The electromyographic shimmer in normal human muscles
Kaplan, P.E.; Kaplan, C.
Electromyography and Clinical Neurophysiology 18(3-4): 179-189
1978
ISSN/ISBN: 0301-150X PMID: 699872 Document Number: 132524
Normal subjects (7) were studied using the electrophysiological techniques of a trigger and delay line to isolate 3 different motor unit action potentials from each subject. Consecutive discharges were identical in shape and size and of optimal amplitude. The random variation and amplitude was expressed as the mean consecutive difference in the amplitudes of successive motor unit potentials. This mean consecutive difference was termed shimmer. The Shimmer Index was obtained by dividing the shimmer by the amplitude of the motor unit action potential .times. 100. The mean Shimmer Index was 1.6 units. The range was 1.2-2.5 units and the SD was 0.39 units. Electrophysiological shimmer may be used with electrophysiological jitter to characterize the motor unit action potential.