Signal-handling characteristics of load-moving skeletal muscle.

PARTRIDGE, LLOYD D. Signabliunding characteristics of loadmoving skeletal muscle. Am. J. Physiol. 210(5): I 178-1191. 1966. -Modulated pulse rate signals were used to stimulate circulated cat triceps surae muscle-nerve preparations attached to inertial loads of physiological size. Effects of load size and signal frequency on movement amplitude and timing showed that load position, not muscle force, is the value most nearly represented by nerve pulse rate. This emphasizes the importance of the internal feedback mechanisms of the muscle that makes force output dependent on load movement as well as on stimulus rate. It was also found that once a signaled position is attained, small downward fluctuations of nerve impulse rates have relatively little effect on this position. It was also demonstrated that the dynamic response of muscle introduced signal lags of from slightly below IOO to over I ,000 msec. Further, at higher physiological frequencies, the muscle response to modulation of pulse rate is greatly attenuated. These complex signal-handling characteristics of muscle are of such a magnitude as to be of major importance in the quantitative analysis of motor activity control.