The application of blood flow restriction during low load exercise has consistently been shown to augment muscle hypertrophy which has been attributed to metabolic accumulation. It remains unknown, however, whether metabolites can augment muscle growth independent of further mechanical tension, specifically when maintained post high-load training. Thirteen untrained individuals performed 24 training sessions. The control arm performed one set of elbow flexion (70% 1RM) exercise to volitional fatigue, while the experimental arm performed the same protocol immediately folloby 3 min of blood flow restriction (70% arterial occlusion). Both conditions completed the same volume (3687 vs. 3638 kg) of exercise. There was an interaction (p=0.031) demonstrating an attenuation of muscle growth at the 60% site in the experimental [pre: 3.1 (0.6), post: 3.1 (0.7) cm] vs. control [pre: 3.1 (0.7), post 3.3 (0.7) cm] condition. Muscle growth at the 50% site did not differ between the experimental [pre: 2.9 (0.6), post 2.9 (0.6) cm] and control [pre: 2.8 (0.7), post: 2.9 (0.6) cm] condition (p=0.31) nor did it differ at the 70% site [experimental pre: 3.3 (0.60), post 3.5 (0.7) cm; control pre: 3.4 (0.7), post 3.6 (0.7) cm]. Although there were no differences at the group level, there were attenuations at the individual level. The number of measured sites displaying growth at or outside the error of the measurement was greater in the control (21) vs. experimental (10) condition. The application of blood flow restriction post high-load exercise did not augment, but appeared to attenuate muscle growth at the group and individual level. With regard to one-repetition maximum strength, increases were observed in both the control [pre: 13.5 (3.8), post: 16.3 (4.5) kg] and experimental [pre: 13.7 (4.1), post: 16.3 (4.6) kg] conditions with no differences between conditions. No changes were observed for isometric or isokinetic strength for either the control or experimental conditions. These results unveil the possibilities that 1) metabolites do not have anabolic properties per se, and may be detrimental for muscle hypertrophy; 2) immediate post-exercise blood flow is important for muscle hypertrophy; and/or 3) metabolites have anabolic properties but this was masked by the restriction of blood flow
