http://www.jneuroengrehab.com The latest research articles published by Journal of NeuroEngineering and Rehabilitation 2009-07-03T00:00:00Z This is an RSS newsfeed from BioMed Central It is intended to be used with an RSS reader. For more information about RSS newsfeeds from BioMed Central, visit http://www.biomedcentral.com/info/about/rss/ Robotics is emerging as a promising tool for functional training of human movement. Much of the research in this area over the last decade has focused on upper extremity orthotic devices. Some recent commercial designs proposed for the lower extremity are powered and expensive - hence, these are unaffordable by most clinics. In this paper, we present a novel un-motorized bilateral exoskeleton that can be used to assist in treadmill training of motor-impaired patients, such as with motor-incomplete spinal cord injury. The exoskeleton is designed such that the human leg will have a desirable swing motion, once it is strapped to the exoskeleton. Since this exoskeleton is un-motorized, it can be produced cheaply and also will have the potential to reduce the physical demand on therapists during treadmill training.The salient features of this swing-assist exoskeleton are: (i) The design uses torsional springs at the hip and the knee joints to assist the swing motion. The springs get charged by the treadmill during stance phase of the leg and provide propulsion forces to the leg during swing. (ii) The design of the exoskeleton uses simple dynamic models of sagittal plane walking, which are used to optimize the parameters of the springs so that the foot can clear the ground and have a desirable forward motion during walking. (iii) This design approach was used to construct a bilateral exoskeleton and was tested during treadmill walking for a range of walking speeds between 1.0 mph and 4.0 mph. Joint encoders and interface force-torque sensors mounted on the exoskeleton were used to evaluate the effectiveness of the exoskeleton in terms of the hip and knee joint torques applied by the human during treadmill walking. http://www.jneuroengrehab.com/content/6/1/24 Kalyan Mankala Sai Banala Sunil Agrawal Journal of NeuroEngineering and Rehabilitation 2009, 6:24 2009-07-03T00:00:00Z doi:10.1186/1743-0003-6-24 Journal of NeuroEngineering and Rehabilitation 1743-0003 6 24 2009-07-03T00:00:00Z PDF Background: The goal of this study was to test the mechanical performance of a prototype knee-ankle-foot orthosis (KAFO) powered by artificial pneumatic muscles during human walking. We had previously built a powered ankle-foot orthosis (AFO) and used it effectively in studies on human motor adaptation, locomotion energetics, and gait rehabilitation. Extending the previous AFO to a KAFO presented additional challenges related to the force-length properties of the artificial pneumatic muscles and the presence of multiple antagonistic artificial pneumatic muscle pairs. Methods: Three healthy males were fitted with custom KAFOs equipped with artificial pneumatic muscles to power ankle plantar flexion/dorsiflexion and knee extension/flexion. Subjects walked over ground at 1.25 m/s under four conditions without extensive practice: 1) without wearing the orthosis, 2) wearing the orthosis with artificial muscles turned off, 3) wearing the orthosis activated under direct proportional myoelectric control, and 4) wearing the orthosis activated under proportional myoelectric control with flexor inhibition produced by leg extensor muscle activation. We collected joint kinematics, ground reaction forces, electromyography, and orthosis kinetics. Results: The KAFO produced ~22%-33% of the peak knee flexor moment, ~15%-33% of the peak extensor moment, ~42%-46% of the peak plantar flexor moment, and ~83%-129% of the peak dorsiflexor moment during normal walking. With flexor inhibition produced by leg extensor muscle activation, ankle (Pearson r-value =0.74+/-0.04) and knee (r=0.95+/-0.04) joint kinematic profiles were more similar to the without orthosis condition compared to when there was no flexor inhibition (r=0.49+/-0.13 for ankle, p=0.05, and r=0.90+/-0.03 for knee, p=0.17). Conclusions: The proportional myoelectric control with flexor inhibition allowed for a more normal gait than direct proportional myoelectric control. The current orthosis design provided knee torques smaller than the ankle torques due to the trade-off in torque and range of motion that occurs with artificial pneumatic muscles. Future KAFO designs could incorporate cams, gears, or different actuators to transmit greater torque to the knee. http://www.jneuroengrehab.com/content/6/1/23 Gregory Sawicki Daniel Ferris Journal of NeuroEngineering and Rehabilitation 2009, 6:23 2009-06-23T00:00:00Z doi:10.1186/1743-0003-6-23 Journal of NeuroEngineering and Rehabilitation 1743-0003 6 23 2009-06-23T00:00:00Z PDF Background: Biomechanical energy harvesting--generating electricity from people during daily activities--is a promising alternative to batteries for powering increasingly sophisticated portable devices. We recently developed a wearable knee-mounted energy harvesting device that generated electricity during human walking. In this methods-focused paper, we explain the physiological principles that guided our design process and present a detailed description of our device design with an emphasis on new analyses.MethodEffectively harvesting energy from walking requires a small lightweight device that efficiently converts intermittent, bi-directional, low speed and high torque mechanical power to electricity, and selectively engages power generation to assist muscles in performing negative mechanical work. To achieve this, our device used a one-way clutch to transmit only knee extension motions, a spur gear transmission to amplify the angular speed, a brushless DC rotary magnetic generator to convert the mechanical power into electrical power, a control system to determine when to open and close the power generation circuit based on measurements of knee angle, and a customized orthopaedic knee brace to distribute the device reaction torque over a large leg surface area. Results: The device selectively engaged power generation towards the end of swing extension, assisting knee flexor muscles by producing substantial flexion torque (6.4 Nm), and efficiently converted the input mechanical power into electricity (54.6%). Consequently, six subjects walking at 1.5 m/s generated 4.8 +/- 0.8 W of electrical power with only a 5.0 +/- 21 W increase in metabolic cost. Conclusions: Biomechanical energy harvesting is capable of generating substantial amounts of electrical power from walking with little additional user effort making future versions of this technology particularly promising for charging portable medical devices. http://www.jneuroengrehab.com/content/6/1/22 Qingguo Li Veronica Naing Maxwell Donelan Journal of NeuroEngineering and Rehabilitation 2009, 6:22 2009-06-23T00:00:00Z doi:10.1186/1743-0003-6-22 Journal of NeuroEngineering and Rehabilitation 1743-0003 6 22 2009-06-23T00:00:00Z PDF For over a century, technologists and scientists have actively sought the development of exoskeletons and orthoses designed to augment human economy, strength, and endurance. While there are still many challenges associated with exoskeletal and orthotic design that have yet to be perfected, the advances in the field have been truly impressive. In this commentary, I first classify exoskeletons and orthoses into devices that act in series and in parallel to a human limb, providing a few examples within each category. This classification is then followed by a discussion of major design challenges and future research directions critical to the field of exoskeletons and orthoses. http://www.jneuroengrehab.com/content/6/1/21 Hugh Herr Journal of NeuroEngineering and Rehabilitation 2009, 6:21 2009-06-18T00:00:00Z doi:10.1186/1743-0003-6-21 Journal of NeuroEngineering and Rehabilitation 1743-0003 6 21 2009-06-18T00:00:00Z PDF There is increasing interest in using robotic devices to assist in movement training following neurologic injuries such as stroke and spinal cord injury. This paper reviews control strategies for robotic therapy devices. Several categories of strategies have been proposed, including, assistive, challenge-based, haptic simulation, and coaching. The greatest amount of work has been done on developing assistive strategies, and thus the majority of this review summarizes techniques for implementing assistive strategies, including impedance-, counterbalance-, and EMG- based controllers, as well as adaptive controllers that modify control parameters based on ongoing participant performance. Clinical evidence regarding the relative effectiveness of different types of robotic therapy controllers is limited, but there is initial evidence that some control strategies are more effective than others. It is also now apparent there may be mechanisms by which some robotic control approaches might actually decrease the recovery possible with comparable, non-robotic forms of training. In future research, there is a need for head-to-head comparison of control algorithms in randomized, controlled clinical trials, and for improved models of human motor recovery to provide a more rational framework for designing robotic therapy control strategies. http://www.jneuroengrehab.com/content/6/1/20 Laura Marchal-Crespo David Reinkensmeyer Journal of NeuroEngineering and Rehabilitation 2009, 6:20 2009-06-16T00:00:00Z doi:10.1186/1743-0003-6-20 Journal of NeuroEngineering and Rehabilitation 1743-0003 6 20 2009-06-16T00:00:00Z PDF Background: A self-contained, self-controlled, pneumatic power harvesting ankle-foot orthosis (PhAFO) to manage foot-drop was developed and tested. Foot-drop is due to a disruption of the motor control pathway and may occur in numerous pathologies such as stroke, spinal cord injury, multiple sclerosis, and cerebral palsy. The objectives for the prototype PhAFO are to provide toe clearance during swing, permit free ankle motion during stance, and harvest the needed power with an underfoot bellow pump pressurized during the stance phase of walking. Methods: The PhAFO was constructed from a two-part (tibia and foot) carbon composite structure with an articulating ankle joint. Ankle motion control was accomplished through a cam-follower locking mechanism actuated via a pneumatic circuit connected to the bellow pump and embedded in the foam sole. Biomechanical performance of the prototype orthosis was assessed during multiple trials of treadmill walking of an able-bodied control subject (n = 1). Motion capture and pressure measurements were used to investigate the effect of the PhAFO on lower limb joint behavior and the capacity of the bellow pump to repeatedly generate the required pneumatic pressure for toe clearance. Results: Toe clearance during swing was successfully achieved during all trials; average clearance 44 ± 5 mm. Free ankle motion was observed during stance and plantarflexion was blocked during swing. In addition, the bellow component repeatedly generated an average of 169 kPa per step of pressure during ten minutes of walking. Conclusion: This study demonstrated that fluid power could be harvested with a pneumatic circuit built into an AFO, and used to operate an actuated cam-lock mechanism that controls ankle-foot motion at specific periods of the gait cycle. http://www.jneuroengrehab.com/content/6/1/19 Robin Chin Elizabeth Hsiao-Wecksler Eric Loth Geza Kogler Scott Manwaring Serena Tyson K. Alex Shorter Joel Gilmer Journal of NeuroEngineering and Rehabilitation 2009, 6:19 2009-06-16T00:00:00Z doi:10.1186/1743-0003-6-19 Journal of NeuroEngineering and Rehabilitation 1743-0003 6 19 2009-06-16T00:00:00Z XML Background: While manually-assisted body-weight supported treadmill training (BWSTT) has revealed improved locomotor function in persons with post-stroke hemiparesis, outcomes are inconsistent and it is very labor intensive. Thus an alternate treatment approach is desirable.Objectives of this pilot study were to: 1) compare the efficacy of body-weight supported treadmill training (BWSTT) combined with the Lokomat robotic gait orthosis versus manually-assisted BWSTT for locomotor training post-stroke, and 2) assess effects of fast versus slow treadmill training speed. Methods: Sixteen volunteers with chronic hemiparetic gait (0.62+/-0.30m/s) post-stroke were randomly allocated to Lokomat (n=8) or manual-BWSTT (n=8) 3x/wk for 4 weeks. Groups were also stratified by fast (mean 0.92+/-0.15m/s) or slow (0.58+/-0.12m/s) training speeds. The primary outcomes were self-selected overground walking speed and paretic step length ratio. Secondary outcomes included: fast overground walking speed, 6-minute walk test, and a battery of clinical measures. Results: No significant differences in primary outcomes were revealed between Lokomat and manual groups as a result of training. However, within the Lokomat group, self-selected walk speed, paretic step length ratio, and four of the six secondary measures improved (p=0.04-0.05, effect sizes=0.19-0.60). Within the manual group, only balance scores improved (p=0.02, effect size=0.57). Group differences between fast and slow training groups were not revealed (p>= 0.28). Conclusions: Results suggest that Lokomat training may have advantages over manual-BWSTT following a modest intervention dose in chronic hemiparetic persons and further, that our training speeds produce similar gait improvements. Suggestions for a larger randomized controlled trial with optimal study parameters are provided. http://www.jneuroengrehab.com/content/6/1/18 Kelly Westlake Carolynn Patten Journal of NeuroEngineering and Rehabilitation 2009, 6:18 2009-06-12T00:00:00Z doi:10.1186/1743-0003-6-18 Journal of NeuroEngineering and Rehabilitation 1743-0003 6 18 2009-06-12T00:00:00Z PDF It is a fantastic time for the field of robotic exoskeletons. Recent advances in actuators, sensors, materials, batteries, and computer processors have given new hope to creating the exoskeletons of yesteryear's science fiction. While the most common goal of an exoskeleton is to provide superhuman strength or endurance, scientists and engineers around the world are building exoskeletons with a wide range of diverse purposes. Exoskeletons can help patients with neurological disabilities improve their motor performance by providing task specific practice. Exoskeletons can help physiologists better understand how the human body works by providing a novel experimental perturbation. Exoskeletons can even help power mobile phones, music players, and other portable electronic devices by siphoning mechanical work performed during human locomotion. This special thematic series on robotic lower limb exoskeletons and orthoses includes eight papers presenting novel contributions to the field. The collective message of the papers is that robotic exoskeletons will contribute in many ways to the future benefit of humankind, and that future is not that distant. http://www.jneuroengrehab.com/content/6/1/17 Daniel Ferris Journal of NeuroEngineering and Rehabilitation 2009, 6:17 2009-06-09T00:00:00Z doi:10.1186/1743-0003-6-17 Journal of NeuroEngineering and Rehabilitation 1743-0003 6 17 2009-06-09T00:00:00Z XML Background: Adapting to external forces during walking has been proposed as a tool to improve locomotion after central nervous system injury. However, sensorimotor integration during walking varies according to the timing in the gait cycle, suggesting that adaptation may also depend on gait phases. In this study, an ElectroHydraulic AFO (EHO) was used to apply forces specifically during mid-stance and push-off to evaluate if feedforward movement control can be adapted in these 2 gait phases. Methods: Eleven healthy subjects walked on a treadmill before (3 min), during (5 min) and after (5 min) exposure to 2 force fields applied by the EHO (mid-stance/push-off; ~10 Nm, towards dorsiflexion). To evaluate modifications in feedforward control, strides with no force field ('catch strides') were unexpectedly inserted during the force field walking period. Results: When initially exposed to a mid-stance force field (FF20%), subjects showed a significant increase in ankle dorsiflexion velocity. Catches applied early into the FF20% were similar to baseline (P > 0.99). Subjects gradually adapted by returning ankle velocity to baseline over ~50 strides. Catches applied thereafter showed decreased ankle velocity where the force field was normally applied, indicating the presence of feedforward adaptation. When initially exposed to a push-off force field (FF50%), plantarflexion velocity was reduced in the zone of force field application. No adaptation occurred over the 5 min exposure. Catch strides kinematics remained similar to control at all times, suggesting no feedforward adaptation. As a control, force fields assisting plantarflexion (-3.5 to -9.5 Nm) were applied and increased ankle plantarflexion during push-off, confirming that the lack of kinematic changes during FF50% catch strides were not simply due to a large ankle impedance. Conclusion: Together these results show that ankle exoskeletons such as the EHO can be used to study phase-specific adaptive control of the ankle during locomotion. Our data suggest that, for short duration exposure, a feedforward modification in torque output occurs during mid-stance but not during push-off. These findings are important for the design of novel rehabilitation methods, as they suggest that the ability to use resistive force fields for training may depend on targeted gait phases. http://www.jneuroengrehab.com/content/6/1/16 Martin Noel Karine Fortin Laurent Bouyer Journal of NeuroEngineering and Rehabilitation 2009, 6:16 2009-06-03T00:00:00Z doi:10.1186/1743-0003-6-16 Journal of NeuroEngineering and Rehabilitation 1743-0003 6 16 2009-06-03T00:00:00Z XML Background: There is a need to develop cost-effective, sensitive stroke assessment instruments. One approach is examining kinematic measures derived from goal-directed tasks, which can potentially be sensitive to the subtle changes in the stroke rehabilitation process. This paper presents the findings from a pilot study that uses a computer-assisted neurorehabilitation platform, interfaced with a conventional force-reflecting joystick, to examine the assessment capability of the system by various types of goal-directed tasks. Methods: Both stroke subjects with hemiparesis and able-bodied subjects used the force-reflecting joystick to complete a suite of goal-directed tasks under various task settings. Kinematic metrics, developed for specific types of goal-directed tasks, were used to assess various aspects of upper-extremity motor performance across subjects. Results: A number of metrics based on kinematic performance were able to differentiate subjects with different impairment levels, with metrics associated with accuracy, steadiness and speed consistency showing the best capability. Significant differences were also shown on these metrics between various force field settings. Conclusion: The results support the potential of using UniTherapy software with a conventional joystick system as an upper-extremity assessment instrument. We demonstrated the ability of using various types of goal-directed tasks to distinguish between subjects with different impairment levels. In addition, we were able to show that different force fields have a significant effect on the performance across subjects with different impairment levels in the trajectory tracking task. These results provide motivation for studies with a larger sample size that can more completely span the impairment space, and can use insights presented here to refine considerations of various task settings so as to generalize and extend our conclusions. http://www.jneuroengrehab.com/content/6/1/15 Xin Feng Jack Winters Journal of NeuroEngineering and Rehabilitation 2009, 6:15 2009-05-28T00:00:00Z doi:10.1186/1743-0003-6-15 Journal of NeuroEngineering and Rehabilitation 1743-0003 6 15 2009-05-28T00:00:00Z XML