COMPARATIVE CHARACTERIZATION OF CREATINE KINASE AND CREATINE KINASE-MB ACTIVITY IN ATHLETES FROM DIFFERENT SPORTS

Background: Elevated creatine kinase (CK) is common after strenuous exercise, but its interpretation in athletes differs from that in the general population. CK-MB may also increase because of skeletal-muscle injury, limiting its specificity for myocardial injury. Objective: To compare total CK and CK-MB activity across four sports disciplines and determine the frequency of values exceeding the laboratory upper reference limits. Methods: We performed a cross-sectional secondary analysis of laboratory data from 50 athletes examined at the Republican Scientific and Practical Center of Sports Medicine in 2025–2026: judo (n=17), freestyle wrestling (n=25), weightlifting (n=4), and modern pentathlon (n=4). The cohort comprised 35 men and 15 women. The laboratory upper reference limits were 190 U/L for CK in judo, freestyle wrestling, and weightlifting, 170 U/L in modern pentathlon, and 25 U/L for CK-MB. Continuous variables were summarized using mean±SD and median [Q1–Q3]. Between-group comparisons used the Kruskal–Wallis test; sex differences were assessed with the Mann–Whitney U test. Results: Elevated CK was observed in 34/50 athletes (68.0%): 15/17 (88.2%) judokas, 16/25 (64.0%) wrestlers, 1/4 (25.0%) weightlifters, and 2/4 (50.0%) modern pentathletes. CK-MB exceeded 25 U/L in 3/50 athletes (6.0%). Mean CK was highest in judo (480.5±305.8 U/L), followed by freestyle wrestling (283.9±152.9 U/L), modern pentathlon (192.5±119.8 U/L), and weightlifting (150.3±118.8 U/L). Between-group differences were significant for CK (H=11.33, p=0.010) and CK-MB (H=8.29, p=0.040), although the two groups with n=4 require cautious interpretation. Men had higher mean CK than women (410.5±242.4 vs 151.2±75.7 U/L; p<0.001). Conclusions: Elevated total CK was common, particularly among judokas, whereas CK-MB elevations were uncommon and modest. In physically active individuals, isolated CK-MB elevation should not be interpreted as evidence of myocardial injury without appropriate clinical, electrocardiographic, and cardiac-troponin assessment. Serial measurements relative to an individual baseline may be more informative than a single comparison with a population reference limit.