Acute effects of dynamic stretching on the mechanical properties of the triceps surae muscles assessed using shear wave ultrasound elastography.

Purpose: Dynamic stretching (DS), characterized by repeated movements through the joint range of motion via antagonist muscle contraction, is thought to reduce muscle stiffness through mechanisms such as reciprocal inhibition. However, whether DS effectively decreases muscle stiffness remains unclear. This study aimed to investigate the acute effects of DS on triceps surae muscle stiffness using shear wave elastography.

Methods: Sixteen healthy young adults performed both 120-s DS and control (no stretching) tasks. Shear wave velocities of the medial gastrocnemius (MG), lateral gastrocnemius (LG), and soleus (SOL) muscles were measured as indicators of muscle stiffness before and after DS.

Results: Our findings indicated that DS significantly reduced the shear wave velocity in the MG. However, no significant changes were observed in the shear wave velocities of the LG and SOL.

Conclusion: DS effectively decreased MG stiffness, with no observed effects in the LG or SOL. These findings highlight inter-muscular variability in response to DS and suggest that DS may be particularly beneficial for targeting stiffness in the MG of the triceps surae muscles.