title: Constant efficiency versus variable economy of cardiac contraction.
abstract: 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.
authors.affiliation: Second Department of Physiology, Okayama University Medical School, Japan.
authors.forename: H
authors.initials: H
authors.lastname: Suga
authors.forename: Y
authors.initials: Y
authors.lastname: Goto
authors.forename: K
authors.initials: K
authors.lastname: Hata
authors.forename: T
authors.initials: T
authors.lastname: Takasago
authors.forename: A
authors.initials: A
authors.lastname: Saeki
authors.forename: T W
authors.initials: TW
authors.lastname: Taylor
authors.forename: T
authors.initials: T
authors.lastname: Nishioka
mesh_terms: D000818:Animals; D001696:Biomechanical Phenomena; D004734:Energy Metabolism; D006801:Humans; D008433:Mathematics; D008955:Models, Cardiovascular; D009200:Myocardial Contraction; D009206:Myocardium / Q000378:metabolism*