Integrating conventional and novel oblique stretching techniques for optimal hamstring flexibility

Background Movements of the upper and lower back have been proven to affect the flexibility of the lower extremities, such as the hip, knee, and ankle. However, conventional hamstring stretching mainly focuses on elongating tissues located in the lower extremities. The study aimed to examine the effects of integrated stretching applied to the lower extremity and the posterior trunk on hamstring flexibility. Methods Before stretching, active straight leg raise (ASLR) and active knee extension (AKE) tests were performed to assess hip and knee flexibility, respectively. One stretching session integrated stretches applied to the lower extremity and the posterior trunk. The ASLR and AKE tests were repeated to measure the increase in flexibility after stretching. Results Lower extremity stretching significantly increased hip ( p < 0.001) and knee flexibility ( p < 0.001). Moreover, posterior trunk stretching combined with trunk flexion and rotation also increased hip ( p = 0.016) and knee flexibility ( p = 0.037). After posterior trunk stretching, knee flexibility assessed using AKE in the contralateral leg was higher than that in the ipsilateral leg ( p < 0.001). Conclusions If the clinical goal is to maximize hamstring flexibility, it would be beneficial to incorporate conventional stretching applied to the lower extremity and novel posterior trunk stretching applied to the upper and lower back. More importantly, the posterior trunk stretching affects the contralateral lower extremity asymmetrically.