This 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.
Dual-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.
%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).
Maximal strength, muscle size, and MU recruitment and firing rate patterns for a non-weight bearing muscle differed between normal-fat and over-fat males.
京公网安备11010802044758号