Fiber type composition of morphologic regions in the macaque multitendoned finger muscles.

The extrinsic multitendoned finger muscles seem likely to contain distinct neuromuscular compartments that can act as independent functional subdivisions serving different fingers. Little evidence of such subdivisions is available, however. Regional specialization of histochemical fiber type composition has been described in a number of monotendoned muscles, and in some muscles different neuromuscular compartments have been shown to have different fiber type proportions. Therefore, we examined the fiber type composition of morphologically defined regions in the macaque multitendoned finger muscles. Although some trends were noted, none of the five multitendoned finger muscles showed significant regional differences in fiber type composition. Nor were differences found between muscles of the flexor group or between muscles of the extensor group. Comparing flexors and extensors revealed a slightly but significantly lower proportion of type I fibers in the flexors. We conclude that unlike certain monotendoned wrist muscles (such as FCU), the multitendoned muscles that flex and extend macaque fingers have minimal histochemical specialization.