Effect of Electrical Stimulation to Prevent Muscle Atrophy on Morphologic and Histologic Properties of Hindlimb Suspended Rat Hindlimb Muscles

OBJECTIVE: To determine the morphologic and histologic effects of electrical stimulation (ES) used to prevent muscle atrophy, and to investigate the effects of ES at different stimulation frequencies in preventing atrophy in different muscle fiber types. DESIGN: Rats in the hindlimb suspended (HS) plus ES group were subjected to 20- and 30-Hz stimulation (ES1, ES2) every other day for 2 wks. RESULTS: In soleus, the muscle weight, muscle fiber cross-sectional area, and the number of type I muscle fibers were significantly decreased in the HS and HS + ES2 groups, whereas they were maintained in the HS + ES1 group. This indicated that ES at 20 Hz could suppress muscle atrophy and retain muscle fiber type proportions, based on histologic properties. In extensor digitorum longus, the muscle weight, muscle fiber cross-sectional area, and the number of type II muscle fibers were significantly decreased in the HS group, whereas they were maintained in the HS + ES groups. This indicated that ES at either 20 Hz or 30 Hz could suppress muscle atrophy, and retain muscle fiber type proportions, based on histologic properties. ES at 30 Hz also had positive effects in maintaining the extensor digitorum longus muscle. CONCLUSIONS: These results suggest that short periods of low-intensity, low-stimulation frequency (20 Hz) ES of muscle during periods of inactivity could maintain changes in both morphologic and histologic properties of the slow-twitch muscle fibers (soleus). Short periods of low-intensity, high-stimulation frequency (30 Hz) ES of muscle during periods of inactivity could maintain changes in both morphologic and histologic properties of the fast-twitch muscle fibers (extensor digitorum longus).