Variation in the distribution of muscle fiber types in equine skeletal muscles

Four skeletal muscles, semitendinosus (Se), longissimus dorsi (Lg), soleus (Su) and gluteus medius (Gm) were removed from a four-year-old female Welsh pony. The muscles were divided into sections which were histochemically examined to determine the variation in the distribution of fast-twitch glycolytic (FG), fast-twitch oxidative glycolytic (FOG) and slow-twitch oxidative (SO) muscle fibers throughout the entire cross section of the muscle. Within both the Se and Gm muscles significant variations were found in the distribution of all three fiber types. The percent of each fiber type differed amongall four adult skeletal muscles. This study demonstrated that there is significant variations in the distribution of the muscle fiber types within an individual muscle.