@article{Richardson2026, 
author = {Lyric D. Richardson and Alex A. Olmos and Allen L. Redinger and Stephanie A. Sontag and Sunggun Jeon and Brenden L. Roth and Emma G. High and Breanne S. Baker and Jerome Hauselle and Michael A. Trevino},
title = {Comparison of maximal strength, muscle morphology, and motor unit recruitment and firing rate patterns of the abductor digiti minimi in normal-fat and over-fat males},
year = {2026},
journal = {Sports Medicine and Health Science},
volume = {8},
number = {2},
pages = {163-171},
keywords = {Abductor digiti minimi, Body fat, Electromyography, Motor unit, Ultrasonography},
url = {https://www.sciopen.com/article/10.1016/j.smhs.2025.02.009},
doi = {10.1016/j.smhs.2025.02.009},
abstract = {PurposeThis study examined potential differences in strength, muscle morphology, and motor unit (MU) behavior of the abductor digiti minimi (ADM) between normal-fat (NF) and over-fat (OF) males.MethodsDual-energy X-ray absorptiometry assessed percent body fat (%BF). Ultrasonography determined muscle cross-sectional area (CSA), echo intensity (EI), and subcutaneous fat (sFAT). MU behavior was assessed during isometric muscle actions at 50% of maximal voluntary contraction (MVC) by analyzing the y-intercepts and slopes for the MU action potential amplitude (MUAPAMP) vs. recruitment threshold (RT) relationships, the A and B terms for the mean firing rate (MFR) vs. RT relationships, and normalized electromyographic amplitude (N-EMGRMS). MU firing times and waveforms were validated with reconstruct-and-test and spike trigger average procedures.Results%BF was greater for OF (25.70% ​± ​5.40%) than NF (16.50% ​± ​2.20%; p < 0.001). MVC was greater for NF (27.13 ​± ​7.16) N than OF ([19.89 ​± ​4.96] N; p ​= ​0.014). CSA was greater for NF (2.48 ​± ​0.39) cm2 than OF ([1.95 ​± ​0.47] cm2; p ​= ​0.011). The y-intercepts for the MUAPAMP vs. RT relationships were greater for NF (0.283 ​± ​0.254) mV than OF ([-0.221 ​± ​0.659] mV; p ​= ​0.004). The B terms for the MFR vs. RT relationships were greater for NF (−0.024 ​± ​0.003) pps/%MVC than OF ([-0.031 ​± ​0.009] pps/%MVC; p ​= ​0.038). N-EMGRMS was similar between groups (p ​= ​0.463).ConclusionMaximal strength, muscle size, and MU recruitment and firing rate patterns for a non-weight bearing muscle differed between normal-fat and over-fat males.}
}