Enzyme activities in serum after extensive exercise, with special reference to creatine kinase MB.

It is well documented that elevations of serum enzymes used as criteria in establishing the diagnosis of acute myocardial infarction (AMI) often show a pattern of AMI after physical exercise without other clinical signs of myocardial damage. Since a clinical condition resembling AMI sometimes appears after strenuous physical exercise, this study was designed to show if the new, almost heart-specific, isoenzyme creatine kinase MB (CK-MB) would solve the diagnostic problems. Ten well trained volunteers took part in a 26 km jogging race. None of them had any cardiovascular symptoms, but the 'old' cardiac enzymes rose in some of them above the discriminatory levels, whereas CK-MB was below these levels in all cases. It is concluded that CK-MB determination is a valuable diagnostic tool, also in patients who have recently exercised extensively.