Fade in Voluntary Muscle Contractions of Patients with Sequelae after Poliomyelitis

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Abstract
The isometric contraction pattern was followed in 3 female and 2 male patients with lower motoneuron paralysis due to sequelae from poliomyelitis in 1942-1948. In uninstructed contractions, force increased slowly to an almost horizontal level which could be kept up for as long as desired. During rapid maximal voluntary contractions, a biphasic mechanogram was seen in 49% of 204 contractions, with a 1st maximum after 0.3 s (0.1-0.9), separated by a notch from a 2nd maximum after 1.1 s (0.3-2.3). In the rest of the contractions, force could not be generated rapidly, despite the intention of the subjects, and a single maximum in the mechanogram was seen after 0.9 s (0.2-2.4). In contractions where a biphasic contraction pattern was seen, the electromyographic activity was greatest during approximately the first 0.5 s of the contraction. In the other contractions the electromyographic activity was about the same during the whole contraction. Evidently the mechanograms are composed of a high innervation threshold, fast phasically active component and a low innervation threshold, slow tonically active component. Fade represents the waning of tension in the phasically active component present in some contractions, while this component appears to be eliminated by poliomyelitis in other muscle contractions.