Electromyography of experimentally immobilized skeletal muscles in cats

¹ Department of Anatomy and Department of Pharmacology and Therapeutics, Graduate School and Stritch School of Medicine, Loyola University, Chicago, Illinois

The hind limbs of ten cats were bilaterally immobilized by external fixation without altering skeletal muscle innervation. Bilateral immobilization was used to rule out the possible effects of reciprocal activation from a nonimmobilized contralateral limb. Limbs were fixed in a neutral position to minimize the effect of muscle spindle activation. An electromyograph with an integrator circuit was used to measure the maximum action-potential output of anterior tibial muscles of both sides. Recordings were made of the maximum integrating meter response of the muscles to a standardized supramaximal electrical stimulus applied percutaneously to the common peroneal nerve while the animals were uniformly anesthetized. Measurements were made every 4 days for a period of 101 days of immobilization. The control or normal response was represented by measurements made at the beginning of the experiment. A highly significant continuing decrease in electrical output of the skeletal muscles was seen during the course of the immobilization. No statistically significant difference was found between the response of the right and left sides.