resistance-training period and at the end of each month. The repetition maximum was measured every 2 weeks. Cardiac hypertrophy was determined by echocardiography, by the absolute weight of the cardiac chambers and by histology of the left ventricle.Results: Before resistance training, both groups had similar repetition maximums, ranging from 1.8-fold to 2-fold the body weight; however, at the end of the resistance-training period, the repetition maximum of the resistance-trained group was 6-fold greater than the body weight.The left ventricular mass as assessed by echocardiography was 8%, 12% and 16% larger in the resistance-trained group than in the control group in the first, second and third months, respectively.This hypertrophy showed a similar increase in the interventricular septum and in the free posterior wall mass. There was no reduction in the end-diastolic left ventricular internal diameter during the 3-month resistance-training period. Systolic function did not differ between the groups throughout the resistance-training period. Conclusion:Resistance training induces the development of concentric cardiac hypertrophy without ventricular dysfunction or cavity reduction. Although diastolic function was not completely investigated, we cannot exclude the possibility that resistance training results in diastolic dysfunction. Resi stance training, also known as weight or strength training, is a specialized method of conditioning designed to increase muscle strength, muscle endurance and muscle power. In response to this kind of training, both skeletal and cardiac muscle adapts. The main muscle adaptation of the athlete's body is the increase in size or mass (hypertrophy) of type II skeletal muscle cells 1 and cardiac hypertrophy. However, different from hypertensive conditions when pressure overload is continuous, the cardiovascular response to this exercise model is characterized by the intermittent increase in blood pressure during exercise. 2 Due to the pressure overload during exercise, practitioners of modalities such as weight training develop a cardiac hypertrophy different from those practitioners of sports with a high dynamic component (e.g., running). This hypertrophy is characterized by increases in the left ventricular (LV) wall and no changes in the diameter of the LV cavity in diastole. Thus, these athletes are presumed to develop concentric LV

Eccentric and concentric cardiac hypertrophy induced by exercise training: microRNAs and molecular determinants

“…The implications of these results are 2-fold: first, AT1 receptor stimulation is necessary for the development of cardiac hypertrophy in response to resistance training even in the absence of increased Ang II; second, the mechanical stretch due to resistance training increases AT1 receptor expression. Other cardiovascular adaptations in this animal model have already been described by us (13,14), as previously documented above.…”

“…This hypertrophy showed a similar increase in the interventricular septum and in the free posterior wall mass. There was no reduction in the end-diastolic left ventricular internal diameter during the 3-month resistance-training period accompanied by maintenance of ventricular function, showing that this stimulus leads to concentric physiological cardiac hypertrophy (13,14).…”

“…We have characterized the cardiac adaptation induced by resistance training (13,14) according to a model adapted from Tamaki et al (15).…”

The Effect of Short-Term Resistance Training on Heart of Nonathletic Healthy Male Students by Echocardiograph

“…In those athletes participating in intense isometric, strength or static training (anaerobic, strength and power training), concentric hypertrophy of the left ventricle is created (14). This hypertrophy is identified by an increase in the thickness of heart septum and creates no changes in the diameter of the hole of the left ventricle in diastole (1).…”

“…Resistance training (RT) is known as weight or strength training, in response to which both skeletal and cardiac muscles adapt (1). Strength training increases the production of end-systolic proteins and muscular hypertrophy-especially in fast twitch strings-that may be along with a decrease in volume density of mitochondories (2)(3)(4).…”