Regulation of Force and Speed of Shortening in Muscle Contraction

The work of Gordon et al. (1966a,b) provided strong evidence for believing that the fundamental event in striated muscle force generation is an interaction between the cross-bridges from the myosin-containing thick filaments and sites on the actin-containing thin filaments. (See A. F. Huxley, 1971, and H. E. Huxley, 1971, for details and present status of sliding filament theory for muscle contraction.) It is clear from the work of Gordon et al. that, in the tetanic steady state condition, the amount of force developed over most of the length-tension diagram can be simply related to the number of cross-bridges available for interaction with thin filament sites. They were also able to account very well for a plateau in the sarcomere length-tension relation by showing that it coincided with the region in the middle of the thick filaments where cross-bridges are absent (H. E. Huxley, 1963).