Test-Retest Reliability, Smallest Worthwhile Change, and Minimal Detectable Change Scores for Frequency Speed of Kick Test in Junior Kickboxing Athletes

Abstract

While there exists a significant body of research dedicated to performance tests specific to combat sports, the current literature lacks valid and functional methodologies for assessing kickboxing-specific tasks. The present study endeavored to establish the test-retest reliability, standard error of measurement (SEM), minimal detectable change (MDC), smallest worthwhile change (SWC), and typical error (TE) values of the Frequency Speed of Kicks Test (FSKT). Furthermore, this study sought to compare the reliability values of the FSKT with those of the countermovement jump test (CMJ). The study cohort consisted of twenty-eight junior male kickboxers. Participants performed the CMJ and FSKT twice across test and retest sessions. Pearson correlation analysis identified a significant correlation (r=0.717) between the CMJ and FSKT. Paired t-tests revealed no significant disparities between the test and retest values for both the CMJ and FSKT. However, the difference between the test and retest in the CMJ demonstrated a small effect size, while the FSKT showed a trivial effect size. Intraclass correlation coefficient (ICC) values for the CMJ and FSKT were deemed "good" (r=0.855) and "excellent" (r=0.963) respectively, in terms of reliability. The FSKT displayed superior absolute agreement between test and retest scores due to its lower SEM values when compared to the CMJ. The TE, used to estimate trial-to-trial variation, was lower in the FSKT than in the CMJ. Moreover, the results indicated a lower MDC value in the FSKT than the CMJ, suggesting that the FSKT could be more effective at detecting smaller performance changes compared to the CMJ. In conclusion, this study posits that the FSKT could be considered a reliable method, demonstrating reproducible results in the performance evaluation of kickboxing athletes, pending the development of a functional kickboxing-specific field test.