Fiber size distribution in the flexor carpi radialis muscle of the cat.

The pennate flexor carpi radialis muscle of the cat has been shown to have a compartmentalized distribution of muscle fiber types. The possibility exists that the oxidative regions of the FCR are primarily concerned with fine movements including postural adjustments, while fast-twitch glycolytic region is used more for phasic movements. Muscle fiber diameters were measured for all three fiber types to determine if there was a compartmentalization of fiber size that might reflect differences in motor performance between the different regions of the same muscle. This study has demonstrated that the oxidative fiber types are significantly larger in the oxidative compartment when compared with the same fiber types in the glycolytic compartment and that the cross-sectional area of the oxidative region is dominated by oxidative fibers. The glycolytic fibers are significantly larger in the glycolytic compartment when compared to those in the oxidative region of the muscle and they constitute the major fiber type in this region.