INTRAMUSCULAR DISTRIBUTION OF FIBER TYPES IN THE GLUTEUS-MEDIUS OF THE HORSE - A HISTOCHEMICAL ANALYSIS

The results from a recent study by BRUCE and SCHURG (1990) indicate th at the gluteus medius (Gm) of the horse is a complex muscle subdivided by an internal tendinous sheet into two regions (dorsal and ventral) which may subserve different functions. In the present study, both reg ions were found to contain a similar proportion of histochemically-det ermined muscle fibre types. Fibre type composition did not generally v ary over the length of the muscle at the same relative depth. In contr ast, there was a significant tendency for the percentage of type I fib res to increase gradually in accordance with depth. These histochemica l results do not suggest that the two regions of the Gm assume distinc t functional roles; they do, however, indicate that at a given relativ e depth the muscle fibre type distribution is relatively uniform over the length of the muscle. Nevertheless, care should be exercised in sa mpling and interpreting data obtained from limited biopsy of equine Gm , due to the substantial histochemical variation of fibre type composi ton as a function of sampling depth.