Effects of aerobic training, resistance training, or combined resistance-aerobic training on the left ventricular myocardium in a rat model.

This study follows the left ventricular (LV) hypertrophy in rats undergoing aerobic training alone (A), resistance training alone (R), or combined resistance and aerobic training (RA) (usually referred as concurrent training) program. A sedentary control group (C) was included. LV remodeling was evaluated using electron and light microscopy. The LV weight to body weight (LVW: BW) increased 11.4% in A group, 35% in the R group, and 18% in the RA group compared to the C group. The LV thickness increased 6% in the A group, 17% in the R group, and 10% in the RA group. The LV internal diameter increased 19% in the A group, 3% in the R group, and 8% in the RA group compared with the C group. The cross-sectional area of cardiomyocyte increased by 1% with the A group, 27% with R group, and 12% with RA training. The capillary density increased by 5.4% with A training, 11.0% with R training, and 7.7% with RA training compared with the C group. The volume fraction of interstitial collagen increased by 0.4% with training A, increased by 2.8% with R training, and 0.9% with RA training. In conclusion, except for the LV internal diameter, which increased more in the A group, the cardiac parameters increased more in the R group than in the other groups and in RA group than in A group. Collagen density increased from 5.4 ± 0.8% in the C group to 5.8 ± 0.6% in the A group (n. s.) (P > 0.05), to 8.2 ± 0.7% in the R group (P < 0.05), and to 6.3 ± 0.4% in the RA group (P < 0.05). These results demonstrate a significant increase for collagen content in the LV with R and RA exercise, but the increase was higher with R training alone than with RA training.

Efeitos do treinamento concomitante hipertrofia e endurance no músculo esquelético / Effects of concurrent training hypertrophy and endurance on skeletal muscle

O objetivo deste estudo foi o de verificar os aspectos fisiológicos envolvidos na interação entre o treinamento de endurance e hipertrofia muscular e se estas modalidades devem ou não ser realizadas na mesma sessão de treinamento. O treinamento de hipertrofia e endurance realizado na mesma sessão parece inibir o desenvolvimento muscular comparado ao treinamento de hipertrofia realizado isoladamente. Algumas hipóteses foram propostas para explicar tal fenômeno, tais como a incapacidade do músculo esquelético de se adaptar metabólica e morfologicamente às duas modalidades de treinamento realizadas numa única sessão, alteração do padrão de recrutamento de unidades motoras pela depleção de glicogênio e cálcio, e ativação do sistema proteolítico cálcio-dependente de calpaínas. Concluímos que as modalidades de treinamento de hipertrofia e endurance apresentam diferentes aspectos de adaptação muscular. Assim, a hipertrofia muscular é mais pronunciada quando a sessão de treino é restrita a apenas uma modalidade de treinamento.

The purpose of this study was to verify the physiological aspects involved in the interaction between endurance training and muscular hypertrophy and if those modalities should or should not be performed in the same training session. The hypertrophy and endurance training performed in the same training session seems to inhibit the muscular development compared with hypertrophy training alone. Some hypotheses have been proposed to explain such phenomenon, such as the incapacity of skeletal muscle to adapt metabolically and morphologically to both training modalities, alteration in the motor unit recruitment pattern due to glycogen and calcium depletion, and activation of the proteolytic calcium-dependent calpain system. In conclusion, the training modalities of hypertrophy and endurance presents different muscular adaptation. Thus, muscular hypertrophy is more pronounced when the training session is restricted to a single modality of training.