Hip fractures are serious injuries that are associated with high rates of morbidity and mortality in older adults. While much of the increased risk of hip fracture with age can be explained by age-related decreases in bone mineral density, muscles and motor control are altered by aging as well. Muscles forces in vivo are thought to have a prophylactic effect that can reduce shear and bending in the femur. This is beneficial because bone is stronger in compression than in shear or tension, and shear plays an important role in fatiguing bone. Understanding how aging and muscular loads affect strains in the proximal femur could lead to improvements in clinical screening and preventative measures for hip fracture. Three studies were performed to investigate age-related changes in neuromuscular function during gait and how these changes affect strains in the proximal femur. Study 1 examined age differences in peak lower extremity joint torques during walking with controlled speed and step length. Studies 2 and 3 applied muscle forces estimated during gait to finite element models of the femur. Study 2 examined age differences in femoral strains, and Study 3 examined the sensitivity of strains to individual muscle forces. The results support the idea that older adults walk with reduced contributions from the ankle plantar flexors and increased contributions from the hip extensors. Interactions between age and speed indicate that older adults utilized a different neuromuscular strategy than young adults to vary the speed of their gait. No age differences were found for the largest magnitude strains in the proximal femur. However, young adults were able to apply larger loads to the femur without corresponding increases in femoral strains. Strains in the femoral neck were found to be sensitive to muscle forces, particularly hip abductor forces. Strains in the sub-trochanteric region tended to be larger than those in the femoral neck, and less sensitive to muscle forces. These results increase our understanding of neuromuscular changes that occur with age, and the effects of these changes on the femur. / Ph. D.

Associations between the built environment and walking are well understood among the general population, but far less is known about how features of the built environment influence walking in older adults. As compared to other age groups, older adults, defined as those 65 years of age and older, are more likely to experience declines in physical activity, social interaction, and loss of community connectivity. Animal companionship can provide older adults the motivation to stay physically active and help them mitigate the feelings of isolation. Built environments that align with the needs and abilities of older adults and their animal companions, like dogs, can encourage and help sustain walking habits. The aim of this study was to identify and prioritize features within the built environment pertinent to older adult dog walkers. Existing literature served as the basis for identifying neighborhood design features associated with general walking and dog walking. Through the use of a three round Delphi study, 25 experts from urban planning and design, management of outdoor spaces, public health, gerontology, and human-animal relationships modified and rated the importance of the identified features as it pertains to older adult dog walkers. Following the Delphi study, 12 older adult dog owners from the Warm Hearth Village participated in a guided walk and interview using the Photovoice technique. The goal was to gather their perceptions of the outdoor walking environment. Among expert panelists, safety from motorized traffic, crime, unleashed dogs, and personal injury was paramount (mean (M)= 93.20, standard deviation (SD) = 11.54). Experts also saw the value and agreed upon the importance of dog supportive features within the built environment, like dog waste stations dog waste stations (desirable; M = 87.95, SD = 11.37), and dog policy signage (desirable; M = 79.91, SD = 11.22). Older adults also believed safety was important. They saw their dog as a protective safety factor against walking deterrents like aggressive or unleashed dogs. However, the feature that resonated most with older adult dog walkers in this study was their interaction with nature. They described the pleasure of observing seasons change and the connection with nature that came from the tree canopy cocooning the walking path. Path design is also a necessary consideration. Older adults emphasized the importance of having options between paved and unpaved walking paths. The panelists stressed the need for creating lines of sight (desirable; M = 66.46, SD = 20.71) and lighting (desirable; M = 77.92, SD =19.77). Those who plan, develop, and maintain spaces that support older adults can prioritize the features I identified in my research. Incorporating these features into the design of spaces for older adults has the potential to translate into increased walking and opportunities to socialize, contributing to mental and physical health. / Doctor of Philosophy / Associations between the built environment and walking are well understood among the general population, but less is known about how features in the built environment influence older adults. As compared to other age groups, older adults are more likely to experience declines in physical activity and social interaction. Animal companionship can provide motivation to stay physically active and help them mitigate feelings of isolation. Built environments that align with the needs of older adults and their animal companions, like dogs, can encourage and help sustain walking habits. My research identified and prioritized features within the built environment pertinent to older adult dog walkers. I implemented an iterative three round study to gain consensus among expert panelists and guided walks and interviews with older adult dog walkers. Among expert panelists, safety from motorized traffic, crime, unleashed dogs, and personal injury was paramount. Experts also saw the value of dog supportive features within the built environment, like dog waste stations. Older adults also believed safety was important. They saw their dog as a protective safety factor against walking deterrents like aggressive dogs. The feature that resonated most with older adult in this study was nature. They described the pleasure of observing seasons change and the connection with nature that came from the tree canopy cocooning the walking path. Path design is also a necessary consideration. Older adults emphasized the importance of having options between paved and unpaved walking paths. Those who plan, develop, and maintain spaces that support older adults can prioritize the features I identified in my research. Incorporating these features into outdoor spaces has the potential to translate into increased walking and opportunities to socialize, contributing to mental and physical health.

Purpose: Race has rarely been the focus of biomechanics investigations, despite affecting the incidence of musculoskeletal injury and disease. Existing racial differences in movement mechanics could drive disease development and help identify factors contributing to racial health disparities. This study aimed to 1) Identify racial differences in walking, running, and landing mechanics between African Americans and white Americans and 2) Determine whether racial differences can be explained by anthropometric, strength, and health status factors. Methods: Venous blood samples, anthropometric measures, lower extremity strength, and a health status assessment were collected for 92 participants (18-30y) in an IRB approved study. After measuring self-selected walking speed, 3D motion capture and force plate data were recorded during 7 trials in the following conditions: regular walking (1.35m/s), fast walking (1.6m/s), running (3.2m/s), and drop vertical jump (31cm box height). Fundamental gait measures and running and landing measures associated with overuse and impact injury risk were extracted using Visual3D and custom Matlab scripts. Multivariate and post-hoc univariate ANOVA models were fit to determine main and interaction effects of gender and race (JMP Pro 15, α=0.05) after which data was separated by gender. Stepwise linear regression models evaluated whether anthropometric, strength, and health status factors explained racial effects. Results: Several racial differences in walking, running, and landing mechanics were observed in both men and women, but differed between genders. Effect sizes of observed racial differences indicate the potential for both statistical and clinical significance. Although several racial differences during all tasks were explained by anthropometric, strength, and health status factors in women, none were explained by these factors in men. In women, explanatory factors were a combination of innate and modifiable. Conclusion: Future steps should include the development of racially diverse databases and the identification of potential factors to target in interventions aimed at reducing racial health disparities. / Doctor of Philosophy / Purpose: Race has rarely been the focus of biomechanics studies, but several injuries and diseases occur at different incidence rates between racial groups. This study aimed to 1) Identify racial differences in walking, running, and landing between African Americans and white Americans and 2) Determine whether racial differences are explained by body proportion, strength, and health status factors. Methods: Blood samples, body proportion measures, lower extremity strength, and a health status assessment were collected for 92 participants (18-30 years old). Motion analysis data was recorded and analyzed during the following tasks: regular walking, fast walking, running, and drop vertical jump. Biomechanical measures were compared between racial groups and genders. When racial differences were found, we evaluated whether the differences could be explained by body proportion, strength, and health status factors. Results: Several racial differences were found during walking, running, and landing tasks in both men and women, but were dependent on gender. Several observed racial differences in women could be explained by body proportion, strength, and health status factors, but no racial differences could be explained in men. In women, some of the factors that explained racial differences were structural and could not be altered while others were potentially modifiable by exercise or were the product of social environment. Conclusion: Based on these findings, biomechanical data should be collected from racially diverse populations. Some factors able to explain racial differences could be targeted to reduce racial health disparities.

Falls are the leading cause of fatal and non-fatal injuries among older adults. Age-related sensory degradation may increase instability and increase the risk of slips and falls in older adults. The integration of three sensory systems (visual, proprioceptive, and vestibular systems) and the respective weighting of each are needed to maintaining balance during unexpected slip-induced falls. The visual system is often thought of as the most important sensory system in playing a major role in stabilizing posture, guiding locomotion and controlling slip response. However, previous studies have focused on the age-related effects of visual input on static postural stability. The age-related effects of visual input associated with locomotion and unexpected slip perturbations (i.e., dynamic tasks) remains unclear. The purpose of this study is to investigate the age-related effects of visual input on multi-sensory processing during locomotion and unexpected slip perturbations. Fifteen young and fifteen old adults were recruited to participate in this study. Motion capture system, force plate, and EMG data were collected during the experiments. Various biomechanical and neuromuscular characteristics were identified to quantify the age-related effects of visual input during locomotion and unexpected slip perturbations. The results indicate that temporary loss of visual input during walking could cause individuals to adopt a more cautious gait strategy to compensate for their physical and neuronal changes as shown in increased double support time and higher co-contraction (i.e., stiffness) of the knee and ankle joints. Older adults also have higher co-contraction at the ankle joint during walking as compared with young adults. Regarding slip-induced falls, temporary loss of visual input causes increased slip distances and response times of upper and lower limbs in both younger and older groups. In terms of kinematics, the combination of age and temporary loss of visual input influenced the perturbed limb. In terms of muscle activation patterns, temporary loss of visual input may increase the proprioceptive gain as shown in early muscle activity onset, increased muscle activation duration, and increased co-contraction at the knee joint. However, stiffness may increase the difficulty to detect a slip event and reduce flexibility and increase slip-induced falls. Although the human body cannot fully compensate for the temporary loss of visual input, the results in this study suggest that the reweighting process increases proprioceptive gain while visual input is unavailable. These findings support the implication of future research in order to understand the potential hazards which could occur while walking and slipping with temporary loss of visual input. The results may also contribute to the design of effective interventions to improve motor learning by applied visual occlusion in slips/falls training to reduce fall risk and enhance safety. The visual occlusion paradigm may assist to increase learning encoded in intrinsic coordination, related to motor performance skill, providing the flexibility required to adapt to complex environments such as slip-induced falls. / Ph. D.

The kinematics and dynamics of two legged or biped walking is considered. The resulting governing equations include actuator torques for a robot and muscle generated torques for a human. These torques are those necessary at each joint of a leg, including the foot, for a successful stride. The equations are developed from a consistent set variables with respect to a single inertial reference frame. This single reference frame approach has not been used by previous investigators. Control of the joint torques makes biped walking an extraordinary complex problem from a dynamics and control viewpoint. The control scheme that is developed incorporates the use of the direction of gravity as an important element in the overall control. The inclusion of gravity in biped robot walking has not previously been properly considered in other works. A way is described to separate gravity and acceleration which are measured by an accelerometer which is on the robot. This system incorporates the use of angular motion sensing of the robot segment that contains the linear accelerometers. This system was formulated based on human motion sensing and what probably is present in the human central nervous system for processing these signals. / Ph. D.

Walking has become a trend in the USA. In recent years, the desire to walk has brought forth specific urban design for walkable places as well as art forms that focus on walking. Whence this trend? This dissertation studies the socio-economic and cultural context that brought forth the aestheticized forms of walking such as walking in designed walkable places and walking as art. The theoretical framework to study this genealogy is based in social anthropology, critical theory, theatre studies and the practice of audio-walks. A "dialectic of aestheticization and commodification" runs through modernity that generates aestheticized forms of walking today. While walking is initially a form of aesthetic struggle against the rational principles of modernity and the forces of capitalism, this struggle is co-opted by the logic of capital in a continuous interlacing of the processes of aestheticization and commodification. The social and spatial consequences of capitalism together with the process of aestheticization of society produce new spatial forms of capitalism, new commodified forms of social interaction, and new forms of walking. What became of the yearning for agency through walking? With "walkable urbanism", capital returns to the city center and creates new markets for a budding walkable life-style which is fed through conspicuous consumption and the commodified "walkable body". With walking as art, the struggle for more physical, intellectual and political agency through walking goes on. While fighting with the self-referential loop of postmodern performing art, art walking opens up doors to new paths for contemporary art that lead out of post-dramatic art, beyond the phenomenology of embodied experience, and out of the manipulating products of the culture industry in order to create art that offers room for imagination -- the source of social change. / Ph. D.

Artificial music generation is a rapidly developing field focused on the complex task of creating neural networks that can produce realistic-sounding music. Generating music is very difficult; components like long and short term structure present time complexity, which can be difficult for neural networks to capture. Additionally, the acoustics of musical features like harmonies and chords, as well as timbre and instrumentation require complex representations for a network to accurately generate them. Various techniques for both music representation and network architecture have been used in the past decade to address these challenges in music generation. The focus of this thesis extends beyond generating music to the challenge of controlling and/or conditioning that generation. Conditional generation involves an additional piece or pieces of information which are input to the generator and constrain aspects of the results. Conditioning can be used to specify a tempo for the generated song, increase the density of notes, or even change the genre. Latent walking is one of the most popular techniques in conditional image generation, but its effectiveness on music-domain generation is largely unexplored. This paper focuses on latent walking techniques for conditioning the music generation network MuseGAN and examines the impact of this conditioning on the generated music. / Master of Science / Artificial music generation is a rapidly developing field focused on the complex task of creating neural networks that can produce realistic-sounding music. Beyond simply generating music lies the challenge of controlling or conditioning that generation. Conditional generation can be used to specify a tempo for the generated song, increase the density of notes, or even change the genre. Latent walking is one of the most popular techniques in conditional image generation, but its effectiveness on music-domain generation is largely unexplored, especially for generative adversarial networks (GANs). This paper focuses on latent walking techniques for conditioning the music generation network MuseGAN and examines the impact and effectiveness of this conditioning on the generated music.

Introduktion: Fall är den vanligaste inläggningsorsaken på sjukhus i Sverige. Faktorer som kan påverka att en människa faller är bl.a gångförmågan, balansförmågan samt fallrädslan.Syfte: Syftet med studien är att undersöka promenaders effekt på gång- och balansförmågan samt på fallrädsla hos personer över 65 år med hemtjänst.  Metod: Tjugo deltagare block-randomiserades till två grupper, tio deltagare per grupp. Medelåldern var 77 ± 8 år. Interventionsgruppen promenerade tre gånger i veckan, en gång med hemtjänst och två gånger med fysioterapeut. Kontrollgruppen promenerade en gång i veckan tillsammans med hemtjänsten. Interventionsperioden varade sex veckor. Mätningar av testen 6 minuters gångtest (6MWT), One Leg Stance (OLS) och Falls Efficacy Scale- International (svenska) (FES-I(s)) utfördes före och efter interventionsperioden. För att analysera skillnad mellan grupperna i interventionseffekt användes ANCOVA med uppföljningsvärdet som beroendevariabel. Det utfördes två analyser per variabel, i den ena var enbart baslinjevärdet kovariat och i den andra även kön och ålder.  Resultat: Interventionsgruppen förbättrade gångförmågan med i genomsnitt 35 meter medan kontrollgruppen försämrade sin gångförmåga med 3 meter (p=0,029 resp. p=0,019). Balansen förbättrades med i genomsnitt 2 sekunder i interventionsgruppen och 1 sekund i kontrollgruppen (p=0,528 resp. p=0,510). Fallrädslan minskade med i genomsnitt 6 poäng i interventionsgruppen och 2 poäng i kontrollgruppen (p=0,064 resp. p=0,054).  Slutsats: Att öka antalet promenader under sex veckor har effekt på gångförmågan, men inte på balans eller fallrädsla, bland äldre personer med hemtjänst. Resultaten indikerar på vikten av att inkludera fler promenadinsatser för äldre personer med hemtjänst som en åtgärd i kommuners fallpreventiva arbete. / Introduction: Accidental falls are the most common reason for hospital admissions in Sweden. Factors influencing fall risk include gait ability, balance and fear of falling. Aims: This study aims to examine the effect of walking on gait ability, balance and fear of falling, in home care recipients over 65 years .  Methods: Twenty participants, age 77 ± 8 years, were block-randomized into two groups. The intervention group walked three times a week and the control group once a week. The intervention lasted six weeks. Before and after the intervention the 6-minute walk test (6MWT), One Leg Stance (OLS), and Falls Efficacy Scale-International (Swedish) (FES- I(s)) were conducted. Intervention effect between groups was analyzed using ANCOVA with the follow-up value as the dependent variable. Two analyzes were conducted for each variable: one included the baseline as covariate, the other included gender and age as additional covariates.  Results: The intervention group improved their walking ability with an average of 35 meters, the control group decreased by 3 meters (p=0,029, p=0,019). Balance improved with an average of 2 seconds in the intervention group, 1 second in the control group (p=0,528, p=0,510). Fear of falling decreased with an average of 6 points in the intervention group, 2 points in the control group (p=0,064, p=0,054).  Conclusion: Increasing walks during six weeks improves gait ability but not balance or fear of falling in elderly home care recipients. The results emphasize the need for more walking interventions in fall prevention strategies for the elderly in municipal home care.

The Multi-Appendage Robotic System (MARS) built for this research is a hexapod robotic platform capable of walking and performing manipulation tasks. Each of the six limbs of MARS incorporates a three-degree of freedom (DOF), kinematically spherical proximal joint, similar to a shoulder or hip joint; and a 1-DOF distal joint, similar to an elbow or knee joint. Designing walking gaits for such multi-limb robots requires a thorough understanding of the kinematics of the limbs, including their workspace. The specic abilities of a walking algorithm dictate the usable workspace for the limbs. Generally speaking, the more general the walking algorithm is, the less constricted the workspace becomes. However, the entire limb workspace cannot be used in a continuous, statically stable, alternating tripedal gait for such a robot; therefore a subset of the limb workspace is dened for walking algorithms. This thesis develops MARS limb workspaces in the knee up conguration, and analyzes its limitations for walking on planar surfaces. The workspaces range from simple 2D geometry to complex 3D volumes. While MARS is a hexapedal robot, the tasks of dening the workspace and walking agorthm for all six limbs can be abstracted to a single limb using the constraint of a tripedal, statically stable gait. Based on understanding the behavior of an individual limb, a walking algorithm was developed to allow MARS to walk on level terrain. The algorithm is adaptive in that it continously updates based on control inputs. Open Tech developed a similar algorithm, based on a 2D workspace. This simpler algorithm developed resulted in smooth gait generation, with near-instantaneous response to control input. This accomplishment demonstrated the feasibility of implementing a more sophisticated algorithm, allowing for inputs of all six DOF: x and y velocity, z velocity or walking height, yaw, pitch and roll. This latter algorithm uses a 3D workspace developed to aord near-maximum step length. The workspace analysis and walking algorithm development in this thesis can be applied to the further advancement of walking gait generation algorithms. / Master of Science

This thesis explores the dynamics of two bipedal, passive-walker models that are free to move in a three-dimensional environment. Specifically, two rigid-bodied walkers that can sustain anthropomorphic gait down an inclined plane with gravity being the only source of energy were studied using standard dynamical systems methods. This includes calculating the stability of periodic orbits and varying the system parameter to create bifurcation diagrams and to address the persistence of a periodic solution under specific parameter variations. These periodic orbits are found by implementing the Newton-Raphson root solving scheme. The dynamical systems associated with these periodic orbits are not completely smooth. Instead, they include discontinuities, such as those produced due to forces at foot contact points and during knee hyper-extension. These discontinuities are addressed in the stability calculations through appropriate discontinuity mappings. The difference between the two walker models is the number of degrees of freedom (DOF) at the hip. Humans possess three DOF at each hip joint, one DOF at each knee joint, and at least two DOF at each ankle joint. The first walker model studied had revolute joints at the hips and knees and completely locked ankles. To make the walking motion more anthropomorphic, additional degrees of freedom were added to the hip. Specifically, the second walker model has ball joints at the hips. Two control algorithms are used for controlling the local stability of periodic motions for both walker models. The methods, reference and delay feedback control, rely on the presence of discontinuities in the system. Moreover, it is possible to predict the effects of the control strategy based entirely on information from the uncontrolled system. Control is applied to both passive walker models to try and stabilize an unstable periodic gait by making small, discrete, changes in the foot orientation during gait. Results show that both methods are successful in stabilizing an unstable walking motion for a 3D model with one DOF in each hip and to reduce the instability of the walking motions for the model having more mobility in the hip joints. / Master of Science