Index reflecting the balance of energy transfer between catabolic and anabolic processes, calculated from the equation \[\rm{AEC} = ([\ce{ATP}] + ½[\ce{ADP})/([\ce{ATP}] + [\ce{ADP}] + [\ce{AMP}])\] where \(\ce{ATP}\), \(\ce{ADP}\), and \(\ce{AMP}\) are the amount concentrations of adenosine tri-, di-, and monophosphate, respectively.