The effect of the yo-yo test, applied to elite athletes in different leagues, on muscle damage markers

This study aimed to compare the acute muscle damage responses of professional soccer players from different league tiers following a standardized high-intensity loading protocol. It was hypothesized that there would be no statistically significant differences in Creatine Kinase (CK) responses among leagues despite varying seasonal match and training intensities. The study population consisted of 75 professional soccer players recruited from the Turkish Football Federation (TFF) 1st (n=26), 2nd (n=25), and 3rd (n=24) Leagues. All participants performed the Yo-Yo Intermittent Recovery Test (Level 1). Venous blood samples were collected 24 hours post-test, a timing chosen based on literature indicating peak CK levels at this interval. Data were analyzed using SPSS (v.24) via One-Way ANOVA, and effect sizes (partial eta-squared, η 2) were calculated to determine the magnitude of differences. The mean CK levels were 462.69±384.44 U/L for the 1st League, 433.00±335.97 U/L for the 2nd League, and 466.25±350.56 U/L for the 3rd League. The ANOVA results revealed no statistically significant differences in CK responses across the leagues (F=0.102,p=0.903, η 2=0.003). The findings suggest that professional league standing does not significantly influence the extent of acute muscle damage when a standardized exercise protocol is applied. The lack of significant variance and the small effect size indicate that professional soccer players across different tiers exhibit comparable physiological adaptations and sarcolemmal stability. Variations in individual responses are likely attributable to intrinsic biochemical signatures and training status rather than league hierarchy.