ABSTRACT
A comparison was made between pre- and post-run serum levels of total creatine kinase (CK), CK-MB isoenzyme, lactate dehydrogenase (LD) and myoglobin (MG) levels in 84 runners in each of three groups; male 5-10 mile run; female 5-10 mile run; and male 15-55 mile run. Levels of CK-MB and MG were quantified using radioimmunoassay, while total CK and LD were measured using spectrophotometric procedures. Post-run levels of all four markers were significantly higher than the pre-run levels (p less than 0.001). Although levels of enzymes and MG correlated with the sex and distance run, the post-run changes did not correlate with age nor with the smoking status of the runners. Elevation of these markers as a result of vigorous exercise in the absence of myocardial infarction requires cautious interpretation of serum enzyme changes in runners.