ATP Utilization in Skeletal and Cardiac Muscle: Economy and Efficiency

During muscle contraction, chemical energy in the form of ATP is continuously converted into mechanical work and heat. Energy turnover in muscle is studied not only to understand the energetic costs of locomotion of the body but also to understand the fundamental properties of the contractile mechanism itself. In this review, an overview will be given of the dependence of the rate of ATP utilization on the level of activity, fiber type and species in permeabilized skeletal and cardiac muscle preparations from amphibian (frog and Xenopus laevis) and mammalian (rat, rabbit, guinea pig and human). Special attention will be paid to the definitions of—and the distinction between— economy and efficiency of muscle contraction. Results in particular with respect to the increase in energy turnover during muscle shortening (the Fenn effect) and the future perspectives of studies on muscle energetics will be discussed in terms of a simplified model for crossbridge interaction.