Blood flow restriction increases motor unit firing rates and input excitation of the biceps brachii during a moderate-load muscle action

• Published in: Journal of sports sciences Vol. 42; no. 20; pp. 1891 - 1903
• Main Authors: Olmos, Alex A., Montgomery, Tony R., Sears, Kylie N., Roth, Brenden L., Richardson, Lyric D., Dinyer-McNeely, Taylor K., Hammer, Shane M., Bergstrom, Haley C., Hill, Ethan C., Succi, Pasquale J., Lubiak, Sean, Trevino, Michael A.
• Format: Journal Article
• Language: English
• Published: England Routledge 17-10-2024; Taylor & Francis Ltd
• Subjects: Action potential; biceps brachii; Blood flow; Blood flow restriction; Elbow; Electromyography; motor unit; Muscle contraction; Sex; Blood flow restriction; motor unit; biceps brachii; electromyography
• ISSN: 0264-0414; 1466-447X; 1466-447X
• DOI: 10.1080/02640414.2024.2413721

This study examined the effects of blood flow restriction (BFR) on motor unit (MU) behaviour of the biceps brachii (BB) during a single non-exhausting submaximal muscle action. Twenty adults performed maximal voluntary contractions (MVCs) of the elbow flexors, followed by an isometric trapezoidal muscle action at 40% MVC during BFR and control (CON) visits. Surface electromyographic signals recorded from the BB during the 40% MVCs were decomposed. Recruitment thresholds (RTs), MU action potential amplitudes (MUAP
AMPS
), initial firing rates (IFRs), mean firing rates (MFRs) at steady force, and normalized EMG amplitude (N-EMG
RMS
) were analysed. Y-intercepts and slopes were calculated for the MUAP
AMP
, IFR, and MFR vs. RT relationships. Y-intercepts for the IFR and MFR vs. RT relationships and N-EMG
RMS
increased during BFR (p < 0.05) collapsed across sex. The slopes for the IFR and MFR vs. RT relationships decreased during BFR (p < 0.05) collapsed across sex. The y-intercepts and slopes for the MUAP
AMP
vs. RT relationships were not different (p > 0.05) between treatments or sex. BFR during the 40% MVC increased IFRs, MFRs, and N-EMG
RMS
. However, the similar MUAP
AMPS
observed between treatments may suggest that a greater load is necessary to recruit additional MUs when performing a single submaximal short-duration muscle action with BFR.