Technique-specific reduction of sciatic nerve stiffness through neurodynamic stretches at submaximal and maximal intensity in asymptomatic individuals

PURPOSE: To compare the immediate effects of two neurodynamic mobilization techniques (flossing vs. tensioning) on the sciatic nerve and hamstring muscle tissues, using different stretching intensities. METHODS: Twenty physically active volunteers performed a randomized, study comprising seven conditions (six stretching + control). Interventions included static stretching (SS), neurodynamic tensioning (TENS), and neurodynamic flossing (FLOS), applied at 100% (pain threshold) or 90% maximal range of motion, using 5 × 60-s sets. Shear wave elastography (SWE) was used to assess sciatic nerve and biceps femoris stiffness before and immediately after the interventions. Measurements included flexibility tests (passive knee extension (PKE), stand and reach (SR), slump), and hamstring strength (MVIC) alongside with electromyography (EMG). RESULTS: SWE of the sciatic nerve showed a significant condition × time interaction (p < 0.001), with a significant decrease only after flossing at maximal intensity (FLOS100); The biceps femoris (BF) shear wave velocity (SWV) decreased over time (p = 0.004) independently of the condition. Flexibility outcomes significantly improved after all stretching interventions (p < 0.001). Nevertheless, FLOS100 produced significantly greater improvements in sciatic nerve mobility than SS at maximal intensity (p = 0.017). MVIC significantly decreased from PRE to POST (p = 0.009) across all conditions, with no condition × time interaction (p = 0.991). The EMG activity remained unchanged for BF muscle while semitendinosus (ST) EMG showed a significant decrease over time (p = 0.017). CONCLUSIONS: Neurodynamic flossing at maximal intensity reduced sciatic nerve stiffness and mobility in asymptomatic individuals. These neural adaptations suggest flossing should be prioritized for neural tissue, while all stretching techniques similarly affect muscle stiffness.