Effects of training on skeletal muscle in protein-deprived rats

The effects of exercise on atrophy of muscle fibres and loss of mitochondria in the extensor digitorum longus (EDL) and soleus muscles were studied in protein deprived rats. They had smaller muscle fibres than aged-matched control rats, the difference being more evident in type 2 than type 1 fibres both in the fast EDL and slow soleus muscles. The loss of weight was more pronounced in the EDL muscle which is composed mainly of type 2 fibres than in the soleus muscle which is composed mainly of type 1 fibres. Protein deprived rats subjected to a programme of periodic running on a treadmill for 12 weeks showed less muscle atrophy than sedentary, protein deprived rats. This effect of exercise in diminishing the degree of atrophy was more pronounced in the type 2 than type 1 fibres. The protein deprived rats which had been sedentary showed a marked loss of subsarcolemmal mitochondria, which was not seen in protein deprived rats undergoing exercise.