Relationship between changes in passive properties and muscle strength after static stretching.

BACKGROUND:The association between decreased muscle strength of rate of force development (RFD) immediately after static stretching (SS) and change in muscle stiffness or muscle slack has remained unclear. OBJECTIVE:This study aimed to investigate the association between changes in muscle strength and RFD and muscle stiffness or muscle slack immediately after SS. METHODS:Sixteen healthy male non-athlete volunteers participated in this study. The maximal voluntary contraction torque and shear elastic modulus of medial gastrocnemius muscle were measured before and after 300 s of SS intervention. RESULTS:The results showed that maximal voluntary contraction torque and RFD at 100, 150, and 200 ms decreased significantly after the 300-s SS (p < 0.01). Additionally, shear elastic modulus at 0° (decrease in muscle stiffness) and slack angle decreased (increase in slack length) significantly after the 300-second SS (p < 0.01). However, no significant association was observed between changes in muscle strength and changes in mechanical properties of the MG. CONCLUSION:These results suggested that the decrease in muscle strength and RFD could not be associated with changes in the passive mechanical properties of the medial gastrocnemius muscle.