[Development of various types of muscle fibers in the quadriceps femoris and the soleus during human ontogenesis].

By means of histological methods for revealing adenosine triphosphatase of myosin (pH 4.6) and succinate dehydrogenase activity, using postmortem material, development of various muscle fibers of the femoral m. quadriceps and m. soleus has been studied in human ontogenesis. The first stage of rearrangements lasts from the 5th-6th month of the uterine development up to 2 years of age and is characterized by formation (from non-differentiated) of oxidative, glycolytic and oxidative-glycolytic fibers. During the period from 2 up to 7-8 years of age the ratio in the types changes slightly, but transversal section size of the muscle fiber increases intensively. Then from 11 up to 17 years of age, together with maximal increment of the fibers transversal section, there is an essential change in the type relation. By the 17th years of age, in the femoral m. quadriceps the part of the fibers with glycolytic type of energy supply increases, while in the m. soleus the oxidative fibers become more numerous. By the 70th years of age in the femoral m. quadriceps relative amount of intermediate fibers increases.