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May 7, 1982

Elevated CK-MB Levels in Marathon Runners-Reply

JAMA. 1982;247(17):2368-2369. doi:10.1001/jama.1982.03320420024014

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In Reply.—  Ali et al and Warkel question whether leakage from myocardium might be the possible source of elevated serum CK-MB in marathon runners. We acknowledge this possibility in our discussion by stating, "Leakage from either skeletal muscle or myocardium are the only possible tissue sources for the sharply increased levels of serum CK-MB consistently detected in these marathon runners after competition." Normal myocardial scintigraphy concurrent with marked CK-MB levels strongly argues against the heart as the principal tissue source in our view. Dr Warkel is correct that traces of CK are present in other organ systems, but only muscle tissue contains sufficient levels of this enzyme to account for the serum findings. Analysis of CK-MB concentrations in skeletal muscle of runners will clarify the specific muscular source, and such studies are in progress.The two references cited in our introductory paragraph do refer to total serum CK alone rather