Creatine kinase isoenzyme MB may be elevated in healthy young women after submaximal eccentric exercise.

Elevations in serum creatine kinase isoenzyme MB (CK MB) after exercise may be of clinical importance for the diagnosis of myocardial infarction. However, CK MB has been observed to increase after exercise in highly trained endurance runners. No data exist relating to the effect of exercise in a heterogeneous female population with regard to CK MB. The purpose of the present investigation was to determine whether an elevation in serum CK MB can be measured in women (heterogeneous for aerobic capacity, estradiol, and lean body mass) and to make a preliminary analysis of the relationships of postexercise serum CK MB concentration and CK activity, estradiol, lean body mass, and peak oxygen consumption. Lean body mass and peak oxygen consumption were measured for 15 college-age women (19 to 29 years) after the performance of a stepping exercise for 40 minutes at 70% of peak oxygen consumption to elicit the efflux of intramuscular enzymes. Serum CK MB concentration, CK activity, and estradiol level were measured before exercise and 24 and 48 hours after exercise. Serum estradiol level was also measured immediately after exercise. Four of the 15 subjects had elevations in CK MB concentrations ranging from 18.4 to 101.2 micrograms/L, many times the upper normal limit (4.7 micrograms/L). All subjects with high serum CK MB concentrations had high CK activity, and the two measures were significantly related (p < 0.01) in the postexercise period. It was concluded that exercise can cause large elevations in serum CK MB in some women.(ABSTRACT TRUNCATED AT 250 WORDS)