It is well known that the strength of cardiac contraction is dependent on the cycle length, evidenced by the forcefrequency relationship and the existence of post-rest potentiation.Because the contractile strength of the steady state force-frequency relationship and force-interval relationship involve both instant intrinsic responses to cycle length as well as slower acting components such as post-translational modification based mechanisms, it remains unclear how cycle length intrinsically affects cardiac contraction and relaxation.To dissect the impact of cycle length changes from slower acting signaling components associated with persisting changes in cycle length, we developed a novel technique/protocol to study cycle-length dependent effects on cardiac function; dynamic twitch contractions of right ventricular rabbit, rat, and dog trabeculae at different cycle lengths were randomized around a steady state frequency.