Fig. 1.

A: length-force relationship of smooth muscle. Gray lines depict the same relationship in striated muscle, redrawn from Gordon et al. (14) as a reference, with permission from John Wiley and Sons, Ltd. Solid lines are linear fits of data from airway smooth muscle (ASM) adapted to different lengths. The red arrows with dotted lines depict sequences and directions of changes in force after shortening from the reference length and after stretch from the reference length during the process of length adaptation. See text for more detail. B: schematic of a smooth muscle contractile unit. Dotted arrows indicate the direction of movement of thin filaments (and their associated dense bodies) during active shortening.