Fig. 3. The calculated time courses of production of initial and recovery enthalpies. The total enthalpy record is the same as that in Fig. 2C. Records are the averages of those for the last 10 cycles of the contraction protocol. The vertical broken line indicates the time at which shortening ended. Initial enthalpy is the sum of the work output and initial heat output. All the energy from recovery processes appeared as heat. In this example, 75% of the initial enthalpy was produced by the end of shortening. Note that, although there was slightly more initial enthalpy than recovery enthalpy produced in the cycle, recovery enthalpy output continued after the contractions were finished so that the total recovery enthalpy output was greater than the total initial enthalpy output.