Creatine kinase and MB-fraction after a long distance race.

In 18 well-trained athletes creatine kinase (CK) and the CK-MB isoenzyme were measured immediately after a 100 km race and 10 days later for control purposes. The CK was 1970 +/- 1505 U/l (mean +/- SD, range 481--5558 U/l) after the race and 50 +/- 23 U/l on the control day (p less than 0.001). The CK-MB fraction was 72 +/- 70 U/l (range 14--228 U/l) and 8.6 +/- 2.3 U/l (p less than 0.01). The ratio CK-MB/CK was 3.4 +/- 1.1% and never exceeded 6%. The study indicates that elevated CK and CK-MB are a common finding after a long distance race. CK-MB/CK ratios up to 6% may be observed.