Optimum Length for Contraction of Rat Circulated Limb Muscles

Abstract

The optimum length for contraction in the rat gastrocnemius was investigated in relation to its range of lengths in situ. Length-tension diagrams for isometric and isotonic tetani under standard conditions indicated that the optimum length at which the force developed was maximal was close to the maximum length in situ. The curves obtained by the isometric method differed from the isotonic curves in that the optimum length and the optimum force developed were greater. The maximum amount of isotonic shortening occurred from an initial length with the in situ range of muscle, as did the optimum amount of external work performed by the muscle. These results are discussed in relation to the isolated from and mammalian muscle.