highly significantP << 0.01
It may be seen in Table III that there was a highly significant (P << 0.01) evolution of UE in the period between 0 and 3 s and between 0 and 6 s, thus these frog muscles resembled muscles of previous studies (e.g., Gilbert et al., 1971; Homsher et al., 1975), because a significant quantity of the enthalpy observed during isometric contraction could not be explained by PC and (or) ATP splitting.