Moderate physical training attenuates muscle-specific effects on fibre type composition in adult rats submitted to a perinatal maternal low-protein diet

Aim: To verify whether moderate physical training affects the muscle fibre composition of adult rats subjected to a low protein diet during the perinatal period. Methods: Male Wistar rats were divided into two groups according to their mother's diet during gestation and lactation: control (17% casein, C) and low-protein (8% casein, LP). On postnatal day 60, half of each group was submitted to moderate physical training (8 weeks, 5 days/week^-1, 60 min/day^-1, at 70% of VO_2max, T) or not. After the physical training period, soleus and extensor digitorum longus (EDL) muscles were removed. Myofibrillar ATPase staining was used to classify muscle fibres as type I, IIa, IIb, and intermediate. Results: In the EDL muscle, LP rats showed no changes in the fibre type proportion. Both the C + T and LP + T groups showed a higher percentage of fibres of type IIa, and a lower proportion of fibres of type IIb. In the soleus muscle, LP animals showed a reduction in the proportion of fibre types I and intermediate. C + T rats showed an increase in the fibre type I and IIa. In the LP + T rats, the proportions of the fibre types remained similar to control rats. Conclusions: Moderate physical training acts as a positive environmental stimulus that reverts the effects of a perinatal low-protein diet on the proportion of fibre types in skeletal muscle.