膝骨关节炎患者膝关节置换后下肢肌的表面肌电图变化

背景：膝骨关节炎患者膝关节置换后下肢肌功能恢复一直存在着争议。 目的：评价膝骨关节炎患者膝关节置换手术后下肢肌肉功能。 方法：应用TELEMYO 2400R G2表面肌电图遥测仪对25例双膝骨关节炎单膝关节置换后患者在平常自然步态下进行双下肢股直肌、胫前肌、股二头肌和腓肠肌内侧的表面肌电信号测试。在肌电图测试前,对患者双膝关节功能进行美国特种外科医院膝关节评分。 结果与结论：患者置换后美国特种外科医院膝关节评置换侧平均分91.44,其优良率达100%;未置换侧平均分54.52。置换侧在疼痛、关节功能方面有明显改善;膝关节置换后置换侧股直肌、胫前肌、股二头肌的肌电振幅、肌电积分、平均频率、中位频率的(平均值、最小值、最大值)与未置换侧相比差异无显著性意义(P > 0.05);置换侧腓肠肌内侧肌电振幅值及肌电积分值显著大于未置换侧(P < 0.05);置换侧腓肠肌内侧平均频率、中位频率与未置换侧相比差异无显著性意义(P > 0.05)。提示膝关节置换后置换侧的下肢肌没有恢复到正常的功能活动水平,因此膝关节置换后康复要特别重视患者的肌肉锻炼。中国组织工程研究杂志出版内容重点：人工关节;骨植入物;脊柱;骨折;内固定;数字化骨科;组织工程全文链接：     

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.     

穿戴塑料踝足矫形器对下肢肌肉疲劳性的影响

背景：目前尚未见到系统研究踝足矫形器对下肢肌肉影响的文献。 目的：提取正常人穿戴固定踝足矫形器时的下肢肌电信号,分析固定踝足矫形器对下肢肌肉疲劳性的影响。 方法：选择5名健康男性受试者参加试验,每名受试者分别进行3组试验：①第1组,在不穿戴任何矫形器的情况下以自然步态行走。②第2组,受试者穿戴平跟踝足矫形器以自然步态行走(此时矫形器踝部包裹超过踝中心1 cm,记1.0 cm),穿戴同一矫形器但在踝部去掉1.0 cm、踝部塑料边缘刚好通过踝中心时采集(记     0 cm),在踝部再去掉1.0 cm后以自然步态行走(记-1.0 cm)。③第3组,受试者穿戴1.5 cm正常跟高踝足矫形器以自然步态行走,穿戴同一矫形器,但跟高分别改为1.0,2.0 cm后以自然步态行走。行走中采用肌电采集仪检测受试者下肢股二头肌、股直肌、胫骨前肌、腓肠肌的表面肌电信号。 结果与结论：①正常不穿戴任何矫形器时,4块肌肉的肌电信号是最弱的。②对于任何一块肌肉,正常不穿戴矫形器时所对应肌电值比穿戴不同硬度矫形器时所对应的肌电值要小。③对于股二头肌,正常不穿戴矫形器时所对应的积分肌电值与穿戴正常跟高矫形器时所对应的值很接近,同时这两个值要比穿戴不正常跟高矫形器时所对应的积分肌电值小。表明固定塑料踝足矫形器会引起股二头肌、股直肌、胫骨前肌、腓肠肌的疲劳,当固定塑料踝足矫形器的跟高不合适时会进一步增加股二头肌的疲劳程度。中国组织工程研究杂志出版内容重点：生物材料;骨生物材料; 口腔生物材料; 纳米材料; 缓释材料; 材料相容性;组织工程全文链接：     

10 m自由步行偏瘫步态胫前后肌群的表面肌电图研究

目的:利用表面肌电图(SEMG),分析偏瘫患者10 m自由步行胫前后肌群的SEMG变化规律,为拓展SEMG的临床应用建立可靠的依据。方法:2名偏瘫患者分别进行10 m自由步行测试,同步记录双下肢胫前肌、腓肠肌内侧头两组肌群的SEMG信号,考察受试肌在步态周期中的SEMG变化规律。结果:偏瘫步态的患侧腓肠肌与胫前肌同步收缩。患侧腓肠肌在迈步期有许多小波存在。患侧肌群的总体波幅显著小于健侧。结论:偏瘫步态的SEMG主要为患侧腓肠肌与患侧胫前肌的正常拮抗收缩状态减弱或丧失,以及患侧腓肠肌过度活跃,同时伴有患侧胫前肌的肌电活动减弱。     

基于AnyBody仿真和肌电测试分析不同体质量指数男性青年球类运动中的生物力学特征

文题释义： Anybody仿真：使用数学建模技术模拟人体肌肉骨骼在不同载荷中的情况,计算各块肌肉和关节的受力、变形、肌腱的弹性能、拮抗肌肉运动和其他对于工作中的人体有用的特性,以计量方式计算出人体对于环境的反应,兼与人机工程学和生物力学分析,为人体运动建模、人机工程学产品性能改进和生物医学工程研究提供平台。 均方根振幅：是将振幅平方的平均值开平方,把振幅值平均然后开方,最原始的是针对正弦波推导出来的,但实际上对所有的波形都适用,均方根值(RMS)也称作为效值,表示在一段周期内,参加肌肉活动的肌肉瞬间肌电图振幅均方根值,是一定时间内肌电位值平方和的平方根。 背景：Anybody肌肉骨骼建模系统,使用数学建模技术模拟人体骨骼、肌肉和环境的关系,可对人体的逆向动力学进行研究,得出下肢三关节最大肌肉力等指标。 目的：研究24名不同体质量指数男大学生在坐瑞士球一个动作周期的下肢肌肉力值,及受试者在坐瑞士球与平凳的均方根肌电平均值对比情况。 方法：将24名男大学生按体质量指数分为正常组、超重组、肥胖组,用BTS三维红外动作捕捉系统、Kistler 三维测力台、BTS表面肌电测试系统,同步记录动力学和肌电参数,以单因素方差分析定性比较不同组间肌力和肌电参数差异,用定量差异分析法对比均值差异。 结果与结论：①肌肉力量方面,由坐到站过程中,正常组与肥胖组相比,股直肌、半膜肌、股二头肌长头、腘肌、比目鱼肌、胫骨前肌差异显著(P < 0.05,0.47≤QD<0.80),股方肌与耻骨肌的两组肌肉力差异极其显著(P < 0.01,QD≥0.80);超重组与肥胖组肌肉力相比,股方肌具有显著性差异(P < 0.05,0.47≤QD<0.80),由站到坐过程中,正常组与肥胖组相比,缝匠肌、拇长伸肌、腓肠肌肌肉力差异显著(P < 0.05,0.47≤QD<0.80);②均方根肌电值方面,坐平凳状态下,由坐到站过程中,正常组与肥胖组相比,股二头肌和腓肠肌差异显著(P < 0.05,0.47≤QD<0.80),由站到坐过程中,正常组与肥胖组相比,股直肌差异显著(P < 0.05,0.47≤QD<0.80);坐瑞士球状态下,由坐到站过程中,正常组与肥胖组相比,胫骨前肌、股二头肌差异显著(P < 0.05,0.47≤QD<0.80);由站到坐过程中,正常组与肥胖组相比,腓肠肌、右竖脊肌肌电值差异显著(P < 0.05,0.47≤QD<0.80)。提示：①各组由坐到站过程中主导发力肌肉是臀中肌、股外侧肌、股二头肌长头、股直肌、腓肠肌、胫骨前肌、比目鱼肌,由站到坐过程中下肢臀中肌、股外侧肌和股二头肌长头、腓肠肌、胫骨前肌、比目鱼肌主导发力;②与坐平凳相比,受试者在坐瑞士球时胫骨前肌、股直肌、股二头肌、腓肠肌均方根肌电值高。ORCID: 0000-0003-0520-5606(庞博) 中国组织工程研究杂志出版内容重点：人工关节;骨植入物;脊柱;骨折;内固定;数字化骨科;组织工程     

痉挛型脑瘫儿童手术后表面肌电信号和关节角度评估

目的 通过表面肌电(surface electromyography, sEMG)和关节角度评估脑瘫儿童手术后运动功能。方法 采集16名痉挛型脑瘫患儿手术前后直线行走时股直肌、股二头肌、半腱肌、胫骨前肌、腓肠肌内外侧sEMG和髋、膝、踝关节角度,计算各步态时期sEMG均方根、积分肌电值和关节角度均值,进行肌力肌张力评估。结果 手术后,患儿下肢肌肉肌张力均显著降低(P<0.05),股直肌和股二头肌在摆动阶段肌力减小。胫骨前肌在摆动中末期肌力增大(P<0.05)。髋、膝关节屈曲角降低(P<0.05)。踝关节背屈角增大(P<0.05),内翻角减小(P<0.05)。结论 治疗后患者蹲伏步态和马蹄内翻足均得到改善,运动功能得到提升。sEMG结合关节角度分析可对患者肌肉功能进行定量评估,为临床诊断提供参考。     

脑瘫尖足患儿站立和行走中下肢肌肉的表面肌电图

文题释义：表面肌电图(surface lectromyography,SEMG)：是分析相关肌肉功能状况的一种无创性检查手段,可以客观评定静止或运动时肌肉的活动情况。在控制良好的情况下,肌电信号活动的变化在很大程度上能够定量反映肌肉功能状态、肌张力、肌力水平、多肌群协调性等肌肉的变化,对肌肉功能状况提供客观指标,对于肌肉相关疾病的康复设计、康复治疗,特别是疗效评定有着不可替代的重要作用。 平均振幅：是用来描述一段时间内肌电幅值的平均变化特征。一般认为与运动单位募集程度和兴奋节律的同步化有关,它间接反映肌肉收缩力大小。一定范围内,平均振幅与肌肉收缩过程中参与工作运动单位数量呈正比,反映了肌肉收缩强度的变化。 背景：在控制良好的情况下,肌电信号活动的变化在很大程度上能够定量反映肌肉功能状态、肌张力、肌力水平、多肌群协调性等肌肉的变化,对肌肉功能状况提供客观指标。 目的：探讨脑瘫尖足患儿站立和行走中下肢肌肉的表面肌电图变化。 方法：应用美国NORAXON公司生产的 TELEMYO 2400R G2表面肌电图遥测仪对20例脑瘫单侧尖足患儿在静止站立、常态行走下进行双下肢胫前肌、腓肠肌内侧的表面肌电测试。比较受试者尖足侧与对侧肌肉的肌电活动。研究方案经过了上海瑞金医院伦理委员会批准,所有受试者及监护人均签署了“知情同意书”。 结果与结论：①受试者静止站立和常态行走时,其尖足侧腓肠肌内侧的平均肌电振幅、平均肌电积分均低于对侧(P < 0.05);②受试者静止站立和常态行走时,其尖足侧胫前肌和腓肠肌内侧的平均频率、中位频率均高于对侧(P < 0.05);③结果说明,脑瘫患儿尖足侧胫前肌、腓肠肌内侧存在表面肌电图信号异常,脑瘫单侧尖足患儿下肢肌肉活动不均衡,提示表面肌电图对脑瘫患儿神经肌肉系统功能状态的评价具有实用价值。 ORCID: 0000-0001-8732-8452(许萍);0000-0001-9909-3355(梁雷超) 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     

基于表面肌电的步态分析

背景：步态分析在人体运动系统和神经系统疾病的病因分析,诊断,功能、疗效与残疾评定中是重要的评价手段,其中肌肉活动是影响步行动力的基础因素。 目的：分析人体自然行走过程中下肢前后肌群的表面肌电变化,分析对应于步态周期不同时相前后肌群的表面肌电特征和机制。 方法：采用德国zebris FDM 步态分析系统(6 m)配套的同步肌电仪采集7例健康人正常步态过程中下肢胫骨前肌和腓肠肌外侧表面肌电信号,利用Matlab软件进行消噪和归一化,得到完整步态周期不同时相对应的表面肌电信号图,观察其峰值变化。采用芬兰ME6000肌电仪测试15 m自由行走人体左右侧下肢胫骨前肌和腓肠肌外侧表面肌电信号,提取时域和频域特征参数。 结果与结论：下肢胫骨前肌和腓肠肌外侧表面肌电信号在一个完整步态周期中呈特征性变化,即胫骨前肌表面肌电的峰值发生在后跟着地处,而腓肠肌外侧其峰值发生在中后支撑相处。进一步分析发现,人体在自由行走时其下肢肌肉优势侧与非优势侧差异有显著性意义(P < 0.05),且不同肌肉其差异趋势不同。     

太极拳转体动作中下肢关节活动顺序性和肌肉力表现及肌肉激活特征

目的 分析太极拳转体与弓步动作中下肢关节活动顺序性、肌肉力表现和肌肉激活程度的差异,揭示太极拳转体动作的特征。 方法 募集 20 名练习时长超过 3 年的健康太极拳练习者,采用三维运动捕捉系统、测力台和表面肌电同步采集转体与弓步两种动作运动学、动力学和肌肉激活信息,并通过 OpenSim 仿真软件获取下肢肌力。结果 与弓步相比,转体动作髋、踝关节外旋幅度显著增大;膝关节外展和外旋力矩显著增大,股二头肌、半腱肌和内外侧腓肠肌峰值肌力显著增强,股二头肌、内外侧腓肠肌峰值肌力时刻显著提前,而股内外侧肌和胫骨前肌峰值肌力显著减小,胫骨前肌肌力最早达到峰值;股二头肌、股内外侧肌和内侧腓肠肌的平均激活水平和激活时间显著增加。 结论 太极拳转体动作由踝、髋关节依次转动组成,肌肉力表现的独特性在于重心两次转移致使支撑腿内外侧肌力曲线呈双峰型,因为全足着地延迟方式引发了腓肠肌与股四头肌激活顺序和肌肉平均激活水平改变。研究结果提示全足着地延迟方式具有调节肌肉激活顺序的作用,合理利用有助于提升临床康复效果。     

Synergistic characteristics of lower extremity muscles with unilateral knee flexion limitation北大核心

背景:膝关节活动受限是一种比较常见的损伤后表现特征,但是对于膝关节活动受限下的肌肉协同有待研究。目的:研究单侧膝关节屈曲受限与正常运动下肢肌肉协同的异同。方法:招募20名健康成年人(男性12名,女性8名)作为受试者,分别采集屈曲受限条件下与无屈曲受限条件下自然行走的下肢表面肌电信号。通过非负矩阵分解算法从受限侧(右腿)的10块肌肉的表面肌电信号中提取肌肉协同,利用单因素方差分析研究在不同条件行走的步态参数显著差异。结果与结论:①屈曲受限条件下,受试者进行行走任务时肌肉协同数量减少,表现出不同的肌肉协调模式控制并且招募新的肌肉协同单元;随着协同模块的减少,内侧腓肠肌、外侧腓肠肌和比目鱼肌激活时间从支撑相向摆动相偏移的越明显;主要依靠股直肌、股内侧肌、股外侧肌和阔筋膜张肌进行代偿,使其在激活水平上表现的异常活跃,同时受限侧表现出划圈、提胯等动作,因此受限后主要以受限侧髋关节代偿;②屈曲受限条件下,受试者受限侧和非受限侧在步态参数(频率、步速、步态周期和支撑相占比)方面对比受限前均存在显著差异(P<0.05),同时非受限侧单腿支撑时间相较于受限前明显增大(P<0.01),受限侧支撑相占比和单腿支撑时间显著小于非受限侧(P<0.01);③因此,膝关节屈曲运动减弱可被认为是导致下肢肢体内协调受损的关键因素,研究结果对运动功能的定量分析以及人体下肢康复指导具有意义,并为了解运动功能受损背后的神经肌肉控制机制提供重要的见解。     

Gait and surface electromyography characteristics in hurdle athletes in a total gait cycle北大核心

BACKGROUND: In recent years, the technical parameters about hurdle athletes are mainly obtained through video analysis and DLT algorithm. However, the gait and surface electromyography (sEMG) characteristics during normal walking are little reported. OBJECTIVE: To explore the changes of the gait and lower limb sEMG signals relative to gait period in hurdle athletes. METHODS: Eight male professional hurdlers were selected to perform gait and lower limb sEMG tests on the trail, and the differences in gait and sEMG signals were analyzed by mathematical statistics. RESULTS AND CONCLUSION: The gait parameters of hurdlers showed no significant differences (except step length). In the total gait cycle, along with the gait changing, the right and left side muscles of the same name moved alternately. The median frequency and average power frequency of the tapping leg in the lower limb muscles were greater than those of the swinging leg (except biceps femoris, tibialis anterior and lateral gastrocnemius), but the mean EMG and EMG integral values of the tapping leg were smaller than those of the swinging leg. At the stand phase, the median frequency and average power frequency of the tapping leg in the lower limb muscles were greater than those of the swinging leg (except tibialis anterior), but the mean EMG and EMG integral values of the tapping leg were smaller than those of the swinging leg (except soleus). At the swing phase, the median frequency and average power frequency of the tapping leg in the lower limb muscles were greater than those of the swinging leg (except tibialis anterior and lateral gastrocnemius), but the mean EMG and EMG integral values of the tapping leg were smaller than those of the swinging leg (except soleus). To conclude, there are different degrees of differences in the frequency domain and time domain of the lower limb muscles between tapping and swinging legs. Additionally, the muscle strength of the tapping leg is less than that of the swinging leg. © 2017, Journal of Clinical Rehabilitative Tissue Engineering Research. All rights reserved.     

Atlas of the muscle motor points for the lower limb: implications for electrical stimulation procedures and electrode positioning

The aim of the study was to investigate the uniformity of the muscle motor point location for lower limb muscles in healthy subjects. Fifty-three subjects of both genders (age range: 18–50 years) were recruited. The muscle motor points were identified for the following ten muscles of the lower limb (dominant side): vastus medialis, rectus femoris, and vastus lateralis of the quadriceps femoris, biceps femoris, semitendinosus, and semimembranosus of the hamstring muscles, tibialis anterior, peroneus longus, lateral and medial gastrocnemius. The muscle motor point was identified by scanning the skin surface with a stimulation pen electrode and corresponded to the location of the skin area above the muscle in which an electrical pulse evoked a muscle twitch with the least injected current. For each investigated muscle, 0.15 ms square pulses were delivered through the pen electrode at low current amplitude (<10 mA) and frequency (2 Hz). 16 motor points were identified in the 10 investigated muscles of almost all subjects: 3 motor points for the vastus lateralis, 2 motor points for rectus femoris, vastus medialis, biceps femoris, and tibialis anterior, 1 motor point for the remaining muscles. An important inter-individual variability was observed for the position of the following 4 out of 16 motor points: vastus lateralis (proximal), biceps femoris (short head), semimembranosus, and medial gastrocnemius. Possible implications for electrical stimulation procedures and electrode positioning different from those commonly applied for thigh and leg muscles are discussed.     

基于表面肌电分析老年人负重跨障行走跌倒风险

目的研究老年人在手部不同负重分布条件下跨越障碍物时导致跌倒风险性增加的因素,并探讨预防老年人在负重跨障时跌倒的步态策略。方法 12名老年人和12名青年人(对照组)以日常行走步速在不同负重分布方式下进行跨越障碍物和无障碍物行走任务,采集股外侧肌、股直肌和股内侧肌双侧的表面肌电信号,进行平均肌电值分析对比,同时记录受试者跨越障碍时触碰障碍物的情况。结果年龄、负重及跨障因素均对老年人下肢肌肉的活动水平产生显著影响。1 152次跨障试验中共发生9次触障事件。另外,老年人和青年人在完成负重和跨障任务时右股内侧肌的肌肉贡献量最大。结论老年人在负重物均匀分布下利用腿部优势侧率先跨障的情况下跌倒的风险性最低。研究结果为系统评估老年人跌倒风险提供参考,对老年人针对性下肢运动锻炼或康复训练具有一定的指导意义。     

Alternate leg movement amplifies locomotor-like muscle activity in spinal cord injured persons

It is now well recognized that muscle activity can be induced even in the paralyzed lower limb muscles of persons with spinal cord injury (SCI) by imposing locomotion-like movements on both of their legs. Although the significant role of the afferent input related to hip joint movement and body load has been emphasized considerably in previous studies, the contribution of the "alternate" leg movement pattern has not been fully investigated. This study was designed to investigate to what extent the alternate leg movement influenced this "locomotor-like" muscle activity. The knee-locked leg swing movement was imposed on 10 complete SCI subjects using a gait training apparatus. The following three different experimental conditions were adopted: 1) bilateral alternate leg movement, 2) unilateral leg movement, and 3) bilateral synchronous (in-phase) leg movement. In all experimental conditions, the passive leg movement induced EMG activity in the soleus and medial head of the gastrocnemius muscles in all SCI subjects and in the biceps femoris muscle in 8 of 10 SCI subjects. On the other hand, the EMG activity was not observed in the tibialis anterior and rectus femoris muscles. The EMG level of these activated muscles, as quantified by integrating the rectified EMG activity recorded from the right leg, was significantly larger for bilateral alternate leg movement than for unilateral and bilateral synchronous movements, although the right hip and ankle joint movements were identical in all experimental conditions. In addition, the difference in the pattern of the load applied to the leg among conditions was unable to explain the enhancement of EMG activity in the bilateral alternate leg movement condition. These results suggest that the sensory information generated by alternate leg movements plays a substantial role in amplifying the induced locomotor-like muscle activity in the lower limbs.     

The effect of long-term immobilization on the motor unit population of the cat medial gastrocnemius muscle

The properties of medial gastrocnemius and soleus muscles and of individual medial gastrocnemius motor units were evaluated after chronic (3–29 weeks) unilateral immobilization of ankle and knee joints in 10 adult female cats. Joint fixation markedly impaired the mobility of the pinned limb and, when prolonged (> 17 weeks; 8 animals), produced marked muscle atrophy and some shortening of whole muscle isometric twitch contraction times (mean contraction time of pinned medial gastrocnemius was 83.3 percent of the contralateral muscle). However, the immobilized muscles were not truly disused, since the patterns of medial gastrocnemius and soleus electromyographic activity during posture and locomotion were qualitatively normal in the 4 animals examined. Despite severe whole muscle atrophy, all but 3 of the 239 individual medial gastrocnemius motor units studied were readily classified into one of the 4 motor unit types (types FF, F(int), FR and S) found in the normal muscle. The histochemical mosaic of immobilized muscles was also the same as in contralateral unoperated muscles. When compared to data from normal cats, there was a highly significant loss of maximum twitch and tetanic force output in all unit types after long-term immobilization (17–29 weeks; N = 187), most marked among the fatigue-resistant unit groups (types FR and S), and mean isometric twitch contraction times were shorter than expected in all unit type groups. The most surprising finding in the present work was that the mean homonymous (medial gastrocnemius) and heteronymous (lateral gastrocnemius-soleus) group Ia excitatory postsynaptic potentials were significantly smaller than expected in all motor unit groups in both short-term and long-term immobilization. The mean axonal conduction velocity of medial gastrocnemius motor axons was unchanged from the normal sample.These results indicate that the essential features that define the motor unit types in normal medial gastrocnemius muscles are resistant to change despite long-term immobilization. We conclude that the motor units types found in normal muscles are robust and essentially unaltered despite severe muscle atrophy. The effects on group Ia excitatory postsynaptic potentials suggest that limb immobilization produces altered patterns of impulse traffic in group Ia afferents that induce significant decreases in synaptic efficacy, although it is unclear whether or not Ia traffic is increased or decreased by immobilization.