Key Takeaway
Flywheel leg curl training improved hamstring muscle structure and eccentric strength in athletes with prior hamstring strain injuries, supporting its use as a targeted rehabilitation tool.
Summary
This randomized controlled trial by Sampietro et al. (2025) examined whether flywheel leg curl exercise could improve muscle structure and function in athletes with a history of hamstring strain injury — a population at high risk of re-injury. Participants with previous hamstring strains were randomized to a flywheel leg curl intervention or a control condition, with outcomes assessed via ultrasound imaging and dynamometry. The flywheel group showed significant improvements in hamstring muscle fascicle length, muscle thickness, and eccentric peak torque compared to controls. These structural changes — particularly increased fascicle length — are considered protective against re-injury because longer fascicles can absorb more energy during high-speed eccentric contractions such as sprinting. The study provides direct evidence that flywheel-based eccentric training addresses the specific deficits that persist after hamstring injury, making it a valuable tool in secondary prevention and return-to-sport protocols for athletes recovering from hamstring strains.