慢性踝关节不稳对膝关节肌群的影响

目的 探究慢性踝关节不稳(chronic ankle instability, CAI)患者踝关节肌力缺失对患侧和健侧膝关节肌群的影响。 方法 建立健康受试者和 CAI 患者逆向动力学模型,通过改变肌肉最大等长收缩力模拟不同程度踝关节肌力缺失,分析步态周期中膝关节峰值肌力和累积肌力的改变规律。 结果 CAI 患者跖屈肌肌力缺失会同时影响患侧和健侧的股四头肌与腘绳肌,背屈肌肌力缺失主要影响患者患侧和健侧的腘绳肌。 CAI 患者患侧和健侧膝关节肌群肌肉累积负荷增大,不同踝关节肌力缺失模型都呈现出患侧股四头肌累积负荷大于健侧,健侧腘绳肌累积负荷大于患侧的规律。 结论 CAI 不仅会影响患者患侧膝关节肌群的肌力,也会影响患者健侧膝关节肌群的肌力。增强踝关节的肌肉力量和保护双侧膝关节肌肉可能对 CAI 康复具有积极的作用。     

偏瘫患者步态特征的动力学仿真分析

目的研究偏瘫步态特征与下肢异常肌力之间的内在关系,阐明导致偏瘫步态的肌力原因并为临床治疗提供建议。方法以偏瘫步态和正常步态为研究对象进行建模仿真,通过正常步态下仿真模型与实测数据对比验证模型有效性,对两种模型的运动学数据、地面反作用力(ground reaction force,GRF)及肌力等特征曲线进行差异分析。结果 LifeMOD仿真结果与测力台实测GRF曲线复相关系数为0.922,动力学模型合理有效。偏瘫步态患者初始着地期胫前肌肌力小导致踝关节背屈不足,摆动前期腓肠肌肌力小,起不到蹬离推动作用。结论胫前肌、腓肠肌软弱无力是偏瘫患者出现足下垂等偏瘫步态特征的主要原因,LifeMOD建模仿真可协助诊断偏瘫患者的异常肌力。     

踝关节等速肌力训练对老年脑卒中患者平衡功能的影响

目的　探讨应用等速肌力训练加强踝关节屈伸肌群的肌力,对老年脑卒中患者平衡功能的影响。 方法　选取40例老年脑卒中患者随机分为对照组（n=20）、治疗组（n=20）,对照组接受常规康复治疗,治疗组在对照组基础上,增加针对踝关节背伸与跖屈肌群的等速肌力训练。2组患者治疗前和治疗3周后均进行Berg平衡量表（Berg balance scale, BBS）;“起立-走”计时测试（Timed up and go test, TUGT）;以及ProKin平衡仪的评估,参数包括Y-COP标准差、运动轨迹长度、运动轨迹面积、踝关节背伸与跖屈肌群的等速峰力矩等平衡功能相关指标的测量。 结果　2组患者经过平衡训练后,平衡功能的各项指标均较治疗前有改善(P<0.05）;治疗组患者治疗后平衡功能与对照组比较,各项评估指标均优于对照组(P<0.05）。 结论　踝关节等速肌力训练,可以明显改善老年脑卒中患者踝关节背伸与跖屈肌群的肌力及平衡功能。     

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。     

有跌倒史老年人坐立运动过程中的肌肉协同分析

目的 探讨有跌倒史的老年人坐立运动中肌肉募集机制是否发生变化。方法 招募17名健康年轻人、17名健康老年人及9名有跌倒史的老年人,采集右下肢16块肌肉的表面肌电信号(sEMG)和足底压力中心(COP)轨迹,使用Falls Efficacy Scale-International(FES-I)评估跌倒风险,通过非负矩阵分解(NNMF)提取肌肉协同。结果 3组在肌肉协同数量上无显著差异。有跌倒史老年人坐立运动初期,提前激活腘绳肌和踝关节跖屈肌,在运动的后期,这种提前激活转变为额外的肌肉活动,与健康组形成对比。此外,COP偏移量和FES-I评分显著增加,指示运动稳定性不足。结论 坐立运动中有跌倒史老年人腘绳肌和踝关节跖屈肌的异常激活可能影响下肢稳定和肌肉募集策略的改变。     

脑瘫儿童下肢肌电信号和踝关节角度特性分析

分析脑瘫儿童下肢肌电信号复杂度特性和行走过程中踝关节跖屈角度和背伸角度大小特性,指导医生选择合适的治疗和康复措施。选择2014年6~7月间深圳市残疾人辅助器具资源中心的脑瘫儿童25例,患者下肢均异常,患者及家长自愿完成实验。25例脑瘫儿童年龄2~8岁,平均(5.44±1.85)岁,平均身高(108.44±13.39)cm,平均体质量(18.24±5.46)kg。受试者沿着5 m步态平台以自己最为舒适的步速行走,采用美国BIOPAC公司的MP150数据采集分析系统,获得下肢腓肠肌和胫骨前肌的表面肌电信号,采用加速度传感器记录踝关节角度参数,采用Footscan足底压力系统记录患儿足底压力参数,并在测试前由专业医师进行粗大运动功能测试。采用SPSS19.0软件对数据进行统计学分析。结果显示行走过程中脑瘫患儿下肢严重侧腓肠肌和胫骨前肌肌电信号平均样本熵分别为1.78和1.76,而较轻侧腓肠肌和胫骨前肌肌电信号平均样本熵分别为1.45和1.39,表明严重侧肌肉参加运动的运动单元数量比较轻侧有所增加。严重侧踝关节跖屈和背伸运动的角度峰值平均值分别为49.89°和-5.29°,而较轻侧踝关节跖屈和背伸运动的角度峰值平均值分别为54.28°和-8.20°,表明严重侧比较轻侧踝关节角度小。脑瘫患儿足底压力分布不均匀,足弓部位压力分布最大,并且足跟触地初期、足前部触地期、整足支撑期和足前部蹬离期时间依次呈增长趋势。     

一种刚度可调的前置式足下垂矫形器研制

目的 针对足下垂步态患者,设计一种刚度可调的前置式踝足矫形器(ankle foot orthosis, AFO),实现对患者踝关节病态跖屈的最佳限制以恢复踝关节自然步态的目的。方法 通过自制实验装置测得10名18～55岁肌肉无力导致足下垂男性患者畸形矫正所需的最小矫治力矩,应用于AFO材料选择。通过力学拉伸实验,研究不同填充结构及填充率参数和弹性模量的关系。选取1名典型性足下垂患者,以其足部几何数据和优选的填充材料和填充结构3D打印快速制作出贴合患者足部形状的前置式AFO,进行赤足和穿戴两种AFO(前置式刚性和前置式柔性)情况下运动学和跖屈肌群表面肌电的测试,验证AFO对跖屈最佳限制的有效性和踝关节外翻、跖屈功能保留的程度。结果 10位足下垂患者所需的最小矫正力矩为2.16 N·m。相比前置式刚性AFO,穿戴前置式柔性AFO时,踝关节跖屈活动度增加67.8%;内外翻活动度增加88.6%;负责跖屈功能的比目鱼肌、腓肠肌内侧头和腓肠肌外侧头激活程度也分别减少38.3%、46.6%和55.8%。结论 该刚度可调式AFO可用于足下垂患者的个性化矫形定制,具备更有效、更适合日常长期使用的矫形功能...     

踝足矫形器人机耦合仿真刚度对步态生物力学影响的评价方法

目的 为更好评价踝足矫形器(ankle-foot orthosis, AFO)的人机工效,提出一种 AFO 人机耦合仿真刚度对步态生物力学影响的评价方法。 方法 首先,评测两种 AFO 的力学特性并量化其刚度;其次,采集 30 名受试者在正常与穿戴两种不同刚度 AFO 行走条件下的运动学及动力学数据;最后,通过仿真计算,定量对比分析 AFO 刚度对 行走中下肢关节角度、关节力矩与肌肉力的影响。 结果 在穿戴两种刚度 AFO 情况下,支撑相踝关节背屈峰值角度、膝关节屈曲峰值角度和髋关节伸展峰值角度均显著增加(P<0. 05),比目鱼肌与腓肠肌峰值肌肉力呈现增加趋势。 踝关节跖屈峰值角度、髋关节屈曲峰值角度与髋关节屈曲峰值力矩均显著降低(P<0. 05)。 结论 本文所提出的 AFO 人机耦合仿真方法可以有效实现不同刚度对步态生物力学影响的定量评估,该方法同样也适用于评估和优化其他辅助器具的人机工效,可以为 AFO 的选配、适配、优化设计提供方法指导。     

新式屈髋肌力训练机在轻重阻力下对下肢肌电与运动范围的影响

目的探讨新式屈髋肌力训练机在轻、重阻力情况下对下肢肌肉兴奋程度与运动范围的影响。方法 6位志愿者在屈髋肌力训练机台上,随机在轻或重阻力条件下进行连续30次的上提与下摆动作,并同时采集运动过程中的肌肉兴奋程度与下肢运动范围。结果肌肉兴奋程度方面,在连续30次动作过程中,重阻力在腹直肌、屈髋肌、臀大肌、股直肌和股二头肌的兴奋程度皆显著高于轻阻力(P<0.05);重阻力在腹直肌、屈髋肌和股直肌后3次的兴奋程度皆显著高于前3次(P<0.05);轻阻力情况下,只有竖脊肌以及股直肌最后3次的兴奋程度显著高于前3次(P<0.05)。运动范围方面,重阻力情况下的动作范围与下摆角度显著小于轻阻力(P<0.05)。结论新式屈髋肌力训练机无论是在轻或重阻力条件下,都能在髋关节合理的活动范围内刺激屈与伸髋主动肌群以及周边协同肌群来完成动作,特别是相对较重阻力的条件下。     

意外滑动过程中人体下肢关节与肌群的自主平衡调节作用研究

针对受扰条件下的步态失稳现象,国内外学者已做了一定的研究工作,但有关失稳过程中自主平衡行为与表面肌电信号及步态参数之间的表征关系却鲜有涉及。本文将步态分析与肌电信号分析相结合,研究在水平步道行走时,足跟着地后发生意外滑动的情况下,人体下肢关节和肌群的自主平衡调节机制。本文募集10位健康受试者,统一着鞋,采集分析了在干燥步道和油面步道两种不同行走条件下的下肢关节力矩、关节角度和主要参与肌群表面肌电信号等参数的变化规律。研究表明:发生意外滑动时人体通过增大踝关节背屈力矩、髋关节和膝关节伸直力矩与膝关节伸直角度,并及时调整相关肌肉激活延迟时间(依次激活胫骨前肌→股直肌→腓肠肌→股二头肌)来调节身体重心位置以维持平衡、避免滑倒。本文的研究结果可为防止滑跌损伤、康复训练以及下肢助行装置的研发等领域开拓新的思路并提供一定参考价值。     

Power output and work in different muscle groups during ergometer cycling

Summary The aim of this study was to calculate the magnitude of the instantaneous muscular power output at the hip, knee and ankle joints during ergometer cycling. Six healthy subjects pedalled a weight-braked bicycle ergometer at 120 watts (W) and 60 revolutions per minute (rpm). The subjects were filmed with a cine camera, and pedal reaction forces were recorded from a force transducer mounted in the pedal. The muscular work at the hip, knee and ankle joint was calculated using a model based upon dynamic mechanics described elsewhere. The mean peak concentric power output was, for the hip extensors, 74.4 W, hip flexors, 18.0 W, knee extensors, 110.1 W, knee flexors, 30.0 W and ankle plantar flexors, 59.4 W. At the ankle joint, energy absorption through eccentric plantar flexor action was observed, with a mean peak power of 11.4 W and negative work of 3.4 J for each limb and complete pedal revolution. The energy production relationships between the different major muscle groups were computed and the contributions to the total positive work were: hip extensors, 27%; hip flexors, 4%; knee extensors, 39%; knee flexors, 10%; and ankle plantar flexors 20%.     

Segmental reflexes and ankle joint stiffness during co-contraction of antagonistic ankle muscles in man

The size of soleus H-reflexes and short-latency stretch reflexes was measured at different levels of plantar flexion or co-contraction (simultaneous activation of dorsi- and plantar flexors) in seven healthy subjects. In four of seven subjects the short-latency stretc reflex was smaller during weak co-contraction than during isolated plantar flexion at matched background electromyogram (EMG) levels in the soleus muscle. In three of these four subjects the stretch reflex was larger during strong co-contraction than during plantar flexion, whereas it had the same size during the two tasks in the last subject. In the remaining subjects the stretch reflex either had the same size or was larger at all levels of co-contraction than at similar levels of plantar flexion. In contrast, the H-reflex was found to decrease with co-contraction at all contraction levels in all subjects. The decrease in the reflexes during weak co-contraction might be caused by presynaptic inhibition of Ia afferents. It is unclear why only the H-reflex decreased during strong co-contraction. The stiffness of the ankle joint was measured from the torque increment following the stretch of the plantar flexors divided by the stretch amplitude. In all subjects the total stiffness of the ankle joint was larger during strong co-contraction than during plantar flexion of similar strength. The stiffness was smaller during weak co-contraction than during weak plantar flexion in three out of seven subjects. The medial gastrocnemius muscle was more active at a given level of soleus activity during the co-contraction task than during the isolated plantar flexion task. It is suggested that the increase in the stiffness during co-contraction as compared to isolated plantar flexion was mainly due to the mechanical contribution of the activity in the tibialis anterior and medial gastrocnemius muscles. The decrease in stiffness during weak co-contraction was, in contrast, most likely mainly caused by modulation of reflex stiffness.     

The potential of human toe flexor muscles to produce force

The maximal force a muscle produces depends among others on the length of the muscle and therefore on the positions of the joints the muscle crosses. Long and short toe flexor muscles (TFM) cross the ankle joints and metatarsal phalangeal joints (MPJ) and work against gravity during human locomotion. The purpose of this study was to describe the maximal moments around the MPJ during maximal voluntary isometric contractions (MVIC) of the TFM as a function of ankle joint and MPJ position. Twenty men performed MVIC of the TFM in a custom-made dynamometer. Ankle and MPJ angles were modified after each contraction. External moments of force around the MPJ were determined. Moments ranged between 6.3 ± 2.6 Nm and 14.2 ± 5.8 Nm. Highest moments were produced at 0°-10° ankle joint dorsal flexion and 25°-45° MPJ dorsal flexion. Lowest moments were generated at 35° ankle joint plantar flexion and 0° MPJ dorsal flexion. In conclusion, if the ankle is plantar-flexed, dorsal flexion of the MPJ avoids a disadvantage of the force-length relationship of TFM. Therefore, MPJ dorsal flexion is a necessary function in the push-off phase of human locomotion to work against the loss of the mechanical output at the forefoot caused by plantar flexion of the ankle.     

Accurate assessment of in situ isometric contractile properties of hindlimb plantar and dorsal flexor muscle complex of intact mice

An isometric torque sensor for measuring in situ contractions of plantar or dorsal flexors of intact mouse hindlimb has been developed and evaluated. With this device, muscle torque can be accurately measured within the range of -14 mN.m to +14 mN.m. Special attention was paid to fixation of the mouse hindlimb to the measurement device. Halothane-anaesthetized Swiss wild-type mice were positioned on the thermostatic measurement platform, and fixated with a hip and foot fixation system. The novel fixation unit was evaluated by measuring knee and ankle displacements during a contraction. A mathematical muscle model was used to quantify the effects of these displacements on the contractile parameters. Measured ankle and knee displacement, due to non-absolute fixation. resulted in a calculated muscle fibre shortening of 2.5%. Simulations of a contraction with this degree of fibre shortening, using the mathematical muscle model, showed only minor effects on maximal torque generation and the temporal parameters (half-relaxation time and 10-50% rise time). Furthermore, we showed that muscle torque in our set-up is hardly affected by eccentricity between ankle and measurement axis. Measured tetanic muscle torques of intact dorsal and plantar flexors were 3.2+/-0.4 mN.m and 11.8+/-1.6 mN.m, respectively. The half-relaxation time of plantar flexors was significantly higher than that of dorsal flexors (12.9+/-2.7 ms versus 8.8+/-1.2 ms), whereas the 10-50% rise time was longer in plantar (14.9+/-0.6 ms) than in dorsal (11.8+/-2.0 ms) flexors.     

Muscle moment arms of pelvic limb muscles of the ostrich (Struthio camelus)

Muscle moment arms were measured for major muscles of the pelvic limb of the ostrich (Struthio camelus) in order to assess specific functional behaviour and to apply this to locomotor performance. Pelvic limbs of six juvenile ostriches were used for this study. The tendon travel technique was used to measure moment arms of 21 muscles at the hip, knee, ankle and metatarsophalangeal joints throughout the ranges of motion observed during level running. Six of the 21 muscles measured were found to have moment arms that did not change with joint angle, whilst the remainder all demonstrated angle-dependent changes for at least one of the joints crossed. Moment arm lengths tended to be longest for the large proximal muscles, whilst the largest relative changes were found for the moment arms of the distal muscles. For muscles where moment arm varied with joint angle: all hip muscles were found to have increasing moment arms with extension of the joint, knee flexors were found to have moment arms that increased with extension, knee extensor moment arms were found to increase with flexion and ankle extensor moment arms increased with extension. The greatest relative changes were observed in the flexors of the metatarsophalangeal joint, for which a three-fold increase in moment arm was observed from flexion to full extension. Changes in muscle moment arm through the range of motion studied appear to optimize muscle function during stance phase, increasing the effective mechanical advantage of these muscles.     

In situ assessment of shortening and lengthening contractile properties of hind limb ankle flexors in intact mice

The availability of animal models with disrupted genes has increased the need for small-scale measurement devices. Recently, we developed an experimental device to assess in situ mechanical properties of isometric contractions of intact muscle complexes of the mouse. Although this apparatus provides valuable information on muscle mechanical performance, it is not appropriate for determining contractile properties during shortening and lengthening contractions. In the present study we therefore developed and evaluated an experimental apparatus for assessment of shortening and lengthening contractile properties of intact plantar and dorsal flexors of the mouse. The current through a custom-built, low-inertia servomotor was measured to assess contractile muscular torque ranging from -50 to mN.m. Evaluation of the fixation procedure of the animal to the apparatus via 3-D monitoring of the muscle-tendon complex length showed that the additional shortening in length due to a contraction with maximal torque output has only minor effects on the measured torque. Furthermore, misalignment of the axis of rotation of the apparatus relative to the axis of rotation in the ankle joint, i.e. eccentricity, during a routine experiment was estimated to be less than 1.0 mm and hence did not influence the measured torque output under our experimental conditions. Peak power per unit muscle mass (mean +/- SD) of intact dorsal and plantar flexors was 0.27 +/- 0.02 and 0.19 +/- 0.03 W.g-1, respectively. The angular velocity at maximal peak power generated by the dorsal flexor complex and the plantar flexor complex was 1100 +/- 190 and 700 +/- 90 degrees.s-1, respectively.     

Effect of ankle-foot orthosis on active ankle moment in patients with hemiparesis

The paper investigates the effect of dorsi/plantar rigidity and the initial angle of ankle-foot orthoses (AFOs) on the moment generated by ankle musculature (referred to as active ankle moment) during gait in patients with hemiparesis. In the early stance phase, the active ankle moment in the direction of dorsiflexion is negligible, and AFOs play an important role in supplementing weak dorsiflexion. In mid to late stance, the moment generated by AFOs is very small compared with the active ankle moment in the direction of plantarflexion. AFOs therefore play only a limited role in assisting plantar flexors during this period. The active ankle moment in the direction of plantarflexion varies significantly with changes in the rigidity and initial angle of AFOs in 11 out of 20 subjects. The implication of this finding is discussed in relation to the need for dynamic matching of AFOs in individual patients with hemiparesis.     

Angle dependency in strength measurements of the ankle plantar flexors

Summary Muscle strength (or muscular moment) generated during dynamic contractions varies with joint angle. This raises the question about the choice of a representative angle in the evaluation of strength capacity. To assess this angle dependency in strength measurements, dynamic moment-angle curves for plantar flexor muscles were obtained in 43 healthy subjects (28 men and 15 women) with a controlled acceleration dynamometer at 0.52 rad s^–1 (30° s^–1) and using maximal static preloading before the beginning of movement to attenuate the force development phase. Differences between gender and correlations between strength and anthropometric measures were calculated at each 0.087 rad (5°). The plantar flexion moment was larger in men, in general, but this difference was largest when the ankle was most dorsiflexed. The correlations between moment and anthropometric measures were also higher in the first half of the plantar flexion movement. These results stress the importance of reporting joint angles at which moment of force measures were made. Furthermore, they show that the maximal strength capacity of the plantar flexors is best represented by the moment measured in dorsiflexion angles when the muscles are lengthened.     

Withdrawal reflex organisation to electrical stimulation of the dorsal foot in humans

The present study investigated excitatory reflex receptive fields for various muscle reflex responses and reflex mediated ankle joint movements using randomised electrical stimulation of the dorsal and plantar surface of the foot in 12 healthy subjects. Eleven electrodes (0.5-cm2 cathodes) were mounted on the dorsal side and three on the plantar side of the foot. A low (1.5 times pain threshold) and a high (2.3 times pain threshold) stimulus intensity were used to elicit the reflexes. EMG signals were recorded from tibialis anterior (TA), gastrocnemius medialis (GM), soleus (SO), biceps femoris (BF), and rectus femoris (RF) muscles together with the ankle movement measured by a goniometer. The withdrawal pattern evoked from the dorsal side consisted of two separate responses with different receptive fields: (1) early EMG responses in GM and BF (50-120 ms) evoking knee flexion, probably of purely spinal origin, and (2) a late response in GM and SO (120-200 ms) that may be under supraspinal control. The ankle flexor TA was significantly activated in both time windows, but in 11 of 12 subjects its contraction was too small to cause significant dorsal flexion. In the ankle joint inversion was the most dominant movement. Stimulation of the plantar side resulted in activation of TA when stimulating the forefoot and in activation of triceps surae when stimulating the heel. These observations show that painful stimuli activate appropriate muscles depending on stimulus location to initiate the adequate withdrawal. For proximal muscles (e.g. knee flexors) the receptive field covers almost the entire foot (dorsal and plantar sides) while more distal muscles have a smaller receptive field covering only a part of the foot. This adequate withdrawal movement suggests a more refined withdrawal reflex organisation than a stereotyped flexion of all joints to avoid tissue damage.