等长收缩诱发肌肉疲劳及恢复过程中表面肌电信号特征变化规律

运用线性和非线性分析方法分析不同强度等长收缩诱发局部肌肉疲劳及恢复过程中表面肌电信号（surface electromyogram,sEMG）特征的变化规律,探讨影响sEMG信号变化的可能原因和机制.结果显示,在肱二头肌疲劳收缩过程中,sEMG的特征指标平均肌电值（average EMG,AEMG）、平均功率频率（mean power frequency,MPF）、Lempel-Ziv复杂度（Lempel-Ziv complexity,C（n））和确定性线段百分数（Determinism%,% DET）的变化具有良好的规律性.恢复期AEMG没有表现出规律性的变化,MPF、C（n）和?T在恢复期2秒即开始显著恢复,在前10秒恢复很快,随后恢复速度变慢.恢复初期sEMG信号特征的快速变化提示中枢控制因素可能发挥更大作用.     

内质网应激在骨骼肌生理及病理中的功能研究进展

骨骼肌拥有高度发达的内质网,又被称为肌浆网,不仅可以作为钙泵完成肌肉的兴奋收缩偶联反应,还可对各种生理或病理性刺激迅速做出反应,通过内质网应激反应,激活下游信号通路,赋予骨骼肌应对外界或内在刺激的能力。因此,骨骼肌内丰富的内质网是骨骼肌具有高度可塑性的细胞学基础。大量研究表明,内质网应激广泛参与了骨骼肌的生理和病理进程,本文就内质网应激在骨骼肌成肌分化、萎缩和运动的作用进行了综述。     

兔膈肌力学模式对慢性电刺激的适应性改变和细胞外Ca …

目的：研究兔膈肌肌条力学对不同频率慢性电刺激（ＣＥＳ）的适应性变化特征和细胞外Ｃａ＾２＋变化夺其力学特征的影响。方法：测定正常对照组和ＣＥＳ组的颤搐收缩张力（Ｐｔ）、峰值张力时间（ＴＰＴ）、１／２松弛时间（１／２ＲＴ）、强直颤搐收缩张力（Ｐｏ）、疲劳指数（ＦＩ）和疲劳恢复指数（ＦＲＩ）;观察在无Ｃａ＾２＋Ｈａｎｋ’ｓ液和标准Ｈａｎｋ’ｓ液时肌条收缩张力消失和恢复的时间差异。结果：①同对照组作比较,     

骨骼肌收缩模式对p38／Akt磷酸化水平的影响

目的：骨骼肌收缩可能通过非胰岛素依赖的途径促进葡萄糖摄取,而p38与Akt可能是其中起重要作用的分子。本文研究骨骼肌不同收缩模式对上述信号分子磷酸化的影响,从而探讨有效降低血糖的运动方式。方法：采用离体比目鱼肌肌条灌流技术及Western blot检测方法,研究不同模式的收缩对骨骼肌p38、Akt磷酸化水平的影响。结果：5min10％DC（dutycycle负荷率）和5min1％Dc的收缩模式可分别使p38的磷酸化较对照组增加30％和34％,是激活p38的适宜刺激。但对Akt的磷酸化水平没有影响。结论：低强度有氧运动可以更好地激活038,但不能有效激活Akt。     

主动肌和拮抗肌的针电极EMG信号中值频率关系研究

主动肌和拮抗肌的针电极ＥＭＧ信号中值频率关系研究杨基海孙路遥胡文军章劲松周平（中国科学技术大学合肥２３００２６神经肌肉系统的“共驱动”现象是当前肌电研究领域的一个重要理论课题。本文将正常人体肘关节的肱二头肌和肱三头肌分别作为主动肌或拮抗肌,在持续恒力...     

肌梭结构和功能的研究进展

肌梭是骨骼肌内一种重要的本体感受器,参与肌紧张的维持和对随意运动的精细调节.本文对肌梭的形态结构、梭内肌纤维的分类及其神经支配、电生理特性、各型梭内肌纤维的功能特点、梭内肌纤维的组织化学特性、肌梭的分化发育、药物及其他因素对肌梭的影响等方面的新进展进行了综述.     

肌梭结构和功能的研究进展

肌梭是骨骼肌内一种重要的本体感受器,参与肌紧张的维持和对随意运动的精细调节。本文对肌梭的形态结构、梭内肌纤维的分类及其神经支配、电生理特性、各型梭内肌纤维的功能特点、梭内肌纤维的组织化学特性、肌梭的分化发育、药物及其他因素对肌梭影响等方面的新进展进行了综述。     

膈肌肌质网非序列依赖性DNA结合蛋白与膈肌功能的关系

目的：探讨膈肌纤维肌质网是否存在非序列依赖性DNA结合蛋白,并观察它与膈肌功能的关系。方法：Wistar大鼠随机分为对照组、急性气胸组和心痛定组,差速离心法分离大鼠膈肌纤维肌质网（sarcoplasmic reticulum,SR）膜蛋白,采用Western免疫印迹技术分离出SR非序列依赖性DNA结合蛋白,并观察此蛋白在急性气胸和给予心痛定时的变化特征。结果：大鼠膈肌SR上存在非序列依赖性DNA结合蛋白,相对分子质量分别为60000道尔顿和78000道尔顿。急性气胸时和给予心痛定时,非序列依赖性DNA结合蛋白的量有变化。结论：大鼠膈肌纤维SR上存在非序列依赖性DNA结合蛋白,该DNA结合蛋白可能与膈肌功能状态和Ca^2 信号系统密切相关,它在膈肌和骨骼肌的病理生理过程中起重要作用。     

肝细胞生长因子在骨骼肌再生中的作用研究进展

骨骼肌损伤后的修复包括炎症反应期、修复期、组织重塑期三个阶段。而骨骼肌卫星细胞的激活、增殖与分化和骨骼肌伤后的修复有着密切的关系。骨骼肌损伤后,肝细胞生长因子(HGF)可以自分泌、旁分泌或内分泌的形式,调控肌卫星细胞功能,从而影响损伤骨骼肌的再生。其机制研究表明,HGF可能通过与其受体c-met结合,启动相关信号途径,参与骨骼肌卫星细胞激活、增殖、分化和迁移,从而影响骨骼肌再生进程。     

骨髓间充质干细胞成肌分化在骨骼肌再生中的应用

骨骼肌良好的再生能力是由于肌卫星细胞的存在,然而肌卫星细胞的数量仅占骨骼肌细胞数量的1%~ 5%,当肌肉损伤时,仅依靠这些卫星细胞还不足以促进骨骼肌修复与再生,并且这种再生能力会随着年龄的增大而衰减,并不能修复损伤严重的骨骼肌。骨髓间充质干细胞（BMSC）因其多向分化潜能,旁分泌潜能,免疫调节能力及容易获取等特点广泛用于损伤骨骼肌的修复与再生。但在某种程度上,仅仅采用BMSC治疗损伤的骨骼肌仍不能达到满意的效果。因此,大量研究采用药物、生物材料、细胞及细胞因子对BMSC进行预处理不仅可改善它的移植率,还可显著促进其向骨骼肌分化,从而最大限度的发掘骨骼肌间充质干细胞的成肌分化潜能以促进骨骼肌的修复。因此,本篇综述旨在概括BMSC成肌分化在骨骼肌再生中的应用。     

SEMG signal analysis at acupressure points for elbow movement

Surface electromyography signals (SEMG) are the most common form of non-invasive-measurement of muscle activities. To acquire proper SEMG for particular limb function, the placement of electrodes on the skin over respective active group of muscles becomes very important. Measurement of SEMG depends on a number of factors/parameters like amplitude, time and frequency domain properties. In the present investigation, analysis was carried firstly; to study the grip force vs. SEMG parameters at acupressure points on arm, using single channel approach. At all the selected acupressure points a linear increment of SEMG was observed. Secondly; to discriminate four elbow movements from different locations on arm using two channel approach with single parameter. The parameter for the analysis chosen was the root of mean of square (RMS) value of SEMG. Further; principal component analysis was used to verify the elbow movement discrimination. Extension and supination were the two operations which were observed to be easy to realize by prosthetic devices. The selection of these locations was done on the basis of acupressure points and anatomy of elbow. Matlab-softscope was used for acquiring the SEMG from line-in input port of PC-sound card. This study will also be helpful for the researchers in understanding the behavior of SEMG for elbow movement in development of prosthetic or exoskeleton devices.     

The effect of accelerometer location on the classification of single-site forearm mechanomyograms

Background  

Recently, pattern recognition methods have been deployed in the classification of multiple activation states from mechanomyogram (MMG) signals for the purpose of controlling switching interfaces. Given the propagative properties of MMG signals, it has been suggested that MMG classification should be robust to changes in sensor placement. Nonetheless, this purported robustness remains speculative to date. This study sought to quantify the change in classification accuracy, if any, when a classifier trained with MMG signals from the muscle belly, is subsequently tested with MMG signals from a nearby location.     

The mechanomyography of persons after stroke during isometric voluntary contractions.

This study was to investigate the properties of mechanomyography (MMG), or muscle sound, of the paretic muscle in the affected side of hemiplegic subjects after stroke during isometric voluntary contractions, in comparison with those from the muscle in the unaffected side of the hemiplegic subjects and from the healthy muscle of unimpaired subjects. MMG and electromyography (EMG) signals were recorded simultaneously from the biceps brachii muscles of the dominant arm of unimpaired subjects (n=5) and the unaffected and affected arms of subjects after stroke (n=8), when performing a fatiguing maximal voluntary contraction (MVC) associated with the decrease in elbow flexion torque, and then submaximal elbow flexions at 20%, 40%, 60% and 80% MVCs. The root mean squared (RMS) values, the mean power frequencies (MPF, in the power density spectrum, PDS) of the EMG and MMG, and the high frequency rate (HF-rate, the ratio of the power above 15Hz in the MMG PDS) were used for the analysis. The MMG RMS decreased more slowly during the MVC in the affected muscle compared to the healthy and unaffected muscles. A transient increase could be observed in the MMG MPFs from the unaffected and healthy muscles during the MVC, associated with the decrease in their simultaneous EMG MPFs due to the muscular fatigue. No significant variation could be seen in the EMG and MMG MPFs in the affected muscles during the MVC. The values in the MPF and HF-rate of MMG from the affected muscles were significantly lower than those from the healthy and unaffected muscles (P<0.05) at the high contraction level (80% MVC). Both the MMG and EMG RMS values in the healthy and unaffected groups were found to be significantly higher than the affected group (P<0.05) at 60% and 80% MVCs. These observations were related to an atrophy of the fast-twitch fibers and a reduction of the neural input in the affected muscles of the hemiplegic subjects. The results in this study suggested MMG could be used as a complementary to EMG for the analysis on muscular characteristics in subjects after stroke.     

Estimation of the muscle fibre semi-length under varying joint positions on the basis of non-invasively extracted motor unit action potentials.

Changes in muscle fibre length and surface electrode position with respect to the muscle fibres affect the amplitude and frequency characteristics of surface electromyography (SEMG) in different ways. Knowledge of changes in muscle fibre length would help towards a better interpretation of the signals. The possibility of estimating the length through SEMG during voluntary contractions was checked in this study. The fibres' semi-length was estimated from the product of the conduction velocity and conduction time during which the wave of excitation propagated from the end-plate region to the ends of the fibres. Short (10 s), moderate (30% of maximum voluntary contraction) isometric contractions were performed by 10 subjects at different elbow joint angles (80-140 degrees in steps of 20 degrees ). Monopolar signals were detected non-invasively, using a two-dimensional electrode array. High spatial resolution EMG and a decomposition technique were utilised to extract single motor unit activities for triggered averaging and to estimate conduction velocity. A significant increase with joint angle was found in conduction time and estimated fibre semi-length. Changes in conduction velocity with joint angle were found to be not significant. The methodology described allows the relative changes in fibres' semi-length to be estimated from SEMG data.     

Experimental muscle pain increases mechanomyographic signal activity during sub-maximal isometric contractions.

This study was designed to investigate the local effect of experimental muscle pain on the MMG and the surface EMG during a range of sub-maximal isometric contractions. Muscle pain was induced by injections of hypertonic saline into the biceps brachii muscle in 12 subjects. Injections of isotonic saline served as a control. Pain intensity and location, MMG and surface EMG from the biceps brachii were assessed during static isometric (0%, 10%, 30%, 50% and, 70% of the maximal voluntary contraction) and ramp isometric (0-50% of the maximal voluntary contraction) elbow flexions. MMG and surface EMG signals were analyzed in the time and frequency domain. Experimentally induced muscle pain induced an increase in root mean square values of the MMG signal while no changes were observed in the surface EMG. Most likely this increase reflects changes in the mechanical contractile properties of the muscle and indicates compensatory mechanisms, i.e. decreased firing rate and increased twitch force to maintain a constant force output in presence of experimental muscle pain. Under well-controlled conditions, MMG recordings may be more sensitive than surface EMG recordings and clinically useful for detecting non-invasively increased muscle mechanical contributions during muscle pain conditions.     

The effect of skinfold on frequency of human muscle mechanomyogram.

The aim of the study was to assess the effect of skinfold thickness on median and peak frequency of mechanomyographic (MMG) signal in relation to subject's age, gender and force during voluntary contraction of elbow flexor and extensor muscles. Seventy-nine healthy subjects participated in the study: 22 young females (age 20.1+/-1.1 years), 22 young males (age 23.4+/-1.1 years), 17 elderly females (age 64.9+/-5.1 years), and 18 elderly males (age 67.4+/-6.2 years). Three identical MMG probes were used to record MMG signals from above the triceps brachii (TB), biceps brachii (BB), and brachioradialis (BR) muscles simultaneously with the force signal. The results showed that the tissue between the muscle and the skin surface has a major contribution to the median and a minor contribution to the peak MMG frequencies independent of subjects' age (with force having more than 2 folds a smaller effect). During antagonistic function of the main elbow flexors and extensors, there is a decreasing effect of skinfold thickness and an increasing effect of force on the MMG frequency, and the relative contribution of both factors to the MMG signal is age related, especially in the TB and BR muscles. The BR muscle differs from the TB and BB muscles in regard to the effects of skinfold thickness and force on the MMG frequency, as well as in the effect of age on the relationship between the MMG frequency and skinfold thickness and force. The effect of age on the relative contribution of skinfolds and force to MMG frequency is specific for muscle and its function. It was concluded that studies that report MMG frequency with different values of skinfold thickness cannot be easily compared, especially when maximally activated prime movers are tested. A use of force and skinfold thickness as covariates is recommended when an MMG frequency is analyzed in subjects differing in the skinfold thickness.     

Mechanomyogram amplitude vs. isometric ankle plantarflexion torque of human medial gastrocnemius muscle at different ankle joint angles

The purpose of this study was to investigate the influence of changes in ankle joint angle on the mechanomyogram (MMG) amplitude of the human medial gastrocnemius (MG) muscle during voluntary isometric plantarflexion contractions. Ten healthy individuals were asked to perform voluntary isometric contractions at six different contraction intensities (from 10% to 100%) and at three different ankle joint angles (plantarflexion of 26°; plantarflexion of 10°; dorsiflexion of 3°). MMG signals were recorded from the surface over the MG muscle, using a 3-axis accelerometer. The relations between root mean square (RMS) MMG and isometric plantarflexion torque at different ankle joint angles were characterized to evaluate the effects of altered muscle mechanical properties on RMS MMG.We found that the relation between RMS MMG and plantarflexion torque is changed at different ankle joint angles: RMS MMG increases monotonically with increasing the plantarflexion torque but decreases as the ankle joint became dorsiflexed. Moreover, RMS MMG shows a negative correlation with muscle length, with passive torque, and with maximum voluntary torque, which were all changed significantly at different ankle joint angles.Our findings demonstrate the potential effects of changing muscle mechanical properties on muscle vibration amplitude. Future studies are required to explore the major sources of this muscle vibration from the perspective of muscle mechanics and muscle activation level, attributable to changes in the neural command.     

Mechanomyography versus Electromyography,in monitoring the muscular fatigue

Background  

The use of the mechanomyogram (MMG) which detects muscular vibrations generated by fused individual fiber twitches has been refined. The study addresses a comparison of the MMG and surface electromyogram (SEMG) in monitoring muscle fatigue.     

Uncovering chaotic structure in mechanomyography signals of fatigue biceps brachii muscle

The mechanomyography (MMG) signal reflects mechanical properties of limb muscles that undergo complex phenomena in different functional states. We undertook the study of the chaotic nature of MMG signals by referring to recent developments in the field of nonlinear dynamics. MMG signals were measured from the biceps brachii muscle of 5 subjects during fatigue of isometric contraction at 80% maximal voluntary contraction (MVC) level. Deterministic chaotic character was detected in all data by using the Volterra–Wiener–Korenberg model and noise titration approach. The noise limit, a power indicator of the chaos of fatigue MMG signals, was 22.20±8.73. Furthermore, we studied the nonlinear dynamic features of MMG signals by computing their correlation dimension D₂, which was 3.35±0.36 across subjects. These results indicate that MMG is a high-dimensional chaotic signal and support the use of the theory of nonlinear dynamics for analysis and modeling of fatigue MMG signals.