Purpose: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.Methods:Dual-energy X-ray absorp...Purpose: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.Methods:Dual-energy X-ray absorptiometry assessed percent body fat(%BF).Ultrasonography determined muscle cross-sectional area(CSA),echo intensity(EI),and subcutaneous fat(s FAT).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)cm^(2)than OF([1.95±0.47]cm^(2);p=0.011).The y-intercepts for the MUAPAMPvs.RT relationships were greater for NF(0.283±0.254)m V than OF([-0.221±0.659]m V;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-EMGRMSwas similar between groups(p=0.463).Conclusion: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.展开更多
文摘Purpose: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.Methods:Dual-energy X-ray absorptiometry assessed percent body fat(%BF).Ultrasonography determined muscle cross-sectional area(CSA),echo intensity(EI),and subcutaneous fat(s FAT).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)cm^(2)than OF([1.95±0.47]cm^(2);p=0.011).The y-intercepts for the MUAPAMPvs.RT relationships were greater for NF(0.283±0.254)m V than OF([-0.221±0.659]m V;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-EMGRMSwas similar between groups(p=0.463).Conclusion: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.
