COMPARTMENTALIZATION OF MUSCLES AND THEIR MOTOR NUCLEI - THE PARTITIONING HYPOTHESIS

This review article is designed to expose physical therapists to an ex amination of muscle organization and the implications that this organi zation has for therapeutic applications The partitioning hypothesis is based on the fact that an individual muscle is arranged in a more com plex array than simply fibers attaching at aponeuroses, tendons, or bo nes with a single muscle nerve innervation. Neuromuscular compartments , which are distinct subvolumes of a muscle, each innervated by an ind ividual muscle nerve branch and each containing motor unit territories with a unique array of physiological attributes, are described. In ad dition, the organization of individual muscles into these subunits is paralleled by the organization of their parent motoneurons within the spinal cord. These notions are detailed in a review of data derived fr om studies performed primarily in cat a rat models Recent data derived from morphological and anatomical study of human muscles support the existence of similar neuromuscular partitions. These data are compleme nted by physiological studies, the results from which suggest that par titions may have functional or task-oriented roles; that is, different portions of one muscle may be called into play depending on the task demands of the situation. The importance of these observations for rec onsidering how we provide clinical applications, such as neuromuscular stimulation or kinesiological monitoring, is discussed.