THE POTENTIAL ROLE OF THE MUSCLE IN KINEMATIC CHARACTERISTICS

This review describes characteristics of equine skeletal muscle fibre types in relation with their potential role in kinematics characterist ics. Equine skeletal muscles are composed by fibres with different met abolic and contractile properties. Histochemical fibre typing has prov en useful in numerous studies in horses concerned with structure-funct ion relationships. More recently, immunohistochemical and electrophore tic methods have established a relationship between histochemical fibr e types and their myosin heavy chain content. Muscle is a tissue which displays a great deal of plasticity, in that it can generally adapt t o the varying demands placed on it. Several studies suggest that not o nly hereditary factors are significant but that certain environmental stimuli are also important in the establishment of the fibre type comp osition of equine muscle. Some other studies justify the attempt to se lect (or reject) horses using muscle fibre type composition as a crite rion. In 30 young Andalusian horses exercised in a working trot, a sig nificant negative correlation was seen between the duration of the sta nce phase of the stride and diameter of fibre types. Conversely, the s tride frequency was correlated positively with the fibre sizes. These correlations indicate that the locomotor pattern of the horse may be p artly dependent on muscle fibre properties.