Effect of novel diagonal stretching combining trunk rotation and trunk flexion on contralateral knee extension

BACKGROUND: Most previous studies have focused on increasing hamstring flexibility when knee extension range of motion (KE ROM) is restricted. However, it was demonstrated that the tensile force generated in the upper body could be transmitted to the contralateral lower extremity. OBJECTIVE: This study examined the effect of novel diagonal stretching combining trunk rotation and trunk flexion on the contralateral KE ROM. METHODS: Two different positions (sitting with a neutral pelvis position and sitting with trunk rotation) were randomly selected and the contralateral and ipsilateral KE ROM was measured in each position. As for the stretching intervention, trunk rotation and slight trunk flexion were applied in sitting with a neutral pelvic position. RESULTS: On the contralateral side, KE ROM was significantly different in all pairwise comparisons (p< 0.001). On the ipsilateral side, a significant difference in KE ROM was only observed between measurements taken after stretching compared to measurements taken during trunk rotation (p= 0.005). CONCLUSIONS: The tensile force in the upper body significantly affects tissue extensibility in the lower extremity in the contralateral side, leading to the restriction of active maximum knee extension. Diagonal stretching techniques may successfully enhance mobility in the contralateral leg.