Effect of muscle stretch during isometric contraction on the time-course or relaxation in mammalian myocardium.

The effect of stretch on the time-course of relaxation has been investigated in rat papillary muscle. In control conditions, a quick stretch carried out at or after the peak of an isometric twitch promotes an earlier and faster relaxation. Following inotropic interventions which decelerate the activation decay rate (caffeine addition and Ca2+ replacement with Sr2+) the onset and time-course of relaxation are unaffected by the stretch.