A biomechanical approach to prevent falls in ergonomic settings

Introduction: Fall-related injuries are exceptionally prevalent in occupational settings. While endangering the workers’ health, falls cause poor productivity and increased economic burden in the workplace. Hence, identifying these threats and training workers to achieve proper postural control is crucial. Purpose: Study 1: To investigate the ankle joint kinematics in unexpected and expected trip responses during single-tasking (ST), dual-tasking (DT), and triple-tasking (TT), before and after a physically fatiguing exercise. Study 2: To investigate the impact of virtual heights, DT, and training on static postural stability and cognitive processing. Methods: Study 1: Twenty collegiate volunteers (10 males and females, one left leg dominant, age 20.35 plus-minus 1.04 years, height 174.83 plus-minus 9.03 cm, mass 73.88 plus-minus 15.55 kg) were recruited. Ankle joint kinematics were recorded while treadmill walking during normal gait (NG), unexpected trip (UT), and expected trip (ET) perturbations with DT and physical fatigue. Study 2: Twenty-eight collegiate volunteers (14 males and females; all right leg dominant; age 20.48 plus-minus 1.26 years; height 172.67 plus-minus 6.66 cm; mass 69.52 plus-minus 13.78 kg; body mass index 23.32 plus-minus 3.54 kg/m2) were recruited. They were exposed to different virtual environments (VEs) over three days with and without DT. Postural sway parameters, lower extremity muscle activity, heart rate, and subjective anxiety parameters were collected. Results: Study 1: Greater maximum ankle angles were observed during UT compared to NG, MDT compared to ST, and TT compared to ST, while greater minimum ankle angles were observed during ET compared to NG and during post-fatigue compared to pre-fatigue. Study 2: Greater postural decrements and poor cognitive processing were observed in high altitudes and DT. Discussion & conclusions: Study 1: Trip recovery responses are different between during DT, TT, and fatigue. Study 2: Static postural stability deteriorates at higher virtual altitudes and with DT, while it improves with a two-day training. Virtual height exposure reduces cognitive performance. Importance: The findings of these studies will provide insights into the biomechanics of falls in ergonomic settings and aid in designing functional and convenient fall prevention programs

Proceedings of the 9th Conference on Autonomous Robot Systems and Competitions

Welcome to ROBOTICA 2009. This is the 9th edition of the conference on Autonomous Robot Systems and Competitions, the third time with IEEE‐Robotics and Automation Society Technical Co‐Sponsorship. Previous editions were held since 2001 in Guimarães, Aveiro, Porto, Lisboa, Coimbra and Algarve. ROBOTICA 2009 is held on the 7th May, 2009, in Castelo Branco , Portugal. ROBOTICA has received 32 paper submissions, from 10 countries, in South America, Asia and Europe. To evaluate each submission, three reviews by paper were performed by the international program committee. 23 papers were published in the proceedings and presented at the conference. Of these, 14 papers were selected for oral presentation and 9 papers were selected for poster presentation. The global acceptance ratio was 72%. After the conference, eighth papers will be published in the Portuguese journal Robótica, and the best student paper will be published in IEEE Multidisciplinary Engineering Education Magazine. Three prizes will be awarded in the conference for: the best conference paper, the best student paper and the best presentation. The last two, sponsored by the IEEE Education Society ‐ Student Activities Committee. We would like to express our thanks to all participants. First of all to the authors, whose quality work is the essence of this conference. Next, to all the members of the international program committee and reviewers, who helped us with their expertise and valuable time. We would also like to deeply thank the invited speaker, Jean Paul Laumond, LAAS‐CNRS France, for their excellent contribution in the field of humanoid robots. Finally, a word of appreciation for the hard work of the secretariat and volunteers. Our deep gratitude goes to the Scientific Organisations that kindly agreed to sponsor the Conference, and made it come true. We look forward to seeing more results of R&D work on Robotics at ROBOTICA 2010, somewhere in Portugal

Aerospace medicine and biology. A continuing bibliography with indexes, supplement 206, May 1980

This bibliography lists 169 reports, articles, and other documents introduced into the NASA scientific and technical information system in April 1980

Fast Sensing and Adaptive Actuation for Robust Legged Locomotion

Robust legged locomotion in complex terrain demands fast perturbation detection and reaction. In animals, due to the neural transmission delays, the high-level control loop involving the brain is absent from mitigating the initial disturbance. Instead, the low-level compliant behavior embedded in mechanics and the mid-level controllers in the spinal cord are believed to provide quick response during fast locomotion. Still, it remains unclear how these low- and mid-level components facilitate robust locomotion. This thesis aims to identify and characterize the underlining elements responsible for fast sensing and actuation. To test individual elements and their interplay, several robotic systems were implemented. The implementations include active and passive mechanisms as a combination of elasticities and dampers in multi-segment robot legs, central pattern generators inspired by intraspinal controllers, and a synthetic robotic version of an intraspinal sensor. The first contribution establishes the notion of effective damping. Effective damping is defined as the total energy dissipation during one step, which allows quantifying how much ground perturbation is mitigated. Using this framework, the optimal damper is identified as viscous and tunable. This study paves the way for integrating effective dampers to legged designs for robust locomotion. The second contribution introduces a novel series elastic actuation system. The proposed system tackles the issue of power transmission over multiple joints, while featuring intrinsic series elasticity. The design is tested on a hopper with two more elastic elements, demonstrating energy recuperation and enhanced dynamic performance. The third contribution proposes a novel tunable damper and reveals its influence on legged hopping. A bio-inspired slack tendon mechanism is implemented in parallel with a spring. The tunable damping is rigorously quantified on a central-pattern-generator-driven hopping robot, which reveals the trade-off between locomotion robustness and efficiency. The last contribution explores the intraspinal sensing hypothesis of birds. We speculate that the observed intraspinal structure functions as an accelerometer. This accelerometer could provide fast state feedback directly to the adjacent central pattern generator circuits, contributing to birds’ running robustness. A biophysical simulation framework is established, which provides new perspectives on the sensing mechanics of the system, including the influence of morphologies and material properties. Giving an overview of the hierarchical control architecture, this thesis investigates the fast sensing and actuation mechanisms in several control layers, including the low-level mechanical response and the mid-level intraspinal controllers. The contributions of this work provide new insight into animal loco-motion robustness and lays the foundation for future legged robot design

On the intrinsic control properties of muscle and relexes: exploring the interaction between neural and musculoskeletal dynamics in the framework of the equilbrium-point hypothesis

The aim of this thesis is to examine the relationship between the intrinsic dynamics of the body and its neural control. Specifically, it investigates the influence of musculoskeletal properties on the control signals needed for simple goal-directed movements in the framework of the equilibriumpoint (EP) hypothesis. To this end, muscle models of varying complexity are studied in isolation and when coupled to feedback laws derived from the EP hypothesis. It is demonstrated that the dynamical landscape formed by non-linear musculoskeletal models features a stable attractor in joint space whose properties, such as position, stiffness and viscosity, can be controlled through differential- and co-activation of antagonistic muscles. The emergence of this attractor creates a new level of control that reduces the system’s degrees of freedom and thus constitutes a low-level motor synergy. It is described how the properties of this stable equilibrium, as well as transient movement dynamics, depend on the various modelling assumptions underlying the muscle model. The EP hypothesis is then tested on a chosen musculoskeletal model by using an optimal feedback control approach: genetic algorithm optimisation is used to identify feedback gains that produce smooth single- and multijoint movements of varying amplitude and duration. The importance of different feedback components is studied for reproducing invariants observed in natural movement kinematics. The resulting controllers are demonstrated to cope with a plausible range of reflex delays, predict the use of velocity-error feedback for the fastest movements, and suggest that experimentally observed triphasic muscle bursts are an emergent feature rather than centrally planned. Also, control schemes which allow for simultaneous control of movement duration and distance are identified. Lastly, it is shown that the generic formulation of the EP hypothesis fails to account for the interaction torques arising in multijoint movements. Extensions are proposed which address this shortcoming while maintaining its two basic assumptions: control signals in positional rather than force-based frames of reference; and the primacy of control properties intrinsic to the body over internal models. It is concluded that the EP hypothesis cannot be rejected for single- or multijoint reaching movements based on claims that predicted movement kinematics are unrealistic

Sensory and methodological aspects in biomechanical research of postural control and clinical fields of application

The human senses constitute a highly complex system based on various sensory organs, afferent pathways, and central processing locations, which allow us to interact with the environment, but also with ourselves. A further domain is important to achieve this interaction: the motor system, which allows linguistic communication and locomotion, for example. It becomes evident that sensory receptors work as a source of information to initiate, optimize, or cease motor activity. One generic term for such sensory sources is the somatosensory system, which is mainly based on receptors located in muscles, tendons, and the skin (cutaneous sensitivity). In this regard, it has been shown that cutaneous sensitivity contributes to human balance regulation. However, there are still debates concerning the exact role of plantar (foot sole) receptor inputs in particular, and how their isolated contribution to, e.g., balance regulation may be assessed accordingly. To investigate the interaction between plantar cutaneous sensitivity and human balance capabilities, several aspects need to be considered which are still controversial and inconclusive in the scientific community. For example, when assessing cutaneous vibration sensitivity, it is well-known that increasing vertical forces of the contactor toward the skin usually result in improved sensitivity. However, it has not been profoundly investigated whether assessing plantar vibratory sensitivity differs when comparing a standing or sitting posture, which obviously involves different contactor forces. In addition, many studies implementing cutaneous sensitivity show certain limitations with respect to adequate data analyses. A similar aspect also applies when assessing balance performance: devices allowing an investigation of dynamic balance performance (induced by unexpected platform perturbations while standing, for example) have only been partially investigated with regard to their biomechanical quality criteria, such as reliability. With these considerations in mind, the present doctoral thesis is based on five published studies. Study 1 investigates if plantar sensitivity is influenced by different body positions when collecting data. Study 2 asks how to appropriatly analze plantar sensitivity data. Study 3 examines the reliability of dynamic balance responses using the so-called Posturomed device, and Study 4 identifies the isolated role of plantar inputs on balance responses, when an acute sensory manipulation is induced that exclusively affects plantar aspects. Ultimately, clinical fields of application (based on the previous four studies) are highlighted in Study 5. The main findings of the first four studies can be summarized as follows. First, higher contact forces when standing compared to sitting did not influence plantar sensitivity. This is an important finding, as plantar sensitivity tests (often performed during sitting) may, hence, be brought into context with balance tests usually performed during standing. Second, plantar sensitivity data are shown to exhibit heteroscedasticity, meaning that the measurement error increases as the values increase. In Study 2, we provided an easy-to-follow example for how to account for heteroscedasticity by logarithmizing the raw data, and how to control whether this approach was successful in eliminating heteroscedasticity. Third, dynamic balance responses assessed via the Posturomed device exhibit an overall good reliability. Occasional significant differences were shown to be clinically non-relevant, identified by root mean square error calculations. Fourth, a permanent plantar sensory manipulation (hypothermia) was successfully achieved and maintained throughout data collection. Study 4 showed that the reduced plantar sensory input due to the hypothermic manipulation was compensated during more unchallenging balance conditions (standing still). There was no full compensation during more challenging balance conditions (unexpected platform perturbations during standing), however, with the body reacting with cautious motor behavior. This became evident by decreased outcome measures following hypothermic plantar sensory manipulation. These four studies shed further light onto investigations combining sensory and motor tests, especially with regard to physiological and methodological aspects that should be considered when analyzing and interpreting associated data. Finally, this doctoral thesis also provides an example of identifying clinical fields of application concerning sensory-focused research. In Study 5, we highlight the role of sensory research in the (early) diagnosis of diseases associated with cognitive decline. For this purpose, various instruments such as sensory tests or coordinative motor tests are implemented. Preliminary results suggest that not only classical cognitive parameters and questionnaires should be used to identify and better understand cognitive decline.Die menschlichen Sinne stellen ein sehr komplexes System dar, welches auf verschiedenen sensorischen Organen, afferenten Leitungsbahnen und zentralen Verarbeitungsstellen basiert und es uns ermöglicht, mit der Umwelt, aber auch mit uns selbst, zu interagieren. Dahingehend ist eine weitere wichtige Domäne wichtig, um diese Interaktion zu bewerkstelligen: das motorische System, welches etwa eine sprachliche Kommunikation oder auch die Fortbewegung ermöglicht. Es wird somit offensichtlich, dass sensorische Rezeptoren eine Informationsquelle darstellen, um motorische Aktivität zu initiieren, zu optimieren oder zu beenden. Ein grundlegender Terminus für solch sensorische Quellen ist das somatosensorische System, welches überwiegend auf Rezeptoren in Muskulatur, Sehnen und der Haut (kutane Sensibilität) beruht. Diesbezüglich wurde bereits aufgezeigt, dass die kutane Sensibilität einen Beitrag bei der menschlichen Gleichgewichtsregulation leistet. Allerdings existieren dabei nachwievor Diskussionen in Bezug auf die genaue Bedeutung plantarer (die Fußsohle betreffend) Rezeptor-Inputs und inwieweit deren isolierte Bedeutung bei der Gleichgewichtsregulation entsprechend ermittelt werden kann. Um die Interaktion zwischen der kutanen Sensorik der Fußsohle und der menschlichen Gleichgewichtsfähigkeit zu erforschen, sollten verschiedene Aspekte berücksichtigt werden, welche nachwievor kontrovers und nicht eindeutig in der Wissenschaft diskutiert werden. Bei Erhebungen der kutanen Vibrationssensibilität, als Beispiel, ist bereits bekannt, dass erhöhte Vertikalkräfte, mit denen der Vibrationsstößel gegen die Haut appliziert ist, generell zu einer verbesserten Sensibilität/Sensorik führen. Allerdings wurde noch nicht klar erforscht, ob sich die plantare Vibrationssensibilität zwischen einer stehenden und sitzenden Haltung der Probanden/innen unterscheidet, wobei hier natürlich unterschiedliche Vertikalkräfte der Stößel wahrscheinlich sind. Darüber hinaus zeigen viele Studien, welche die Hautsensibilität untersuchen, gewisse Limitierungen in Bezug auf eine adäquate Datenanalyse. Ein sehr ähnlicher Aspekt trifft auch auf die Evaluierung der Gleichgewichtsfähigkeit zu: Messgeräte, welche dabei eine Erfassung der dynamischen Gleichgewichtsfähigkeit zulassen (z.B. eingeleitet durch unerwartete Plattform-Perturbationen während des Stehens), wurden bisher nur teilweise auf die biomechanischen Gütekriterien hin untersucht, wie etwa die Reliabilität. Aufgrund dieser Überlegungen basiert die vorliegende Dissertation auf fünf publizierten Studien, welche folgende Aspekte untersuchten: Wird die plantare Sensibilität durch verschiedene Körperpositionen während der Datenaufnahme beeinflusst (Studie 1)? Wie können plantare Sensibilitätsdaten angemessen analysiert werden (Studie 2)? Darüber hinaus wurde ebenso untersucht, inwiefern das sogenannte 'Posturomed'-Messgerät bei der Beurteilung dynamischer Gleichgewichtsantworten reliable Messwerte liefert (Studie 3). Ferner wurde in Studie 4 untersucht, inwiefern isoliert plantare Inputsignale bei Gleichgewichtsantworten relevant sind (anhand einer akuten sensorischen Manipulation, welche ausschließlich die Fußsohle betrifft). In Studie 5 werden konkrete klinische Anwendungsbeispiele aufgrund der vier hier vorgestellten Studien aufgezeigt. Die Hauptergebnisse der ersten vier Studien können wie folgt zusammengefasst werden: Erstens, höhere vertikale Kontaktkräfte während des Stehens verglichen mit sitzenden Positionen führten zu keinen Unterschieden bzgl. der plantaren Sensibilität. Dies ist eine wichtige Erkenntnis, da plantare Sensorikmessungen (oft während des Sitzens durchgeführt) dadurch in Kontext mit Gleichgewichtstests gebracht werden können, welche normalerweise im Stehen erfolgen. Zweitens, Daten der plantaren Sensorik zeigten Heteroskedastizität, was bedeutet, dass sich der Messfehler mit Größenzunahme der Messwerte ebenso erhöht. Wir konnten in Studie 2 ein leicht zu erschließendes Beispiel aufzeigen, wie das Problem der Heteroskedastizität durch eine Logarithmierung der Rohdaten behandelt werden konnte und wie kontrolliert werden konnte, ob diese Behandlung erfolgreich war. Drittens, die dynamischen Gleichgewichtsantworten, welche mittels des 'Posturomed' ermittelt wurden, zeigen insgesamt eine gute Reliabilität. Gelegentlich auftretende signifikante Unterschiede wurden anhand von Berechnungen der Wurzel der mittleren Fehlerquadratsumme (root mean square error, RMSE) als klinisch nicht relevant eingestuft. Viertens, eine anhaltende plantar-sensorische Manipulation (Hypothermie) wurde erfolgreich eingeleitet und während der Datenerhebung aufrecht erhalten. Studie 4 zeigte ferner, dass die hypothermisch eingeleiteten reduzierten plantaren Sensorik-Inputs während der eher nicht herausfordernden quasi-statischen Gleichgewichtsbedingungen (einfaches aufrechtes Stehen) kompensiert werden konnten. Während der herausfordernden Gleichgewichtskonditionen (unerwartete Perturbationen der Plattform während des Stehens) hingegen wurde keine vollständige Kompensation erreicht. Allerdings reagierten die Probanden mit einem vorsichtigen motorischen Verhalten. Dies wurde durch die reduzierten Ergebnisparameter infolge der plantaren hypothermischen Manipulation ersichtlich. Die vier hier genannten Studien zeigen weitere Erkenntnisse in Bezug auf Forschungsaktivitäten, welche sensorische und motorische Tests vereinen. Dies trifft speziell in Hinblick auf physiologische und methodologische Aspekte zu, welche bei der Analyse und Interpretation derartiger Daten in Betracht gezogen werden sollten. Zuletzt bietet diese Arbeit auch ein Beispiel dafür, welche klinischen Anwendungsfelder im Bereich der sensorisch-fokussierten Forschung identifiziert werden können. In Studie 5 wird dafür die Bedeutung sensorischer Forschung bei der (Früh-) Diagnose von Erkrankungen aufgezeigt, welche mit kognitiven Einschränkungen in Verbindung gebracht werden. Für diesen Zweck werden verschiedene Instrumente eingebracht, wie etwa sensorische oder koordinativ-motorische Tests. Vorläufige Ergebnisse deuten dabei bereits an, dass nicht nur die klassischen kognitiven Parameter und Fragebögen bei der Identifizierung oder zum Zwecke des besseren Verstehens kognitiven Verfalls einbezogen werden sollten

Biomechanical Spectrum of Human Sport Performance

Writing or managing a scientific book, as it is known today, depends on a series of major activities, such as regrouping researchers, reviewing chapters, informing and exchanging with contributors, and at the very least, motivating them to achieve the objective of publication. The idea of this book arose from many years of work in biomechanics, health disease, and rehabilitation. Through exchanges with authors from several countries, we learned much from each other, and we decided with the publisher to transfer this knowledge to readers interested in the current understanding of the impact of biomechanics in the analysis of movement and its optimization. The main objective is to provide some interesting articles that show the scope of biomechanical analysis and technologies in human behavior tasks. Engineers, researchers, and students from biomedical engineering and health sciences, as well as industrial professionals, can benefit from this compendium of knowledge about biomechanics applied to the human body

Human inspired humanoid robots control architecture

This PhD Thesis tries to present a different point of view when talking about the development of control architectures for humanoid robots. Specifically, this Thesis is focused on studying the human postural control system as well as on the use of this knowledge to develop a novel architecture for postural control in humanoid robots. The research carried on in this thesis shows that there are two types of components for postural control: a reactive one, and other predictive or anticipatory. This work has focused on the development of the second component through the implementation of a predictive system complementing the reactive one. The anticipative control system has been analysed in the human case and it has been extrapolated to the architecture for controlling the humanoid robot TEO. In this way, its different components have been developed based on how humans work without forgetting the tasks it has been designed for. This control system is based on the composition of sensorial perceptions, the evaluation of stimulus through the use of the psychophysics theory of the surprise, and the creation of events that can be used for activating some reaction strategies (synergies) The control system developed in this Thesis, as well as the human being does, processes information coming from different sensorial sources. It also composes the named perceptions, which depend on the type of task the postural control acts over. The value of those perceptions is obtained using bio-inspired evaluation techniques of sensorial inference. Once the sensorial input has been obtained, it is necessary to process it in order to foresee possible disturbances that may provoke an incorrect performance of a task. The system developed in this Thesis evaluates the sensorial information, previously transformed into perceptions, through the use of the “Surprise Theory”, and it generates some events called “surprises” used for predicting the evolution of a task. Finally, the anticipative system for postural control can compose, if necessary, the proper reactions through the use of predefined movement patterns called synergies. Those reactions can complement or substitute completely the normal performance of a task. The performance of the anticipative system for postural control as well as the performance of each one of its components have been tested through simulations and the application of the results in the humanoid robot TEO from the RoboticsLab research group in the Systems Engineering and Automation Department from the Carlos III University of Madrid. ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------Esta Tesis Doctoral pretende aportar un punto de vista diferente en el desarrollo de arquitecturas de control para robots humanoides. En concreto, esta Tesis se centra en el estudio del sistema de control postural humano y en la aplicación de este conocimiento en el desarrollo de una nueva arquitectura de control postural para robots humanoides. El estudio realizado en esta Tesis pone de manifiesto la existencia de una componente de control postural reactiva y otra predictiva o anticipativa. Este trabajo se ha centrado en el desarrollo de la segunda componente mediante la implementación de un sistema predictivo que complemente al sistema reactivo. El sistema de control anticipativo ha sido estudiado en el caso humano y extrapolado para la arquitectura de control del robot humanoide TEO. De este modo, sus diferentes componentes han sido desarrollados inspirándose en el funcionamiento humano y considerando las tareas para las que dicho robot ha sido concebido. Dicho sistema está basado en la composición de percepciones sensoriales, la evaluación de los estímulos mediante el uso de la teoría psicofísica de la sorpresa y la generación de eventos que sirvan para activar estrategias de reacción (sinergias). El sistema de control desarrollado en esta Tesis, al igual que el ser humano, procesa información de múltiples fuentes sensoriales y compone las denominadas percepciones, que dependen del tipo de tarea sobre la que actúa el control postural. El valor de estas percepciones es obtenido utilizando técnicas de evaluación bioinspiradas de inferencia sensorial. Una vez la entrada sensorial ha sido obtenida, es necesario procesarla para prever posibles perturbaciones que puedan ocasionar una incorrecta realización de una tarea. El sistema desarrollado en esta Tesis evalúa la información sensorial, previamente transformada en percepciones, mediante la ‘Teoría de la Sorpresa’ y genera eventos llamados ‘sorpresas’ que sirven para predecir la evolución de una tarea. Por último, el sistema anticipativo de control postural puede componer, si fuese necesario, las reacciones adecuadas mediante el uso de patrones de movimientos predefinidos llamados sinergias. Dichas reacciones pueden complementar o sustituir por completo la ejecución normal de una tarea. El funcionamiento del sistema anticipativo de control postural y de cada uno de sus componentes ha sido probado tanto por medio de simulaciones como por su aplicación en el robot humanoide TEO del grupo de investigación RoboticsLab en el Departamento de Ingeniería de Sistemas y Automática de la Universidad Carlos III de Madrid

The effects of a moving environment on postural control and performance during manual materials handling, visual tracking and arithmetic tasks

The purpose of this study was to evaluate the performance of cognitive tasks and manual materials handling in a moving environment. In particular we were interested in how task performance, postural control and lower limb muscle activation changed when tasks were performed in motion compared to no motion conditions. The motion trials were performed on a MOOG 2000E that created a 5-degrees of freedom simulated environment. The tasks examined were a lifting task, a mental arithmetic task and a visual tracking task. Results of this experiment indicated that two outcome measures of a visual tracking task (time to task completion and performance errors) were negatively affected by motion, while arithmetic task performance was unaffected. Additionally, postural control was not affected by the presence of motion in the two cognitive tasks. Lifting was the only task where postural control appeared to be negatively affected as participants exhibited significant increases in lower limb muscle activation and non-significant increases in number of steps taken. The significant increase in time to completion and errors suggest that workers doing these type of tasks in an offshore environment may be more prone to committing human factors errors. Furthermore, the results suggest that the risk of falls and injury due to loss of balance may be highest in workers regularly performing lifting tasks as this was the only task where task performance in a moving environment negatively impacted postural control. These findings were attributed to greater demands placed on the postural control system when lifting during the motion condition. This study provides ergonomists with a resource they can use to better appreciate the risks associated with performance of job related tasks in a moving environment