RESUMO
The present study was undertaken in order to investigate effects of short-term, high intensity training on the total number and histochemical properties of fast tibialis anterior, slow soleus muscle fibres and their dominant motor neurons in male rats.<BR>The animals were subjected to 4 meters of sprint-running by the operant conditioning, 12 times a day interposed with 5 minutes rest periods for 14 weeks.<BR>This training had no effect on the total number and enzyme activities of muscle fibres and dominant neurons. However, hypertrophy of FOG and FG fibres in tibialis anterior muscle was caused by the training.<BR>The conclusion, therefore, is that short-term but high intensity training causes selec. tive hypertrophy of fast twitch muscle fibres, but does not have an influence on the histochemical properties of motor units because the training is far a short period of time.
