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. Author manuscript; available in PMC: 2015 May 18.
Published in final edited form as: Phys Med Rehabil Clin N Am. 2012 Oct 16;24(1):193–207. doi: 10.1016/j.pmr.2012.08.017

Fig. 1.

Fig. 1

Physiologic model of motor units in myopathies. The pathologic process in myopathies results in dysfunction and dropout of individual muscle fibers located randomly within the motor unit. Motor neurons and motor axons are not affected. As a result, each MUAP is generated by fewer motor fibers. MUAPs become polyphasic, short in duration, and low in amplitude.