Leg stiffness is an important factor in human walking. Understanding the ways in which stiffness impacts walking could lead to improvements in gait rehabilitation, exoskeleton design, and exoskeleton control. Three studies were conducted to better understand the effects of stiffness on walking. The first study investigated how changing stiffness of the foot itself affects walking. To do this, a rigid foot plate was attached to the foot of 16 subjects in order to increase the stiffness of the foot. This is because many exoskeletons and orthoses use a rigid foot plate, but this may affect the natural mechanics of the foot. The resulting spatiotemporal parameters, kinematics, and kinetics were compared with normal walking. It was found that the foot plate did not have an effect on spatiotemporal parameters, but did decrease the ankle range of motion and decreased the intersegmental motion of the different parts of the foot. It was also found that a foot plate that ends before the toes has less of an effect than a foot plate that extends to the end of the toes. Therefore, exoskeletons and orthoses should implement a jointed toe segment or a shorter foot plate in order to increase the transparency of the device. For the second study, an ankle exoskeleton was developed with the requirement that it was capable of a versatile range of control modes, and was robust. Versatility is important for an exoskeleton because the type of rehabilitation a person may require can vary due to a number of factors. The exoskeleton must also be robust in uncertain environments because humans undergoing rehabilitation may act unpredictably. Therefore, a pneumatically powered exoskeleton was designed and controlled using sliding mode control. This exoskeleton is capable of position, force, and impedance control. Four subjects were used to test the performance of these controllers while following position and force trajectories. The tests showed that regardless of the behavior of the wearer, the exoskeleton acted appropriately and under an acceptable degree of error. This demonstrates that sliding mode control can be used to make exoskeletons capable of the versatility required for rehabilitation. Lastly, in the third study, the control of leg stiffness while walking was investigated. This was done by using human data from 12 subjects to extract system models and leg stiffness controllers for walking using three different methods and informed by the spring-loaded inverted pendulum model. The first method used ordinary least squares to linearize the system about a Poincaré section; the second linearized the spring-loaded inverted pendulum model and combined that with the results from the first method. The third method used the sparse identification of nonlinear dynamics procedure to identify linear combinations of nonlinear functions that describe the system. These methods were evaluated based on how well they predicted experimental data, and based on how well they controlled a spring-loaded inverted pendulum model walker in simulation. Results showed that all three methods resulted in similarly accurate models and controllers. Therefore, using human data in conjunction with data driven identification techniques may be used to reveal the mechanics of gait or to design robotic controllers for walking.

This book is about the ways which human behavior is affected concerns with people may be doing, their public impressions they typically prefer that No matter what else other people perceive them in certain desired ways and not perceive them in other, undesired ways. Put simply, human beings have a pervasive and ongoing concern with their self-presentations. Sometimes they act in ceflain ways just to make a particular impression on someone else mras when a job applicant responds inthat will satisfactorily impress the interviewer. But more often, people 5 concerns with others’ impressions simply constrain their behavioural options. Most of the time inclined to do things that will lead others to see us as incompetent, inwnoral, maladjusted, or otherwise socially undesirable. As a result, our concerns with others’ impressions limit what we are willing to do.Self-presentation almotives underlie and pervade near corner of interpersonal life.

Every year workers' low-back, hand, and arm problems lead to time away from jobs and reduce the nation's economic productivity. The connection of these problems to workplace activities-from carrying boxes to lifting patients to pounding computer keyboards-is the subject of major disagreements among workers, employers, advocacy groups, and researchers. Musculoskeletal Disorders and the Workplace examines the scientific basis for connecting musculoskeletal disorders with the workplace, considering people, job tasks, and work environments. A multidisciplinary panel draws conclusions about the likelihood of causal links and the effectiveness of various intervention strategies. The panel also offers recommendations for what actions can be considered on the basis of current information and for closing information gaps. This book presents the latest information on the prevalence, incidence, and costs of musculoskeletal disorders and identifies factors that influence injury reporting. It reviews the broad scope of evidence: epidemiological studies of physical and psychosocial variables, basic biology, biomechanics, and physical and behavioral responses to stress. Given the magnitude of the problem-approximately 1 million people miss some work each year-and the current trends in workplace practices, this volume will be a must for advocates for workplace health, policy makers, employers, employees, medical professionals, engineers, lawyers, and labor officials.

Biomechanics and Motor Control: Defining Central Concepts provides a thorough update to the rapidly evolving fields of biomechanics of human motion and motor control with research published in biology, psychology, physics, medicine, physical therapy, robotics, and engineering consistently breaking new ground. This book clarifies the meaning of the most frequently used terms, and consists of four parts, with part one covering biomechanical concepts, including joint torques, stiffness and stiffness-like measures, viscosity, damping and impedance, and mechanical work and energy. Other sections deal with neurophysiological concepts used in motor control, such as muscle tone, reflex, pre-programmed reactions, efferent copy, and central pattern generator, and central motor control concepts, including redundancy and abundance, synergy, equilibrium-point hypothesis, and motor program, and posture and prehension from the field of motor behavior. The book is organized to cover smaller concepts within the context of larger concepts. For example, internal models are covered in the chapter on motor programs. Major concepts are not only defined, but given context as to how research came to use the term in this manner. Presents a unified approach to an interdisciplinary, fragmented area Defines key terms for understanding Identifies key theories, concepts, and applications across theoretical perspectives Provides historical context for definitions and theory evolution

The Social Security Administration (SSA) administers two programs that provide disability benefits: the Social Security Disability Insurance (SSDI) program and the Supplemental Security Income (SSI) program. SSDI provides disability benefits to people (under the full retirement age) who are no longer able to work because of a disabling medical condition. SSI provides income assistance for disabled, blind, and aged people who have limited income and resources regardless of their prior participation in the labor force. Both programs share a common disability determination process administered by SSA and state agencies as well as a common definition of disability for adults: "the inability to engage in any substantial gainful activity by reason of any medically determinable physical or mental impairment which can be expected to result in death or which has lasted or can be expected to last for a continuous period of not less than 12 months." Disabled workers might receive either SSDI benefits or SSI payments, or both, depending on their recent work history and current income and assets. Disabled workers might also receive benefits from other public programs such as workers' compensation, which insures against work-related illness or injuries occurring on the job, but those other programs have their own definitions and eligibility criteria. Selected Health Conditions and Likelihood of Improvement with Treatment identifies and defines the professionally accepted, standard measurements of outcomes improvement for medical conditions. This report also identifies specific, long-lasting medical conditions for adults in the categories of mental health disorders, cancers, and musculoskeletal disorders. Specifically, these conditions are disabling for a length of time, but typically don't result in permanently disabling limitations; are responsive to treatment; and after a specific length of time of treatment, improve to the point at which the conditions are no longer disabling.