Muscle fibre variation in the gluteus medius of the horse

Abstract

The gluteus medius of 2 killed thoroughbred horses were sampled along the muscle and across the muscle at 4 different depths. This distribution of fibers types in these 2 horses was assessed by staining cross sections of the muscle sample for ATPase. A non-uniform distribution of fiber types was found within the gluteus medius in both horses and there was a significant increase in percentage of slow twitch (ST) fibers from the surface to the deeper regions of the muscle. The rate of increase, depended on the individual site along the muscle. Averages ranges from a low of 2.4% ST fibers to a high of 64.5%. Small biopsy samples of fibers are not necessarily representative of the whole muscle and there is a need to define precisely biopsy location.