Effects of resistance training on ventricular function and hypertrophy in a rat model.
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.


METHODS
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.


CONCLUSIONS
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.
Barauna
Valério Garrone
VG
School of Physical Education and Sport, University of São Paulo, São Paulo, Brazil.
Rosa
Kaleizu Teodoro
KT
Irigoyen
Maria Cláudia
MC
de Oliveira
Edilamar Menezes
EM
D000222:Adaptation, Physiological; D000758:Anesthesia; D000818:Animals; D003971:Diastole; D004195:Disease Models, Animal; D004452:Echocardiography; D006339:Heart Rate; D017379:Hypertrophy, Left Ventricular / Q000000981:diagnostic imaging / Q000473:pathology / Q000503:physiopathology*; D008297:Male; D009206:Myocardium / Q000473:pathology; D009929:Organ Size; D010805:Physical Conditioning, Animal / Q000379:methods*; D051381:Rats; D017208:Rats, Wistar; D013599:Systole; D018487:Ventricular Dysfunction, Left / Q000000981:diagnostic imaging / Q000473:pathology / Q000503:physiopathology*