Publications

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

Background: Dynamic knee valgus (DKV) is considered a risk factor for knee injuries, particularly in female athletes. Muscle activation and biomechanical properties are thought to play a role in its development, yet their exact contributions remain unclear. This study aimed to investigate the biomechanical properties and electromyographic activity of lower extremity muscles in female volleyball players with and without DKV.

Methods: Thirty-six female volleyball athletes aged 12–18 were allocated to DKV (n = 18) and control (n = 18) groups based on single-leg squat test. Biomechanical properties (muscle tone, elasticity, stiffness) of the muscles were measured using MyotonPRO®. Surface electromyography was used to assess muscle activation and onset times of the gluteus medius (GM), adductor magnus (AM), vastus medialis (VM), vastus lateralis (VL), semimembranosus (HM), and biceps femoris (HL) during landing phase of the volleyball spike.

Results: There were no significant demographic or sport-specific differences between the groups. VM/VL and HM/HL muscle tone ratios and AM/GM, VM/VL and HM/HL stiffness ratios were significantly higher in DKV group (p < 0.05). DKV group showed significantly lower activation in GM and HL and higher AM/GM and HM/HL ratios (p = 0.001 and p = 0.015). GM-AM onset time difference was significantly lower in DKV group (p < 0.001). Multiple linear regression analysis did not reveal any statistically significant predictors of knee valgus angle during the landing phase of the spike.

Conclusion: The tone and stiffness ratios of the medial thigh muscles to the lateral ones (AM/GM and HM/HL) were increased. Activation of GM and HL muscles were decreased in athletes with DKV. Since neither biomechanical properties nor muscle activation affected frontal knee valgus angle during the spike, it is speculated that the change may reflect a musculoskeletal adaptation.

Keywords: dynamic knee valgus, electromyography, muscle activity, volleyball

In this study, athletes with DKV demonstrated higher medial-to-lateral muscle tone (VM/VL and HM/HL) and stiffness ratios (VM/VL, HM/HL, and AM/GM) compared with those without DKV. However, these biomechanical properties, along with muscle activation levels, did not significantly influence the frontal-plane knee valgus angle during the landing phase of the volleyball spike. Future research is warranted to determine whether these biomechanical alterations reflect a functional adaptation or constitute a potential risk factor for knee dysfunction.