Mechanomyographic Amplitude-Force Relationships of the Biceps Brachii Differ Between Sexes During Linearly Varying Muscle Actions and Provide Insight on Muscle Morphology
DOI:
https://doi.org/10.63750/9j1ghf75Keywords:
Biceps brachii, Log-transform model, Mechanomyography, Motor unit activation/deactivation, UltrasonographyAbstract
This study compared mechanomyographic amplitude (MMGRMS)-force relationships of the biceps brachii (BB) between sexes during moderate- and high-intensity increasing, steady, and decreasing isometric motor tasks. Twenty participants (ten males, ten females) performed maximal voluntary contractions (MVCs) of the elbow flexors followed by isometric trapezoidal muscle actions at 40% and 70% MVC. MMG signals were recorded from the BB. MMGRMS-force relationships during the increasing and decreasing segments were log-transformed to calculate a (gain) and b (slope) terms. MMGRMS was averaged during steady force. BB muscle cross-sectional area (mCSA) was measured via ultrasonography. The b terms, collapsed across segment and intensity, were greater for males (0.665±0.160) than the females (0.360±0.184; p<0.001). The a terms for the females during the 40% MVC (0.103±0.101) were greater than the males (0.018±0.014; p=0.026). MMGRMS, collapsed across intensity, was greater in males (0.256±0.091 m·s-2) than females (0.159±0.041 m·s-2; p=0.006). mCSA was correlated with the b terms (p=0.001; r=0.67) and MMGRMS (p<0.001; r=0.75). The greater b terms for the males and the relationships between b terms and mCSA may result from larger MUs producing greater twitch forces throughout the recruitment spectrum. MMGRMS differentiated BB MU behavior between sexes during various muscle actions and was sensitive to muscle size.
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Copyright (c) 2025 Brenden Roth, Alex Olmos, Kylie Sears, Tony Montgomery, Taylor Dinyer-McNeely, Shane Hammer, Haley Bergstrom, Ethan Hill, Pasquale Succi, Lyric Richardson, Sean Lubiak, Michael Trevino (Author)
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