Adding blood flow restriction to isokinetic resistance training provides no additional benefit for strength, but may improve local muscular endurance: a randomized controlled trial

This study investigated the effects of adding blood flow restriction (BFR) to high-load isokinetic resistance training on muscle strength and local muscular endurance. Forty-two middle- and long-distance runners were randomly assigned to an isokinetic training group with BFR (BFR group; n = 21) or an isokinetic training group without BFR (non-BFR group; n = 21). The training protocol consisted of concentric knee flexion and extension exercises performed at angular velocities of 60°/s (3 sets of 10 maximal repetitions) and 180°/s (3 sets of 30 maximal repetitions), twice weekly for 8 weeks. BFR was applied at 80% of arterial occlusion pressure (AOP) in the BFR group. Muscle strength (peak torque PT) and local muscular endurance (fatigue index FI) were evaluated before and after the intervention. Both groups demonstrated significant increases in muscle strength for both knee flexors and extensors at angular velocities of 60°/s and 180°/s. However, no significant between-group differences were observed for strength gains (p > 0.05 for all comparisons). Regarding local muscular endurance, the magnitude of improvement in FI was significantly greater in the BFR group compared to the non-BFR group for both flexors (p = 0.003, η²= 0.102) and extensors (p = 0.005, η²= 0.091). This study demonstrates that adding BFR to high-load isokinetic resistance training does not enhance muscle strength beyond high-load isokinetic resistance training but significantly improves local muscular endurance, as evidenced by greater reductions in FI in the BFR group. These findings suggest that BFR may be a valuable tool for optimizing endurance-specific adaptations in athletic populations requiring sustained performance. Future research should explore optimal BFR protocols for endurance-focused training across diverse athletic disciplines. Registration date: 04/11/2024, ClinicalTrials: NCT06678009.