Abnormal muscle fiber morphology Abnormal muscle fiber-type distribution 2021-03-07T22:37:42Z Ay deviation from the normal distribution of fiber types in skeletal muscle. The skeletal muscle groups of the mammalian body are made up of bundles of muscle fibers. These fibers can be assigned to different Types, with characteristic movement rates, response to neural inputs, and metabolic styles. Skeletal muscle fibers are broadly classified as slow-twitch (type 1) and fast-twitch (type 2). Multiple fiber types are generally intermingled within a single muscle group, and different muscle groups have varying proportions of fiber types