The variation in isometric tension with sarcomere length in vertebrate muscle fibres

Abstract

The variation of isometric tetanus tension with sarcomere length in single fibers from frog striated muscle was investigated with special precautions to insure uniformity of sarcomere length within the part of the studied fiber. The peak of the curve consisted of a plateau between sarcomere lengths of 2.05 and 2.2 [mu]; the decline of tension above this plateau is steeper than previously found and the decline of tension below the plateau becomes suddenly steeper at a sarcomere length of about 1.67 [mu]. Many features of this length-tension relation explained by the slidtog-filament theory. The tension on each thinf ilament is made up of equal contributions from each bridge which it overlaps on adjacent thick filaments in the plateau and at greater lengths. Internal resistance to shortening which is negligible in this range becomes progressievly more important with shortening below the plateau.