不同负荷运动中下肢肌表面肌电图的变化

背景：尝试应用曲线拟合分析方法对表面肌电图进行分析和研究国内外尚处于起步阶段,将其应用于功率自行车运动至疲劳的研究鲜见报道。 目的：探讨功率自行车不同负荷运动中下肢肌中值频率值的变化特征和规律,分析肌肉疲劳拟合曲线的特点及其影响肌肉疲劳的相关因素。 方法：受试者为苏州大学体育学院8名男性青年,利用MONARK功率自行车,对受试者在不同负荷以及不同踏蹬频率下进行测试至疲劳,同时对股直肌、股外侧肌、股内侧肌、胫骨前肌、腓肠肌内侧头和腓肠肌外侧头进行表面肌电信号的采集与记录。分析中值频率指标的变化,并用minitab.15统计软件,按照在F检验的统计学差异有非常显著性意义(P < 0.001)的前提下,选取判定系数R2最大,偏差的平方和最小的原则,对实验结果进行曲线优度拟合。 结果与结论：①功率自行车150 W运动时,肌纤维的募集形式由运动初始快肌纤维募集数量逐渐增多向慢肌纤维募集比例增高转变。②功率自行车300 W运动时,肌纤维的募集形式从运动初期的快肌纤维募集为主逐渐向慢肌纤维募集比例增高转变。③功率自行车150 W运动时,肌肉疲劳的拟合曲线均为三次项曲线,提示影响肌肉疲劳的主要因素有3个。300 W运动时,肌肉疲劳的拟合曲线均为二次项曲线,提示影响肌肉疲劳的主要因素有2个。     

基于表面肌电信号的康复过程中肌疲劳有效性分析

肌肉疲劳分析在康复医学领域具有广泛的应用。本文以康复训练系统为应用背景,研究基于表面肌电信号的肌肉疲劳分析。通过对10名健康测试者在负载可调的功率自行车上进行负载递增骑行实验,同步采集了股外侧肌、股直肌和竖脊肌的表面肌电信号和通气阈值,并分析了各肌肉的肌电疲劳阈。同时分析了等长收缩和等张收缩对肌电疲劳阈测定的影响。实验结果显示在负载递增骑行运动中,肌电疲劳阈值的出现要早于通气阈值,但两者差异很小,验证了基于肌电疲劳阈来分析肌肉疲劳的有效性。对比分析骑行运动中等张收缩股外侧肌和等长收缩竖脊肌的肌电疲劳阈,发现肌电疲劳阈对不同收缩方式的肌肉均具有效果。肌电疲劳阈不受肌肉运动形式限制,在康复训练过程中能够用于防止过度训练引起的肌肉损伤,对于股骨干骨折患者康复训练过程中的疲劳监护具有重要的意义。     

长时间颈部后仰相关局部肌肉表面肌电特征分析

目的 为降低长时间颈部后仰对航空机务人员身心健康造成影响,探讨航空机务人员在托举作业过程中长时间保持颈部后仰姿势对颈部肌肉表面肌电的影响。方法 择12名在校大学生作为研究对象,受试者站立在飞机机翼下方保持颈部后仰固定姿势模拟机务人员进行托举作业,记录受试者主观疲劳感觉评分(rating of perceived exertion, RPE),同时采集斜方肌、胸锁乳头肌和颈部夹肌的表面肌电信号,分析并计算肌电信号均方根(root mean square, RMS)、积分肌电(integral electromyography, iEMG)、中值频率(median frequency, MF)和平均功率频率(mean power frequency, MPF),并结合主观疲劳感觉评分进行相关性和回归分析。结果 胸锁乳突肌、斜方肌和颈部夹肌的iEMG和RMS变化与托举时间呈正相关关系,其中颈部夹肌的iEMG和胸锁乳突肌RMS相关程度最高,其相关系数分别为0.48和0.84,拟合程度分别为0.69和0.71,差异具有统计学意义(P<0.05);胸锁乳突肌、斜方肌和颈部夹肌的MPF和MF变...     

经穴位电刺激下的表面肌电信号特征分析

目的:探究人体穴位电刺激与相关肌肉活动的关系,通过对经穴刺激诱发的表面肌电信号进行特征分析,阐明经穴电刺激下的肌电信号时域、频域特征参数变化与肌肉的激活程度、疲劳程度之间的定量关系,为康复工程和运动医学研究提供参考依据。方法:以8名健康青年志愿者为研究对象,设计穴位电刺激和自主收缩两种实验模式,采集记录两种模式下对应的指伸肌和尺侧腕屈肌的表面肌电信号,提取表面肌电信号均方根值、平均功率频率、中值频率等特征值,并分析其功率谱变化。通过配对t检验,分析经穴电刺激和自主动作模式的肌电信号特征差异。结果:在经穴电刺激模式下,对应的表面肌电信号均方根幅度增大,且经穴电刺激后,肌电信号的谱分布向高频方向移动,肌电的平均功率频率和中值频率随着刺激时间的延长保持稳定。结论:表明对曲池穴和内关穴位电刺激,能够激活对应的指伸肌和尺侧腕屈肌更多的快肌纤维,使肌肉激活程度提高,对缓解肌肉疲劳具有一定作用。     

髋受力后蹬式骑行无氧功率测试:与传统Wingate法骑行方式的对比

背景:前下蹬式骑行方式不适合以后蹬、后趴为主要技术特征的奔跑类运动,但迄今为止还未见模拟奔跑后扒或后蹬动作的无氧功率测试方法。目的:通过自主研发的髋受力装置实现后蹬式功率自行车抗阻骑行模式,并通过与传统Wingate法骑行方式的对比,以探索奔跑类运动项目无氧功率测试法的适宜骑行方式。方法:采用瑞士Monark自行车功量计和髋受力前伸式座椅,运用自身对比法对10名短跑运动员进行后蹬式骑行方式和经典前下蹬骑行方式无氧功率实验。观察两种骑行方式所测得的无氧功率之间的差异,并分析造成差异的生物学原因。结果与结论:髋受力后蹬式骑行方式所获得的无氧功率明显低于传统的Wingate法前下蹬骑行方式(P0.05)。后蹬式骑行方式无论是动作结构还是肌群动员配比均较Wingate传统前下蹬骑行方式更加接近奔跑技术动作。实验结果证明用后蹬式骑行方式测得的无氧功率能够更真实地反映奔跑运动时的无氧能力。     

基于表面肌电的人体背部负重行走肌肉疲劳特性研究

通过研究人体双肩背部负重行走时躯干及下肢主肌肉群表面肌电信号,探讨人体肌肉功能状态和疲劳特性,为改进负重方式、负重方法、背包性能、背包设计以及更加符合人体工效学的负重系统提供依据。测试20名实验对象颈肩部、背腰部及腿部主肌肉群在双肩背不同负重载荷下行走的表面肌电信号,利用统计分析软件SPSS16.0对其频域评价指标平均功率频率(MPF)进行数据处理与分析。结果表明,随着负重的增加,男性受试者斜方肌MPF下降最为显著、最易疲劳,女性受试者颈伸肌MPF下降最为显著、最易疲劳,且当负重达到一定重量时表面肌电信号出现显著差异(P0.05),男性双肩背负重上限值为自身体重的12%,女性双肩背负重上限值为自身体重的9%。     

自然行走对人体足底压力与下肢表面肌电信号影响的研究

目的 探究自然行走对正常人足底压力与下肢肌肉表面肌电信号(sEMG)的影响.方法 分别测量28例健康青年男性受试者在30 min平地自然行走前后足底压力与下肢肌肉的sEMG,得到行走前后峰值压强、冲量等足底压力参数及胫骨前肌、腓肠肌、股直肌与股二头肌的表面肌电时域参数积分肌电(iEMG)和频域参数平均功率频率(MPF),并检验峰值压强与身高、体质量的相关性.结果 平地自然行走开始时和30 min后,其左、右侧的峰值压强、冲量等各特征参数的差异均有统计学意义(均P＜0.05),不同参数的左、右侧差异分别体现在足底不同区域,而在跖骨区M3、M4、M5处各参数均表现出左侧大于右侧;行走前后左侧胫骨前肌、腓肠肌、骨直肌与股二头肌sEMG的iEMG均大于右侧;行走前后左侧胫骨前肌、腓肠肌的MPF大于右侧,其差异具有统计学意义(P＜0.05).30 min行走后右足脚趾区Toe2-5的峰值压强降低,其差异具有统计学意义(P＜0.05);各肌肉表面肌电iEMG无显著性变化,左侧股直肌的表面肌电信号的MPF显著性下降;峰值压强与身高、体质量均呈弱相关.结论 正常人自然行走中,足底压力和下肢表面肌电均具有左右侧的差异;30 min自然行走尚未导致足底压力出现明显疲劳状态的相应结果,因此自然行走30 min可维持步态的稳定性;30 min行走将导致左侧股直肌出现疲劳.     

模型生理参数对表面肌电信号影响的仿真研究

通过模型研究肌肉生理参数对表面肌电信号的影响。根据肌肉的形态结构和生理特征,从肌电信号的信号源-细胞内动作电位开始,仿真了单肌纤维动作电位,由此合成了运动单位动作电位,再利用运动单位的募集发放模型,进一步仿真了运动单位动作电位序列,并最终完成了对表面肌电信号的仿真。在此基础上研究了极化区域宽度、跨膜电流密度分布和肌肉组织各向异性3个重要的模型生理参数对表面肌电信号统计特征的影响,得到了一些有价值的结果。实验结果表明,仿真肌电信号能够有效表征肌肉电生理变化过程。     

基于幅频联合分析法对肌肉疲劳状态下表面肌电信号时、频域变化规律的研究

目的:通过对肌肉疲劳状态下表面肌电信号(sEMG)的提取,利用幅频联合分析的方法探讨sEMG作为肌肉生理特征信号在疲劳发生过程中的变化规律。方法:5名健康男性左右手臂分别进行一次实验,实验过程中,手臂自然下垂,前臂抬起至水平,与上臂成90°角,前臂上悬挂重量为5 Kg的重物,使肌肉等长收缩8 min,采用英国BIOPAC公司生产的MP150及其肌电采集模块同步记录肌肉的表面肌电信号,使用The MathWorks公司的MATLAB7.0软件,在信号3min、5 min、7 min后各取20 s进行幅频联合分析。结果:sEMG随着肌肉疲劳状态的加剧,信号幅值平均值明显增大,功率谱密度发生变化,平均功率频率(MPF)、中位频率(MF)明显减小。结论:表面肌电信号的幅频联合分析法为进一步深入研究肌肉疲劳状态下表面肌电信号的变化提供了方法支撑和理论依据。     

基于自回归模型表面肌电信号检测肌肉疲劳研究

针对表面肌电信号的非平稳特性,采用自回归模型对表面肌电信号进行分析,对短时间内的表面肌电信号肌肉疲劳迅速做出判定。应用非平稳时间序列的时变系统建模方法对10例受试者疲劳前、疲劳后表面肌电信号进行特征提取。建立时变参数自回归模型,通过引入Legendre基函数将线性非平稳过程参数辨识转化为线性时不变系统参数辨识,结合相关指数可以获得时变系统参数估计的最优Legendre基函数维数,进而可以获得最佳模型拟合效果,并采用最小二乘法解出时不变参数。用疲劳前、后的自回归模型的第一个时变参数(ARC1)的变化率作为检测肌肉疲劳敏感性指标,并采用双尾t检验,分别与平均功率频率(MPF)和中值频率(MF)的变化率进行统计学对比分析。结果表明, ARC1、MPF和MF疲劳前后的变化率分别为34.33%±2.41%、25.68%±2.03%、22.80%±2.19%,且ACR1的变化率分别显著高于MPF和MF(P<0.05).所提出的方法通过表面肌电信号对肌肉疲劳检测时,具有时间短和敏感性高等优点,可用于在线实时分析肌肉疲劳程度,为肢肌肉劳损的评估、康复治疗及人体工效学的研究提供一个潜在的分析工具。     

Mechanomyographic and electromyographic amplitude and frequency responses from the superficial quadriceps femoris muscles during maximal,eccentric isokinetic muscle actions

The purposes of this study were to examine the effects of gender and muscle (vastus lateralis = VL, rectus femoris = RF, and vastus medialis = VM) on the velocity-related patterns for peak torque (PT), mean power output (MP), mechanomyographic (MMG) amplitude, electromyographic (EMG) amplitude, MMG mean power frequency (MPF), and EMG MPF during maximal, eccentric isokinetic muscle actions. Thirteen females (mean +/- SD age = 21 +/- 1 years) and eleven males (mean +/- SD age = 21 +/- 2 years) volunteered for this investigation. PT and MP were measured on a calibrated Cybex 6000 dynamometer at randomly ordered velocities of 60, 120, and 180 degrees.s-1, while MMG and EMG signals were recorded simultaneously from the VL, RF, and VM muscles. The results indicated no gender-related differences for the patterns of PT, MP, MMG amplitude, EMG amplitude, MMG MPF, or EMG MPF. Furthermore, no muscle-related differences were found for the patterns of MMG amplitude, EMG amplitude, or MMG MPF. The normalized values for MP and MMG amplitude increased from 60 to 180 degrees.s-1 (60 degrees.s-1 < 120 degrees.s-1 < 180 degrees.s-1). PT and EMG MPF remained unchanged across velocity, while EMG amplitude remained unchanged from 60 to 120 degrees.s-1, but decreased (approximately 10%) from 120 to 180 degrees.s-1. The findings indicated a close association between the patterns for MP and MMG amplitude, and a similarity between the patterns for PT, EMG amplitude, and EMG MPF across velocity. Therefore, the present findings suggested that motor unit recruitment (EMG amplitude), firing rate (MMG MPF), and muscle fiber action potential conduction velocity (EMG MPF) exhibited velocity-related patterns that were similar to PT production, while MMG amplitude was more closely associated with MP.     

Anaerobic power of arms in teenage boys and girls: relationship to lean tissue

Summary The purpose of this study was to describe anaerobic peak and mean power characteristics of arms as a function of age, gender and body composition among 50 girls and 50 boys 14 to 19 years of age. Peak (pP) and mean power (MP) output were determined during arm cranking (Wingate anaerobic test). Fat-free weight (FFW) was estimated from skinfolds, and lean arm volume (LAV) was determined by water displacement, corrected for fat volume. PP and MP increased progressively and significantly (P<0.05) with age for boys but not for the girls. Boys had significantly larger absolute PP and MP outputs than girls at comparable ages. PP and MP corrected for lean tissue volume were greater in older than younger boys (P<0.05), but did not vary significantly with age for girls. Absolute (W) PP and MP were highly correlated with LAV (r = 0.82;r = 0.75) and FFW (r = 0.84;r = 0.78) among boys. The respectiver values for girls were 0.60 and 0.49 (LAV); 0.78 and 0.60 (FFW). Absolute peak and mean power, respectively, were more highly correlated with LAV (r = 0.90;r = 0.84) and FFW (r = 0.90;r = 0.85) for the combined data for boys and girls than for similar gender specific comparisons. In conclusion, both anaerobic PP and MP of arms during adolescence are highly correlated with lean tissue volume and fat-free weight, particularly among boys.This study was supported in part by a grant from the Conn Smythe Research Foundation For Crippled Children Canada, and from the Medical Research Council of Canada's Post-Doctoral Fellowship Program     

Inter-relationship between muscle morphology, mechanical output and electromyographic activity during fatiguing dynamic knee-extensions in untrained females

Changes in mechanical performance and electromyographic activity during fatiguing dynamic knee-extensions were evaluated with respect to muscle fibre type composition of the vastus lateralis muscle in nine sedentary female [23 (3) years] volunteers. The subjects performed 150 repetitive maximum knee-extensions using a Cybex dynamometer at 1.57?rad?·?s^?1. EMG activity was recorded from the vastus lateralis, the vastus medialis and the rectus femoris muscles. For each contraction, mean power frequency (MPF) and the root mean square (RMS) of the EMG were calculated, simultaneously with the peak torque (PT), contractional work (CW) and the mean power (MP). The MPF showed an initial decrease followed by a stable phase. The RMS increased during the initial seven contractions, after which a period of variability was displayed until about the 60th contraction. At the plateau level (last 50 contractions) the relative RMS values were not significantly different from the initial values. The PT, CW and MP increased during the initial five to ten contractions, after which a two-phase pattern was displayed, with a gradual decline followed by a stable phase. The absolute plateau level of MPF for the vastus lateralis muscle showed a significant negative correlation with the area percentage of type-1 fibres (r?=??0.71). Significant correlations were also demonstrated to occur between the absolute plateau levels of PT, CW and MP and the relative proportion of type-1 fibres (r?=?0.80, r?=?0.82 and r?=?0.82 respectively). Thus, in female subjects the mechanical performance and the MPF during fatigue are at least partly determined by muscle morphology.     

膝关节最大和次最大等速运动至疲劳过程中主动肌与拮抗肌肌电特征分析

背景：人体关节力量输出主要取决于关节周围主动肌与拮抗肌的激活效果,而拮抗肌通过共激活形式参与肢体活动,从而协助维持关节稳定性。但是肌肉不同收缩模式下拮抗肌共激活的不同中枢策略的报道较少。目的：观察健康受试者膝关节伸肌在最大和次最大等速运动至疲劳过程中主动肌与拮抗肌表面肌电信号的特征与差别。方法：对16名在校学生使用Biodex等速训练仪诱发下肢右侧膝关节伸肌等速屈伸运动直至疲劳,同时使用表面肌电仪采集单侧股内侧肌、股外侧肌以及股二头肌的表面肌电信号。分析时域指标均方根振幅百分比以及频域指标平均频率的变化规律。结果与结论：在膝关节最大等速屈伸运动中峰值力矩下降了40.3%(P < 0.05),主动肌活动先增加后下降(P < 0.05),而拮抗肌电活动保持不变。在次最大等速运动中峰值力矩平均下降了40.0%(P < 0.05),主动肌肌电活动逐渐增加(P < 0.05),而拮抗肌电活动先增加随后又降低。在指定的交互收缩屈伸运动中作为拮抗肌的股内和股外侧肌的均方根振幅和平均频率没有显著变化(P > 0.05)。结果提示,在不同强度的等速疲劳运动中中枢神经系统对主动肌和拮抗肌采取了不同神经支配策略。中国组织工程研究杂志出版内容重点：组织构建;骨细胞;软骨细胞;细胞培养;成纤维细胞;血管内皮细胞;骨质疏松;组织工程     

Frequency analysis of surface EMG on knee extensors with anterior cruciate ligament insufficiency

The muscle strength of knees with an injured anterior cruciate ligament (ACL) is generally assessed by the peak of the isokinetic muscle contraction. However, assessment of the characteristics of muscle contraction, such as the contraction velocity and contraction endurance, has been largely ignored due to a lack of data. In this study, we have performed frequency analysis of the surface electromyograms during sustained isometric contraction of the quadriceps femoris muscle in 22 knees with ACL deficiency to evaluate the characteristics of muscle contraction. Concerning the time-related changes in the mean power frequency (MPF), the decrease with time was smaller than normal (reflecting a deficiency in the number of fast-twitch fibers) in the rectus femoris and vastus medialis muscles of the injured limb in many subjects. However, a slightly different pattern was observed in the vastus lateralis muscle, which showed little difference between the injured and intact limbs. Therefore the vastus lateralis muscle was considered to be less affected by an ACL deficiency than the other two muscles. The time-related changes in the MPF in the ACL deficient limb were clearly different from those in the intact limb and a deficiency in the fast-twitch fibers was suggested. Therefore a frequency analysis of the surface electromyograms was considered to allow detection of qualitative changes, such as of muscle fiber deficiency, as well as detection of changes in the simple muscle strength.     

Anaerobic Power of the Arms and Legs of Young and Older Men

The purpose of this study was to examine differences in the anaerobic exercise performance of young and older men. Eight healthy, active older (68.5 +/- 2.4 years old, mean S.D.) and eight healthy, active young (30.6 +/- 4.5 years old) subjects were assessed for peak and mean power output (PP and MP, respectively) of the legs and arms, during 30 s Wingate tests. PP during leg exercise was significantly (P < 0.05) higher in the young (14.6 +/- 1.6 W kg-1) compared with the older (10.7 +/- 1.0 W kg-1) group. MP of the legs was also greater in the young subjects (10.7 +/- 0.7 vs. 7.4 +/- 0.9 W kg-1). These differences in PP and MP remained significant when expressed relative to lean leg volume. PP during arm cranking was significantly greater in the young subjects (8.9 +/- 0.7 vs. 7.5 +/- 0.6 W kg-1) as was MP (6.4 +/- 0.7 vs. 5.0 +/- 0.7 W kg-1). Post-exercise blood lactate concentration in the older group (7.0 +/- 1.6 mmol l-1) was less (P < 0.05) than in the young group (10.6 +/- 2.0 mmol l-1), for leg work only. The significant loss of anaerobic power in the older group could not be explained by a difference in muscle mass. Power output was also lower in the arms, but to a lesser extent. The results of this study suggest that a reduction in the ability to perform high intensity exercise may be an inevitable consequence of ageing. The extent, however, of this decline varies with different muscle groups.     

Do the fibre-type proportion and the angular velocity influence the mean power frequency of the electromyogram?

The dependence of the mean-power frequency and the signal amplitude of the electromyogram (EMG) on the angular velocity and the fiber-type proportion were investigated in nine female volunteers. The subjects were required to perform maximum knee extensions using an isokinetic dynamometer at different angular velocities; 0.57, 1.05, 1.57, 2.09 and 3.14 rad s-1. Electromyographic signals were obtained from the vastus lateralis, vastus medialis and the rectus femoris muscles. The angle and the torque signals were recorded simultaneously with the three EMG signals on a tape-recorder. From the EMG recordings the mean power frequency (MPF) and the signal amplitude were determined. Muscle biopsies were later obtained from the right vastus lateralis and stained for alkaline and acid mATPase for the determination of fibre-type proportions and areas. Neither the signal amplitude nor the MPF of the EMG of the three muscles were dependent on the angular velocity. The MPF of the vastus lateralis correlated significantly (r = -0.93) with the type 1 fibre proportion at 1.57 rad s-1. However, there was no significant correlation between the areas of the fibre types, alone or together, and the MPF. In conclusion the fibre-type proportion was the major factor behind the MPF irrespective of angular velocity.     

Influence of exercise intensity and joint angle on endurance time prediction of sustained submaximal isometric knee extensions

The purpose of endurance time (T (lim)) prediction is to determine the exertion time of a muscle contraction before it occurs. T (lim) prediction would then allow the evaluation of muscle capacities limiting fatigue and deleterious effects associated with exhaustive exercises. The present study aimed to analyze the influence of exercise intensity and joint angle on T (lim) prediction using changes in surface electromyographic (sEMG) signals recorded during the first moments of the exercise. Fifteen male performed four knee extensions sustained until exhaustion that were different in exercise intensity (20% or 50% of maximal voluntary torque-MVT) and in joint angle (40 or 70o, 0° = full extension). T (lim) prediction was explored using some parameters of the sEMG signals from rectus femoris, vastus medialis and vastus lateralis muscles. Changes in sEMG parameters (root mean square, mean power frequency and frequency banding 6-30 Hz) were expressed using the slope of the linear regression and the area ratio index. Results indicated that relationships between changes in sEMG signal and T (lim) (0.51 < r < 0.83) were greater for experimental conditions associated with higher exercise intensity (50% MVT) and so to lower time duration. Knee joint angle had little influence on T (lim) prediction results. Results also showed higher T (lim) prediction considering spectral parameters and area ratio. This could be in relation to differences in relative contribution of central and peripheral fatigue that seems to change according to the exercise intensity, but also to the influence of psychological factors that increases with the duration of the task.     

Association between anaerobic components of the maximal accumulated oxygen deficit and 30-second Wingate test

The purpose of this study was to analyze the relationship between the anaerobic components of the maximal accumulated oxygen deficit (MAOD) and of the 30-second Wingate anaerobic test (30-WAnT). Nine male physical education students performed: a) a maximal incremental exercise test; b) a supramaximal constant workload test to determine the anaerobic components of the MAOD; and c) a 30-WAnT to measure the peak power (PP) and mean power (MP). The fast component of the excess post-exercise oxygen consumption and blood lactate accumulation were measured after the supramaximal constant workload test in order to determine the contributions made by alactic (AL_MET) and lactic (LA_MET) metabolism. Significant correlations were found between PP and AL_MET (r=0.71; P=0.033) and between MP and LA_MET (r=0.72; P=0.030). The study results suggested that the anaerobic components of the MAOD and of the 30-WAnT are similarly applicable in the assessment of AL_MET and LA_MET during high-intensity exercise.