170,677 research outputs found

    Evaluation of muscle synergies stability in human locomotion: A comparison between normal and fast walking speed

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    Motor control strategies can be described by muscle synergies, a model of functional muscle recruitment to perform a movement. However, stability of muscle synergies during locomotion has not yet been investigated. The objective of this work was the evaluation of the stability of muscle synergies while walking at normal (NS) and fast (FS) speed. Each walking condition was tested during a prolonged session lasting 5 minutes on five healthy subjects. After data processing with statistical gait analysis, 168±29 valid strides in NS and 181±48 in FS were obtained. They were aggregated in subgroups, with 10 strides each. Muscle synergies were extracted for all subgroups with non-negative matrix factorization. On the average, 6 synergies were suitable to reconstruct the original electromyographic signal. They were functionally correlated to the activities of propulsion, trunk stability, limb deceleration at the end of swing, forefoot control, and limb stiffening for initial contact stability. To compare muscle synergy stability over time, a similarity measurement was carried out. This showed that from 1 to 3 synergies were unstable in NS. As for the FS condition, only one subject showed unstable synergies, corresponding to the hip stabilizing synergy

    Severity of degenerative lumbar spinal stenosis affects pelvic rigidity during walking

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    To understand the role of compensation mechanisms in the development and treatment of symptomatic degenerative lumbar spinal stenosis (DLSS), pelvic stability during walking should be objectively assessed in the context of clinical parameters.; To determine the association among duration of symptoms, lumbar muscle atrophy, disease severity, pelvic stability during walking, and surgical outcome in patients with DLSS scheduled for decompression surgery.; Prospective observational study with intervention.; Patients with symptomatic DLSS.; Oswestry Disability Index score; duration of symptoms; lumbar muscle atrophy; severity grade; pelvis rigidity during walking.; Patients with symptomatic DLSS were analyzed on the day before surgery and 10 weeks and 12 months postoperatively. Duration of symptoms was categorized as: <2years, <5years, and >5years. Muscle atrophy at the stenosis level was categorized according to Goutallier. Bilateral cross-sectional areas of the erector spinae and psoas muscles were quantified from magnetic resonance imaging. Stenosis grade was assessed using the Schizas classification. Pelvic tilt was measured in standing radiographs. Pelvic rigidity during walking was assessed as root mean square of the pelvic acceleration in each direction (anteroposterior, mediolateral, and vertical) normalized to walking speed measured using an inertial sensor attached to the skin between the posterior superior iliac spine.; Body mass index but not duration of symptoms, lumbar muscle atrophy, pelvic rigidity, and stenosis grade explained changes in Oswestry Disability Index from before to after surgery. Patients with greater stenosis grade had greater pelvic rigidity during walking. Lumbar muscle atrophy did not correlate with pelvic rigidity during walking. Patients with lower stenosis grade had greater muscle atrophy and patients with smaller erector spinae and psoas muscle cross-sectional areas had a greater pelvis tilt.; Greater pelvic rigidity during walking may represent a compensatory mechanism of adopting a protective body position to keep the spinal canal more open during walking and hence reduce pain. Pelvic rigidity during walking may be a useful screening parameter for identifying early compensating mechanisms. Whether it can be used as a parameter for personalized treatment planning or outcome prognosis necessitates further evaluation

    Human-activity-centered measurement system:challenges from laboratory to the real environment in assistive gait wearable robotics

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    Assistive gait wearable robots (AGWR) have shown a great advancement in developing intelligent devices to assist human in their activities of daily living (ADLs). The rapid technological advancement in sensory technology, actuators, materials and computational intelligence has sped up this development process towards more practical and smart AGWR. However, most assistive gait wearable robots are still confined to be controlled, assessed indoor and within laboratory environments, limiting any potential to provide a real assistance and rehabilitation required to humans in the real environments. The gait assessment parameters play an important role not only in evaluating the patient progress and assistive device performance but also in controlling smart self-adaptable AGWR in real-time. The self-adaptable wearable robots must interactively conform to the changing environments and between users to provide optimal functionality and comfort. This paper discusses the performance parameters, such as comfortability, safety, adaptability, and energy consumption, which are required for the development of an intelligent AGWR for outdoor environments. The challenges to measuring the parameters using current systems for data collection and analysis using vision capture and wearable sensors are presented and discussed

    Low impact weight-bearing exercise in an upright posture achieves greater lumbopelvic stability than overground walking

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    The aim of this study was to determine the kinematic differences between movements on a new exercise device (EX) that promotes a stable trunk over a moving, unstable base of support, and overground walking (OW). Sixteen male participants performed EX and OW trials while their movements were tracked using a 3D motion capture system. Trunk and pelvis range of motion (ROM) were similar between EX and OW in the sagittal and frontal planes, and reduced for EX in the transverse plane. The pelvis was tilted anteriorly, on average, by about 16 degrees in EX compared to OW. Hip and knee ROM were reduced in EX compared to OW. The exercise device appears to promote similar or reduced lumbopelvic motion, compared to walking, which could contribute to more tonic activity of the local lumbopelvic musculature

    Foot pressure distribution during walking in young and old adults

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    BACKGROUND: Measurement of foot pressure distribution (FPD) is clinically useful for evaluation of foot and gait pathologies. The effects of healthy aging on FPD during walking are not well known. This study evaluated FPD during normal walking in healthy young and elderly subjects. METHODS: We studied 9 young (30 ± 5.2 years), and 6 elderly subjects (68.7 ± 4.8 years). FPD was measured during normal walking speed using shoe insoles with 99 capacitive sensors. Measured parameters included gait phase characteristics, mean and maximum pressure and force, and relative load. Time-series measurements of each variable for all sensors were grouped into 9 anatomical masks. RESULTS: Elderly subjects had lower normalized maximum pressure for the medial and lateral calcaneal masks, and for all medial masks combined. In the medial calcaneus mask, the elderly group also had a lower absolute maximum and lower mean and normalized mean pressures and forces, compared to young subjects. Elderly subjects had lower maximum force and normalized maximum force and lower mean force and normalized mean forces in the medial masks as well. CONCLUSION: FPD differences between the young and elderly groups were confined to the calcaneus and hallux regions and to the medial side of the foot. In elderly subjects, weight bearing on the lateral side of the foot during heel touch and toe-off phases may affect stability during walking

    Autonomous Locomotion Mode Transition Simulation of a Track-legged Quadruped Robot Step Negotiation

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    Multi-modal locomotion (e.g. terrestrial, aerial, and aquatic) is gaining increasing interest in robotics research as it improves the robots environmental adaptability, locomotion versatility, and operational flexibility. Within the terrestrial multiple locomotion robots, the advantage of hybrid robots stems from their multiple (two or more) locomotion modes, among which robots can select from depending on the encountering terrain conditions. However, there are many challenges in improving the autonomy of the locomotion mode transition between their multiple locomotion modes. This work proposed a method to realize an autonomous locomotion mode transition of a track-legged quadruped robot steps negotiation. The autonomy of the decision-making process was realized by the proposed criterion to comparing energy performances of the rolling and walking locomotion modes. Two climbing gaits were proposed to achieve smooth steps negotiation behaviours for energy evaluation purposes. Simulations showed autonomous locomotion mode transitions were realized for negotiations of steps with different height. The proposed method is generic enough to be utilized to other hybrid robots after some pre-studies of their locomotion energy performances

    A STEP TOWARDS UNDERSTANDING BALANCE CONTROL IN INDIVIDUALS WITH INCOMPLETE SPINAL CORD INJURY

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    Purpose: Frequent falls are reported by individuals with spinal cord injury (SCI) suggesting impairments in their balance control. This thesis examined balance assessment and balance control in individuals with SCI. Methods and Results: To investigate the effects of light touch on standing balance, center of pressure (COP) sway during standing was measured in 16 participants with incomplete SCI (iSCI) and 13 able-bodied (AB) participants. Participants with iSCI showed reduction in COP sway with light touch similar to AB participants. To study the association between stability during normal walking (NW) and unexpected slip intensity, NW behaviour and intensity of an unexpected slip perturbation were assessed in 20 participants with iSCI, and 16 AB participants. Participants with iSCI demonstrated greater stability by walking slower, taking shorter steps, and more time in double support. Walking slower was associated with lower slip intensity in individuals with iSCI. To study reactive balance control, change in margin of stability with a compensatory step, activation of lower extremity muscles, and change in limb velocity trajectories in response to an unexpected slip perturbation were studied in 16 participants with iSCI and 13 AB participants. Participants with iSCI demonstrated limitations in reactive responses including a smaller increase in lateral margin of stability, slower onset of trail limb tibialis anterior activity, and decreased magnitude of trail limb soleus activity. To identify balance measures specific to individuals with SCI, a systematic review of 127 articles was conducted. Thirty balance measures were identified; 11 evaluated a biomechanical construct and 19 were balance scales designed for use in clinical settings. All balance scales had high clinical utility. The Berg Balance Scale and Functional Reach Test were valid and reliable, while the Mini Balance Evaluation Systems Test was most comprehensive. Conclusions: Individuals with iSCI have impaired balance control, as evidenced by limitations in reactive balance; however, they have the ability to modify their balance, as demonstrated by greater stability during NW and with light touch while standing. No single balance measure met all criteria of a useful measure - high clinical utility, strong psychometric properties, and comprehensiveness in the SCI population. Combined, the findings highlight the need for the comprehensive assessment and rehabilitation of balance control after iSCI

    Genetically evolved dynamic control for quadruped walking

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    The aim of this dissertation is to show that dynamic control of quadruped locomotion is achievable through the use of genetically evolved central pattern generators. This strategy is tested both in simulation and on a walking robot. The design of the walker has been chosen to be statically unstable, so that during motion less than three supporting feet may be in contact with the ground. The control strategy adopted is capable of propelling the artificial walker at a forward locomotion speed of ~1.5 Km/h on rugged terrain and provides for stability of motion. The learning of walking, based on simulated genetic evolution, is carried out in simulation to speed up the process and reduce the amount of damage to the hardware of the walking robot. For this reason a general-purpose fast dynamic simulator has been developed, able to efficiently compute the forward dynamics of tree-like robotic mechanisms. An optimization process to select stable walking patterns is implemented through a purposely designed genetic algorithm, which implements stochastic mutation and cross-over operators. The algorithm has been tailored to address the high cost of evaluation of the optimization function, as well as the characteristics of the parameter space chosen to represent controllers. Experiments carried out on different conditions give clear indications on the potential of the approach adopted. A proof of concept is achieved, that stable dynamic walking can be obtained through a search process which identifies attractors in the dynamics of the motor-control system of an artificial walker
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