Blood flow restriction combined with nordic hamstring exercise does not impair endothelial function but does not increase neuromuscular activation.

Background: Optimizing hamstring exercises is crucial for injury prevention and performance. This study explored the effects of blood flow restriction (BFR) during Nordic hamstring exercises (NHE) on hamstring muscle activation and vascular function.

Methods: A randomized, single-blind study included 14 healthy, physically active males (mean age: 27.5 years). Each participant's lower extremities were randomly assigned to BFR or control groups. In the BFR group, blood flow was restricted to 60% of arterial occlusion pressure. Participants performed three sets of five NHE repetitions. Endothelial function was assessed by flow-mediated dilation (FMD) via Doppler ultrasound before and after exercise. Surface electromyography (EMG) recorded neuromuscular activation of the semitendinosus (ST) and biceps femoris (BF) muscles during exercises.

Results: FMD values showed no significant differences between BFR and control groups (F(1,13) = 0.156, p = 0.7, partial η² = 0.012). Neuromuscular activations of ST and BF muscles decreased across sets in both groups but did not differ significantly between groups (ST: F(2,26) = 1.172, p = 0.448, partial η² = 0.09; BF: F(2,26) = 1.442, p = 0.527, partial η² = 0.1).

Conclusions: BFR did not produce acute additional effects on muscle activation or endothelial function compared to standard NHE. This suggests that incorporating BFR in NHE may not enhance immediate neuromuscular or vascular responses. Further research is needed to evaluate its long-term benefits.