Effects of short-term electrical stimulation on the ultrastructure of rat skeletal muscles

The purpose of this study was to determine the effects of short-term, 2,500-Hz carrier-wave frequency electrical stimulation on the ultrastructure of fast-twitch rat skeletal muscles. Thirteen Sprague-Dawley male rats were divided into three groups: daily treatment (Group 1), every-other-day treatment (Group 2), and control (Group 3). The medial quadriceps femoris and hamstring (semitendinosus and semimembranosus) muscles of the right thigh were treated with short-term electrical stimulation. After treatment, the animals were sacrificed, and their treated and sham quadriceps femoris and hamstring muscles were removed, fixed by immersion, and processed for electron microscopy. Morphometric measurements were made on electron micrographs using a Videoplan computer system, and the results were analyzed statistically. The results revealed that mitochondria, triads, and glycogen content of the fast-twitch muscles changed to resemble those of slow-twitch muscles. In view of these results, clinicians should consider the possibility that similar changes also might occur in human subjects under clinical conditions.