Morphological and histochemical characteristics of muscle fibre types in the flexor carpi radialis of the dog.

The canine flexor carpi radialis is subdivided into 2 portions. The radial portion which occupies one third of the cross-section is located caudomedially and is composed only of large type I fibres (43.53 +/- 0.6 microns minimum diameter) in levels close to the insertion. The cubital portion is located craniolaterally and contains fewer and smaller type I fibres (26.10 +/- 0.3 microns minimum diameter). It is hypothesised that the radial portion of the muscle, with its larger slow fibre population, contributes to forelimb postural function. The cubital portion, with its generally fast fibre population (IIA), may be more important in the muscle's recognised function (flexion of the carpal joint during locomotion).