Blood flow restriction increases necessary muscle excitation of the elbow flexors during a single high-load contraction

Purpose To investigate the effects of blood flow restriction (BFR) on electromyographic amplitude (EMG RMS )–force relationships of the biceps brachii (BB) during a single high-load muscle action. Methods Twelve recreationally active males and eleven recreationally active females performed maximal voluntary contractions (MVCs), followed by an isometric trapezoidal muscle action of the elbow flexors at 70% MVC. Surface EMG was recorded from the BB during BFR and control (CON) visits. For BFR, cuff pressure was 60% of the pressure required to completely occlude blood at rest. Individual b (slope) and a terms (gain) were calculated from the log-transformed EMG RMS –force relationships during the linearly increasing and decreasing segments of the trapezoid. EMG RMS during the steady force segment was normalized to MVC EMG RMS . Results For BFR, the b terms were greater during the linearly increasing segment than the linearly decreasing segment ( p < 0.001), and compared to the linearly increasing segment for CON ( p < 0.001). The a terms for BFR were greater during the linearly decreasing than linearly increasing segment ( p = 0.028). Steady force N-EMG RMS was greater for BFR than CON collapsed across sex ( p = 0.041). Conclusion BFR likely elicited additional recruitment of higher threshold motor units during the linearly increasing- and steady force-segment. The differences between activation and deactivation strategies were only observed with BFR, such as the b terms decreased and the a terms increased for the linearly decreasing segment in comparison to the increasing segment. However, EMG RMS –force relationships during the linearly increasing- and decreasing-segments were not different between sexes during BFR and CON.