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

Abstract

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.

Keywords: Biceps brachii; Blood flow restriction; Electromyography; Motor unit control strategies.