Serum Creatine Kinase Monitoring In Elite Soccer Players Across A Competitive Season

Creatine Kinase (CK) has been used as a marker of skeletal muscle damage and might reflect the physical loading experienced by soccer players during their training and matches. PURPOSE: This study aimed to monitor serum CK levels in elite soccer players across a full season and examine potential correlations between CK levels and performance metrics in these athletes. METHODS: Twenty-five male professional soccer players from the Greek Super League were assessed across 19 official matches. Performance metrics, including sprint distances, accelerations, and total number of jumps, were measured using GPS monitoring system, while CK levels were measured in blood samples obtained 64 hours post each match of the competitive season. Additional data regarding recovery status (utilizing the Total Quality Recovery-TQR scale) and weekly training intensity (via the Rate of Perceived Exertion-RPE) were collected through self-administered questionnaires. RESULTS: Creatine kinase concentrations peaked remarkably during the first half of the season; Post-game CK levels were significantly (p < 0.05) increased by 217% after the 5th game, 251% after the 9th game, 212% after the 12th game and by 194% after the 16th game. These increases indicate a consistent elevation of CK levels in the first half of the season. Additionally, total number of jumps recorded showed a positive correlation with CK percentage increases (R2 = 0.291, p < 0.05), as did body mass (r = 0.34, p < 0.05). CONCLUSIONS: These findings suggest that regular CK measurement might serve as a valuable tool for monitoring physical and/or muscle loading and recovery throughout the competitive season in elite soccer players. Elevated CK levels, particularly during the first half of the season, highlight the need for tailored recovery strategies to optimize performance and reduce injury risk in these athletes.