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Motor Unit Threshold and EMG Amplitude

Camille B. Olson, PhD; David O. Carpenter, MD; Elwood Henneman, MD

Arch Neurol. 1968;19(6):591-597.

	Since this article does not have an abstract, we have provided the first 150 words of the full text PDF and any section headings.

RECENT studies from this laboratory¹ have shown that there is a functionally significant relationship between the size of individual motor neurons and their susceptibility to discharge by physiological stimuli. The smaller the cell, the more readily it is discharged by all normal stimuli. This sizeprinciple has been demonstrated in a variety of experiments in which discharge of motor neurons has been brought about by stimulation of the motor cortex, basal ganglia, cerebellum, or brainstem,² or by evoking stretch reflexes, flexor reflexes, or crossed reflexes.^1,3

The present study was begun after recordings of muscle action potentials in stretch reflexes revealed an orderly recruitment of units of increasing amplitude, which was strikingly similar to that seen in records from ventral root filaments. There have been several reports^4-7 in which it was noted that the amplitude of individual electromyographic (EMG) potentials increased with the total amount of excitation. . . . [Full Text PDF of this Article]

Author Affiliations
Boston

From the Department of Physiology, Harvard Medical School, Boston.

Footnotes
Submitted for publication July 5, 1968; accepted August 19.

A preliminary report of some of this material appeared as Olson, C.B.; Carpenter, D.O.; and Henneman, E.: Relation Between the Reflex Thresholds of Motor Units and the Amplitude of Their Action Potentials, Fed Proc 25:269 (March-April) 1966.

Reprint requests to Department of Physiology, Harvard Medical School, Boston 02115 (Dr. Henneman).

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