ALL MUSCLES ARE NOT CREATED EQUAL

The muscles of an individual vary in their morphological and contracti le properties and in their patterns of innervation. At one time, it wa s thought that a fairly homogeneous population of myoblasts gave rise to myotubes that were subsequently instructed to diversify by various extramuscular factors. There is now, however, considerable evidence th at myoblasts are heterogeneous, anti that heritable differences among them interact with environmental influences to give each muscle its di stinct characteristics.