Figure 3.

Sarcomere length dependence of the rate constant of force redevelopment (k _tr⁡). (a) Slow time-based recordings of sarcomere length and force obtained using an IonOptix SarLen system during a slack restretch maneuver during submaximal Ca²⁺ activation. (b) Sarcomere length-dependence of k _tr⁡ for rat slow-twitch skeletal muscle fibers, rat cardiac myocytes, and pig cardiac myocytes. Although pig cardiac myocyte k _tr⁡ was much slower at all sarcomere lengths compared to rat cardiac myocytes, both pig and rat cardiac cell preparations showed that k _tr⁡ increased at short sarcomere lengths despite reductions in force implicating that sarcomere length overrides the Ca²⁺ activation dependence of k _tr⁡.