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Proprioceptors and normal tremor.
Author(s) -
Burne J A,
Lippold O C,
Pryor M
Publication year - 1984
Publication title -
the journal of physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.802
H-Index - 240
eISSN - 1469-7793
pISSN - 0022-3751
DOI - 10.1113/jphysiol.1984.sp015125
Subject(s) - isometric exercise , proprioception , wrist , isotonic , accelerometer , physics , motor unit , electromyography , anatomy , amplitude , muscle contraction , contraction (grammar) , beat (acoustics) , mathematics , physical medicine and rehabilitation , acoustics , medicine , physical therapy , optics , quantum mechanics
The tremor of the hand, rotating about the wrist joint, was measured using an accelerometer, and groups of muscle action potentials were simultaneously recorded from the wrist extensor muscles using surface electrodes. The accelerometer signal and the rectified, demodulated electromyogram were submitted to Fourier analysis in order to quantify the tremor in terms of its frequency components and the amplitudes of those components. The amplitudes of the 8‐12 Hz peak in the frequency spectrum obtained from muscle electrical activity were compared (a) when the hand was held raised against gravity (i.e. the contraction was isotonic) with (b) when it was held raised, with the same force and in the same position against a rigid bar (i.e. the contraction was isometric). In the isotonic condition (a) a prominent 8‐12 Hz peak was observed in the spectrum. In the isometric condition (b) the peak was small or absent. The conclusion is drawn that the grouping (synchronization) of motor unit action potentials underlying tremor cannot be due to any process in the central nervous system generating them and they depend on cyclic alterations in muscle length activating proprioceptors.