Dynamic properties of denervated rat muscle treated with electrotherapy

¹ Department of Physiology, State University of Iowa, Iowa City, Iowa

Denervated rat gastrocnemii, compared with normal controls, showed slower shortening velocity and less shortening, performed less work, exhibited decreased values for Hill's constant a (shortening heat per centimeter shortening), a low P₀ (maximum isometric tetanus tension) value and a higher a/P₀ ratio, but showed no change in Hill's constant b (rate of extra energy released per gram tension decline from P₀). Muscle not allowed to shorten during treatment ("isometric") showed greater shortening velocity than did denervated untreated muscle or muscle allowed to shorten freely during treatment ("isotonic"). Isotonically treated muscle showed a greater amount of shortening and a higher value for constant a than did denervated untreated or isometrically treated muscle, but no corresponding change in constant b. While isotonic treatment resulted in better maintenance of the amount of shortening and of the value for a than did isometric treatment, and isometric treatment resulted in better maintenance of velocity of shortening than did isotonic treatment, isometric treatment reduced constants a and b to values below those for denervated untreated muscle.