Influence of relative blood flow restriction pressure on muscle activation and muscle adaptation.

INTRODUCTION: The aim of this study was to investigate the acute and chronic skeletal muscle response to differing levels of blood flow restriction (BFR) pressure. METHODS: Fourteen participants completed elbow flexion exercise with pressures from 40% to 90% of arterial occlusion. Pre/post torque measurements and electromyographic (EMG) amplitude of each set were quantified for each condition. This was followed by a separate 8-week training study of the effect of high (90% arterial occlusion) and low (40% arterial occlusion) pressure on muscle size and function. RESULTS: For the acute study, decreases in torque were similar between pressures [-15.5 (5.9) Nm, P = 0.344]. For amplitude of the first 3 and last 3 reps there was a time effect. After training, increases in muscle size (10%), peak isotonic strength (18%), peak isokinetic torque (180°/s = 23%, 60°/s = 11%), and muscular endurance (62%) changed similarly between pressures. CONCLUSION: We suggest that higher relative pressures may not be necessary when exercising under BFR.