Modeling of a Non-Rigid Passive Exoskeleton-Mathematical Description and Musculoskeletal Simulations

There is a growing application of passive exoskeletons in the industrial sector with the purpose to reduce the incidence of work-related musculoskeletal disorders (MSDs). Nowadays, while many passive shoulder exoskeletons have been developed to support overhead tasks, they present limitations in supporting tasks such as load lifting and carrying. Further developments are therefore needed to have a wider application of these devices in the industrial sector. This paper presents a modelling procedure of a passive non-rigid exoskeleton for shoulder support that can be used to evaluate the device in its development phase. The modelling began with the definition of the equations to describe the exoskeleton kinematics and dynamics to obtain the support force profile provided by the device over the shoulder flexion angle. A musculoskeletal simulation software was then used to evaluate the effect of the device on the human body. The computed support force profile is in agreement with the purpose of the device, with the maximal support force obtained for a shoulder flexion angle of 85–90°. The maximum support force value had the same magnitude as the one reported by the device user manual (3.5 kg). In particular, for a determined exoskeleton configuration, the maximum support force value computed was 34.3 N, equal to the reported by the manufacturer. The subsequent musculoskeletal simulation showed the ability of the device to reduce the muscular activation of agonist muscles such as the anterior deltoid (−36.01%) compared to the case when the exoskeleton is not used. The musculoskeletal results showed a positive effect of the device on the joint reaction forces at the glenohumeral joint with a reduction up to 41.91%. Overall the methodology and the mathematical model proposed can be used to further develop these devices, making them suitable for a wider range of tasks

Predicting Vertical Ground Reaction Forces in Running from the Sound of Footsteps

From the point of view of measurement, footstep sounds represent a simple, wearable and inexpensive sensing opportunity to assess running biomechanical parameters. Therefore, the aim of this study was to investigate whether the sounds of footsteps can be used to predict the vertical ground reaction force profiles during running. Thirty-seven recreational runners performed overground running, and their sounds of footsteps were recorded from four microphones, while the vertical ground reaction force was recorded using a force plate. We generated nine different combinations of microphone data, ranging from individual recordings up to all four microphones combined. We trained machine learning models using these microphone combinations and predicted the ground reaction force profiles by a leave-one-out approach on the subject level. There were no significant differences in the prediction accuracy between the different microphone combinations (p < 0.05). Moreover, the machine learning model was able to predict the ground reaction force profiles with a mean Pearson correlation coefficient of 0.99 (range 0.79–0.999), mean relative root-mean-square error of 9.96% (range 2–23%) and mean accuracy to define rearfoot or forefoot strike of 77%. Our results demonstrate the feasibility of using the sounds of footsteps in combination with machine learning algorithms based on Fourier transforms to predict the ground reaction force curves. The results are encouraging in terms of the opportunity to create wearable technology to assess the ground reaction force profiles for runners in the interests of injury prevention and performance optimization

Electrocortical Activity in Older Adults Is More Influenced by Cognitive Task Complexity Than Concurrent Walking

Human cognitive-motor performance largely depends on how brain resources are allocated during simultaneous tasks. Nonetheless, little is known regarding the age-related changes in electrocortical activity when dual-task during walking presents higher complexity levels. Thus, the aim of this study was to investigate whether there are distinct changes in walking performance and electrocortical activation between young and older adults performing simple and complex upper limb response time tasks. Physically active young (23 ± 3 years, n = 21) and older adults (69 ± 5 years, n = 19) were asked to respond as fast as possible to a single stimuli or a double stimuli appearing on a touch screen during standing and walking. Response time, step frequency, step frequency variability and electroencephalographic (EEG) N200 and P300 amplitudes and latencies from frontal central and parietal brain regions were recorded. The results demonstrated that older adults were 23% slower to respond to double stimuli, whereas younger adults were only 12% slower (p 0.05). More importantly, the P300 amplitude was significantly reduced for older adults when responding to double stimuli regardless of standing or walking tasks (p < 0.05), with no changes in younger participants. Therefore, physically active older adults can attenuate potential walking deficits experienced during dual-task walking in simple cognitive tasks. However, cognitive tasks involving decision making influence electrocortical activation due to reduced cognitive resources to cope with the task demands

Leadership in the context of new public management: an analysis from the perspective of public managers of Minas Gerais and Rio de Janeiro

Novas incursões orientadas à modernização do estado, centradas na adoção de modelos de gestão pública que visam enfatizar a noção de resultado, assim como de instrumentos gerenciais típicos do management, leadership e do mundo corporativo vêm caracterizando a gestão pública brasileira. Nessa perspectiva, há de se salientar iniciativas como as dos estados de Minas Gerais, por meio de seu programa de choque de gestão, e do Rio de Janeiro. Tendo por base tais movimentos e experiências, novas questões emergem e demandam ser melhor compreendidas. A partir da análise de relações entre iniciativas associadas ao movimento em torno da chamada nova administração pública e o construto liderança, este trabalho tem como propósito central investigar, a partir de levantamento empírico de dados realizado junto a ocupantes de posições chave no setor público dos governos de Minas Gerais e Rio de Janeiro, temas, questões e desafios que emergem de tais iniciativas, assim como suas implicações sobre a demanda por novos perfis de liderança e formas de seu desenvolvimento. Com o auxílio do software de tratamento qualitativo NVivo 8 foi possível agrupar os principais temas e desafios identificados em torno das relações entre nova administração pública e liderança. O estudo permitiu, também, identificar um elenco de atributos de competências requeridas ao gestor e líder do setor público.New schools of thought targeted at the modernization of the state and centered on the adoption of public management models designed to emphasize the notion of outcome as well as of managerial tools typical of management, leadership and the corporate world have characterized public management in Brazil. From this perspective, initiatives such as those of the states of Minas Gerais and Rio de Janeiro, with their modernization of state programs should be pointed out. Based on such experiences and movements, new issues emerge and demand to be better understood. From the analysis of the relations between initiatives associated to the movement around the so-called new public management and the category leadership, this study's main goal is to investigate, using empirical data collection conducted with occupants of key positions in the public sector of both Minas Gerais and Rio de Janeiro's governments, themes, issues and challenges that emerge from such initiatives, as well as their implications on the demand for new kinds of leadership and ways of its development. With the help of the qualitative data research software NVivo 8, it was possible to group the main issues and challenges identified around the relations between public administration and new leadership. The study also allowed us to identify a list of competency attributes required of the manager and leader of the public sector