CREATINE KINASE ACTIVITY AS A MARKER FOR ASSESSING EXERCISE TOLERANCE IN ATHLETES FROM SPORTS OF VARYING INTENSITY

Abstract

Aim. This study aims to enhance training efficacy in athletes experiencing loads of varying intensity by assessing changes in creatine kinase activity and possible strategies for its correction. Materials and methods. This comparative, analytical, descriptive, evaluative, observational, and cross-sectional study involved 187 professional male athletes (mean age: 23 ± 5 years; sports rank: CMS, MS) from sports of varying intensity between May and November 2025. Based on training load, they were divided into five groups: Group 1 (n = 40) – swimmers; Group 2 (n = 41) – rowers; Group 3 (n = 36) – boxers; Group 4 (n = 30) – freestyle wrestlers; and Group 5 (n = 40) – handball players. Creatine kinase activity in blood serum was measured in all athletes post-exercise, in the morning, on an empty stomach. Results. Athletes demonstrated differences in creatine kinase activity, which negatively affects exercise tolerance. In Group 1, mean creatine kinase activity was 255 ± 167 IU/L, compared to the upper reference limit of 190 IU/L. The corresponding values in the other groups were as follows: Group 2 – 270 ± 255 IU/L, Group 3 – 598 ± 419 IU/L, Group 4 – 359 ± 239 IU/L, and Group 5 – 258 ± 189 IU/L. Elevated creatine kinase acti­vity in blood serum reflects the degree of muscle fiber damage, which requires time for recovery. Conclusion. Changes in creatine kinase activity remain a key but complex-to-interpret marker in assessing exercise tolerance in athletes. Elevated creatine kinase in blood serum reflects the degree of muscle fiber damage. However, its dynamics are affected by multiple factors, requiring further research and a personalized approach.