The Effects of 4 Weeks of Blood Flow Restriction and Low-load Resistance Training on Muscle Strength, Power, Hypertrophy, and Neuromuscular Adaptation

The purposes of this study were to examine the effects of 4-wks of forearm flexion and extension blood flow restriction (BFR) resistance training versus non-BFR resistance training versus BFR without resistance training on: 1) muscle strength; 2) muscle power; 3) muscle size; and 4) neuromuscular adaptation. Forty women (mean±SD; 22±3 years) volunteered to participate in this investigation and were randomly assigned to either the resistance training with BFR (RT+BFR) (n=10), resistance training only (RT) (n=10), BFR without resistance training (n=10), or control (n=10) group. Resistance training included 75 (1×30, 3×15) repetitions of reciprocal isokinetic forearm flexion-extension muscle actions performed at 30% of concentric peak torque relative to forearm flexion and forearm extension peak torque, respectively. Blood flow restriction was applied using a KAATSU training device and was applied at a pressure that corresponded to 40% of arterial occlusion. Training was performed 3 times per week for 4-wks and all training and testing procedures were performed on a calibrated isokinetic dynamometer at a velocity of 120°˙s -1. The results of the present study indicated that there were similar mean increases in concentric peak torque, maximal voluntary isometric contraction (MVIC), muscle cross-sectional area, and muscle thickness for the forearm flexors and forearm extensors as a result of RT+BFR and RT. As a result of BFR only, there were smaller, but significant mean increases in concentric peak torque, but there were no changes in MVIC torque, muscle thickness or muscle cross-sectional area. In addition to the increases in muscle strength, there were also training-induced increases (collapsed across Group) in forearm flexion peak power and mean power and forearm extension mean power, but no changes in forearm extension peak power. There were training-induced changes in the electromyographic (EMG) and mechanomyographic (MMG) responses that, in general, included increases (collapsed across Group) in EMG mean power frequency, MMG amplitude, and MMG mean power frequency, but no changes in EMG amplitude. The simultaneous increases in EMG mean power frequency and MMG mean power frequency may have reflected increases in motor unit firing rate, while the training-induced increases in MMG amplitude likely reflected the increases in muscle size