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ATP production and mechanical work in exercising skeletal muscle: A theoretical analysis applied to 31 P magnetic resonance spectroscopic studies of dialyzed uremic patients
Author(s) -
Kemp Graham J.,
Thompson Campbell H.,
Taylor Doris J.,
Radda George K.
Publication year - 1995
Publication title -
magnetic resonance in medicine
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.696
H-Index - 225
eISSN - 1522-2594
pISSN - 0740-3194
DOI - 10.1002/mrm.1910330504
Subject(s) - nuclear magnetic resonance , skeletal muscle , magnetic resonance imaging , work (physics) , chemistry , medicine , materials science , physics , radiology , thermodynamics
31 P magnetic resonance spectroscopy ( 31 P MRS) can yield much information about bioenergetics in skeletal muscle. During mixed aerobic/glycolytic exercise, changes in phos‐phocreatine (PCr) concentration and pH may be abnormal because of reduced muscle mass or reduced efficiency (which the authors combine here as “effective muscle mass”) or because of reduced oxidative capacity. The authors show how these can be distinguished by calculating the nonoxidative and oxidative costs of mechanical work, and also of work per unit of effective muscle mass (measured using the initial rate of ATP turnover). These quantities are substantially time‐independent during incremental exercise, and so can be used to compare exercise studies of differing duration. The authors illustrate this analysis by showing that in dialyzed patients with chronic renal failure, the substantial exercise abnormalities seen by 31 P MRS are due mainly to a decrease in effective muscle mass, which outweighs the oxidative defect implied by the abnormal PCr recovery kinetics.