SEX-RELATED DIFFERENCES IN MECHANOMYOGRAPHIC AMPLITUDE OF THE BICEPS BRACHII DURING MOTOR UNIT ACTIVATION AND DEACTIVATION

Authors

BL Roth
AA Olmos
TR Montgomery, Jr
KN Sears
TK Dinyer
SM Hammer
HC Bergstrom
EC Hill
PJ Succi
L Richardson
MA Trevino

Abstract

Brenden L. Roth¹, Alex A. Olmos¹, Tony R. Montgomery Jr.¹, Kylie N. Sears¹, Taylor K. Dinyer¹, Shane M. Hammer¹, Haley C. Bergstrom², Ethan C. Hill³, Pasquale J. Succi², Lyric Richardson¹, & Michael A. Trevino¹

¹Oklahoma State University, Stillwater, Oklahoma; ²University of Kentucky, Lexington, Kentucky; ³University of Central Florida, Orlando, Florida

PURPOSE: To investigate mechanomyographic amplitude (MMG_RMS)-force relationships of the biceps brachii (BB) between females and males during a high-intensity muscle action. METHODS: Ten healthy females (age = 20 ± 3 yrs) and twelve healthy males (age = 24 ± 4 yrs) participated in this study. Participants performed maximal voluntary contractions (MVCs) of the elbow flexors on a dynamometer, followed by an isometric trapezoidal muscle action at 70% MVC. Surface MMG was recorded from the BB. Subcutaneous fat (sFAT) of the BB was measured via ultrasonography. Individual a (gain) and b (slope) terms were calculated from the log-transformed MMG_RMS-force relationships for the linearly increasing and decreasing segments. MMG_RMS during the steady force segment was normalized (N-MMG_RMS) to MVC MMG_RMS. A 2-way mixed factorial repeated measures ANOVA (sex [males vs. females] x segment [increase vs. decrease]) examined the a and b terms. Independent samples t-tests compared N-MMG_RMS and sFAT between sexes. Alpha was set at ≤ 0.05. RESULTS: For b terms, there were neither a significant two-way interaction (p = 0.856) nor a main effect for segment (p = 0.248). However, there was a main effect for sex (p < 0.001). The b terms were greater for the males (0.800 ± 0.231) than the females (0.548 ± 0.170) when collapsed across segment. For a terms, there was neither a significant two-way interaction nor main effects for sex and segment (p = 0.564 – 0.910). Additionally, there were no significant differences between groups for N-MMG_RMS (p = 0.241) and sFAT (p = 0.219). CONCLUSION: Males exhibited greater b terms (slopes) than the females during the 70% MVC; however, there was no significant difference in the a terms (gain) of the log-transformed MMG_RMS-force relationships between sexes. Therefore, motor unit activation and deactivation strategies were influenced as a function of sex. The similar sFAT between sexes provides confidence the differences in the b terms between the males and females was not due to sFAT filtering of MMG signal. Furthermore, the lack of differences between the males and females for N-MMG_RMS during the steady force segment may suggest that linearly increasing and decreasing muscle actions are more appropriate for investigating sex-related differences in the mechanical behavior (MMG_RMS) of the BB.

Recommended Citation

Roth, BL; Olmos, AA; Montgomery, Jr, TR; Sears, KN; Dinyer, TK; Hammer, SM; Bergstrom, HC; Hill, EC; Succi, PJ; Richardson, L; and Trevino, MA (2024) "SEX-RELATED DIFFERENCES IN MECHANOMYOGRAPHIC AMPLITUDE OF THE BICEPS BRACHII DURING MOTOR UNIT ACTIVATION AND DEACTIVATION," International Journal of Exercise Science: Conference Proceedings: Vol. 11: Iss. 11, Article 43.
Available at: https://digitalcommons.wku.edu/ijesab/vol11/iss11/43