Less pain, same gain? A randomized controlled trial comparing assisted- versus non-assisted Nordic Hamstring exercise training in elite youth football players.

Introduction: The Nordic Hamstring exercise (NHE) increases hamstring strength, but muscle soreness and excessive fatigue may hinder adoption. The assisted NHE (A-NHE), with an elastic band around the chest lowering the force in the eccentric lowering phase, may be a less demanding alternative. We investigated the effectiveness of A-NHE versus NHE on hamstring strength, muscle soreness, and perceived exertion.

Methods: We randomized 31 youth elite football players (under-14 and -15) from a single professional football academy to either NHE or A-NHE, who performed the same supervised 8-week program. The A-NHE was performed with an elastic band, progressing from heavy to light assistance. A blinded tester assessed Nordic hamstring strength, while hamstring muscle soreness and perceived exertion were assessed during each session.

Results: Intention-to-treat analysis showed no group by time interaction (p = 0.61) for Nordic hamstring strength. Both groups improved significantly (A-NHE mean difference: 3.7 kg, 95% CI [2.1; 5.3]; NHE mean difference: 3.2 kg, 95% CI [1.2; 5.2]) corresponding to approximately 20%. The NHE group reported significantly higher hamstring muscle soreness (beta = 1.77, p < 0.01) and perceived exertion (beta = 1.54, p < 0.01).

Conclusion: Eight weeks of assisted-versus regular Nordic Hamstring training led to similar strength gains, but with lower hamstring muscle soreness and perceived exertion.