Acute Region-Specific Effects of Static and Dynamic Stretching on Gastrocnemius Medialis Shear Modulus Assessed by Shear-Wave Elastography

Stretching acutely modifies muscle–tendon mechanical behavior. Whether these effects vary across muscle regions and stretching modalities remains unclear. This study investigated the acute effects of passive static stretching (PS) of different durations and dynamic stretching (DS) on the regional gastrocnemius medialis (GM) shear modulus. Twelve healthy adults (4 women; mean ± SD: age = 23.9 ± 2.4 years, body mass = 69.8 ± 10.6 kg, height = 1.72 ± 0.08 m) completed three randomized conditions: 5 × 30 s PS (PS30), 5 × 45 s PS (PS45), and 5 × 30 repetitions of DS. Shear-wave elastography assessed the shear modulus at mid-belly (GMmid) and towards the myotendinous junction (GMMTJ) at 0° and 80% of maximal dorsiflexion range of motion (ROMmax). ROMmax, passive resistive torque (PRT), myotendinous junction displacement (ΔMTJ), muscle architecture, and maximal voluntary contraction (MVC) were also evaluated. The GMmid modulus decreased at 80%ROMmax after all stretching protocols (p < 0.05), with no changes at 0°. At GMMTJ, the modulus decreased after PS45 and DS at both ankle positions (p < 0.05); no significant changes occurred after PS30. After all protocols, ROMmax increased (p < 0.05), while PRT and MVC decreased (p < 0.05), ΔMTJ increased post PS45 (p < 0.05), and muscle architecture remained unchanged. These findings indicate that stretching-induced changes in GM mechanical behavior can be region and muscle-length dependent, while the distal response may also be influenced by stretching duration and type.