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The Mini-Balance Evaluation Systems Test (Mini-BESTest), a 14-item scale, has high content validity for balance assessment. This study further examines the construct validity of the Mini-BESTest with an emphasis on its measurement invariance. The Mini-BESTest was administered to 292 neurological patients in two sessions (before and after rehabilitation) and evaluated with the Rasch analysis (Many-Facet Rating Scale Model: persons, items, sessions). Categories’ order and fit to the model were assessed. Next, maps, dimensionality, and differential item functioning (DIF) were examined for construct validity evaluation. DIF was inspected for several clinically important variables, including session, diagnosis, and assistive devices. Mini-BESTest items had ordered categories and fitted the Rasch model. The item map did not flag severe construct underrepresentation. The dimensionality analysis showed that another variable extraneous to balance affected the score of a few items. However, this multidimensionality had only a modest impact on measures. Session did not cause DIF. DIF for assistive devices affected six items and caused a severe measurement artefact. The measurement artefact caused by DIF for diagnosis was negligible. The Mini-BESTest returns interval measures with robust construct validity and measurement invariance. However, caution should be used when comparing Mini-BESTest measures obtained with and without assistive devices.

BACKGROUND In the last few years, new noninvasive strategies have emerged as rehabilitative treatments for patients with stroke. Action observation treatment (AOT) is a rehabilitation approach based on the properties of the mirror neuron system with a positive impact on modifying cortical activation patterns and improving the upper limb kinematics. AOT involves the dynamic process of observing purposeful actions with the intention of imitating and then practicing those actions. In recent years, several clinical studies suggested the effectiveness of AOT in patients with stroke to improve motor recovery and autonomy in activities of daily living. However, a deeper knowledge of the behavior of the sensorimotor cortex during AOT seems to be essential. OBJECTIVE The aim of this clinical trial, conducted in 2 neurorehabilitation centers and in patients’ homes, is to investigate the effectiveness of AOT in patients with stroke, confirming the translational power of a tailored treatment. Particular emphasis will be placed on the predictive value of neurophysiological biomarkers. In addition, the feasibility and impact of a home-based AOT program will be investigated. METHODS A 3-arm, assessor-blinded, randomized controlled trial will be performed by enrolling patients with stroke in the chronic stage. A total of 60 participants will be randomly allocated to receive 15 sessions of AOT with different protocols (AOT at the hospital, AOT at home, and sham AOT), 3 sessions per week. The primary outcome will be assessed using the Fugl-Meyer Assessment-Upper Extremity scores. Secondary outcomes will be clinical, biomechanical, and neurophysiological assessment. RESULTS The study protocol is part of a project (project code GR-2016–02361678) approved and funded by the Italian Ministry of Health. The study began with the recruitment phase in January 2022, and enrollment was expected to end in October 2022. Recruitment is now closed (December 2022). The results of this study are expected to be published in spring 2023. Upon completion of the analyses, we will examine the preliminary effectiveness of the intervention and neurophysiological outcomes. CONCLUSIONS This study will be used to evaluate the effectiveness of 2 different AOT scenarios (ie, AOT at the hospital and AOT at home) in patients with chronic stroke and to assess the predictive value of neurophysiological biomarkers. Specifically, we will attempt to induce the functional modification of the cortical components by exploiting the features of the mirror neuron system, demonstrating relevant clinical, kinematic, and neurophysiological changes after AOT. With our study, we also want to provide, for the first time in Italy, the AOT home-based program while assessing its feasibility and impact. CLINICALTRIAL ClinicalTrials.gov NCT04047134; https://clinicaltrials.gov/ct2/show/NCT04047134 INTERNATIONAL REGISTERED REPORT DERR1-10.2196/42094

BACKGROUND With what has been known as the ‘triple-win effect’, introducing information and communication technologies (ICTs) in the healthcare of neurodegenerative diseases is beneficial in, “(1) delaying the need for institutional care, and reduction of the associated healthcare costs, (2) reducing the caregiving burden and (3) improving individuals’ quality of life (QoL)”. Nevertheless, the mismatch between the users’ expectations and their actual needs remains one of the main challenges that can reduce the usability of technology solutions. Therefore, the European project PROCare4Life (Personalized Integrated Care Promoting Quality of Life for Older People) that aims to develop an ICT-based platform for all parties involved in the healthcare of neurodegenerative diseases, adopts a user-centered design approach, where all users are involved from the inception and throughout the platform development and implementation in order integrate their needs and requirements in the proposed platform. OBJECTIVE This paper presents the results of the study which aimed to identify the needs and requirements of the potential end-users (older people with neurodegenerative diseases, caregivers, and healthcare professionals), and other key stakeholders. in the development of the PROCare4Life platform. METHODS A mixed qualitative and quantitative study design is utilized, including 2 online surveys, 40 interviews, and 4 workshops, conducted in five European countries: Germany; Italy; Portugal; Romania; and Spain. Both data types were analyzed separately, then merged and interpreted. This study placed a greater priority on the qualitative research, with quantitative research playing a supportive role. RESULTS The study took place between April and September 2020. A total of 217 participants were recruited, 157 completed the 2 online surveys (85 patients and 72 caregivers). 60 participants took part in the qualitative research (20 healthcare professionals, 5 patients, 5 caregivers, and 30 key stakeholders). We identified three main themes (T): (T1) experiences associated with illness; (T2) thoughts about the platform technology; (T3) desired properties. Alerts for adverse events, communication tools, reminders, monitoring are constantly needed functionalities. While, ease of use, personalization, and user-friendliness are foreseen as necessary features. CONCLUSIONS The paper identified the key personal, social, and health factors that influence the daily lives of the potential end-users, as well as reflecting on their needs and expectations regarding the design of the proposed PROCare4Life platform. The collected data were useful for the development of the PROCare4Life platform. While combination and collections of features for diverse user groups are typical for integrated care platforms, results in exponential complexity for designers, developers and users. Contradicting opinions and several concerns in the present study demonstrate that an ICT integrated care platform should not promise too much for too many. Instead, selection and focus, and sometimes restriction to essentials is necessary. Users and other stakeholders should be involved in these decisions. International Registered Report Identifier (IRRID): DERR1-10.2196/22463 INTERNATIONAL REGISTERED REPORT RR2-10.2196/22463

Introduction: The use of commercially available automatic speech recognition (ASR) software is challenged when dysarthria accompanies a physical disability. To overcome this issue, a mobile and personal speech assistant (mPASS) platform was developed, using a speaker-dependent ASR software. Objective: The aim of this study was to evaluate the performance of the proposed platform and to compare mPASS recognition accuracy to a commercial speaker-independent ASR software. In addition, secondary aims were to investigate the relationship between severity of dysarthria and accuracy and to explore people with dysarthria perceptions on the proposed platform. Methods: Fifteen individuals with dysarthric speech and 20 individuals with nondysarthric speech recorded 24 words and 5 sentences in a clinical environment. Differences in recognition accuracy between the two systems were evaluated. In addition, mPASS usability was assessed with a technology acceptance model (TAM) questionnaire. Results: In both groups, mean accuracy rates were significantly higher with mPASS compared to the commercial ASR for words and for sentences. mPASS reached good levels of usefulness and ease of use according to the TAM questionnaire. Conclusions: Practical applicability of this technology is realistic: the mPASS platform is accurate, and it could be easily used by individuals with dysarthria.

Background The Action Observation Therapy (AOT) is a well-established post-stroke rehabilitation treatment based on the theoretical framework of the Mirror Neuron System (MNS) activation. However, AOT protocols are still heterogeneous in terms of video contents of observed actions. Objective The aim of this study was to analyze electroencephalographic (EEG) recordings in stroke patients during the observation of different videos of task-specific upper limb movements, and to define which category of actions can elicit a stronger cortical activation in the observer’s brain. Methods Signals were analyzed from 19 chronic stroke subjects observing customized videos that represented 3 different categories of upper limb actions: Finalized Actions, Non-Finalized Actions, and Control Videos. The Event-Related Desynchronization in the µ and β bands was chosen to identify the involvement of the cerebral cortex: the area of the normalized power spectral density was calculated for each category and, deepening, for the reaching and completion sub-phases of Finalized Actions. For descriptive purposes, the time course of averaged signal power was described. The Kruskal–Wallis test ( P Results The analysis showed a greater desynchronization when subjects observed Finalized Actions with respect to Non-Finalized in all recorded areas; Control videos provoked a synchronization in the same areas and frequency bands. The reaching phase of feeding and self-care actions evoked a greater suppression both in µ and β bands. Conclusions The observation of finalized arm movements seems to elicit the strongest activation of the MNS in chronic stroke patients. This finding may help the clinicians to design future AOT-based stroke rehabilitation protocols. Clinical Trial Registration: Clinical Trial Registration—URL: http://www.clinicaltrials.gov . Unique identifier: NCT04047134.

Background Dementias—including Alzheimer disease—and Parkinson disease profoundly impact the quality of life of older population members and their families. PROCare4Life (Personalized Integrated Care Promoting Quality of Life for Older Adults) is a European project that recognizes the benefit of technology-based integrated care models in improving the care coordination and the quality of life of these target groups. This project proposes an integrated, scalable, and interactive care platform targeting older people suffering from neurodegenerative diseases, their caregivers, and socio-health professionals. PROCare4Life adopts a user-centered design approach from the early stage and throughout platform development and implementation, during which the platform is designed and adapted to the needs and requirements of all the involved users. Objective This paper presents the study protocol for investigating users’ needs and requirements regarding the design of the proposed PROCare4Life platform. Methods A mixed qualitative and quantitative study design is utilized, including online surveys, interviews, and workshops. The study aimed to recruit approximately 200 participants, including patients diagnosed with dementia or Parkinson disease, caregivers, socio-health professionals, and other stakeholders, from five different European countries: Germany, Italy, Portugal, Romania, and Spain. Results The study took place between April and September 2020. Recruitment is now closed, and all the data have been collected and analyzed in order to be used in shaping the large-scale pilot phase of the PROCare4Life project. Results of the study are expected to be published in spring 2021. Conclusions This paper charts the protocol for a user-centered design approach at the early stage of the PROCare4Life project in order to shape and influence an integrated health platform suitable for its intended target group and purpose. International Registered Report Identifier (IRRID) DERR1-10.2196/22463

The swallowing process involves the coordinated activation of several muscles to ensure the transfer of nutrients from the mouth to the stomach. A proper segmentation of swallowing into its constituent phases is relevant to obtain a quantitative biomechanical and electrophysiological description of this sensorimotor task.

Post-stroke locomotion is usually characterized by asymmetrical gait patterns, compensatory movements of trunk and nonparetic limb, altered motor coordination, and wide inter-stride variability. This pilot study was designed to test a twofold hypothesis: post-stroke survivors can exploit the redundancy of the segmental angles to stabilize the 3D footpath trajectory during the swing phase, in accordance with the Uncontrolled Manifold (UCM) theory; an intense rehabilitative treatment improves both motor performance and outcomes of the UCM analysis. Ten stroke survivors underwent two evaluation sessions, before and after a conventional multidisciplinary intensive rehabilitation program, encompassing clinical tests and gait analysis, both overground and on treadmill. In addition, the UCM analysis was implemented to investigate whether variance of segmental angles is structured to minimize the inter-stride variability of the 3D footpath during the swing phase of treadmill locomotion. Both clinical and spatio-temporal parameters improved after the treatment, even if the statistical significance was reached for a limited set of them. The UCM analysis suggested that post-stroke survivors exploit the redundancy of lower limbs segmental angles mainly during the late swing, without significant differences between affected and unaffected sides. Thereafter, the main significant effects of the rehabilitative treatment consisted in strengthening the synergistic organization of the redundant segmental angles involving a more accurate control of the 3D footpath. Concluding, the UCM theory can be a promising tool to appraise the effects of a specific rehabilitative protocol on motor coordination in post-stroke survivors.

BACKGROUND Dementias—including Alzheimer disease—and Parkinson disease profoundly impact the quality of life of older population members and their families. PROCare4Life (Personalized Integrated Care Promoting Quality of Life for Older Adults) is a European project that recognizes the benefit of technology-based integrated care models in improving the care coordination and the quality of life of these target groups. This project proposes an integrated, scalable, and interactive care platform targeting older people suffering from neurodegenerative diseases, their caregivers, and socio-health professionals. PROCare4Life adopts a user-centered design approach from the early stage and throughout platform development and implementation, during which the platform is designed and adapted to the needs and requirements of all the involved users. OBJECTIVE This paper presents the study protocol for investigating users’ needs and requirements regarding the design of the proposed PROCare4Life platform. METHODS A mixed qualitative and quantitative study design is utilized, including online surveys, interviews, and workshops. The study aimed to recruit approximately 200 participants, including patients diagnosed with dementia or Parkinson disease, caregivers, socio-health professionals, and other stakeholders, from five different European countries: Germany, Italy, Portugal, Romania, and Spain. RESULTS The study took place between April and September 2020. Recruitment is now closed, and all the data have been collected and analyzed in order to be used in shaping the large-scale pilot phase of the PROCare4Life project. Results of the study are expected to be published in spring 2021. CONCLUSIONS This paper charts the protocol for a user-centered design approach at the early stage of the PROCare4Life project in order to shape and influence an integrated health platform suitable for its intended target group and purpose. INTERNATIONAL REGISTERED REPORT DERR1-10.2196/22463

Home-based rehabilitation after an acute episode or following an exacerbation of a chronic disease is often problematic with a clear lack of continuity of care between hospital and home care. Secondary prevention is an essential element of long-term rehabilitation where strategies oriented toward risk reduction, treatment adherence, and optimization of quality of life need to be applied. Frail and sometimes isolated, the patient fails to adhere to the proposed post-discharge clinical pathway due to lack of appropriate clinical, emotional, and informational support. Providing a suitable rehabilitation after an acute episode or a chronic disease is a major issue, as it helps people to live independently and enhance their quality of life. However, as the rehabilitation period usually lasts some months, the continuity of care is often interrupted in the transition from hospital to home. Virtual coaches could help these patients to engage in a personalized rehabilitation program that complies with age-related conditions. These coaches could be a key technology for empowering patients toward increasing their adherence to the care plan and to improve their secondary prevention measures. In this paper, we are presenting a novel virtual coaching system that will address these challenges by combining recent technological advances with clinical pathways, based on joint research and validation activities from researchers from the medical and information and communication technology (ICT) domains.

Muscle synergies have been used for decades to explain a variety of motor behaviors, both in humans and animals and, more recently, to steer rehabilitation strategies. However, many sources of variability such as factorization algorithms, criteria for dimensionality reduction and data pre-processing constitute a major obstacle to the successful comparison of the results obtained by different research groups. Starting from the canonical EMG processing we determined how variations in filter cut-off frequencies and normalization methods, commonly found in literature, affect synergy weights and inter-subject similarity (ISS) using experimental data related to a 15-muscles upper-limb reaching task. Synergy weights were not significantly altered by either normalization (maximum voluntary contraction - MVC - or maximum amplitude of the signal - SELF) or band-pass filter ([20-500 Hz] or [50-500] Hz). Normalization did, however, alter the amount of variance explained by a set of synergies, which is a criterion often used for model order selection. Comparing different low-pass (LP) filters (0.5 Hz, 4 Hz, 10 Hz, 20 Hz cut-offs) we showed that increasing the low pass filter cut-off had the effect of decreasing the variance accounted for by a set number of synergies and affected individual muscle contributions. Extreme smoothing (i.e., LP cut-off 0.5 Hz) enhanced the contrast between active and inactive muscles but had an unpredictable effect on the ISS. The results presented here constitute a further step towards a thoughtful EMG pre-processing for the extraction of muscle synergies.

Objective:Developing functional artificial limbs for amputees has been a centuries-old challenge in medicine. We review the mechanical and neurologic principles of “cineplastic operations” and “plastic motors” used to restore movements in prostheses, with special attention to the work of Giuliano Vanghetti.Methods:We evaluated original publications describing cineplastic operations, biographic information, writings, drawings, and unpublished letters from the Vanghetti library, preserved in Empoli, Italy, and performed a bibliographic search and comparison for similar procedures in the literature.Results:Vanghetti's method for cineplastic operations differs from similar previous methods, being the first aimed at exploiting natural movements of the remnant muscles to activate the mechanical prosthesis, and the first to do so by directly connecting the prosthesis to the residual muscles and tendons. This represented a frame-changing innovation for that time and paved the way for current neuroprosthetic approaches. The first description of the method was published in 1898 and human studies started in 1900. The results of these studies were presented in 1905 and published in 1906 in Plastic and Kinematic Prosthesis. A German surgeon, Ferdinand Sauerbruch, often acknowledged as the inventor of the method, published his first results in 1915.Conclusions:Vanghetti was the first to accurately perform and describe cineplastic operations for patients following an upper arm amputation. He considered the neurologic implications of the problem and, perhaps in an effort to provide more appropriate proprioceptive feedback, he intuitively applied the prostheses so that they were functionally activated by the muscles of the proximal stump.

Elderly people with peripheral neuropathy of the lower limbs (PNLL) demonstrate a typical balance and gait impairment because of sensory ataxia. There is evidence that rehabilitation produces important gains on balance and gait. However, responsiveness to rehabilitation of balance and gait measures is unknown in PNLL. Aim of the current work is to evaluate the responsiveness to rehabilitation of balance, gait and sensory ataxia measures in elderly with PNLL. Twenty-five elderly with PNLL attending physiotherapy and occupational therapy during inpatient rehabilitation were recruited. Balance and gait measures (including static posturography, TUG test and the 10 m walking test) were administered on admission and discharge. An accelerometer secured to the trunk was used for TUG recording and static balance assessment. Static balance was tested with open and closed eyes, so as to assess sensory ataxia. Following rehabilitation, patients improved gait [admission vs discharge, mean(SD): 0.86(0.33) vs 0.98(0.32) m/s], TUG [18.7(7.8) vs 15.1(5.2) s] and turning [46.2(15.3) vs 53.3(15.3) °/s]. However, none of 12 static balance parameters derived from trunk acceleration significantly changed. Principal component analysis showed that before training, eyes closed and eyes open balance correlated with orthogonal components (one and two vs. three and four). After training, eyes open and eyes closed balance were more similar to each other being both correlated with component one. Responsiveness to rehabilitation is larger for gait than static balance measured by trunk acceleration. However, exercise can also have a beneficial effect on sensory ataxia by making eyes closed balance more similar to eyes open balance.

SummaryThis study investigates the effectiveness of a robot-mediated strategy aimed at promoting balance recovery after multidirectional slippages. Six older adults were asked to manage anteroposterior and mediolateral slippages while donning an active pelvis orthosis (APO). The APO was set up either to assist volunteers during balance loss or to be transparent. The margin of stability, in sagittal and frontal planes, was the main metric to assess the effectiveness of balance recovery. Results showed that the assistive strategy is effective at promoting balance recovery in the sagittal plane, for both perturbing paradigms; however, it is not effective at controlling stability in the frontal plane.

BACKGROUND In the last few years, several studies have focused on describing and understanding how virtual coaches (ie, coaching program or smart device aiming to provide coaching support through a variety of application contexts) could be key drivers for health promotion in home care settings. As there has been enormous technological progress in the field of artificial intelligence and data processing in the past decade, the use of virtual coaches gains an augmented attention in the considerations of medical innovations. OBJECTIVE This scoping review aimed at providing an overview of the applications of a virtual coach in the clinical field. In particular, the review focused on the papers that provide tangible information for coaching activities with an active implication for engaging and guiding patients who have an ongoing plan of care. METHODS We aimed to investigate the use of the term virtual coach in the clinical field performing a methodical review of the relevant literature indexed on PubMed, Scopus, and Embase databases to find virtual coach papers focused on specific activities dealing with clinical or medical contexts, excluding those aimed at surgical settings or electronic learning purposes. RESULTS After a careful revision of the inclusion and exclusion criteria, 46 records were selected for the full-text review. Most of the identified articles directly or indirectly addressed the topic of physical activity. Some papers were focused on the use of virtual coaching (VC) to manage overweight or nutritional issues. Other papers dealt with technological interfaces to facilitate interactions with patients suffering from different chronic clinical conditions such as heart failure, chronic obstructive pulmonary disease, depression, and chronic pain. CONCLUSIONS Although physical activity is a healthy practice that is most encouraged by a virtual coach system, in the current scenario, rehabilitation is the great absentee. This paper gives an overview of the tangible applications of this tool in the medical field and may inspire new ideas for future research on VC.

Gait and balance deficits are major impairments for Charcot-Marie-Tooth 1A (CMT1A) patients. However, motor rehabilitation is a challenge in CMT1A patients. There are poor evidences of clinical efficacy and low responsive outcome measures. Instrumented assessment (like inertial sensors) might be new tools to detect patient’s changes. A small sample of CMT1A was assessed before and after the rehabilitation period. Traditional and instrumented assessment measures of gait and balance were used. Results shown that only six-minute walking test showed an improvement after rehabilitation, in all patients. The Instrumented Timed Up and Go subtasks duration did not show responsiveness in CMT1A patients.

The evaluation of cervical spine mobility and the measurement of cervical range of motion are important methods used in clinical settings for diagnosis and prognosis of patients with cervical spine disorders but also to quantify manipulation effects. Therefore, the primary objective of this paper was the development of a “wear and forget” device able to monitor head posture. This paper consists of three parts: 1) identification and characterization of the piezoresistive textile employed both in static and dynamic conditions; 2) development of the sensor design; and 3) validation study concerning the investigation of sensor performances using Vicon measurements, as the reference standard. The proposed smart textile allowed the development of a light, comfortable, and non-invasive wearable system. The sensor accuracy and repeatability in measuring cervical range of motion in each primary plane (lateral bending, axial rotation, and flexion/extension) for five healthy subjects were evaluated. The results show a good accuracy and satisfactory repeatability with maximum standard deviation value close to 10°. We demonstrated the effectiveness of the wearable system as a valid, accurate, and suitable device for evaluating single plane neck movements.

Muscle synergies have been described as a neural strategy to simplify the control of the redundant motor actuators leading human movement and have been used to investigate motor coordination in healthy subjects and patients with neurological disorders. Here, we recap the theoretical framework underlying the identification of muscle synergies. Then, we summarize how muscle synergies are modified by neuropathologies and their potential for neurorehabilitation. Finally, we report on how they can be used to both assess the effectiveness of robot-aided rehabilitation and design innovative control strategies. This chapter is expected to highlight novel perspectives for robot-aided rehabilitation based on the analysis of muscle synergies. It is suitable for readers new to the concept of muscle synergies willing to be introduced to this topic, or already familiar with the matter and interested in a deeper analysis of its implications in neurorehabilitation, or for roboticists looking for new strategies to improve robotic rehabilitation.

The evolution to bipedalism forced humans to develop suitable strategies for dynamically controlling their balance, ensuring stability, and preventing falling. The natural aging process and traumatic events such as lower-limb loss can alter the human ability to control stability significantly increasing the risk of fall and reducing the overall autonomy. Accordingly, there is an urgent need, from both end-users and society, for novel solutions that can counteract the lack of balance, thus preventing falls among older and fragile citizens. In this study, we show a novel ecological approach relying on a wearable robotic device (the Active Pelvis Orthosis, APO) aimed at facilitating balance recovery after unexpected slippages. Specifically, if the APO detects signs of balance loss, then it supplies counteracting torques at the hips to assist balance recovery. Experimental tests conducted on eight elderly persons and two transfemoral amputees revealed that stability against falls improved due to the “assisting when needed” behavior of the APO. Interestingly, our approach required a very limited personalization for each subject, and this makes it promising for real-life applications. Our findings demonstrate the potential of closed-loop controlled wearable robots to assist elderly and disabled subjects and to improve their quality of life.

This study aimed at investigating the organization of joint angle variability during walking by using the uncontrolled manifold (UCM) theory. We tested two hypotheses: i. the coordinative mechanism underlying joint angle variance during the stance phase is compatible with a kinematic synergy that stabilizes the centre of mass (CoM) position; ii. the walking speed affects the variance components onto and orthogonal to the UCM. Eight healthy subjects (26.0±2.0years old) steadily walked on a treadmill at five normalised speeds (from 0.62±0.03m/s to 1.15±0.07m/s). Joint angles and foot orientation, and components of the CoM position were, respectively, used as elemental variables and task performance for the UCM implementation. The effect of speed, time events, and variance components on the distribution of data variance in the space of joint angles was analyzed by the ANOVA test. Results corroborated the hypothesis that the variance of elemental variables is structured in order to minimize the stride-to-stride variability of the CoM position, at all speeds. Noticeably, both variance components increase during the propulsive phase, albeit that parallel to the UCM was always grater than the orthogonal one. Accordingly, the observed kinematic synergy is supposed to contribute to accomplishing an efficient transition between two steps. Results also revealed that the walking speed does not affect the partitioning of elemental variables-related variance onto and orthogonal to the UCM. Accordingly, the organization of leg joint variance underlying the stabilization of CoM position remains almost unaltered across speeds.

This study was aimed at verifying whether aging modifies intralimb coordination strategy during corrective responses elicited by unexpected slip-like perturbations delivered during steady walking on a treadmill. To this end, 10 young and 10 elderly subjects were asked to manage unexpected slippages of different intensities. We analyzed the planar covariation law of the lower limb segments, using the principal component analysis, to verify whether elevation angles of older subjects covaried along a plan before and after the perturbation. Results showed that segments related to the perturbed limbs of both younger and older people do not covary after all perturbations. Conversely, the planar covariation law of the unperturbed limb was systematically held for younger and older subjects. These results occurred despite differences in spatio-temporal and kinematic parameters being observed among groups and perturbation intensities. Overall, our analysis revealed that aging does not affect intralimb coordination during corrective responses induced by slip-like perturbation, suggesting that both younger and older subjects adopt this control strategy while managing sudden and unexpected postural transitions of increasing intensities. Accordingly, results corroborate the hypothesis that balance control emerges from a governing set of biomechanical invariants, that is, suitable control schemes (e.g., planar covariation law) shared across voluntary and corrective motor behaviors, and across different sensory contexts due to different perturbation intensities, in both younger and older subjects. In this respect, our findings provide further support to investigate the effects of specific task training programs to counteract the risk of fall. NEW & NOTEWORTHY This study was aimed at investigating how aging affects the intralimb coordination of lower limb segments, described by the planar covariation law, during unexpected slip-like perturbations of increasing intensity. Results revealed that neither the aging nor the perturbation intensity affects this coordination strategy. Accordingly, we proposed that the balance control emerges from an invariant set of control schemes shared across different sensory motor contexts and despite age-related neuromuscular adaptations.

Background Common scales for clinical evaluation of post-stroke upper-limb motor recovery are often complemented with kinematic parameters extracted from movement trajectories. However, there is no a general consensus on which parameters to use. Moreover, the selected variables may be redundant and highly correlated or, conversely, may incompletely sample the kinematic information from the trajectories. Here we sought to identify a set of clinically useful variables for an exhaustive but yet economical kinematic characterization of upper limb movements performed by post-stroke hemiparetic subjects. Methods For this purpose, we pursued a top-down model-driven approach, seeking which kinematic parameters were pivotal for a computational model to generate trajectories of point-to-point planar movements similar to those made by post-stroke subjects at different levels of impairment. Results The set of kinematic variables used in the model allowed for the generation of trajectories significantly similar to those of either sub-acute or chronic post-stroke patients at different time points during the therapy. Simulated trajectories also correctly reproduced many kinematic features of real movements, as assessed by an extensive set of kinematic metrics computed on both real and simulated curves. When inspected for redundancy, we found that variations in the variables used in the model were explained by three different underlying and unobserved factors related to movement efficiency, speed, and accuracy, possibly revealing different working mechanisms of recovery. Conclusion This study identified a set of measures capable of extensively characterizing the kinematics of upper limb movements performed by post-stroke subjects and of tracking changes of different motor improvement aspects throughout the rehabilitation process. Electronic supplementary material The online version of this article (doi:10.1186/s12984-016-0187-9) contains supplementary material, which is available to authorized users.

This study introduces a novel algorithm to detect unexpected slipping-like perturbations based on the comparison between actual leg joint angles and those predicted by a pool of adaptive oscillators. The approach grounds on the hypothesis that during postural transitions, the difference between these datasets diverges and can early signal that the dynamic balance is challenged. To test this hypothesis, leg joint angles of twelve healthy young participants were recorded while undergoing four different perturbations delivered during steady locomotion. Joint angles were estimated after spanning the whole domain of the adaptive oscillator dynamics. Results confirmed that the implemented strategy allows to early detect a postural transition induced by a slipping-like perturbation: the best performance is represented by a mean detection time ranging between 150 and 250 ms and a low rate (lower than 10%) of false alarms. On the whole, the proposed approach is efficient even if it is based on a quite simple threshold-based algorithm. Moreover, it does not need any falling-based training before being implemented, is not computationally heavy, and is not subject dependent. Finally, since it is based on leg joint angles, it appears well suited to be implemented in lower-limb orthoses/prostheses already equipped with joint position sensors.

SUMMARYFall-related accidents are among the most serious concerns in elderly people, amputees and subjects with neurological disorders. The aim of this paper was to investigate the behaviour of healthy subjects wearing a novel light-weight pelvis exoskeleton controlled in zero-torque mode while carrying out unperturbed locomotion and managing unexpected perturbations. Results showed that the proposed exoskeleton was unobtrusive and had a minimum loading effect on the human biomechanics during unperturbed locomotion. Conversely, it affected the movement of the trailing leg while subjects managed unexpected slipping-like perturbations. These findings support further investigations on the potential use of powered exoskeletons to assist locomotion and, possibly prevent incipient falls.

Muscle synergies are considered as a potential strategy to reduce the computational workload undergoing the estimation of muscle activity during different motor tasks. They are usually extracted by means of algebraic factorization algorithms able to capture the greatest communality of a set of electromyographic (EMG) signals. Usually EMG signals are pooled across different sub-movements (e.g., going forward and backward during reaching) in order to increase the complexity of the data set and, consequently, capture the maximum communality. Despite of these, this preliminary study was designed to investigate how the communality of EMG signals can be explained looking at narrow subset of recorded signals. Results corroborate the hypothesis that using a suitable subset of the whole dataset can significantly modify the values of weight coefficients. In this regard, further methodological investigations of algorithms adopted for synergy extraction are still required.

Muscle synergies are considered a possible approach used by the Central Nervous System (CNS) to reduce the computational workload to achieve movements such as locomotion and reaching in an effective and smooth way. This abstract summarizes our recent results about the modifications induced by a stroke on muscle synergies. Finally, some considerations about the possible design of novel protocols for neurorehabilitation starting from these findings are also provided.

Support against gravity is a promising strategy to enable upper extremity rehabilitation in neurological patients. While such support facilitates reaching in subjects with severe impairments, its effect on the reorganization of muscle activations has not been investigated. In particular, it remains unclear what amount of weight compensation should be employed to achieve maximal functional recovery. To provide insights into these issues, we studied muscle synergies during the execution of 3D reaching movements under six different levels of arm-weight support. Our preliminary results suggest that gravity compensation decreases the level of muscle synergy activations required for task performance. However, whether weight support could induce changes in the muscle-synergy structures awaits further confirmation.

This paper aimed at investigating the effects of a novel robotic-aided rehabilitation treatment for the recovery of the upper limb related capabilities in chronic post stroke patients. Eighteen post-stroke patients were enrolled in a six-week therapy program and divided into two groups. They were all required to perform horizontal pointing movements both in the presence of a robot-generated divergent force field (DF) that pushed their hands proportional to the trajectory error and perpendicular to the direction of motion, and according to the typical active assistive (AA) approach used in robotic therapy. We used a crossover experimental paradigm where the two groups switched from one therapy treatment to the other. The hypothesis underlying this paper was that the use of the destabilizing scenario forced the patient to keep the end-point position as close as possible to the ideal path, hence requiring a more active control of the arm with respect to the AA approach. Our findings confirmed this hypothesis. In addition, when the DF treatment was provided in the first therapy cycle, patients also showed straighter and smoother paths during the subsequent AA therapy cycle, while this was not true in the opposite case. In conclusion, the results herein reported provide evidence that the use of an unstable DF field can lead to better recovery outcomes, and therefore it potentially more effective than solely active assistance therapy alone.

Background: Several studies investigating the use of electromyographic (EMG) signals in robot-based stroke neuro-rehabilitation to enhance functional recovery. Here we explored whether a classical EMG-based patterns recognition approach could be employed to predict patients’ intentions while attempting to generate goal-directed movements in the horizontal plane. Methods: Nine right-handed healthy subjects and seven right-handed stroke survivors performed reaching movements in the horizontal plane. EMG signals were recorded and used to identify the intended motion direction of the subjects. To this aim, a standard pattern recognition algorithm (i.e., Support Vector Machine, SVM) was used. Different tests were carried out to understand the role of the inter- and intra-subjects’ variability in affecting classifier accuracy. Abnormal muscular spatial patterns generating misclassification were evaluated by means of an assessment index calculated from the results achieved with the PCA, i.e., the so-called Coefficient of Expressiveness (CoE). Results: Processing the EMG signals of the healthy subjects, in most of the cases we were able to build a static functional map of the EMG activation patterns for point-to-point reaching movements on the horizontal plane. On the contrary, when processing the EMG signals of the pathological subjects a good classification was not possible. In particular, patients’ aimed movement direction was not predictable with sufficient accuracy either when using the general map extracted from data of normal subjects and when tuning the classifier on the EMG signals recorded from each patient. Conclusions: The experimental findings herein reported show that the use of EMG patterns recognition approach might not be practical to decode movement intention in subjects with neurological injury such as stroke. Rather than estimate motion from EMGs, future scenarios should encourage the utilization of these signals to detect and interpret the normal and abnormal muscle patterns and provide feedback on their correct recruitment.

It is well known that people exposed to a robotgenerated force field disturbing arm motion, are able to recover their unperturbed kinematic patterns. It has been also reported that muscle synergies undergoing the activation of many muscle groups are strongly consistent apart from external (e.g., reaching movements in the frontal or in the sagittal plane) or internal (e.g., severity and location of a cerebrovascular accident) constraints. Here, we investigated whether and how muscle synergies underlying the activation of upper limb related motor tasks, can be modified due to a divergent force field exposure. Results showed that muscle synergies can be significantly modified during the ongoing of the training. This open up new possibilities for the development of more effective neuro-rehabilitation protocols.

Introduction: Object manipulation is an essential functional motor action, critical for activities of daily living. Successful object manipulation depends on factors which include one’s ability to identify object characteristics, and usable grasp types [1], and to exert an adequate magnitude of grip force [2]. To assess a subset of the hand’s movements, we designed a sensorized glove, capable of detecting hand kinematic and force applied to the digits–object surface. Methods: Glove design focuses on lightness, ease of donning, transparency, ability to detect grasp force and kinematic information while preserving as much as possible residual touch sensing capabilities, and inexpensiveness. The sensorized glove is able to detect metacarpal (MCP) and proximal interphalangeal (PIP) joints flexion of the fingers and the force applied during grasp. Contact with objects is detected using Force Sensing Resistors (FSR). We used two FSR sensors sizes (1.2 and 2.5 cm). Small FSRs, used for detecting force applied to the fingers are positioned on fingertips to minimize grasp obstruction. A large FSR detects force on hand palm. Finger flexion movements are detected using bend sensor placed onMCP and PIP joints. Each bend sensor locationwas chosen empirically for each subject. The first four fingers are monitored, the fifth finger was decided to leave unmonitored because minimally used during grasp movements. Results: The main goal of the glove is to identify the hand state, opened or closed, and the conditions of grasping. Kinematic and force data was acquired from a few healthy subjects during grasp of three differently sized objects. Sensors information is shown in Fig. 1. During small object grasp, MCP and PIP joints were most involved; in particular, depending on the relative size of hand, objects and grasping style, large differences can be seen in the PIP bend sensors trajectories (second row). Discussion: Our system can detect hand kinematic and force during grasp, without introducing significant movement restriction, and provides useful information that other devices, used in clinical practice, are not able to detect (e.g. grasp pre-shaping). Moreover the glove has proved to be comfortable and adaptable, allowing its use in multiple clinical applications. The intention in a future step is to optimize the therapeutic intervention on patients with upper limb impairments.