Key result
Theoretical analysis demonstrated that the variability of mechanical efficiency is smaller than that of Po/a, and that energy economy changes approximately with the cube of Po/a.
Theoretical relations between mechanical efficiency and Po/a may explain the small variability of empirically observed contractile efficiency despite wide changes in energy economy.
Theoretical model links efficiency stability to Po/a; leaves open empirical validation in clinical cardiac energetics.
An intriguing aspect of cardiac mechanoenergetics is the smaller variability of the contractile efficiency than the energy economy of force. We theoretically speculated about this dissociation by relating the mechanical efficiency with Po/a (the curvature of the force-velocity curve) in Hill's characteristic equation of muscle; Po/a is known to change with the energy economy and inversely with Vmax and myosin ATPase activity. The analysis showed that the variability is smaller for the mechanical efficiency than for Po/a and that the energy economy changes approximately with (Po/a)3. These theoretical relations may partly explain the small variability of the empirically observed contractile efficiency under various experimental conditions which are known to widely change the energy economy.
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Suga et al. (1992) studied Cardiac contraction. Theoretical modeling using Hill's characteristic equation was evaluated on Variability of mechanical efficiency vs Po/a and energy economy. Theoretical analysis demonstrated that the variability of mechanical efficiency is smaller than that of Po/a, and that energy economy changes approximately with the cube of Po/a.
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