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June 1971

Muscular Tone and Relaxation

Author Affiliations

Department of Biomedical Communications Mayo Foundation Rochester, Minn

Arch Intern Med. 1971;127(6):999-1003. doi:10.1001/archinte.1971.00310180015001

It is now generally conceded by neurophysiologists that electromyography shows conclusively the complete relaxation of normal human striated muscle at rest. In other words, by relaxing a muscle, a normal human being can abolish neuromuscular activity in it. This does not mean that there is no "tone" (or "tonus") in skeletal muscle, as some enthusiasts have claimed. It does mean, however, that the usual definition of "tone" should be modified to state that the general tone of a muscle is determined both by the passive elasticity or turgor of muscular (and fibrous) tissues and by the active (though not continuous) contraction of muscle in response to the reaction of the nervous system to stimuli. Thus, at complete rest, a muscle has not lost its tone even though there is no neuromuscular activity in it.

In the clinical appreciation of tone the more important of the above two elements is the

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