Foot trajectory approximation using the pendulum model of walking

Generating a natural foot trajectory is an important objective in robotic systems for rehabilitation of walking. Human walking has pendular properties, so the pendulum model of walking has been used in bipedal robots which produce rhythmic gait patterns. Whether natural foot trajectories can be produced by the pendulum model needs to be addressed as a first step towards applying the pendulum concept in gait orthosis design. This study investigated circle approximation of the foot trajectories, with focus on the geometry of the pendulum model of walking. Three able-bodied subjects walked overground at various speeds, and foot trajectories relative to the hip were analysed. Four circle approximation approaches were developed, and best-fit circle algorithms were derived to fit the trajectories of the ankle, heel and toe. The study confirmed that the ankle and heel trajectories during stance and the toe trajectory in both the stance and the swing phases during walking at various speeds could be well modelled by a rigid pendulum. All the pendulum models were centred around the hip with pendular lengths approximately equal to the segment distances from the hip. This observation provides a new approach for using the pendulum model of walking in gait orthosis design.     

机器人模式设计对脊髓损伤患者步态的影响

背景：治疗师帮助的减重运动平板训练方法是一种效果较好的步态训练方法,但因其对治疗师体力消耗较大,且人员需要较多,临床应用受到一定限制。机器人帮助的减重运动平板训练受到广泛关注。 目的：总结机器人在脊髓损伤患者步态康复中的作用及其对下肢运动及肌肉活动模式的影响。 方法：由第一作者检索PubMed数据库(http://www.ncbi.nlm.nih.gov/PubMed)1995-01/2010-12涉及机器人、Lokomat、减重运动平板训练及脊髓损伤步态康复内容的文献,英文关键词为“spinal cord injury,gait,walking,locomotor,locomotion,rehabilitation,robot,robotic,Lokomat ”,排除陈旧性、重复性文献,保留30篇文献归纳总结。 结果与结论：虽然到时目前为止还没有证据证明机器人运动训练方法优越于其他方法,但其在脊髓损伤康复领域的应用也有明显的优势。机器人设备对下肢运动的被动引导及固定步行模式的重复训练不利于患者最大自主肌力的发挥及步行循环周期之间的变动,不能做到治疗师那样敏感地感受患者的运动表现。治疗师只有全面了解机器人设备并根据患者的运动能力不断调整训练参数,以致使患者在精确控制环境下最大限度地发挥自主运动能力,才能获得最佳的运动训练效果。     

Robot assisted treadmill training: mechanisms and training strategies

The rehabilitation engineering community is working towards the development of robotic devices that can assist during gait training of patients suffering from neurologic injuries such as stroke and spinal cord injuries (SCI). The field of robot assisted treadmill training has rapidly evolved during the last decade. The robotic devices can provide repetitive, systematic and prolonged gait training sessions. This paper presents a review of the treadmill based robotic gait training devices. An overview of design configurations and actuation methods used for these devices is provided. Training strategies designed to actively involve the patient in robot assisted treadmill training are studied. These training strategies assist the patient according to the level of disability and type of neurologic injury. Although the efficacy of these training strategies is not clinically proven, adaptive strategies may result in substantial improvements. We end our review with a discussion covering major advancements made at device design and training strategies level and potential challenges to the field.     

Robotic assistance that encourages the generation of stepping rather than fully assisting movements is best for learning to step in spinally contused rats

Robotic devices have been developed to assist body weight-supported treadmill training (BWSTT) in individuals with spinal cord injuries (SCIs) and stroke. Recent findings have raised questions about the effectiveness of robotic training that fully assisted (FA) stepping movements. The purpose of this study was to examine whether assist-as-needed robotic (AAN) training was better than FA movements in rats with incomplete SCI. Electromyography (EMG) electrodes were implanted in the tibialis anterior and medial gastrocnemius hindlimb muscles of 14 adult rats. Afterward, the rats received a severe midthoracic spinal cord contusion and began daily weight-supported treadmill training 1 wk later using a rodent robotic system. During training, assistive forces were applied to the ankle when it strayed from a desired stepping trajectory. The amount of force was proportional to the magnitude of the movement error, and this was multiplied by either a high or low scale factor to implement the FA (n = 7) or AAN algorithms (n = 7), respectively. Thus FA training drove the ankle along the desired trajectory, whereas greater variety in ankle movements occurred during AAN training. After 4 wk of training, locomotor recovery was greater in the AAN group, as demonstrated by the ability to generate steps without assistance, more normal-like kinematic characteristics, and greater EMG activity. The findings suggested that flexible robotic assistance facilitated learning to step after a SCI. These findings support the rationale for the use of AAN robotic training algorithms in human robotic-assisted BWSTT.     

Contribution of feedback and feedforward strategies to locomotor adaptations

The aim of this study was to examine the strategies used by human subjects to adapt their walking pattern to a velocity-dependent resistance applied against hip and knee movements. Subjects first walked on a treadmill with their lower limbs strapped to an exoskeletal robotic gait orthosis with no resistance against leg motions (null condition). Afterward, a velocity-dependent resistance was applied against left hip and knee movements (force condition). Catch trials were interspersed throughout the experiment to track the development of adaptive changes in the walking pattern. After 188 steps in the force condition, subjects continued to step in the null condition for another 100 steps (washout period). Leg muscle activity and joint kinematics were recorded and analyzed. The adaptive modifications in the locomotor pattern suggest the involvement of both feedback and feedforward control strategies. Feedback-driven adaptations were reflected in increases in rectus femoris and tibialis anterior activity during swing, which occurred immediately, only in the presence of resistance, and not during the catch trials. Locomotor adaptations involving feedforward strategies were reflected in enhanced pre-swing activity in the biceps femoris and medial hamstrings muscles, which required experience and persisted in the catch trials. During washout subjects showed a gradual deadaptation of locomotor activity to control levels. In summary, adaptive changes in the walking pattern were driven by both feedback and feedforward adjustments in the walking pattern appropriate for overcoming the effects of resistance.     

A knee and ankle flexing hybrid orthosis for paraplegic ambulation

Limitations of mechanical walking orthoses for paraplegics are high energy consumption and upper limb loading. Flexing of the knee during swing phase has been used as a means of attempting to reduce these. It has been found that this has little effect because using knee flexion results in no change in the compensatory mechanisms required for swing foot clearance. This is because knee flexion can result in an increase in effective leg length, i.e. hip to toe distance. A combination of knee flexion and ankle dorsiflexion during swing phase is suggested as a means of reducing compensatory mechanisms. To examine this hypothesis, an orthosis incorporating knee and ankle flexion was constructed. The design used a novel mechanism to link the motion of the knee to that of the ankle, and also used functional electrical stimulation. Two spinal cord-injured subjects were trained to use the orthosis in two configurations. The first configuration used knee flexion and ankle dorsiflexion and the second configuration used knee flexion alone. Kinematic data were obtained to measure the compensatory mechanisms used during gait. The results showed that a combination of knee flexion and ankle dorsiflexion during swing phase resulted in a reduction in compensatory mechanisms when compared with knee flexion alone.     

Locomotor adaptations and aftereffects to resistance during walking in individuals with spinal cord injury

Muscle activity during the swing phase of walking is influenced by proprioceptive feedback pathways. Previous studies have shown that feedback and anticipatory motor commands contribute to locomotor adaptive strategies to prolonged exposure to a resistance against leg movements during walking. The purpose of this study was to determine whether people with motor-incomplete spinal cord injuries (SCI) modulate flexor muscle activity in response to different levels of resistance in a similar way as uninjured controls. A second purpose was to determine whether people with motor-incomplete SCI have the capacity to form anticipatory motor commands following exposure to resistance. Subjects walked on a treadmill with the Lokomat robotic gait orthosis. The Lokomat applied different levels of a velocity-dependent resistance, normalized to each subject's maximum voluntary contraction of the hip flexors. Each condition consisted of 20 steps against resistance followed by 20 steps without. Electromyography and kinematics of the lower limb were recorded. Although both groups responded to the resistance with an overall increase in rectus femoris activity during swing, the SCI group showed weak modulation of muscle activity to different levels of resistance. Following removal of the resistance, both groups showed aftereffects, but they were manifested differently. Controls responded to the removal of resistance with a high step, whereas the SCI subjects exhibited increased step length. The size of the aftereffect was related to the amount of added resistance. In addition, the SCI group showed a negative relationship between the size of the aftereffect and locomotor function.     

Motor balance and coordination training enhances functional outcome in rat with transient middle cerebral artery occlusion

The goal of this study was to determine if relatively complex motor training on Rota-rod involving balance and coordination plays an essential role in improving motor function in ischemic rats, as compared with simple locomotor exercise on treadmill.Adult male Sprague-Dawley rats with (n=40) or without (n=40) ischemia were trained under each of three conditions: (1) motor balance and coordination training on Rota-rod; (2) simple exercise on treadmill; and (3) non-trained controls. Motor function was evaluated by a series of tests (foot fault placing, parallel bar crossing, rope and ladder climbing) before and at 14 or 28 days after training procedures in both ischemic and normal animals. Infarct volume in ischemic animals was determined with Nissl staining.Compared with both treadmill exercised and non-trained animals, Rota-rod-trained animals with or without ischemia significantly (P<0.01) improved motor performance of all tasks except for foot fault placing after 14 days of training, with normal rats having better performance. Animals trained for up to 28 days on the treadmill did not show significantly improved function. With regard to foot fault placing task, performance on foot placing was improved in ischemic rats across the three measurements at 0, 14 and 28 days regardless of training condition, while the normal group reached their best performance at the beginning of measurement.No significant differences in infarct volume were found in rats trained either with Rota-rod (47+/-4%; mean+/-S.E.), treadmill (45+/-5%) or non-exercised control (45+/-3%). In addition, no obvious difference could be detected in the location of the damage which included the dorso-lateral portion of the neostriatum and the frontoparietal cortex, the main regions supplied by the middle cerebral artery.The data suggest that complex motor training rather than simple exercise effectively improves functional outcome.     

Parametric design of pressure-relieving foot orthosis using statistics-based finite element method

Custom-molded foot orthoses are frequently prescribed in routine clinical practice to prevent or treat plantar ulcers in diabetes by reducing the peak plantar pressure. However, the design and fabrication of foot orthosis vary among clinical practitioners and manufacturers. Moreover, little information about the parametric effect of different combinations of design factors is available. As an alternative to the experimental approach, therefore, computational models of the foot and footwear can provide efficient evaluations of different combinations of structural and material design factors on plantar pressure distribution. In this study, a combined finite element and Taguchi method was used to identify the sensitivity of five design factors (arch type, insole and midsole thickness, insole and midsole stiffness) of foot orthosis on peak plantar pressure relief. From the FE predictions, the custom-molded shape was found to be the most important design factor in reducing peak plantar pressure. Besides the use of an arch-conforming foot orthosis, the insole stiffness was found to be the second most important factor for peak pressure reduction. Other design factors, such as insole thickness, midsole stiffness and midsole thickness, contributed to less important roles in peak pressure reduction in the given order. The statistics-based FE method was found to be an effective approach in evaluating and optimizing the design of foot orthosis.     

截瘫步行器的仿生效果

背景：截瘫步行器的临床应用,使截瘫患者重建步行功能成为可能,但截瘫步行器只为进行步行康复训练及简单的行走,距离真正意义上的步行功能代偿相差还很远。 目的：对目前几种截瘫步行器的结构特点、作用机制及仿生效果进行归纳、分析。 方法：应用计算机检索1990-01/2008-12 PubMed数据库及万方数据库有关截瘫步行器的特点、仿生效果及临床应用方面的相关文献,英文检索词“reciprocation gait orthosis,walkabout,bionice”,中文检索词“截瘫步行器,仿生”。检索文献量总计32篇。 结果与结论：目前无动力截瘫步行器运用较广泛,但对截瘫患者来说,通常只为进行步行康复训练及简单的行走,距离真正意义上的步行功能代偿相差还很远。运用最广的往复式截瘫步行器和互动截瘫步行器这两种截瘫步行器仿生效果较差,步态严重失真,体能消耗大,而由外部能源补充能耗的步行器则可以克服无动力步行器的不足,随着人工智能技术在机器人和许多工业领域得到了广泛应用,它的发展可为患者提供性能优良,安全可靠,更具有仿生性的截瘫步行器产品。     

足部姿态变化对静态姿势稳定控制的即刻作用

背景：既往研究表明异常足部的姿态影响人体姿势控制能力,而足部姿态中立化可改善人体姿势控制能力,但机制不明。 目的：观察足部姿态中立化后即刻对健康成人静态站立姿势控制能力的影响。 方法：健康成人受试者30名,应用足部姿态指数评价足部姿态。测量小腿后足角评价受试者应用非特制足部矫形垫对其足部姿态的中立化的效果。非特质足部矫形垫采用VASYLI-HowardDananber^TM保健系列足部矫形垫。同时评测受试者改变足部姿态前后静态单腿站立姿势控制能力。静态单腿站立姿势控制能力应用电脑平衡仪(ACTIVE BALANCER EAB-100)测试。 结果与结论：应用非特制足垫后,足部姿态较前更趋中立化,差异有显著性意义。但单腿站立姿势控制能力没有显著变化。说明应用非特制足部矫形垫后可使轻度旋前的足部姿态中立化,但没有对姿势控制能力产生即刻影响。虽然足部姿态中立化对静态姿势控制具有远期效果,但其机制不单纯为改善足部力线结构,需要进一步的研究。     

胸段脊髓损伤患者应用截瘫步行矫形器对下肢康复的影响

背景：胸段脊髓损伤常导致双下肢截瘫,截瘫步行矫形器能帮助截瘫患者改善下肢功能障碍,提高日常生活活动能力,重获站立和行走能力。 目的：探讨截瘫步行矫形器对胸段脊髓损伤患者下肢肌肉痉挛及功能恢复的影响。 方法：将20例胸段脊髓(T5-12)损伤患者根据损伤平面按美国脊髓损伤协会(American Spinal Injury Association,ASIA)标准分为完全损伤组和不完全损伤组,各10例,均装配截瘫步行矫形器。分别于装配前进行残余肌力训练、坐位平衡训练、转移训练;装配后平行杆内站立训练、平衡及转移训练;室内、户外助行器、肘拐步行训练。 结果与结论：与治疗前相比,胸髓完全性损伤患者装配截瘫步行器治疗12周后ASIA评分增加,感觉无明显变化,痉挛随病程的延长而加重;不完全性损伤患者治疗12周后ASIA评分增加,感觉明显改善,痉挛随病程的延长无改变;两组患者日常生活活动能力(改良Barthel指数、功能独立性评测)有显著改善。与治疗2周时相比,治疗12周时2组患者10 m行走时间显著减少,6 min步行距离延长。说明胸段脊髓损伤患者装配截瘫步行器,能显著改善患者的运动功能、日常生活活动能力和步行能力,对肌痉挛控制也有一定的影响。 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     

Use and fabrication of temporary orthotics

Orthotics are effective for altering compensatory motions which result from abnormalities in the foot and lower extremity. In specific cases, temporary use of an orthosis is beneficial for reducing abnormal stresses while allowing involved structures to heal. Additionally, a temporary orthotic may provide a trial period to determine if the athlete would benefit from a permanent orthosis. A step-by-step procedure is presented for the fabrication of a temporary semirigid orthotic. Used as an adjunct to the treatment and rehabilitation program, temporary orthotics are effective in encouraging early weight-bearing tolerance, while placing the foot near the subtalar joint neutral position.     

Effect of sensory inputs on the soleus H-reflex amplitude during robotic passive stepping in humans

We investigated the modulation of the soleus (Sol) Hoffmann (H-) reflex excitability by peripheral sensory inputs during passive stepping using a robotic-driven gait orthosis in healthy subjects and spinal cord-injured patients. The Sol H-reflex was evoked at standing and at six phases during passive stepping in 40 and 100% body weight unloaded conditions. The Sol H-reflex excitability was significantly inhibited during passive stepping when compared with standing posture at each unloaded condition. During passive stepping, the H-reflex amplitude was significantly smaller in the early- and mid-swing phases than in the stance phase, which was similar to the modulation pattern previously reported for normal walking. No significant differences were observed in the H-reflex amplitude between the two unloaded conditions during passive stepping. The reflex depression observed at the early part of the swing phase during passive stepping might be attributed to the sensory inputs elicited by flexion of the hip and knee joints. The present study provides evidence that peripheral sensory inputs have a significant role in phase-dependent modulation of the Sol H-reflex during walking, and that the Sol H-reflex excitability might be less affected by load-related afferents during walking.     

Stretch reflex modulation during imposed static and dynamic hip movements in standing humans

The purpose of this study was to investigate the effects of hip proprioceptors on soleus stretch reflex excitability in standing humans. A custom-made device to stretch the ankle extensors was mounted on the lower leg portion of a gait orthosis and was used to elicit stretch reflex responses while standing. Six subjects with motor complete spinal cord injury (SCI) and six spinal intact subjects were placed in the orthosis, and stretch reflex responses were elicited when static and/or dynamic hip joint angle changes were imposed. We found that static hip extension significantly enhanced the stretch reflex responses as compared to the neutral position and the hip flexion position only in the SCI group. The EMG magnitude induced by hip extension was 142 ± 16.6% greater than that induced by the neutral position. When the leg was dynamically swung, the reflex responses also changed with the phase of the hip angle in the SCI group; in particular, the reflex amplitude was enhanced with hip extension and in the transition phase from flexion to extension. Although the magnitude of the changes was less than that in the SCI group, a similar type of modulation was found in the normal group. Given the fact that the persons with SCI had lost the neural connection between higher nervous center and the paralyzed lower limb muscles, the mechanism underlying the present results can be attributed to the peripheral afferent input due to the hip angle changes. We concluded that hip mediated afferent input has a significant influence on the excitability modulation of the soleus stretch reflex pathway. Such neural modulation may play a role in the mechanism responsible for the phase-dependent modulation of the stretch reflex while walking.     

Recovery of forward stepping in spinal cord injured patients does not transfer to untrained backward stepping

Six spinal cord injured (SCI) patients were trained to step on a treadmill with body-weight support for 1.5–3 months. At the end of training, foot motion recovered the shape and the step-by-step reproducibility that characterize normal gait. They were then asked to step backward on the treadmill belt that moved in the opposite direction relative to standard forward training. In contrast to healthy subjects, who can immediately reverse the direction of walking by time-reversing the kinematic waveforms, patients were unable to step backward. Similarly patients were unable to perform another untrained locomotor task, namely stepping in place on the idle treadmill. Two patients who were trained to step backward for 2–3 weeks were able to develop control of foot motion appropriate for this task. The results show that locomotor improvement does not transfer to untrained tasks, thus supporting the idea of task-dependent plasticity in human locomotor networks.R. Grasso died on 6 October 2000     

Contribution of cutaneous inputs from the hindpaw to the control of locomotion. II. Spinal cats

The goal of these experiments was to define the contribution of hindpaw cutaneous inputs in the expression of spinal locomotion in cats. In 3 cats, some (n = 1) or all (n = 2) cutaneous nerves were cut bilaterally at ankle level before spinalization. This denervation caused small deficits that were gradually compensated as reported in the companion study. After spinalization, the completely denervated cats never recovered plantar foot placement or weight bearing of the hindquarters despite more than 35 days of treadmill training. Although normal electromyographic rhythmic activity developed at the hip and knee, ankle flexors and extensors were abnormally coactivated during stance. In contrast, the partially denervated cat regained foot placement and weight support 15 days after spinalization. However, after completing the denervation, foot placement and weight bearing were lost as in previous cats. In a 4th cat, spinalization was performed before denervation and the cutaneous nerves were cut sequentially in the right hindlimb only. Rapid locomotor adaptation occurred after cutting the deep peroneal, saphenous, and sural nerves. Later, cutting the superficial peroneal nerve produced paw drag, which was compensated within 8 days. On cutting the last cutaneous nerve (tibial), plantar foot placement was lost despite another 71 days of training. On the one hand, these experiments show that some cutaneous inputs are necessary for appropriate plantar foot placement and weight bearing of the hindquarters during spinal locomotion and, on the other hand, that locomotor compensation to partial cutaneous denervation after spinalization reveals important adaptive capacities of the spinal cord.     

Exercise effects stress-induced analgesia and spatial learning in rats

Previous studies indicated that intensity level may be a determining factor in the beneficial or detrimental effects of exercise on spatial memory, as chronic low-intensity level exercise appears to enhance learning and memory which stressful situations may impair. This study examines the effects of different intensity levels of acute exercise (treadmill running) on spatial memory in rats. Using the Morris water maze, spatial learning was measured in animals exposed to treadmill running at low- (20-22 m/min for 25 min daily) and high-intensity (25 m/min for 25 min daily) levels of exercise. A stress control using an electric foot shock was used to examine if the high-intensity exercise was sufficient to serve as a stressor. Stress level was estimated by examining tail flick latencies as a measure of stress-induced analgesia. The results indicate that high-intensity exercise at a level that may not induce an analgesic state is sufficient to impair early acquisition of spatial learning. However, with additional trials, all animals are capable of learning the task. Acute exposure to the electric foot shock impaired learning in the Morris water maze. Surprisingly, across all studies, there was a significantly higher analgesic state post-swim as compared to pre-swim. The results indicate that irrespective of stress level prior to water maze testing, swimming in the Morris water maze repeatedly for short durations of time is enough to induce an analgesic state.     

Post-effect of forward and backward locomotion on body orientation in space during quiet stance

Neural circuits responsible for stance control serve other motor tasks as well. We investigated the effect of prior locomotor tasks on stance, hypothesizing that postural post-effects of walking are dependent on walking direction. Subjects walked forward (WF) and backward (WB) on a treadmill. Prior to and after walking they maintained quiet stance. Ground reaction forces and centre of foot pressure (CoP), ankle and hip angles, and trunk inclination were measured during locomotion and stance. In WF compared to WB, joint angle changes were reversed, trunk was more flexed, and movement of CoP along the foot sole during the support phase of walking was opposite. During subsequent standing tasks, WB induced ankle extension, hip flexion, trunk backward leaning; WF induced ankle flexion and hip extension. The body CoP was displaced backward post-WB and forward post-WF. The post-effects are walking-direction dependent, and possibly related to foot-sole stimulation pattern and trunk inclination during walking.     

不同材料矫形器的生物学性能

背景：矫形器通过力的作用以预防、矫正畸形,达到治疗骨骼、关节、肌肉和神经疾患并补偿其功能的效果。 目的：介绍了矫形器的分类,不同材料矫形器的性能及应用效果。 方法：以“矫形器,生物学性能,先天性马蹄内翻足,婴幼儿”为中文关键词,以“orthosis,Congenital Club Foot” 为英文关键词,采用计算机检索中国期刊全文数据库、PubMed数据库(1996-01/2010-12)相关文章。纳入与矫形器材料、以及先天性马蹄内翻足治疗相关内容的文献,排除重复研究或Meta分析类文章,共入选20篇文章进入结果分析。并回顾性分析应用低温热塑板或高温热塑板,根据3点力作用原理设计制作静态足踝矫形器或动态足踝矫形器,结合手法推拿等综合治疗婴幼儿先天性马蹄内翻足96例(106足)临床效果。 结果与结论：文章重点从矫形器的分类、矫形器的材料、矫形器的基本作用及临床验证几方面进行了叙述。目前常用的矫形器材料主要有金属材料(钢材和铝合金)、皮革、橡胶、塑料及各种纤维等。临床验证结果：随访1年优86例(93足);良8例(10足);可2例(3足)。提示选用高温热塑板制作成静态踝足矫形器或动态踝足矫形器治疗婴幼儿先天性马蹄内翻足早期效果满意。