Blood flow restricted and traditional resistance training performed to fatigue produce equal muscle hypertrophy

This study investigated the hypertrophic potential of load‐matched blood‐flow restricted resistance training ( BFR ) vs free‐flow traditional resistance training (low‐load TRT ) performed to fatigue. Ten healthy young subjects performed unilateral BFR and contralateral low‐load TRT elbow flexor dumbbell curl with 40% of one repetition maximum until volitional concentric failure 3 days per week for 6 weeks. Prior to and at 3 (post‐3) and 10 (post‐10) days post‐training, magnetic resonance imaging ( MRI ) was used to estimate elbow flexor muscle volume and muscle water content accumulation through training. Acute changes in muscle thickness following an early vs a late exercise bout were measured with ultrasound to determine muscle swelling during the immediate 0–48 h post‐exercise. Total work was threefold lower for BFR compared with low‐load TRT ( P < 0.001). Both BRF and low‐load TRT increased muscle volume by approximately 12% at post‐3 and post‐10 ( P < 0.01) with no changes in MRI ‐determined water content. Training increased muscle thickness during the immediate 48 h post‐exercise ( P < 0.001) and to greater extent with BRF ( P < 0.05) in the early training phase. In conclusion, BFR and low‐load TRT , when performed to fatigue, produce equal muscle hypertrophy, which may partly rely on transient exercise‐induced increases in muscle water content.