Acute effects of flossing band application on hamstring muscle mechanical properties and stretch tolerance: a randomized controlled crossover trial.

PURPOSE: Flossing bands have been reported to improve hamstring flexibility; however, the underlying mechanisms remain unclear. This study investigated whether increases in range of motion (ROM) result from changes in muscle mechanical properties, stretch tolerance, or both. METHODS: Sixteen healthy adult males (27.0 ± 2.9 years) participated in a randomized crossover trial with two conditions: a flossing condition (FLOSS), in which a compression elastic band was wrapped around the thigh and participants performed four passive twisting-like movements followed by two sets of 20 active knee extension stretches; and a sham condition (SHAM) using an ice wrap with the same stretching protocol. Maximal passive knee extension ROM, passive knee flexion torque during passive joint movement, and the shear modulus of the biceps femoris long head (BFlh), semitendinosus (ST), and semimembranosus (SM) were measured before (Pre) and after the intervention (Post). RESULTS: Results revealed that knee extension ROM increased significantly in both conditions, but was greater in FLOSS (+ 10.5%) than SHAM (+ 2.9%, P < 0.05). Peak passive flexion torque increased significantly only in FLOSS (+ 11.1%, P < 0.05), indicating enhanced stretch tolerance. Shear modulus significantly decreased in the BFlh (− 8.7%) and SM (− 7.9%) after FLOSS, with post-intervention BFlh values lower than SHAM (P < 0.05). No significant changes were found in the ST in either FLOSS or SHAM. CONCLUSION: These findings demonstrate that flossing acutely increases knee extension ROM through a combination of decreased passive mechanical properties in specific hamstring muscles and enhanced stretch tolerance. Flossing may serve as a strategy to improve flexibility and aid hamstring injury prevention.