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。     

连续疲劳干预对膝关节主被动生物力学特性的影响

目的 探究连续疲劳干预对膝关节主被动生物力学特性的影响。方法 招募27位健康大学生在等速力量测试系统上进行疲劳实验。疲劳实验包括3个疲劳周期,每个疲劳周期至少30次股四头肌连续等长收缩。对比不同疲劳周期的最大被动力矩、平均最大自主收缩（maximum voluntary contraction,MVC）力矩、股外侧肌和股二头肌肌电积分值以及协同收缩指数（co-contraction index,CI）。结果 疲劳周期3后,最大被动力矩显著下降（P<0.05）。疲劳周期1、2、3过程内平均MVC力矩、股外侧肌和股二头肌肌电积分值都显著下降（P<0.05）,然而二者CI全程无显著变化（P>0.05）。结论 股四头肌等长收缩训练剂量为90次的连续疲劳干预会显著影响膝关节主被动生物力学特性。疲劳干预后,膝关节抵抗被动屈伸能力下降。并且随着疲劳干预进程,股四头肌主动收缩能力下降,股四头肌和腘绳肌肌肉激活也下降,但二者肌群协同收缩水平不变。这种温和的肌群协同收缩模式有益于保持良性膝关节力学加载环境。研究结果有助于理解疲劳后膝关节主被动生物力学特性。     

等长肌力测试的研究与应用

背景：等长肌力测试是目前肌力测定方法中较为实用的一种测试手段,当某些关节保持一定的位置时,肌肉通过等长收缩,完成等长肌力测试。 目的：综述等长肌力测试技术的研究进展及应用,并对此测试技术的未来发展进行讨论。 方法：由第一作者检索ScienceDirect数据库,HighWire Press数据库,中国期刊全文数据库及万方数据库中发表于2000/2010有关肌力测试和等长肌力测试的实验研究及临床应用文献。英文检索词为“muscle force, muscle force testing, isometric contraction,  isometric muscle force testing”,中文检索词为“肌力、肌力测试、等长收缩、等长肌力测试”。同一领域文献则选择近期发表及发表在权威杂志的文章。 结果及结论：共检索到76篇文章,按纳入和排除标准对文献进行筛选,保留32篇文章进行综述。等长肌力测试并不能全面的反应人体肌力的情况,再加上由于其测试技术的不成熟性,使其应用受到了限制。等速肌力测试和等张肌力测试也是测试肌力的主要方法,它们各有优势,但也各有不足;而等张肌力测试系统无法测定与角度有关的参数。同时,表面肌电信号对评估肌力也有不错的效果。因此,将等长肌力测试与等速、等张测试系统及表面肌电信号结合或许会有更好的测试效果。     

脑卒中患者步态启动时早期姿势调节阶段时间和强度参数特点

背景：早期姿势调节为即将执行的动作或面临的姿势干扰做出准备，从而有助于更好地执行动作以及减少干扰对姿势造成的不稳定影响。目的：探索不同平衡能力的脑卒中患者在以舒适速度启动步行时下肢关键肌在早期姿势调节阶段的时间和强度参数特点。方法：观察16例脑卒中恢复期患者早期姿势调节特点，根据有无跌倒史及Berg平衡量表得分分为无跌倒组8例和跌倒组8例。使用Noraxon惯性传感器、Noraxon Ultium EMG无线表面肌电仪采集步态启动过程中患者身体运动学数据和表面肌电数据。分析早期姿势调节阶段下肢胫骨前肌、腓肠肌内外侧、股直肌、股外侧肌和股二头肌6块关键肌的肌肉激活时间和激活顺序，以及步态启动前4个时间窗(各150 ms)的标准化的肌电积分值。结果与结论：(1)有跌倒史的患者在步态启动时，下肢6块关键肌的肌肉激活时间均早于无跌倒组，胫骨前肌、腓肠肌外侧头和股外侧肌的激活时间显著早于无跌倒组(P <0.01,P <0.05)；无跌倒组的肌肉激活顺序呈现出了比较规律的先激活伸肌后激活屈肌、大腿部肌肉激活早于小腿肌肉激活的特点；而跌倒组小腿部伸肌的激活要早于大腿部伸肌的激活，股外侧肌...     

搂膝拗步膝踝关节预激活与共收缩的表面肌电分析

目的 分析长期太极拳练习者进行搂膝拗步和正常行走时下肢膝、踝关节肌群预激活与共收缩的表面肌电（surface electromyography, sEMG）特征,探讨太极预防跌倒的神经肌肉控制策略。方法 采用Vicon运动捕捉系统、Kistler测力板和Noraxon表面肌电图系统同步采集搂膝拗步和正常行走时股直肌、股二头肌、胫骨前肌、外侧腓肠肌的sEMG信号和体位信息。通过股直肌和股二头肌、胫骨前肌和外侧腓肠肌两对肌肉的积分肌电分别计算膝、踝关节预激活和共收缩。结果 与正常行走相比,搂膝拗步在4个阶段的平均用时显著增加;搂膝拗步在4个阶段内时间百分比存在显著性差异;搂膝拗步膝关节共收缩水平和预激活水平降低,踝关节共收缩水平和预激活水平升高。结论 长期的太极拳练习可能使膝关节周围肌肉的激活水平提高,增强肌肉群之间的协同作用,以帮助稳定关节。研究结果为神经肌肉控制障碍疾病的康复评估和训练提供参考。     

高精度经颅直流电刺激对踝关节跖背屈疲劳任务中脊髓运动神经元兴奋性的影响

目的 探究踝关节跖背屈疲劳任务中高精度经颅直流电刺激(high-definition transcranial direct current stimulation, HD-tDCS)对H-反射和M-波的调控效果,为HD-tDCS减轻神经肌肉疲劳的实际应用提供方向。方法 招募20名健康青年男性受试者,随机分为真刺激组和假刺激组各10名。对受试者采取连续5 d的单盲HD-tDCS干预(时间20 min;强度2 mA;靶点Cz),干预前1天采集受试者安静条件下的H-反射和M-波,跖屈肌最大自主收缩(maximal voluntary isometric contraction, MVIC)时的M-波,跖屈肌和背屈肌MVIC力矩,并进行一次踝关节跖背屈运动性疲劳任务,以确定受试者达到该任务疲劳的时间。干预后1天进行与第1次疲劳任务相同的运动时间,并进行后测的数据采集。采用重复测量双因素(刺激方案×疲劳前后)方差分析其自变量对受试者肌肉力学特性、α运动神经元传导特性各指标的影响。结果 相较于疲劳前,两组疲劳后的自主激活值(voluntary activation, VA)、H-反射最大值(ma...     

不同关节角度肌肉等长最大自主收缩抗阻力训练的神经适应分析

目的 研究不同关节角度下肌肉等长最大自主收缩(maximum voluntary contraction,MVC)抗阻力训练神经适应特点.方法 将30名健康男性大学生随机分成3组,每组分别做肘关节角度在45°、90°、135° MVC等长收缩抗阻力训练,测量训练前后肱二头肌的表面肌电(surface electromy...     

长期太极拳和慢跑锻炼对侧向突发干扰下老年男性神经肌肉反应时和肌电达峰值时间影响

目的比较长期太极拳和慢跑锻炼对老年男性突发侧向姿势干扰下神经肌肉反应时和肌电达峰值时间的差异,探索提高老年男性侧向姿势挑战下神经肌肉反应和肌肉收缩效率的有效锻炼方式。方法利用足底水平干扰触发平台对年轻男性、无规律锻炼的老年男性、长期慢跑锻炼的老年男性、长期太极拳锻炼的老年男性进行突发侧向姿势干扰。表面肌电测试和分析系统用于收集腓骨长肌、胫骨前肌、臀中肌和竖脊肌的肌电信号。结果突发侧向干扰下,无规律锻炼老年男性腓骨长肌、胫骨前肌和臀中肌的神经肌肉反应时明显地慢于年轻男性,长期太极拳锻炼老年男性胫骨前肌和竖脊肌的神经肌肉反应明显地快于老年对照组;年轻男性腓骨长肌、胫骨前肌和臀中肌的收缩速度明显地快于3组老年人。结论长期太极拳锻炼可以使老年男性踝关节和躯干肌的神经肌肉反应更加迅速以应对侧向的姿势挑战,而对于提高老年男性肌肉收缩效率的效果不明显。     

不同目标力矩时距小腿关节肌肉力觉的重测信度**☆

背景：目前对于距小腿关节矢状面内肌肉力觉的研究较为缺乏,距小腿关节肌肉力觉的测试没有统一的标准。 目的：通过分析不同目标力矩时距小腿关节矢状面内运动肌肉力觉的重测信度,探讨距小腿关节肌肉力觉的测量方法。 方法：选取跖屈肌群最大等长峰值力矩值的25%,50%和75%作为距小腿关节肌肉力觉的目标力矩值,测试距小腿关节肌肉对这些目标力矩值的复制能力;运用组内相关系数和测量的标准误来判断肌肉力觉的重复测量结果的一致性程度。 结果与结论：结果显示用来衡量关节肌肉力觉的可变误差和绝对误差的组内相关系数均大于0.75,而且测量的标准误相对较小;常数误差的组内相关系数均小于0.75,而且测量的标准误相对较大。在目标力矩较小时,用来衡量肌肉力觉的可变误差和绝对误差重测信度较好。     

踝关节位置觉和肌肉力觉的重测信度

背景:目前对于踝关节矢状面内本体感觉的研究较为缺乏,踝关节本体感觉的测试没有统一的标准。目的:分析踝关节矢状面内运动位置觉和力觉的重测信度。方法:踝关节位置觉采用对踝关节跖屈5°的被动定位被动复位能力进行测试,肌肉力觉采用受试者踝关节对跖屈肌群25%最大等长峰值力矩值的复制能力进行测试;运用组内相关系数和测量的标准误来判断位置觉和力觉重复测量结果的一致性程度。结果与结论:用来衡量关节位置觉和肌肉力觉的可变误差和绝对误差的组内相关系数均大于0.75,而且测量的标准误相对较小。常数误差的组内相关系数均小于0.75,而且测量的标准误相对较大。提示用来衡量位置觉和力觉的常数误差重测信度较差,用来衡量位置觉和力觉的可变误差和绝对误差重测信度较好。     

Effect of muscular ultrasound stimulation on power spectrum electromyography during a strengthening training

The purpose of this study is to describe the electromyographic (EMG) power spectral evolution during a muscle strengthening training based on ultrasound stimulation applied to the right rectus femoris muscle simultaneously with its maximum voluntary isometric contraction (MVIC) in ten healthy subjects. From the surface EMG of rectus femoris the Zero Crossing (ZC) and integrated EMG (IEMG) were calculated. The Mean Power Frequency (MPF) and Median Frequency (MF) from the EMG power spectrum were obtained using a maximum entropy method. An Analysis of Variance (ANOVA) for repeated measures showed significant changes for IEMG and ZC throughout sessions and for MPF, MF and ZC between the pretest and posttest. Immediate increases in MPF, MF and ZC were observed (paired t-test, p < 0.05) after training and an increment of IEMG during sessions (one-way ANOVA, p = 0.01). The ultrasound pulsed stimulation applied simultaneously with a MVIC produced the development of the muscle force. The mechanism of action of this application could be the mechanical effect, compression and rarefaction, produced by the ultrasound stimulation during the muscle contraction process.     

EMG differences between concentric and eccentric maximum voluntary contractions are evident prior to movement onset

This investigation addressed the question of whether the muscle activation signal prior to movement onset, as measured by surface EMG, differs if the contraction to be performed is concentric (shortening) or eccentric (lengthening). Specifically, the purpose was to determine if differences in knee extensor muscle EMG prior to voluntary maximum concentric and eccentric contractions and initiated from the same knee joint angle are evident at a time before muscle length changes could be influential. A protocol was designed using isokinetic knee extensions. The EMG of the vastus lateralis, vastus medialis, rectus femoris, and hamstrings muscles and the associated knee extension moment were measured during the isometric phase preceding the onset of dynamometer motion. During this isometric phase the muscles initially contracted under identical conditions, irrespective of whether the contraction was to be concentric or eccentric. The EMG of the eccentric contractions was significantly smaller than that of the concentric contractions. However, the rate of change of knee extension moment generally did not differ between the two conditions. This was found for both the monoarticular and multiarticular knee extensor muscles. The results suggest that initial differences between the EMG of maximum voluntary concentric and eccentric knee extensor contractions are selected a priori and support the contention that the central nervous system distinguishes between maximum eccentric and concentric contractions. The emergence of differences in activation prior to muscle length changes suggests supraspinal influences.     

Plantar flexor muscle function in open and closed chain.

In the present study, the torque or work produced during isometric, pure concentric and eccentric-concentric plantar flexions, performed in sitting, standing and prone were measured. The electromyographic (EMG) activity was measured from the soleus, gastrocnemius medialis, tibialis anterior and rectus femoris muscles. The isometric tests showed the highest torques in the standing test. The rectus femoris and gastrocnemius activities were lower in the prone than in the standing test. The sitting test showed lower activities in all muscles of the lower leg compared with the standing test. No differences in work between the prone and sitting tests were found during the concentric phases. Higher rectus femoris activity in the eccentric-concentric test and lower activity in the triceps surae during the concentric phases were seen in the sitting compared with the prone test. We conclude that tests of overall functional ability should be performed in the standing position while specific tests of the plantar flexors should be performed in the prone position.     

Dynamic and isometric protocols of knee extension: effect of fatigue on the EMG signal

The objective of this study was to analyze the electromyographic (EMG) signal behavior of rectus femoris (RF), vastus medialis (VM), vastus lateralis (VL) and biceps femoris (caput longum) (BFCL) from nine women during fatiguing dynamic and isometric knee extensions tests and to determine their EMGFT (Electromyographic Fatigue Threshold). Surface electrodes, biological signal acquisition module, analogical-digital converter board and specific software were used. The RMS (Root Mean Square) values obtained from concentric phase (80 to 30 degrees) of the dynamic knee extension and from isometric contraction were correlated with time on each load by linear regression analysis. The respective slopes were correlated with the correspondent load to determine the EMGFT. Force (Kgf) and median frequency--MF (Hz) obtained during MIVC (Maximal Isometric Voluntary Contraction) performed before and after the fatiguing tests were calculated in Matlab environment. The results demonstrated that the endurance time decreases with higher loads, the EMG amplitude increase with time and was greater at higher loads, between muscles in dynamic exercise the RF and VL showed higher slopes, and in isometric exercise the VL showed the same behavior. The EMGFT values were similar in both exercises; the force values predominantly decreased after fatiguing tests; however the MF only decreased after some loads. The protocols proposed allowed standardizing protocols at least to induce the fatigue process and to determine the EMGFT as an endurance indicative, which may be used to evaluate the effectiveness of rehabilitative or training interventions indicated to reduce muscle weakness and fatigue.     

Normalized EMG to normalized torque relationship of vastus intermedius muscle during isometric knee extension

The purpose of the present study was to investigate the electromyography (EMG) to torque relationship of the vastus intermedius (VI) muscle. Thirteen healthy men performed maximal voluntary contraction (MVC) and submaximal contraction during isometric knee extension at 10% of the MVC to 90% of the MVC at intervals of 10% of the MVC level. Surface EMG was detected from four muscle components of the QF muscle group, i.e., VI, vastus lateralis (VL), vastus medialis, and rectus femoris (RF) muscles. Normalized muscle activation in the VI muscle was significantly lower than in the VL muscle at a lower torque level (20 and 40% of MVC) and significantly lower compared to the RF muscle at a higher torque level (from 60 to 90% of MVC). These results suggest that neuromuscular activation in the VI muscle is not consistent with the other components of QF muscle group during submaximal knee extension contractions.     

EMG activities in mono- and bi-articular thigh muscles in combined hip and knee extension

Summary 8 male subjects were tested to elucidate the organization of EMG activities in mono- and bi- articular thigh muscles when hip and knee extension are combined. 2 types of isometric movement, single and dual joint movements, were studied: 1) 20% of maximal voluntary contraction (MVC) in separate hip extension (HE20) and knee extension (KE20), 2) simultaneous HE20 and KE20, combined voluntarily (HE20 · KE20). In HE20 · KE20, the value of the integrated EMG (IEMG) from the muscles tested was normalized as a percentage (%IEMG) of the IEMG of each muscle in HE20 for gluteus maximus (GM) and semimembranosus (SM), and in KE20 for vastus medialis (VM) and rectus femoris (RF). The average %IEMG was 50.5±16.9% for GM, 42.1±6.1% for SM, 153.4±22.8% for VM and 66.6±18.7% for RF. These data suggest that the EMG activities of GM, SM and RF are inhibited and the EMG activity of VM is facilitated by combining hip extension with knee extension.     

Modulation of the human nociceptive reflex by cyclic movements

During static conditions the nociceptive reflex is known to vary as a function of, for example, the stimulus position, stimulus intensity, and muscle contraction. The aim of the present human study was to investigate whether the reflex and the corresponding perception of pain are modulated by cyclic movements of the limb involved. Reflexes, evoked by nociceptive electric stimulation of the sural nerve, were recorded from the biceps femoris and the rectus femoris muscles in eight volunteers. Four different experiments were performed to compare the nociceptive reflex and pain score elicited during active isometric/dynamic flexion/extension of the knee joint. The amplitudes of the reflexes were largest for the dynamic conditions. The reflexes, evoked during dynamic extension and isometric contraction of the rectus femoris muscle, had the shortest latencies but the recordings from the biceps femoris muscle were larger than from the rectus femoris muscle. Knee joint angle recordings showed that the largest angle variations occurred for the dynamic conditions and were only marginally disturbed for the isometric conditions. A given stimulus intensity evoked the highest pain intensity during isometric contractions. This indicates that there would seem to be no causal relationship between the size of the nociceptive reflex and the pain intensity.     

Surface electromyographic amplitude-to-work ratios during isokinetic and isotonic muscle actions

Context: Isokinetic and isotonic resistance training exercises are commonly used to increase strength during musculoskeletal rehabilitation programs. Our study was designed to examine the efficacy of isokinetic and isotonic muscle actions using surface electromyographic (EMG) amplitude-to-work ratios (EMG/WK) and to extend previous findings to include a range of isokinetic velocities and isotonic loads. Objective: To examine work (WK), surface EMG amplitude, and EMG/WK during concentric-only maximal isokinetic muscle actions at 60, 120, 180, 240, and 300 degrees /s and isotonic muscle actions at 10%, 20%, 30%, 40%, and 50% of the maximal voluntary isometric contraction (MVIC) torque during leg extension exercises. Design: A randomized, counterbalanced, cross-sectional, repeated-measures design. Setting: A university-based human muscle physiology research laboratory. Patients or Other Participants: Ten women (mean age = 22.0 +/- 2.6 years) and 10 men (mean age = 20.8 +/- 1.7 years) who were apparently healthy and recreationally active. Intervention(s): Using the dominant leg, each participant performed 5 maximal voluntary concentric isokinetic leg extension exercises at randomly ordered angular velocities of 60, 120, 180, 240, and 300 degrees /s and 5 concentric isotonic leg extension exercises at randomly ordered loads of 10%, 20%, 30%, 40%, and 50% of the isometric MVIC. Main Outcome Measure(s): Work was recorded by a Biodex System 3 dynamometer, and surface EMG was recorded from the superficial quadriceps femoris muscles (vastus lateralis, rectus femoris, and vastus medialis) during the testing and was normalized to the MVIC. The EMG/WK ratios were calculated as the quotient of EMG amplitude (muVrms) and WK (J) during the concentric phase of each exercise. Results: Isotonic EMG/WK remained unchanged ( P > .05) from 10% to 50% MVIC, but isokinetic EMG/WK increased ( P < .05) from 60 to 300 degrees /s. Isotonic EMG/WK was greater ( P < .05) than isokinetic EMG/WK for 50% MVIC versus 60 degrees /s, 40% MVIC versus 120 degrees /s, and 30% MVIC versus 180 degrees /s; however, no differences were noted ( P > .05) between 20% MVIC versus 240 degrees /s or 10% MVIC versus 300 degrees /s. An 18% decrease in active range of motion was seen for the isotonic muscle actions, from 10% to 50% MVIC, and a 3% increase in range of motion for the isokinetic muscle actions from 60 to 300 degrees /s was also observed. Furthermore, the peak angular velocities for the isotonic muscle actions ranged from 272.9 to 483.0 degrees /s for 50% and 10% MVIC, respectively. Conclusions: When considering EMG/WK, peak angular velocity, and range of motion together, our data indicate that maximal isokinetic muscle actions at 240 degrees /s or controlled-velocity isotonic muscle actions at 10%, 20%, or 30% MVIC may maximize the amount of muscle activation per unit of WK done during the early stages of musculoskeletal rehabilitation. These results may be useful to allied health professionals who incorporate open-chain resistance training exercises during the early phases of rehabilitation and researchers who use isotonic or isokinetic modes of resistance exercise to examine muscle function.     

Reliability of leg muscle electromyography in vertical jumping

In this study we aimed to determine the reliability of the surface electromyography (EMG) of leg muscles during vertical jumping between two test sessions, held 2 weeks apart. Fifteen females performed three maximal vertical jumps with countermovement. The displacement of the body centre of mass (BCM), duration of propulsion phase (time), range of motion (ROM) and angular velocity of the knee and surface EMG of four leg muscles (rectus femoris, vastus medialis, biceps femoris and gastrocnemius) were recorded during the jumps. All variables were analysed throughout the propulsion and mid-propulsion phases. Intraclass correlation coefficients (ICC) for the rectus femoris, vastus medialis, biceps femoris and gastrocnemius were calculated to be 0.88, 0.70, 0.24 and 0.01, respectively. BCM, ROM and time values all indicated ICC values greater than 0.90, and the mean knee angular velocity was slightly lower, at 0.75. ICCs between displacement of the BCM and integrated EMG (IEMG) of the muscles studied were less than 0.50. The angular velocity of the knee did not correlate well with muscle activity. Factors that may have affected reliability were variations in the position of electrode replacement, skin resistance, cross-talk between muscles and jump mechanics. The results of this study suggest that while kinematic variables are reproducible over successive vertical jumps, the degree of repeatability of an IEMG signal is dependent upon the muscle studied.     

Sonomyographic responses during voluntary isometric ramp contraction of the human rectus femoris muscle

This paper aims to investigate the relationship between torque and muscle morphological change, which is derived from ultrasound image sequence and termed as sonomyography (SMG), during isometric ramp contraction of the rectus femoris (RF) muscle, and to further compare SMG with the electromyography (EMG) and mechanomyography (MMG), which represent the electrical and mechanical activities of the muscle. Nine subjects performed isometric ramp contraction of knee up to 90% of the maximal voluntary contraction (MVC) at speeds of 45, 22.5 and 15% MVC/s, and EMG, MMG and ultrasonography were simultaneously recorded from the RF muscle. Cross-sectional area, which was referred to as SMG, was automatically extracted from continuously captured ultrasound images using a newly developed image tracking algorithm. Polynomial regression analyses were applied to fit the EMG/MMG/SMG-to-torque relationships, and the regression coefficients of EMG, MMG, and SMG were compared. Moreover, the effect of contraction speed on SMG/EMG/MMG-to-torque relationships was tested by pair-wise comparisons of the mean relationship curves at different speeds for EMG, MMG and SMG. The results show that continuous SMG could provide important morphological parameters of continuous muscle contraction. Compared with EMG and MMG, SMG exhibits different changing patterns with the increase of torque during voluntary isometric ramp contraction, and it is less influenced by the contraction speed.