Purpose The purpose of this study was to examine the responses of electromyographic(EMG)and mechanomyographic(MMG)amplitude across the torque spectrum in pre-and post-pubescent males and females.Methods Forty pre-pube...Purpose The purpose of this study was to examine the responses of electromyographic(EMG)and mechanomyographic(MMG)amplitude across the torque spectrum in pre-and post-pubescent males and females.Methods Forty pre-pubescent(mean±95%confidence interval,age=9.79±0.35 years,n=10 males,n=10 females)and post-pubescent(age=17.23±0.58 years,n=10 males,n=10 females)participants completed this study.Participants completed maximal voluntary isometric contractions(MVICs)of the forearm flexors and extensors,as well as isometric ramp muscle actions.EMG and MMG amplitude were quantified from the biceps brachii,brachialis,and brachioradialis during all muscle actions.EMG and MMG amplitude during the isometric ramp muscle actions were normalized to EMG and MMG amplitude from the MVICs.Results The pre-pubertal group tended to have greater relative EMG amplitude across intensity(P<0.050),while the post-pubertal group had a more pronounced increase in EMG amplitude at higher intensities.Similarly,the pre-pubertal group tended to have greater relative MMG amplitude across intensity(P≤0.004)that plateaued earlier than the post-pubertal group(55%vs.65%-75%of MVIC).Additionally,the pre-pubertal group had greater coactivation across intensity(P≤0.001).Conclusion The greater relative EMG and MMG amplitude in the pre-pubertal group,in conjunction with the earlier plateau in MMG amplitude for the pre-pubertal group and greater coactivation,suggests less efficient muscle activation and motor unit recruitment strategies during pre-pubescence.Taken together,the findings of the present study suggest that growth-mediated changes in neuromuscular function lead to improvements in the efficiency of muscular activation and augmentations in motor unit recruitment strategies.展开更多
Purpose The purpose of this study was to examine peak torque(PT),mean power(MP),electromyographic(EMG)amplitude,mechanomyographic(MMG)amplitude,and neuromuscular efficiency from EMG and MMG amplitude(NME_(EMG)and NME_...Purpose The purpose of this study was to examine peak torque(PT),mean power(MP),electromyographic(EMG)amplitude,mechanomyographic(MMG)amplitude,and neuromuscular efficiency from EMG and MMG amplitude(NME_(EMG)and NME_(MMG),respectively)across the velocity spectrum in children versus adolescents.Methods Seventeen children(n=8 males,n=9 females)and 22 adolescents(n=11 males,n=11 females)participated.Participants completed maximal concentric isokinetic leg extensions at 60,120,180,240 and 300°/s.PT,MP,EMG amplitude,and MMG amplitude were quantified during all muscle actions.NME_(EMG)and NME_(MMG)were quantified by expressing PT relative to EMG and MMG amplitude,respectively,for each muscle action.Results PT,MP,NME_(EMG),and NME_(MMG)were greater for the adolescents than the children collapsed across sex and veloc-ity(P≤0.021).There were no significant differences for EMG amplitude(P≥0.051),while MMG amplitude increased significantly from 60 to 240°/s(P<0.001)then decreased significantly from 240 to 300°/s(P<0.001)for all groups.Conclusion Overall,regardless of velocity,the expression of PT relative to EMG and MMG amplitude(NME_(EMG)and NME_(MMG),respectively),in conjunction with measurements of torque and power production,may provide practitioners a unique method of examining growth and development-related augmentations in neuromuscular function during dynamic movements.展开更多
Purpose The purpose of this study was to examine the relationships among leg extension strength,explosive strength,muscle activation,and measurements of growth to predictions of vertical jump performance in youth athl...Purpose The purpose of this study was to examine the relationships among leg extension strength,explosive strength,muscle activation,and measurements of growth to predictions of vertical jump performance in youth athletes.Methods Height,body mass,skinfolds,and quadriceps femoris muscle cross-sectional area were measured in 39 sports active children(20 females,19 males,age=12.52±0.62 years old).Peak torque(PT),rate of torque development(RTD),rate of velocity development(RVD),and rate of electromyographic amplitude rise(RER)were measured during isometric and isokinetic leg extensions.PT,RTD,and RVD were expressed in absolute terms and normalized to body mass.Estimated jump height(JH)and peak power(PP)were assessed during static(SJ),counter-movement(CMJ),and drop(DJ)jumps.Results JH exhibited greater correlations with PT normalized to body mass(r=0.387-0.758)than absolute PT(r=0.338-0.417),whereas PP exhibited greater correlations with absolute PT(r=0.368-0.837).Only negligible to moderate relation-ships existed between JH and PP across all jumps(r=0.053-0.605).Over 50%of the variability in PP was predicted in 24 of 30 regression models with absolute muscle strength,muscle activation,and measurements of growth,while only 6 of 30 models predicted more than 50%of the variability in JH.Conclusion Overall,absolute static and dynamic muscle strength,muscle activation,and growth better explained PP meas-ured during vertical jumps than estimated JH.展开更多
Purpose This study examined changes in vertical jump performance with progressively greater eccentric pre-loading in relation to growth and development in young female athletes.Methods Twenty young female athletes ran...Purpose This study examined changes in vertical jump performance with progressively greater eccentric pre-loading in relation to growth and development in young female athletes.Methods Twenty young female athletes ranging from 9 to 17 years old performed the following vertical jumps in random order:static jumps(SJs),counter-movement jumps(CMJs),and drop jumps(DJs)from drop heights of 20,30,and 40 cm(DJ20,DJ30,and DJ40,respectively).Measurements included peak force(PF),peak rate of force development(RFD),peak power(PP),eccentric impulse(ECC),and concentric impulse(CON).Measurements of growth included age,maturity offset,height,body mass,fat-free mass,and thigh muscle cross-sectional area(CSA).Results PF increased from the SJ-DJ20(P<0.009),then plateaued from DJ20-DJ40(P=1.000).RFD remained the same from SJ-CMJ(P=1.000),increased from CMJ-DJ20(P<0.001),and plateaued from DJ20-DJ40(P=0.874).PP increased from the SJ-CMJ(P<0.001),then plateaued from the CMJ-DJ40(P≥0.486).CON remained the same across all verti-cal jumps(P=1.000),while ECC increased from the SJ-DJ40(P≤0.038).Jump height(JH)increased from the SJ-CMJ(P<0.001),decreased from CMJ-DJ20(P<0.001),and plateaued from DJ20-DJ40(P=1.000).The change in PP from the SJ-CMJ(ΔCMJ-SJ)was related to all measurements of growth except CSA(r=0.558-0.815).Conclusion Young females produced greater power during the CMJ than SJ,but equivalent power from the CMJ-DJ40,despite increases in ECC.Additionally,ΔCMJ-SJ was not related to CSA,which suggests other underlying mechanisms affect stretch-shortening cycle utilization in young female athletes.展开更多
基金National Strength and Conditioning Association Foundation(NSCAF)Graduate Research Doctoral Grant,the University of Nebraska Agriculture Research Division with funds provided by the Hatch Act(Agency:U.S.Department of Agriculture,National Institute of Food and AgricultureAccession No:1000080,Project No:NEB-36-078)and a grant from Abbott Nutrition,Columbus,OH.
文摘Purpose The purpose of this study was to examine the responses of electromyographic(EMG)and mechanomyographic(MMG)amplitude across the torque spectrum in pre-and post-pubescent males and females.Methods Forty pre-pubescent(mean±95%confidence interval,age=9.79±0.35 years,n=10 males,n=10 females)and post-pubescent(age=17.23±0.58 years,n=10 males,n=10 females)participants completed this study.Participants completed maximal voluntary isometric contractions(MVICs)of the forearm flexors and extensors,as well as isometric ramp muscle actions.EMG and MMG amplitude were quantified from the biceps brachii,brachialis,and brachioradialis during all muscle actions.EMG and MMG amplitude during the isometric ramp muscle actions were normalized to EMG and MMG amplitude from the MVICs.Results The pre-pubertal group tended to have greater relative EMG amplitude across intensity(P<0.050),while the post-pubertal group had a more pronounced increase in EMG amplitude at higher intensities.Similarly,the pre-pubertal group tended to have greater relative MMG amplitude across intensity(P≤0.004)that plateaued earlier than the post-pubertal group(55%vs.65%-75%of MVIC).Additionally,the pre-pubertal group had greater coactivation across intensity(P≤0.001).Conclusion The greater relative EMG and MMG amplitude in the pre-pubertal group,in conjunction with the earlier plateau in MMG amplitude for the pre-pubertal group and greater coactivation,suggests less efficient muscle activation and motor unit recruitment strategies during pre-pubescence.Taken together,the findings of the present study suggest that growth-mediated changes in neuromuscular function lead to improvements in the efficiency of muscular activation and augmentations in motor unit recruitment strategies.
基金the University of Nebraska Agriculture Research Division with funds provided by the Hatch Act(Agency:U.S.Department of Agriculture,National Institute of Food and Agriculture,Accession No:1000080,Project No:NEB-36-078)a grant from Abbott Nutrition,Columbus,OH.
文摘Purpose The purpose of this study was to examine peak torque(PT),mean power(MP),electromyographic(EMG)amplitude,mechanomyographic(MMG)amplitude,and neuromuscular efficiency from EMG and MMG amplitude(NME_(EMG)and NME_(MMG),respectively)across the velocity spectrum in children versus adolescents.Methods Seventeen children(n=8 males,n=9 females)and 22 adolescents(n=11 males,n=11 females)participated.Participants completed maximal concentric isokinetic leg extensions at 60,120,180,240 and 300°/s.PT,MP,EMG amplitude,and MMG amplitude were quantified during all muscle actions.NME_(EMG)and NME_(MMG)were quantified by expressing PT relative to EMG and MMG amplitude,respectively,for each muscle action.Results PT,MP,NME_(EMG),and NME_(MMG)were greater for the adolescents than the children collapsed across sex and veloc-ity(P≤0.021).There were no significant differences for EMG amplitude(P≥0.051),while MMG amplitude increased significantly from 60 to 240°/s(P<0.001)then decreased significantly from 240 to 300°/s(P<0.001)for all groups.Conclusion Overall,regardless of velocity,the expression of PT relative to EMG and MMG amplitude(NME_(EMG)and NME_(MMG),respectively),in conjunction with measurements of torque and power production,may provide practitioners a unique method of examining growth and development-related augmentations in neuromuscular function during dynamic movements.
基金Efforts for this study were funded,in part,by the University of Nebraska Agriculture Research Division with funds provided by the Hatch Act(Agency:U.S.Department of Agriculture,National Institute of Food and AgricultureAccession No:1000080+1 种基金Project No:NEB-36-078)a grant from Abbott Nutrition,Columbus。
文摘Purpose The purpose of this study was to examine the relationships among leg extension strength,explosive strength,muscle activation,and measurements of growth to predictions of vertical jump performance in youth athletes.Methods Height,body mass,skinfolds,and quadriceps femoris muscle cross-sectional area were measured in 39 sports active children(20 females,19 males,age=12.52±0.62 years old).Peak torque(PT),rate of torque development(RTD),rate of velocity development(RVD),and rate of electromyographic amplitude rise(RER)were measured during isometric and isokinetic leg extensions.PT,RTD,and RVD were expressed in absolute terms and normalized to body mass.Estimated jump height(JH)and peak power(PP)were assessed during static(SJ),counter-movement(CMJ),and drop(DJ)jumps.Results JH exhibited greater correlations with PT normalized to body mass(r=0.387-0.758)than absolute PT(r=0.338-0.417),whereas PP exhibited greater correlations with absolute PT(r=0.368-0.837).Only negligible to moderate relation-ships existed between JH and PP across all jumps(r=0.053-0.605).Over 50%of the variability in PP was predicted in 24 of 30 regression models with absolute muscle strength,muscle activation,and measurements of growth,while only 6 of 30 models predicted more than 50%of the variability in JH.Conclusion Overall,absolute static and dynamic muscle strength,muscle activation,and growth better explained PP meas-ured during vertical jumps than estimated JH.
基金Efforts for this study were funded,in part,by the University of Nebraska Agriculture Research Division with funds provided by the Hatch Act(Agency:U.S.Department of Agriculture,National Institute of Food and Agriculture,Accession No:1000080,Project No:NEB-36-078)a grant from Abbott Nutrition,Columbus,OH.
文摘Purpose This study examined changes in vertical jump performance with progressively greater eccentric pre-loading in relation to growth and development in young female athletes.Methods Twenty young female athletes ranging from 9 to 17 years old performed the following vertical jumps in random order:static jumps(SJs),counter-movement jumps(CMJs),and drop jumps(DJs)from drop heights of 20,30,and 40 cm(DJ20,DJ30,and DJ40,respectively).Measurements included peak force(PF),peak rate of force development(RFD),peak power(PP),eccentric impulse(ECC),and concentric impulse(CON).Measurements of growth included age,maturity offset,height,body mass,fat-free mass,and thigh muscle cross-sectional area(CSA).Results PF increased from the SJ-DJ20(P<0.009),then plateaued from DJ20-DJ40(P=1.000).RFD remained the same from SJ-CMJ(P=1.000),increased from CMJ-DJ20(P<0.001),and plateaued from DJ20-DJ40(P=0.874).PP increased from the SJ-CMJ(P<0.001),then plateaued from the CMJ-DJ40(P≥0.486).CON remained the same across all verti-cal jumps(P=1.000),while ECC increased from the SJ-DJ40(P≤0.038).Jump height(JH)increased from the SJ-CMJ(P<0.001),decreased from CMJ-DJ20(P<0.001),and plateaued from DJ20-DJ40(P=1.000).The change in PP from the SJ-CMJ(ΔCMJ-SJ)was related to all measurements of growth except CSA(r=0.558-0.815).Conclusion Young females produced greater power during the CMJ than SJ,but equivalent power from the CMJ-DJ40,despite increases in ECC.Additionally,ΔCMJ-SJ was not related to CSA,which suggests other underlying mechanisms affect stretch-shortening cycle utilization in young female athletes.
