Muscle compositions were determined by the fast and slow myosin heavy chains isoforms and were compared to the histochemical muscle fibers compositions reported.
　Muscles were obtained from a 9-week-old male Sprague-Dawley rat (310g). The soleus, the extensor digitorum longus, the plantaris, the red portion of the gastrocnemius, the white portion of the vastus lateralis the diaphragm, and the left ventricle muscles were examined with SDS-polyacrylamide gel electrophoresis. The fractionated myosin heavy chain isoforms were quantified with the densitometric method.
　Muscle compositions determined with heavy chain isoforms were similar to the reported results with histochemical methods. These biochemical results support the use of the histochemical method to examine the sports aptitude.

DESCENTE SPORTS SCIENCE Vol.8/THE DESCENTE AND ISHIMOTO MEMORIAL FOUNDATION FOR THE PROMOTION SPORTS SCIENCE