Ratio of Creatine Kinase 2 Mass Concentration to Total Creatine Kinase Activity Not Altered by Heavy Physical Exercise

mass) were measured in marathon runners during train-ing and 1 and 2 days after a race and compared with values from 36 acute myocardial infarction (AMI) patients whose total CK and (or) CK 2 activities were similar to those of runners in the basal state. During training, runners had CK and CK 2 activities 53 % and 43 % above reference values, respectively, and 36 % had CK 2 activity>5 % of total CK. Nine runners (26%) showed CK 2 mass values>6 g/L but 1 0 p..gIL; 35 of the AMI subjects, despite having CK activities similar to those of runners, had values> 1 0 pg/L. The ratio of CK 2 mass to total CK activity was significantly (P <0.0002) different between sexes for runners. At 1 and 2 days after racing, 100 % of CK and CK 2 activities and 71 % and 57 % of the percent-ages of CK 2 activity, respectively, were abnormally high; 57 % and 43 % of CK 2 mass values were>10 pIL, bein