The increase in Ca²⁺ sensitivity of isometric force development along with sarcomere length (SL) is considered as the basis of the Frank-Starling law of the heart, possibly involving the regulation of cross-bridge turnover kinetics. Therefore, the Ca²⁺ dependencies of isometric force production and of the cross-bridge sensitive rate constant of force redevelopment (k_tr) were determined at different SLs (1.9 µm and 2.3 µm) in isolated human, murine and porcine permeabilized cardiomyocytes. k_tr was also determined in the presence of 10 mM inorganic phosphate (P_i), which interfered with the force-generating cross-bridge transitions. The increases in Ca²⁺ sensitivities of force with SL were very similar in human, murine and porcine cardiomyocytes (pCa₅₀:~0.11). k_tr was higher (P<0.05) in mice than in humans or pigs at all [Ca²⁺] levels (k_tr,max at a SL of 1.9 µm and pCa 4.75: 1.33±0.11 s^-1, 7.44±0.15 s^-1 and 1.02±0.05 s^-1, in humans, mice and pigs, respectively) but k_tr did not depend on SL in any species. Moreover, when the k_tr values for each species were expressed relative to their respective maxima, similar Ca²⁺ dependencies were obtained. 10 mM Pi decreased force to ~60-65% and left pCa₅₀ unaltered in all three species. P_i increased k_tr,max by a factor of ~1.6 in humans and pigs, and by a factor of ~3 in mice, independently of SL. In conclusion: species differences exert a major influence on k_tr, but SL does not appear to modulate the cross-bridge turnover rates in human, murine and porcine hearts.