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
This study examined the repeated bout effect(RBE)on muscle damage markers following two bouts of neuromuscular electrical stimulation(NMES)in untrained individuals.Following familiarization,participants received 45 co...This study examined the repeated bout effect(RBE)on muscle damage markers following two bouts of neuromuscular electrical stimulation(NMES)in untrained individuals.Following familiarization,participants received 45 consecutive NMES to the biceps brachii at an intensity that produced low evoked force for the elbow flexors.Muscle damage markers(maximal voluntary isometric contraction[MVIC],elbow range of motion[ROM],muscle soreness via visual analogue scale[VAS]scores,pressure pain threshold[PPT],and muscle thickness)were measured before(PRE),after(POST),1 day after(24 POST),and 2 days after(48 POST)NMES.Following 1 week of rest,procedures were replicated.Separate repeated measures two-way ANOVAs examined each measure.There were no interactions or bout main effects for MVIC or ROM.Time main effects indicated PRE MVIC was greater than POST(p=0.002)and 24-POST(p=0.024),and PRE ROM was greater than POST(p=0.036).There was no interaction for muscle thickness.Respective time and bout main effects indicated muscle thickness at PRE was less than POST(p=0.017),and second-bout muscle thickness(p=0.050)was less compared to the initial-bout.For PPT,there was an interaction(p=0.019).Initial-bout PRE PPT was less than POST(p=0.033).Initial-bout 48-POST PPT was less than second-bout 48-POST(p=0.037).There was a significant interaction for VAS(p=0.009).Initial-bout PRE VAS was less than POST(p=0.033)and 24-POST(p=0.015).Initial-bout POST and 24-POST VAS were greater than second-bout POST(p=0.023)and 24-POST(p=0.006),respectively.The results support RBE on muscle damage markers related to inflammation,but not MVIC and ROM.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.
文摘This study examined the repeated bout effect(RBE)on muscle damage markers following two bouts of neuromuscular electrical stimulation(NMES)in untrained individuals.Following familiarization,participants received 45 consecutive NMES to the biceps brachii at an intensity that produced low evoked force for the elbow flexors.Muscle damage markers(maximal voluntary isometric contraction[MVIC],elbow range of motion[ROM],muscle soreness via visual analogue scale[VAS]scores,pressure pain threshold[PPT],and muscle thickness)were measured before(PRE),after(POST),1 day after(24 POST),and 2 days after(48 POST)NMES.Following 1 week of rest,procedures were replicated.Separate repeated measures two-way ANOVAs examined each measure.There were no interactions or bout main effects for MVIC or ROM.Time main effects indicated PRE MVIC was greater than POST(p=0.002)and 24-POST(p=0.024),and PRE ROM was greater than POST(p=0.036).There was no interaction for muscle thickness.Respective time and bout main effects indicated muscle thickness at PRE was less than POST(p=0.017),and second-bout muscle thickness(p=0.050)was less compared to the initial-bout.For PPT,there was an interaction(p=0.019).Initial-bout PRE PPT was less than POST(p=0.033).Initial-bout 48-POST PPT was less than second-bout 48-POST(p=0.037).There was a significant interaction for VAS(p=0.009).Initial-bout PRE VAS was less than POST(p=0.033)and 24-POST(p=0.015).Initial-bout POST and 24-POST VAS were greater than second-bout POST(p=0.023)and 24-POST(p=0.006),respectively.The results support RBE on muscle damage markers related to inflammation,but not MVIC and ROM.
