肌肉疲劳是由运动引起的肌肉最大随意收缩力减小的现象,其研究可应用于生理医学的职业病预防或体育工程的运动员训练等方面。本文采用短时傅里叶变换对肌音信号进行处理,提取频域特征平均功率频率(Mean Power Frequency,MPF)和中值频率(...肌肉疲劳是由运动引起的肌肉最大随意收缩力减小的现象,其研究可应用于生理医学的职业病预防或体育工程的运动员训练等方面。本文采用短时傅里叶变换对肌音信号进行处理,提取频域特征平均功率频率(Mean Power Frequency,MPF)和中值频率(Median Frequency,MDF),研究其与肌肉疲劳程度之间的关系。9名健康的男性志愿者参与了本次试验,采用等值于60%最大随意收缩力(MVC)的力产生恒力肌肉疲劳,同步记录每一位受试者桡侧腕屈肌的肌音信号,对提取的频域参数进行分析。将持续30s的肌肉疲劳过程分为6个时间阶段(每个阶段为5s),并对每个时间阶段内的MPF和MDF计算均值。结果表明,随着肌肉疲劳程度加深,肌音信号的MPF和MDF在每个时间阶段内的均值均呈现近似线性下降的趋势。在30s肌肉疲劳过程中,从第1阶段(1~5s)到第6阶段(26~30s),MPF均值下降了15.8%,MDF均值下降了26.1%。基于短时傅里叶变换提取的MPF和MDF指标能良好地反映疲劳敏感性和稳定性,在评定肌肉静态疲劳方面是较好的参考指标。本文采用的方法和得到的结果为后期更深入地使用肌音信号对肌肉疲劳程度进行量化研究提供了依据。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 effects of caffeine on peak torque(PT),rate of torque development(RTD),and muscle activation in college-age men.Methods Fifteen men(23.3±2.2 years,177.6±8...Purpose The purpose of this study was to examine the effects of caffeine on peak torque(PT),rate of torque development(RTD),and muscle activation in college-age men.Methods Fifteen men(23.3±2.2 years,177.6±8.7 cm,90.3±19.1 kg)volunteered to participate in this study.During each of two test sessions,maximal leg extension PT and RTD were determined and electromyographic(EMG)and mechano-myographic(MMG)signals were collected to examine electrical and mechanical aspects of muscle activation,respectively.Participants also performed the Wingate Anaerobic Test(WAnT)for the determination of peak power(PP),mean power(MP),and fatigue percentage(FP).For the first test session,participants were randomly assigned to ingest either a caffein-ated drink(6 mg/kg)or a placebo 1 h prior to testing.The second test session was identical to the first,but the drink not previously administered was ingested prior to testing.Results The results indicated there were no significant effects of caffeine on PT,PP,MP,FP,or EMG and MMG measures.However,RTD was positively affected by caffeine(856.4±246.4 Nm/s)compared to the placebo condition(710.9±267.9 Nm/s).Conclusions These results suggest that caffeine can be an effective aid for sport activities requiring maximal rates of force or torque development during very short time periods.展开更多
Mechanomyography (MMG) acquires the oscillatory waves of contracting muscles. Electromyography (EMG) is a tool for monitoring muscle overall electrical activity. During muscle contractions, both techniques can investi...Mechanomyography (MMG) acquires the oscillatory waves of contracting muscles. Electromyography (EMG) is a tool for monitoring muscle overall electrical activity. During muscle contractions, both techniques can investigate the changes that occur in the muscle properties. EMG and MMG parameters have been used for detecting muscle fatigue with diverse test protocols, sensors and filtering. Depending on the analysis window length (WLA), monitoring physiological events could be compromised due to imprecision in the determination of parameters. Therefore, this study investigated the influence of WLA variation on different MMG and EMG parameters during submaximal isometric contractions monitoring MMG and EMG parameters. Ten male volunteers performed isometric contractions of elbow joint. Triaxial accelerometer-based MMG sensor and EMG electrodes were positioned on the biceps brachii muscle belly. Torque was monitored with a load cell. Volunteers remained seated with hip and elbow joint at angles of 110° and 90°, respectively. The protocol consisted in maintaining torque at 70% of maximum voluntary contraction as long as they could. Parameter data of EMG and the modulus of MMG were determined for four segments of the signal. Statistical analysis consisted of analyses of variance and Fisher’s least square differences post-hoc test. Also, Pearson’s correlation was calculated to determine whether parameters that monitor similar physiological events would have strong correlation. The modulus of MMG mean power frequency (MPF) and the number of crossings in the baseline could detect changes between fresh and fatigued muscle with 1.0 s WLA. MPF and the skewness of the spectrum (μ3), parameters related to the compression of the spectrum, behaved differently when monitored with a triaxial MMG sensor. The EMG results show that for the 1.0 s and 2.0 s WLAs have normalized RMS difference with fatigued muscle and that there was strong correlation between parameters of different domains.展开更多
The purpose of this investigation was to use the RPE clamp protocol to examine sex-related differences in performance fati-gability and neuromuscular responses as the result of a sustained isometric leg extension musc...The purpose of this investigation was to use the RPE clamp protocol to examine sex-related differences in performance fati-gability and neuromuscular responses as the result of a sustained isometric leg extension muscle action anchored to RPE=2.Twenty adults(10 men,10 women)performed sustained muscle actions at RPE=2 for 5-min.Maximal voluntary isometric contractions(MVIC)were performed prior to and following the sustained muscle actions.Neuromuscular(electromyographic and mechanomyographic)parameters and force were recorded,and the values were normalized to respective MVICs and cal-culated every 5%across the 5-min work bout.Femoral artery blood flow(FABF)was assessed at pretest,immediately posttest,and 5-min posttest.Polynomial regression was used to define the individual and composite normalized neuromuscular and force versus time relationships during the sustained muscle action.Mixed factorial ANOVAs were used to examine differences in performance fatigability and blood flow.For performance fatigability,the men(62.4±14.4 kg-43.1±11.5 kg)exhibited a significantly(P<0.05)greater decrease pretest to posttest in MVIC than the women(44.1±4.8 kg vs.38.1±6.1 kg).There were different fatigue-induced neuromuscular patterns of responses between the men and women across time.For blood flow responses,however,there was no sex-related difference,but pretest(283.3±70.8 mL/min)was significantly(P<0.05)less than immediately posttest(424.5±133.5 mL/min)and 5-min posttest(324.4±78.3 mL/min).Thus,men demonstrated a greater degree of performance fatigability than the women,which was independent of differences in FABF.Factors such as the neuromuscular system and muscle morphology likely contributed to the difference in performance fatigability.展开更多
Purpose The purpose of the present study was to examine the day-to-day consistency and inter-subject variability of com-posite and individual,neuromuscular and torque patterns of responses as a result of a fatiguing b...Purpose The purpose of the present study was to examine the day-to-day consistency and inter-subject variability of com-posite and individual,neuromuscular and torque patterns of responses as a result of a fatiguing bout of maximal,bilateral,isokinetic leg extension muscle actions.Methods Ten men (Mean ± SD =21.6 ± 2.5 years) completed two testing visits consisting of pretest and posttest maximal voluntary isometric contractions (MVIC) as well as 25 maximal,bilateral,isokinetic (180°/s),leg extension muscle actions.Electromyographic (EMG) and mechanomyographic (MMG) signals were collected from the vastus lateralis and normalized to the MVIC.Performance fatigability was defined as the percent decline in torque between the average of repetitions 1,2,and 3 and repetitions 23,24,and 25.Polynomial regression was used to examine the individual and composite relation-ships between EMG amplitude (AMP),EMG mean power frequency (MPF),MMG AMP,MMG MPF,and torque versus repetitions.Results There was no significant difference (d =0.80;P =0.17) in the performance fatigability between Day 1 (19.3% ± 7.1%)and Day 2 (26.9% ± 11.3%).Polynomial regression indicated substantial inter-subject variability,but high day-to-day consistency.Conclusion The composite EMG AMP,MMG AMP,and MMG MPF patterns of responses demonstrated consistency across days.The composite EMG MPF patterns of responses,however,were not consistent between Day 1 and Day 2.In addition,based on the high inter-subject variability,future studies should present both composite patterns of neuromuscular responses and the patterns of responses on a subject-by-subject basis to make inferences regarding fatigue-induced changes in motor unit activation strategies.展开更多
Aim:To evaluate the clinical usability of mechanomyography(MMG)in the evaluation of upper-limb spasticity states of hemiplegia patients with likelihood ratio analysis.Methods:The MMG signals from the 30 hemiplegia pat...Aim:To evaluate the clinical usability of mechanomyography(MMG)in the evaluation of upper-limb spasticity states of hemiplegia patients with likelihood ratio analysis.Methods:The MMG signals from the 30 hemiplegia patients'biceps and triceps were recorded with three-dimensional wireless accelerometer(Trigno Wireless System,Delsys Inc),when they extended or bent their elbow passively.At the same time,the physiotherapist assessed the MAS(Modified Ashworth Scale)of all the patients who participated in the study and would be divided them into four groups based on the MAS values(MAS0,MAS1,MAS1+and MAS2).The MMG sensors were built with triaxial accelerometers named as X,Y and Z that represent the muscle fibers lengthwise movement,the cross movement and the vertical the muscle moving direction,respectively.The root mean square(RMS)value of the MMG signal was calculated for analysis.Likelihood ratio analysis were used in the study.Results:All of the variables of the X,Y,Z axis of signals of MMG of BB and TB have related with muscle spasticity grading during passive elbow flexion in multinomial logistic regression(P=0.000,P<0.001).The regression coefficient of Y axis signal of MMG of BB is the largest.The 5 variables of the X,Y,Z axis of signals of MMG of BB and X,Y axis of TB have related with Muscle spasticity grading during passive elbow extension in multinomial logistic regression(P=0.000,P<0.001).The regression coefficient ofY axis signal of MMG of BB is the largest in equation and the Y axis signal of MMG of TB is second large.Conclusions:The effect of agonist is more than the antagonist during the MAS assessment,especially the muscle fibers cross movement and the vertical movement by the MMG assessment.展开更多
文摘目的利用采集的上斜方肌的肌音信号,研究肌音信号的非线性特征分形维数(fractal dimension,FD)趋势与肌肉疲劳的对应关系。方法在恒力做耸肩静态动作时,提取上斜方肌的肌音信号,采用一种自适应噪声的完备经验模态分解(complete ensemble empirical mode decomposition with adaptive noise,CEEMDAN)算法去噪,选用平均功率频率(mean power frequency,MPF)和中值频率(median frequency MDF),提取肌音信号的特征值,并用非线性特征分形维数来表征疲劳程度。结果 CEEMDAN算法去噪效果明显,肌音信号的分形维数随肌肉疲劳程度的加深呈现近似线性下降的趋势,在肌肉疲劳评估中与MPF、MDF效果相似。结论肌音信号的分形维数特征可评估肌肉疲劳程度。
文摘肌肉疲劳是由运动引起的肌肉最大随意收缩力减小的现象,其研究可应用于生理医学的职业病预防或体育工程的运动员训练等方面。本文采用短时傅里叶变换对肌音信号进行处理,提取频域特征平均功率频率(Mean Power Frequency,MPF)和中值频率(Median Frequency,MDF),研究其与肌肉疲劳程度之间的关系。9名健康的男性志愿者参与了本次试验,采用等值于60%最大随意收缩力(MVC)的力产生恒力肌肉疲劳,同步记录每一位受试者桡侧腕屈肌的肌音信号,对提取的频域参数进行分析。将持续30s的肌肉疲劳过程分为6个时间阶段(每个阶段为5s),并对每个时间阶段内的MPF和MDF计算均值。结果表明,随着肌肉疲劳程度加深,肌音信号的MPF和MDF在每个时间阶段内的均值均呈现近似线性下降的趋势。在30s肌肉疲劳过程中,从第1阶段(1~5s)到第6阶段(26~30s),MPF均值下降了15.8%,MDF均值下降了26.1%。基于短时傅里叶变换提取的MPF和MDF指标能良好地反映疲劳敏感性和稳定性,在评定肌肉静态疲劳方面是较好的参考指标。本文采用的方法和得到的结果为后期更深入地使用肌音信号对肌肉疲劳程度进行量化研究提供了依据。
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.
文摘Purpose The purpose of this study was to examine the effects of caffeine on peak torque(PT),rate of torque development(RTD),and muscle activation in college-age men.Methods Fifteen men(23.3±2.2 years,177.6±8.7 cm,90.3±19.1 kg)volunteered to participate in this study.During each of two test sessions,maximal leg extension PT and RTD were determined and electromyographic(EMG)and mechano-myographic(MMG)signals were collected to examine electrical and mechanical aspects of muscle activation,respectively.Participants also performed the Wingate Anaerobic Test(WAnT)for the determination of peak power(PP),mean power(MP),and fatigue percentage(FP).For the first test session,participants were randomly assigned to ingest either a caffein-ated drink(6 mg/kg)or a placebo 1 h prior to testing.The second test session was identical to the first,but the drink not previously administered was ingested prior to testing.Results The results indicated there were no significant effects of caffeine on PT,PP,MP,FP,or EMG and MMG measures.However,RTD was positively affected by caffeine(856.4±246.4 Nm/s)compared to the placebo condition(710.9±267.9 Nm/s).Conclusions These results suggest that caffeine can be an effective aid for sport activities requiring maximal rates of force or torque development during very short time periods.
基金CNPq and CAPES for the financial support and grants received.
文摘Mechanomyography (MMG) acquires the oscillatory waves of contracting muscles. Electromyography (EMG) is a tool for monitoring muscle overall electrical activity. During muscle contractions, both techniques can investigate the changes that occur in the muscle properties. EMG and MMG parameters have been used for detecting muscle fatigue with diverse test protocols, sensors and filtering. Depending on the analysis window length (WLA), monitoring physiological events could be compromised due to imprecision in the determination of parameters. Therefore, this study investigated the influence of WLA variation on different MMG and EMG parameters during submaximal isometric contractions monitoring MMG and EMG parameters. Ten male volunteers performed isometric contractions of elbow joint. Triaxial accelerometer-based MMG sensor and EMG electrodes were positioned on the biceps brachii muscle belly. Torque was monitored with a load cell. Volunteers remained seated with hip and elbow joint at angles of 110° and 90°, respectively. The protocol consisted in maintaining torque at 70% of maximum voluntary contraction as long as they could. Parameter data of EMG and the modulus of MMG were determined for four segments of the signal. Statistical analysis consisted of analyses of variance and Fisher’s least square differences post-hoc test. Also, Pearson’s correlation was calculated to determine whether parameters that monitor similar physiological events would have strong correlation. The modulus of MMG mean power frequency (MPF) and the number of crossings in the baseline could detect changes between fresh and fatigued muscle with 1.0 s WLA. MPF and the skewness of the spectrum (μ3), parameters related to the compression of the spectrum, behaved differently when monitored with a triaxial MMG sensor. The EMG results show that for the 1.0 s and 2.0 s WLAs have normalized RMS difference with fatigued muscle and that there was strong correlation between parameters of different domains.
文摘The purpose of this investigation was to use the RPE clamp protocol to examine sex-related differences in performance fati-gability and neuromuscular responses as the result of a sustained isometric leg extension muscle action anchored to RPE=2.Twenty adults(10 men,10 women)performed sustained muscle actions at RPE=2 for 5-min.Maximal voluntary isometric contractions(MVIC)were performed prior to and following the sustained muscle actions.Neuromuscular(electromyographic and mechanomyographic)parameters and force were recorded,and the values were normalized to respective MVICs and cal-culated every 5%across the 5-min work bout.Femoral artery blood flow(FABF)was assessed at pretest,immediately posttest,and 5-min posttest.Polynomial regression was used to define the individual and composite normalized neuromuscular and force versus time relationships during the sustained muscle action.Mixed factorial ANOVAs were used to examine differences in performance fatigability and blood flow.For performance fatigability,the men(62.4±14.4 kg-43.1±11.5 kg)exhibited a significantly(P<0.05)greater decrease pretest to posttest in MVIC than the women(44.1±4.8 kg vs.38.1±6.1 kg).There were different fatigue-induced neuromuscular patterns of responses between the men and women across time.For blood flow responses,however,there was no sex-related difference,but pretest(283.3±70.8 mL/min)was significantly(P<0.05)less than immediately posttest(424.5±133.5 mL/min)and 5-min posttest(324.4±78.3 mL/min).Thus,men demonstrated a greater degree of performance fatigability than the women,which was independent of differences in FABF.Factors such as the neuromuscular system and muscle morphology likely contributed to the difference in performance fatigability.
文摘Purpose The purpose of the present study was to examine the day-to-day consistency and inter-subject variability of com-posite and individual,neuromuscular and torque patterns of responses as a result of a fatiguing bout of maximal,bilateral,isokinetic leg extension muscle actions.Methods Ten men (Mean ± SD =21.6 ± 2.5 years) completed two testing visits consisting of pretest and posttest maximal voluntary isometric contractions (MVIC) as well as 25 maximal,bilateral,isokinetic (180°/s),leg extension muscle actions.Electromyographic (EMG) and mechanomyographic (MMG) signals were collected from the vastus lateralis and normalized to the MVIC.Performance fatigability was defined as the percent decline in torque between the average of repetitions 1,2,and 3 and repetitions 23,24,and 25.Polynomial regression was used to examine the individual and composite relation-ships between EMG amplitude (AMP),EMG mean power frequency (MPF),MMG AMP,MMG MPF,and torque versus repetitions.Results There was no significant difference (d =0.80;P =0.17) in the performance fatigability between Day 1 (19.3% ± 7.1%)and Day 2 (26.9% ± 11.3%).Polynomial regression indicated substantial inter-subject variability,but high day-to-day consistency.Conclusion The composite EMG AMP,MMG AMP,and MMG MPF patterns of responses demonstrated consistency across days.The composite EMG MPF patterns of responses,however,were not consistent between Day 1 and Day 2.In addition,based on the high inter-subject variability,future studies should present both composite patterns of neuromuscular responses and the patterns of responses on a subject-by-subject basis to make inferences regarding fatigue-induced changes in motor unit activation strategies.
基金funded by the National Natural Science Foundation of China(#61135004,#51275101).
文摘Aim:To evaluate the clinical usability of mechanomyography(MMG)in the evaluation of upper-limb spasticity states of hemiplegia patients with likelihood ratio analysis.Methods:The MMG signals from the 30 hemiplegia patients'biceps and triceps were recorded with three-dimensional wireless accelerometer(Trigno Wireless System,Delsys Inc),when they extended or bent their elbow passively.At the same time,the physiotherapist assessed the MAS(Modified Ashworth Scale)of all the patients who participated in the study and would be divided them into four groups based on the MAS values(MAS0,MAS1,MAS1+and MAS2).The MMG sensors were built with triaxial accelerometers named as X,Y and Z that represent the muscle fibers lengthwise movement,the cross movement and the vertical the muscle moving direction,respectively.The root mean square(RMS)value of the MMG signal was calculated for analysis.Likelihood ratio analysis were used in the study.Results:All of the variables of the X,Y,Z axis of signals of MMG of BB and TB have related with muscle spasticity grading during passive elbow flexion in multinomial logistic regression(P=0.000,P<0.001).The regression coefficient of Y axis signal of MMG of BB is the largest.The 5 variables of the X,Y,Z axis of signals of MMG of BB and X,Y axis of TB have related with Muscle spasticity grading during passive elbow extension in multinomial logistic regression(P=0.000,P<0.001).The regression coefficient ofY axis signal of MMG of BB is the largest in equation and the Y axis signal of MMG of TB is second large.Conclusions:The effect of agonist is more than the antagonist during the MAS assessment,especially the muscle fibers cross movement and the vertical movement by the MMG assessment.
