Abstract
Mammalian skeletal muscles are comprised of heterogeneous types of fibers based on their enzyme histochemical or immunohistochemical properties. Regardless of the muscle type, muscle region, or fiber type, an inverse relationship between cross-sectional area and oxidative enzyme activity of fibers is observed in the rat hindlimb muscles including the soleus, plantaris, extensor digitorum longus, and tibialis anterior muscles. This indicates that smaller-sized fibers have higher oxidative enzyme activities than larger-sized fibers even within the same fiber type. In addition, there is a matching of cell sizes and oxidative enzyme activities of spinal motoneurons and the muscle fibers that they innervate, which is important for maintaining their functional and metabolic properties.
