Creatine kinase correlation with muscle stiffness and elasticity: A simplified methodology for fatigue monitoring in athletes

Abstract

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.