The Relationship Between Muscle Endurance and the Frequency Speed of Kick Test in Martial Arts Athletes

Purpose: Martial arts are combat sports that are practiced globally that require a combination of strength, power, and endurance. One of the most popular assessments used to assess muscular endurance in martial arts is the frequency speed of kick test (FSKT). The FSKT measures the number of kicks an athlete can perform continuously over a short duration which has been used as a correlate for sparring performance. However, it is unclear if the FSKT actually measures muscular endurance and strength. Therefore, the purpose of this study was to compare muscle strength and endurance between the FSKT and a gold standard laboratory measurement. Methods: Ten participants (6M/4F, 30.29.9 years, 170.712.2 cm, 73.115.0 kg, 17.011.1 years of experience) volunteered for the study. All participants completed the FSKT and isokinetic and isometric strength and endurance measures. The FSKT included 5 rounds (10 seconds on, 10 seconds rest) of as many alternating kicks as possible. Isokinetic testing included 10 repetitions of knee extension and flexion at 180 deg/s and isometric testing included one 30 second hold at 90 degrees of knee flexion for both knee extensors and flexors. Paired t-tests were used to compare limbs and Pearson correlations were used to quantify the relationship between strength variables and the FSKT performance. Significant correlations were retained for a stepwise regression model. Results: There were no significant differences between limbs except for the hamstring fatigue index (p=0.03). The nondominant quadriceps fatigue index (r=-0.71) and the dominant hamstring fatigue index (r=-0.63) were significantly correlated with FSKT performance. The nondominant quadriceps fatigue index was retained in a regression model as a significant predictor for FSKT and explained 50.5% of the variance in performance. Conclusion: Greater endurance of the nondominant quadriceps are associated with increased performance on the FSKT. Therefore, it may be beneficial for martial arts athletes to focus on building the endurance of the nondominant leg to reduce the risk of injury and increased performance.