Skeletal muscle is a heterogeneous tissue that exhibits numerous inter-and intramuscular differences (i.e., architecture, fiber composition, and muscle function). An individual muscle cannot be simplistically described as a compilation of muscle fibers that span from origin to insertion. In fact, there are unique differences within a single muscle and within single muscle fibers with respect to fiber size and protein composition. Electromyographic data indicate that there is selective recruitment of different regions of a muscle that can be altered, depending on the type of exercise performed. Longitudinal resistance-training studies also demonstrate that individual muscles as well as groups of synergist muscles adapt in a regional-specific manner. The author speculates that no single exercise can maximize the hypertrophic response of all regions of a particular muscle. Thus, for maximal hypertrophy of an entire muscle, athletes (particularly bodybuilders) are justified in incorporating various exercises that purportedly stimulate growth in a regional-specific manner.
(C) 2000 National Strength and Conditioning Association