Abstract

To search for morphological changes in muscle, related to overuse syndromes of muscle due to exercise, groups of untrained rats ran on a treadmill for 1 h at submaximal intensity. Each group was sacrificed at a different interval after the end of the exercise. Immediately after exercise, only minor signs of degeneration were observed at the ultrastructural level, while after 2-3 h degeneration became clearly visible at the light microscopic level. The most pronounced changes were observed 24-48 h after exercise, whereafter regeneration occurred. Only 2 - 5 of all fibers in the soleus muscle showed signs of degeneration, while in the vastus lateralis and rectus femoralis muscle less than 0,5 of the fibers were affected. The affected fibers in the soleus and vastus lateralis muscles belong to the type I population while in the rectus femoris typ I as well as type II fibers were affected. Verf.-Referat