Muscle heat: a window into the thermodynamics of a molecular machine

The contraction of muscle is characterized by the development of force and movement (mechanics) together with the generation of heat (metabolism). Heat represents that component of the enthalpy of ATP hydrolysis that is not captured by the microscopic machinery of the cell for the performance of wor...

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Bibliographic Details
Published in:American journal of physiology. Heart and circulatory physiology 2016-02, Vol.310 (3), p.H311-H325
Main Authors: Loiselle, Denis Scott, Johnston, Callum Michael, Han, June-Chiew, Nielsen, Poul Michael Fønss, Taberner, Andrew James
Format: Article
Language:English
Subjects:
Adenosine Triphosphate - metabolism
Animals
Energy Metabolism
Excitation Contraction Coupling - physiology
Heat
Humans
Hydrolysis
Molecules
Movement
Muscle Contraction - physiology
Muscle, Skeletal - metabolism
Muscle, Skeletal - physiology
Muscle, Smooth - metabolism
Muscle, Smooth - physiology
Muscles - metabolism
Muscles - physiology
Muscular system
Myocardial Contraction - physiology
Myocardium - metabolism
Phosphocreatine - metabolism
Thermodynamics
Thermogenesis - physiology
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Summary:The contraction of muscle is characterized by the development of force and movement (mechanics) together with the generation of heat (metabolism). Heat represents that component of the enthalpy of ATP hydrolysis that is not captured by the microscopic machinery of the cell for the performance of work. It arises from two conceptually and temporally distinct sources: initial metabolism and recovery metabolism. Initial metabolism comprises the hydrolysis of ATP and its rapid regeneration by hydrolysis of phosphocreatine (PCr) in the processes underlying excitation-contraction coupling and subsequent cross-bridge cycling and sliding of the contractile filaments. Recovery metabolism describes those process, both aerobic (mitochondrial) and anaerobic (cytoplasmic), that produce ATP, thereby allowing the regeneration of PCr from its hydrolysis products. An equivalent partitioning of muscle heat production is often invoked by muscle physiologists. In this formulation, total enthalpy expenditure is separated into external mechanical work (W) and heat (Q). Heat is again partitioned into three conceptually distinct components: basal, activation, and force dependent. In the following mini-review, we trace the development of these ideas in parallel with the development of measurement techniques for separating the various thermal components.
ISSN:0363-6135
1522-1539
DOI:10.1152/ajpheart.00569.2015