Predictive Simulations with OpenSim Moco to Investigate the Interaction Between Human and Assistive Exoskeleton.

The purpose of this work was to investigate the interaction between human and lower limbs assistive exoskeleton under different levels of assistance, by using computational simulations. To this, a human-exoskeleton interaction model was used and three predictive simulations were carried out with the OpenSim Moco. The results proved that the increase in the level of robot assistance causes a reduction in human effort. In addition, it was possible to verify the RMS torque of both the robot and the human, as well as the muscle activations, for the different levels of assistance simulated. For future work, we intend to run predictive simulations with more complex movements, such as gait free and with obstacles, in addition to using models that can represent a human being with muscle weakness on one side of the body (hemiparesis).

Towards Visual-Tactile Integration of Shoulder and Hand Using Immersive Virtual Reality.

Shoulder-controlled hand neuroprostheses are wearable devices designed to assist hand function in people with cervical spinal cord injury (SCI). They use preserved shoulder movements to control artificial actuators. Due to the concurrent afferent (i.e., shoulder proprioception) and visual (i.e., hand response) feedback, these wearables may affect the user's body somatosensory representation. To investigate this effect, we propose an experimental paradigm that uses immersive virtual reality (VR) environment to emulate the use of a shoulder-controlled hand neuroprostheses and an adapted version of a visual-tactile integration task (i.e., Crossmodal Congruency Task) as an assessment tool. Data from seven non-disabled participants validates the experimental setup, with preliminary statistical analysis revealing no significant difference across the means of VR and visual-tactile integration tasks. The results serve as a proof-of-concept for the proposed paradigm, paving the way for further research with improvements in the experimental design and a larger sample size.

Patient Experience in Adjunct Controller-Free Hand Tracking Virtual Reality Tasks for Upper-Limb Occupational Therapy Rehabilitation.

Benefits of immersive virtual reality rehabilitation (VRR) include increased motivation and improved transfer of skills to real-world tasks. The introduction of Oculus hand-tracking technology allowed for the development of VRR games that do not need virtual reality (VR) hand controllers. This is beneficial as participants with upper limb impairments/injuries may have difficulties with/be limited in using/manipulating VR hand controllers. In this project, a VRR game was developed and evaluated. The aim of this study was to determine patient experience when using VRR as an adjunct to upper-limb rehabilitation. N = 20 participants receiving upper limb rehabilitation completed a series of VRR tasks by playing the "smoothie bar" VRR game. After the completion of the VRR tasks, the participant experience was evaluated via a study-specific questionnaire. Key findings include 95% agreement that VRR tasks were fun and engaging and 75% agreed that VR tasks will be helpful to include in their rehabilitation. Hands-tracking VRR has a high potential to be used as an adjunct intervention in upper limb rehabilitation.

A Kinematic Information Acquisition Model That Uses Digital Signals from an Inertial and Magnetic Motion Capture System.

This paper presents a model that enables the transformation of digital signals generated by an inertial and magnetic motion capture system into kinematic information. First, the operation and data generated by the used inertial and magnetic system are described. Subsequently, the five stages of the proposed model are described, concluding with its implementation in a virtual environment to display the kinematic information. Finally, the applied tests are presented to evaluate the performance of the model through the execution of four exercises on the upper limb: flexion and extension of the elbow, and pronation and supination of the forearm. The results show a mean squared error of 3.82° in elbow flexion-extension movements and 3.46° in forearm pronation-supination movements. The results were obtained by comparing the inertial and magnetic system versus an optical motion capture system, allowing for the identification of the usability and functionality of the proposed model.

Soft robotics and functional electrical stimulation advances for restoring hand function in people with SCI: a narrative review, clinical guidelines and future directions.

BACKGROUND: Recovery of hand function is crucial for the independence of people with spinal cord injury (SCI). Wearable devices based on soft robotics (SR) or functional electrical stimulation (FES) have been employed to assist the recovery of hand function both during activities of daily living (ADLs) and during therapy. However, the implementation of these wearable devices has not been compiled in a review focusing on the functional outcomes they can activate/elicit/stimulate/potentiate. This narrative review aims at providing a guide both for engineers to help in the development of new technologies and for clinicians to serve as clinical guidelines based on the available technology in order to assist and/or recover hand function in people with SCI. METHODS: A literature search was performed in Scopus, Pubmed and IEEE Xplore for articles involving SR devices or FES systems designed for hand therapy or assistance, published since 2010. Only studies that reported functional outcomes from individuals with SCI were selected. The final collections of both groups (SR and FES) were analysed based on the technical aspects and reported functional outcomes. RESULTS: A total of 37 out of 1101 articles were selected, 12 regarding SR and 25 involving FES devices. Most studies were limited to research prototypes, designed either for assistance or therapy. From an engineering perspective, technological improvements for home-based use such as portability, donning/doffing and the time spent with calibration were identified. From the clinician point of view, the most suitable technical features (e.g., user intent detection) and assessment tools should be determined according to the particular patient condition. A wide range of functional assessment tests were adopted, moreover, most studies used non-standardized tests. CONCLUSION: SR and FES wearable devices are promising technologies to support hand function recovery in subjects with SCI. Technical improvements in aspects such as the user intent detection, portability or calibration as well as consistent assessment of functional outcomes were the main identified limitations. These limitations seem to be be preventing the translation into clinical practice of these technological devices created in the laboratory.

User-centered design and spatially-distributed sequential electrical stimulation in cycling for individuals with paraplegia.

BACKGROUND: In this work, we share the enhancements made in our system to take part in the CYBATHLON 2020 Global Edition Functional Electrical Stimulation (FES) Bike Race. Among the main improvements, firstly an overhaul, an overhaul of the system and user interface developed with User-centered design principles with remote access to enable telerehabilitation. Secondly, the implementation and experimental comparison between the traditional single electrode stimulation (SES) and spatially distributed sequential stimulation (SDSS) applied for FES Cycling. METHODS: We report on the main aspects of the developed system. To evaluate the user perception of the system, we applied a System Usability Scale (SUS) questionnaire. In comparing SDSS and SES, we collected data from one subject in four sessions, each simulating one race in the CYBATHLON format. RESULTS: User perception measured with SUS indicates a positive outcome in the developed system. The SDSS trials were superior in absolute and average values to SES regarding total distance covered and velocity. We successfully competed in the CYBATHLON 2020 Global Edition, finishing in 6th position in the FES Bike Race category. CONCLUSIONS: The CYBATHLON format induced us to put the end-user in the center of our system design principle, which was well perceived. However, further improvements are required if the intention is to progress to a commercial product. FES Cycling performance in SDSS trials was superior when compared to SES trials, indicating that this technique may enable faster and possibly longer FES cycling sessions for individuals with paraplegia. More extensive studies are required to assess these aspects.

Tracking and Classification of Head Movement for Augmentative and Alternative Communication Systems.

The use of assistive technologies can mitigate or reduce the challenges faced by individuals with motor disabilities to use computer systems. However, those who feature severe involuntary movements often have fewer options at hand. This work describes an application that can recognize the user's head using a conventional webcam, track its motion, model the desired functional movement, and recognize it to enable the use of a virtual keyboard. The proposed classifier features a flexible structure and may be personalized for different user need. Experimental results obtained with participants with no neurological disorders have shown that classifiers based on Hidden Markov Models provided similar or better performance than a classifier based on position threshold. However, motion segmentation and interpretation modules were sensitive to involuntary movements featured by participants with cerebral palsy that took part in the study.

Towards balance assessment using Openpose.

The ability to assess balance is essential to determine a patients ability to mitigate any risk of falling. While current assessment tools exist, they either have limitations in that there is no quantitative data recorded, or that they are impractical for general use in clinical settings. In this work, we aim at assessing balance using single-camera videos. In particular, the proposed method uses OpenPose to calculate the Center of Mass and Center of Pressure trajectories. To determine the validity of this approach, estimates obtained in an experimental study were compared to recordings obtained through the use of 3D motion capture and force plate. Our results indicate that this inexpensive, easy to use, and portable alternative has the potential to act as a suitable replacement to assess balance in clinical settings.

Passive Knee Orthoses Assistance in Functional Electrical Stimulation Cycling in an Individual With Spinal Cord Injury.

Functional Electrical Stimulation (FES) may be used in rehabilitation and assistance of people with Spinal Cord Injury (SCI). One significant application is facilitating physical exercise, mainly when combining FES with mechanical platforms, such as tricycles. However, there are still technical challenges in FES cycling protocols, such as improving control and cycling performance. Here we show how passive elements in knee orthoses during FES cycling could increase the average cadence, taking advantage of the cycling movement. Our approach is twofold. First, we simulated the forward dynamics of a detailed musculoskeletal model with passive elements over the knees. Simulations showed that specific spring stiffness ranges increased the crankset speed during cycling by more than 50%. Using parameters found in simulations, we built a pair of passive orthoses and performed experiments with one individual with SCI. During two days, the volunteer cycled with similar stimulation magnitude with and without the passive elements. We observed that the average crankset speed was higher by more than 10% when the springs were attached to the passive orthoses. These results show the potential of using passive elements to increase cycling speed for FES cycling with similar or even lower stimulation magnitude, leading to longer exercise duration.

Comparing Spatially Distributed and Single Electrode Stimulation on Individuals with Spinal Cord Injury.

It is still a challenge to delay the onset of fatigue on muscle contraction induced by Functional Electrical Stimulation (FES). We explored the use of two stimulation methods with the same total area, single electrode stimulation (SES), and spatially distributed electrical stimulation (SDSS) during isometric knee extension with spinal cord injured (SCI) volunteers. We applied stimulation on the left and right quadriceps of two SCI participants with both methods and recorded isometric force and evoked electromyography (eEMG). We calculated the force-time integral (FTI) and eEMG-time integral (eTI) for each stimulation series and used a linear regression as a measure of decay ratio. Moreover, we also estimated the contribution from each channel from eEMG.

Upper Limb Physical Rehabilitation Using Serious Videogames and Motion Capture Systems: A Systematic Review.

The use of videogames and motion capture systems in rehabilitation contributes to the recovery of the patient. This systematic review aimed to explore the works related to these technologies. The PRISMA method (Preferred Reporting Items for Systematic reviews and Meta-Analyses) was used to search the databases Scopus, PubMed, IEEE Xplore, and Web of Science, taking into consideration four aspects: physical rehabilitation, the use of videogames, motion capture technologies, and upper limb rehabilitation. The literature selection was limited to open access works published between 2015 and 2020, obtaining 19 articles that met the inclusion criteria. The works reported the use of inertial measurement units (37%), a Kinect sensor (48%), and other technologies (15%). It was identified that 26% used commercial products, while 74% were developed independently. Another finding was that 47% of the works focus on post-stroke motor recovery. Finally, diverse studies sought to support physical rehabilitation using motion capture systems incorporating inertial units, which offer precision and accessibility at a low cost. There is a clear need to continue generating proposals that confront the challenges of rehabilitation with technologies which offer precision and healthcare coverage, and which, additionally, integrate elements that foster the patient's motivation and participation.

Symmetry Analysis of Amputee Gait Based on Body Center of Mass Trajectory and Discrete Fourier Transform.

The calculation of symmetry in amputee gait is a valuable tool to assess the functional aspects of lower limb prostheses and how it impacts the overall gait mechanics. This paper analyzes the vertical trajectory of the body center of mass (CoM) of a group formed by transfemoral amputees and non-amputees to quantitatively compare the symmetry level of this parameter for both cases. A decomposition of the vertical CoM into discrete Fourier series (DFS) components is performed for each subject's CoM trajectory to identify the main components of each pattern. A DFS-based index is then calculated to quantify the CoM symmetry level. The obtained results show that the CoM displays different patterns along a gait cycle for each amputee, which differ from the sine-wave shape obtained in the non-amputee case. The CoM magnitude spectrum also reveals more coefficients for the amputee waveforms. The different CoM trajectories found in the studied subjects can be thought as the manifestation of developed compensatory mechanisms, which lead to gait asymmetries. The presence of odd components in the magnitude spectrum is related to the asymmetric behavior of the CoM trajectory, given the fact that this signal is an even function for a non-amputee gait. The DFS-based index reflects this fact due to the high value obtained for the non-amputee reference, in comparison to the low values for each amputee.

Assisted Grasping in Individuals with Tetraplegia: Improving Control through Residual Muscle Contraction and Movement.

Individuals who sustained a spinal cord injury often lose important motor skills, and cannot perform basic daily living activities. Several assistive technologies, including robotic assistance and functional electrical stimulation, have been developed to restore lost functions. However, designing reliable interfaces to control assistive devices for individuals with C4-C8 complete tetraplegia remains challenging. Although with limited grasping ability, they can often control upper arm movements via residual muscle contraction. In this article, we explore the feasibility of drawing upon these residual functions to pilot two devices, a robotic hand and an electrical stimulator. We studied two modalities, supra-lesional electromyography (EMG), and upper arm inertial sensors (IMU). We interpreted the muscle activity or arm movements of subjects with tetraplegia attempting to control the opening/closing of a robotic hand, and the extension/flexion of their own contralateral hand muscles activated by electrical stimulation. Two groups were recruited: eight subjects issued EMG-based commands; nine other subjects issued IMU-based commands. For each participant, we selected at least two muscles or gestures detectable by our algorithms. Despite little training, all participants could control the robot's gestures or electrical stimulation of their own arm via muscle contraction or limb motion.

Simulation of the assistance of passive knee orthoses in FES cycling.

Although advances in technology promoted new physiotherapy approaches, there is still an urge for equipment and techniques to improve the quality of patients lives with motor disabilities. Functional electrical stimulation cycling (FES cycling) is an example of this type of technology, in which the control of stimulation parameters enables a spinal cord injured person to ride a bicycle. In this work, we aim to investigate the use of passive knee orthoses for FES cycling assistance. Hence, we compared the cycling cadence and quadriceps excitation using an FES cycling simulation platform for different spring torques and ranges. In this paper, we obtained spring parameters that increased cycling cadence by 10.60% while decreasing by 7.33% the quadriceps activity, which indicates that this type of passive orthosis may diminish fatigue caused by FES.

Investigating Upper Limb Movement Classification on Users with Tetraplegia as a Possible Neuroprosthesis Interface.

Spinal cord injury (SCI), stroke and other nervous system conditions can result in partial or total paralysis of individual's limbs. Numerous technologies have been proposed to assist neurorehabilitation or movement restoration, e.g. robotics or neuroprosthesis. However, individuals with tetraplegia often find difficult to pilot these devices. We developed a system based on a single inertial measurement unit located on the upper limb that is able to classify performed movements using principal component analysis. We analyzed three calibration algorithms: unsupervised learning, supervised learning and adaptive learning. Eight participants with tetraplegia (C4C7) piloted three different postures in a robotic hand. We achieved 89% accuracy using the supervised learning algorithm. Through offline simulation, we found accuracies of 76% on the unsupervised learning, and 88% on the adaptive one.

Overview of FES-Assisted Cycling Approaches and Their Benefits on Functional Rehabilitation and Muscle Atrophy.

Central nervous system diseases include brain or spinal cord impairments and may result in movement disorders almost always manifested by paralyzed muscles with preserved innervations and therefore susceptible to be activated by electrical stimulation. Functional electrical stimulation (FES)-assisted cycling is an approach mainly used for rehabilitation purposes contributing, among other effects, to restore muscle trophism. FES-assisted cycling has also been adapted for mobile devices adding a leisure and recreational benefit to the physical training. In October 2016, our teams (Freewheels and EMA-trike) took part in FES-bike discipline at the Cybathlon competition, presenting technologies that allow pilots with spinal cord injury to use their paralyzed lower limb muscles to propel a tricycle. Among the many benefits observed and reported in our study cases for the pilots during preparation period, we achieved a muscle remodeling in response to FES-assisted cycling that is discussed in this chapter. Then, we have organized some sections to explore how FES-assisted cycling could contribute to functional rehabilitation by means of changes in the skeletal muscle disuse atrophy.

Cadence Tracking and Disturbance Rejection in Functional Electrical Stimulation Cycling for Paraplegic Subjects: A Case Study.

Functional electrical stimulation cycling has been proposed as an assistive technology with numerous health and fitness benefits for people with spinal cord injury, such as improvement in cardiovascular function, increase in muscular mass, and reduction of bone mass loss. However, some limitations, for example, lack of optimal control strategies that would delay fatigue, may still prevent this technology from achieving its full potential. In this work, we performed experiments on a person with complete spinal cord injury using a stationary tadpole trike when both cadence tracking and disturbance rejection were evaluated. In addition, two sets of experiments were conducted 6 months apart and considering activation of different muscles. The results showed that reference tracking is achieved above the cadence of 25 rpm with mean absolute errors between 1.9 and 10% when only quadriceps are activated. The disturbance test revealed that interferences may drop the cadence but do not interrupt a continuous movement if the cadence does not drop below 25 rpm, again when only quadriceps are activated. When other muscle groups were added, strong spasticity caused larger errors on reference tracking, but not when a disturbance was applied. In addition, spasticity caused the last experiments to result in less smooth cycling.

Automatic Human Movement Assessment With Switching Linear Dynamic System: Motion Segmentation and Motor Performance.

Performance assessment of human movement is critical in diagnosis and motor-control rehabilitation. Recent developments in portable sensor technology enable clinicians to measure spatiotemporal aspects to aid in the neurological assessment. However, the extraction of quantitative information from such measurements is usually done manually through visual inspection. This paper presents a novel framework for automatic human movement assessment that executes segmentation and motor performance parameter extraction in time-series of measurements from a sequence of human movements. We use the elements of a Switching Linear Dynamic System model as building blocks to translate formal definitions and procedures from human movement analysis. Our approach provides a method for users with no expertise in signal processing to create models for movements using labeled dataset and later use it for automatic assessment. We validated our framework on preliminary tests involving six healthy adult subjects that executed common movements in functional tests and rehabilitation exercise sessions, such as sit-to-stand and lateral elevation of the arms and five elderly subjects, two of which with limited mobility, that executed the sit-to-stand movement. The proposed method worked on random motion sequences for the dual purpose of movement segmentation (accuracy of 72%-100%) and motor performance assessment (mean error of 0%-12%).

Kilohertz and Low-Frequency Electrical Stimulation With the Same Pulse Duration Have Similar Efficiency for Inducing Isometric Knee Extension Torque and Discomfort.

OBJECTIVE: To test the hypotheses that, as compared with pulsed current with the same pulse duration, kilohertz frequency alternating current would not differ in terms of evoked-torque production and perceived discomfort, and as a result, it would show the same current efficiency. DESIGN: A repeated-measures design with 4 stimuli presented in random order was used to test 25 women: (1) 500-microsecond pulse duration, (2) 250-microsecond pulse duration, (3) 500-microsecond pulse duration and low carrier frequency (1 kHz), (4) 250-microsecond pulse duration and high carrier frequency (4 kHz). Isometric peak torque of quadriceps muscle was measured using an isokinetic dynamometer. Discomfort was measured using a visual analog scale. RESULTS: Currents with long pulse durations induced approximately 21% higher evoked torque than short pulse durations. In addition, currents with 500 microseconds delivered greater amounts of charge than stimulation patterns using 250-microsecond pulse durations (P < 0.05). All currents presented similar discomfort. There was no difference on stimulation efficiency with the same pulse duration. CONCLUSIONS: Both kilohertz frequency alternating current and pulsed current, with the same pulse duration, have similar efficiency for inducing isometric knee extension torque and discomfort. However, neuromuscular electrical stimulation (NMES) with longer pulse duration induces higher NMES-evoked torque, regardless of the carrier frequency. Pulse duration is an important variable that should receive more attention for an optimal application of NMES in clinical settings.

FES Bike Race preparation to Cybathlon 2016 by EMA team: a short case report.

FES-assisted cycling has been recommended to people struggling to emerge from a disability to more functioning life after spinal cord injury. Recommendations issued by a gowing number of scientific papershas promised toimprove body composition and physical activity levels, as well as to controlinvoluntary muscle response; favoring activity and participation which break new grounds in expanding locomotion, leisure and occupational options for people with paraplegia and tetraplegia. In this report we described our experience to select and prepare a pilot to compete in the FES Bike Race modality at Cybathlon 2016 in Kloten (Zurick). He was a man, 38 years old, with a complete spinal cord injury, level T9, three years of injury. He took part in a two preparation phases lasting respectively 18 and 12 weeks each: (1st) pre-FES-cycling and a (2nd) FES-cycling. The 1st phase aimed to explore electrical stimulation response in the quadricps, hamstrings and gluteus muscles; searching for a standard muscular recruitment enable to propel the pedals of a trike. Following, in the 2nd phase, stationary to mobile FES-cycling was performed at the same time the development of the automation and control systems were being incorporated in the trike. We adapted a commercial tadpole trycicle anda pilot controlled system. Although we had planned a three session by week protocol, for reasons of term and time to finish the trike development and be prepared to compete, in the last two weeks before the Cybatlhon an intense level of exercise was maintained. After the race, we noticedinflammatory signs on the left knee which later revealed a patella fracture. The video footage analysis confirmed ithappened during the race's first lap.