Quantification of Muscle Stiffness and the Relationship between Muscle Stiffness and Pain in Muscle Knots

Abstract

[Purpose] In the first part of the study (S1), we quantified muscle stiffness and gender differences in healthy persons. In the second part (S2), we clarified the relationship between muscle stiffness and pain in myofascial pain syndrome (MPS) which has muscle knots. [Subjects] The subjects of S1 were 52 healthy adults in their twenties. The subjects of S2 were 44 patients complaining of chronic lumbago, who showed no imaging or neurological findings and had muscle knots in the longissimus thoracis. [Methods] In S1, we measured the stiffness of the longissimus thoracis, and the trapezius and major rhomboid muscles with a muscle hardness meter; gender differences were verified with the t test. In S2, muscle stiffness was measured with the muscle hardness meter, and pain was evaluated using a numerical rating scale. The relationship between muscle stiffness and pain was investigated using Pearson's correlation coefficient. [Results] In S1, for the trapezius muscle, females showed significantly higher values, but no significant differences were seen for the other two muscles. In S2, the correlation between muscle stiffness and pain in muscle knots was weak. [Conclusion] We revealed that females have comparatively higher muscle stiffness in the trapezius muscle than males; however, the level of pain had no influence on muscle stiffness in MPS which has muscle knots.