Publications

Myoton Clarification Note: A Guide to Interpreting the Inverse Relationship Between Logarithmic Decrement and Tissue Elasticity

Objective: This study aimed to investigate the relationship between creatine kinase (CK) levels and the mechanical properties of lower limb muscles — specifically stiffness and elasticity — in order to propose a practical and time-efficient methodology for fatigue monitoring in professional athletes.

Methods: Twenty-seven male professional soccer players participated in the study. Muscle stiffness and elasticity were measured using a handheld myotonometer (MyotonPRO) at 23 reference points across the dominant lower limb. CK levels were assessed via venous blood samples collected 48 h post-match. Pearson correlation analysis was conducted to examine associations between CK and mechanical muscle properties.

Results: Significant positive correlations were observed between CK levels and the stiffness of adductor longus (r = 0.57, p < 0.01), rectus femoris (r = 0.51, p < 0.05), and vastus medialis (r = 0.38, p = 0.05). A strong correlation was also found between CK and the elasticity of the biceps femoris (r = 0.56, p < 0.01). No significant relationships were detected for relaxation or creep parameters. These findings suggest that only a select group of CK-sensitive muscles may be sufficient for monitoring neuromuscular fatigue.

Conclusion: While current fatigue monitoring practices often involve extensive muscle group assessments, this study proposes a simplified protocol based on the identification of fatigue-sensitive muscles with strong CK associations. By bridging the gap between biochemical and biomechanical evaluations, this approach offers a practical and scalable solution for fatigue monitoring in both clinical and sports performance settings.

Keywords: creatine kinase, muscle stiffness, elasticity, fatigue monitoring, MyotonPRO, soccer players

In conclusion, this study identified significant correlations between creatine kinase (CK) levels and the mechanical properties of selected lower limb muscles, particularly the adductor longus, rectus femoris, vastus medialis, and biceps femoris. These associations suggest that a targeted assessment of CK-sensitive muscles may serve as a practical approach for monitoring neuromuscular fatigue in professional athletes. Importantly, no significant relationship was observed in the majority of the evaluated muscles, indicating that whole-limb or full-muscle-group screening may not be necessary for effective fatigue evaluation. Rather than generalizing the findings across all muscle groups, our results support the feasibility of a focused measurement strategy, which could enhance efficiency in field applications. Further studies involving larger and more diverse athletic populations, as well as longitudinal designs with pre- and post-competition comparisons, are needed to validate and refine this targeted methodology.