Acute Changes in Muscle Contractile Properties Following Specific Training Load in Elite Kickboxers: A pilot study

<ns3:p> Background. Acute neuromuscular responses to training are key for optimizing performance and mitigating injury risk. This study evaluated immediate changes in muscle contractile properties after a sport-specific load in elite kickboxers. Methods. Six elite Slovak male kickboxers underwent tensiomyography (TMG) immediately before and after a standardized 75-minute session. TMG was recorded bilaterally in ten muscles: biceps brachii, triceps brachii, pectoralis major, rectus abdominis, rectus femoris, vastus medialis, vastus lateralis, tibialis anterior, gastrocnemius medialis, and gluteus maximus. Primary outcomes were contraction time (Tc), maximal radial displacement (Dm) and contraction velocity (Vc) were also derived. Pre- to post-differences were tested with Wilcoxon matched pairs. Results. After the 75-minute high-intensity kickboxing session, Tc increased significantly in both vastus medialis and rectus femoris (p = 0.046). Dm increased locally in the left biceps femoris and right gastrocnemius medialis (p = 0.028). Vc was largely unchanged overall but increased significantly in the left biceps femoris, right gastrocnemius medialis, right and left tibialis anterior, and right triceps brachii (p ≤ 0.046). Conclusion. A single high-intensity kickboxing session elicits clear, asymmetric, and muscle-specific changes in contractile behavior, reflecting the coexistence of transient fatigue and potentiation across the lower and upper limbs. These findings underscore the heterogeneous neuromuscular demands of kickboxing and support the use of TMG for individualized, post-session monitoring and recovery planning in high-intensity combat sports. </ns3:p>