A Thermodynamic Optimization Analysis of a Possible Relation between the Parameters that Determine the Energetics of Muscle Contraction in Steady State
✍ Scribed by Moisés Santillán
- Publisher
- Elsevier Science
- Year
- 1999
- Tongue
- English
- Weight
- 173 KB
- Volume
- 199
- Category
- Article
- ISSN
- 0022-5193
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✦ Synopsis
Given the phenomenological relations for muscle's steady-state contraction and proper de"nitions of power p and e$ciency , the behavior of these quantities is analysed in terms of the parameters that determine the energetics of the muscle, here denoted by sM and . sM is proportional to the so-called maintenance heat, while is the parameter that determines the curvature of the Hill's force}velocity curve. The dependence of the muscle's power and e$ciency, averaged over the whole range of force the muscle can exert, on the parameters sM and is studied. The average power p ?TE is a function only of , and is a growing function that approaches 1/6 asymptotically as goes to in"nity. The average e$ciency ?TE is a function of both and sM. With the value of sM "xed, the graph of the function ?TE (sM, ) is a convex curve with a single maximum. The value and the position of this maximum point both depend on sM. In the limit P0, sMP0, ?TE tends to 1. The points (sM, K (sM)), with K (sM) the value of that maximizes ?TE for a given sM, are "tted by the curve "sM. This relation was experimentally found by A. V. Hill in his early studies of muscle energetics. Other experimental data are found to qualitatively satisfy the same relation. Although some dynamical microscopic models for muscle contraction, based upon Huxley's cross-bridge model, show that the same kinetic parameters control both the maintenance heat (sM) and the muscle's power output ( ), we suggest that the exact relation between them has been reached due to the evolutive stresses that made individuals with equally powerful and more e$cient muscles more suitable to reproduce.