Low Load With BFR vs. High Load Without BFR Eccentric Hamstring Training Have Similar Outcomes on Muscle Adaptation.

Jones, MJ, Dominguez, JF, Macatugal, C, Coleman, K, Reed, B, and Schroeder, ET. Low load with BFR vs. high load without BFR eccentric hamstring training have similar outcomes on muscle adaptation. J Strength Cond Res 37(1): 55-61, 2023-A key principle of hamstring injury rehabilitation is developing high eccentric force capability through resistance training (RT). However, it can take months before high-load RT is deemed safe and appropriate for rehabilitating serious hamstring injuries. Low-load blood flow restriction (BFR) RT has been identified as an effective alternative when high-load RT is contraindicated but has been scarcely investigated in the hamstring. To address this gap in knowledge, we sought to compare the effect of longitudinal BFR RT with traditional RT on eccentric hamstring power, strength, lean mass, perceived soreness, and acute muscle swell in healthy adults (n = 40; 19 F, 21 M; mean ± SD; age: 24.3 ± 2.6 years). Our crossover design compared the effects of low-load (30% 1RM) eccentric lower extremity training with BFR (BFR-ELET) with traditional high-load (80% 1RM) eccentric lower extremity training (TRAD-ELET) without BFR biweekly for 6 weeks. Outcomes were tested pre/post-intervention with significance at α = 0.05. Both interventions yielded dependent variable outcomes that did not differ significantly except for muscle swell assessed by bioelectrical impedance analysis, which decreased significantly more in the BFR-ELET condition compared with TRAD-ELET (mean ± SD: -0.32 ± 0.02, Φ° 50 kHz), CI: -0.35 to -0.28, Φ° 50 kHz, p < 0.001, Cohen's d = 2.95). Our findings support BFT-ELET as an effective alternative to TRAD-ELET for enhancing strength and identify myocellular swelling as a potential mediator for strength outcomes associated with BFR training.