Distribution of myofiber types in the crural musculature of sheep.

In domestic animals, the legs function in both postural maintenance and propulsion. The crural muscles participate in actions of the tarsal and toe joints. Mammalian skeletal muscles consist of myofibers, which are histochemically classified into three myofiber types, slow-twitch/oxidative (SO) or type I, fast-twitch/oxidative/glycolytic (FOG) or type IIA, and fast-twitch/glycolytic (FG) or type IIB myofibers. The histochemical characteristics of myofiber types reflect an aspect of function that myofibers possess. In the present study, we investigated the composition and average diameter of myofiber types of each muscle in crus of sheep and determined their roles in the movement of tarsal and toe joints. The tibialis cranialis muscle was a flat unipennate muscle and not capable to generate a large tension; however, it could function primarily in posture maintenance and play a cooperative role in adjusting standing posture. The flexor hallucis longus and flexor digitorum superficialis muscles were the major muscles that contributed to posture maintenance in leg musculature. These muscles were capable to generate a large tension and participate primarily in standing posture maintenance. The composition and diameter of myofiber types in ovine crural musculature reflected the role of each muscle in posture maintenance and locomotion.