THE EFFECTS OF SHOE TYPE ON BIOMECHANICAL AND PHYSIOLOGICAL RESPONSES TO STEPPING AND INCLINED WALKING

The purpose of this study was to examine the effect of hiking shoes and hiking boots on the biomechanical responses to a stepping task and physiological responses to an inclined walking task. Participants (n = 16) performed six two minute stepping trials at a stepping rate of 72 bpm; three trials in hiking boots and three trials in hiking shoes. Following the stepping task, participants (n = 19) walked at 3.0 mph and 10% grade for five minutes in hiking shoes and hiking boots. Lower limb joint angles and moments were calculated using Visual 3D. Physiological data was averaged over the last three minutes of the stepping task to determine mean variables during steady state exercise. Results showed that during the lowering phase of the stepping cycle, ankle ROM and ankle and knee moments were significantly greater in hiking shoes than hiking boots, indicating that no compensatory mechanisms of the knee and hip were implemented due to restricted ankle ROM. Additionally, VO2 and VE were significantly greater in the hiking shoe condition during the inclined walking task. While these variables are statistically significant, they may not be practically significant in an actual hiking scenario, as the magnitudes of differences observed in variables were minimal. Use of either shoe or boot may not result in an increased risk of injury, therefore leaving the choice of footwear up to the hiker’s personal preference

A Three-Dimensional Analysis of Subtalar and Knee Joint Coupling During Running Over Obstacles

Running has been associated with a number of lower extremity overuse injuries. Attention has been given to biomechanical factors, specifically, excessive pronation and excessive tibial rotation. It has been suggested that excessive tibial rotation is due to excessive foot pronation transferred through a coupling mechanism. The ankle and knee are mechanically linked via the tibia and excessive tibial internal rotation may delay tibial external rotation as the knee begins to extend. Increased impact forces have also been implicated as a cause of running injuries, although little is known about this possible relationship. Obstacle heights have been used previously to produce increases in impact forces. Investigation of biomechanical factors has traditionally been two-dimensional. However, recent literature has shown limitation to two-dimensional analysis. Therefore, the purpose of this study was to investigate the coupling mechanism between the subtalar and knee joints during running over obstacles of varying heights using a three-dimensional analysis. Ten, heel strike subjects ran at a self-selected pace under a no obstacle condition and four obstacle conditions (5, 7.5, 10, & 12.5% of standing height) on day 1 and underwent an orthopedic exam on day 2. The obstacle was placed directly before a force platform (960 Hz). Videography was collected using two high-speed cameras (240 Hz). Seven reflective markers were placed on the right limb to identify a three-dimensional 3-segment model. Increasing obstacle height resulted in increased impact forces. This allowed examination of the coupling mechanism over a spectrum of various impact force magnitudes. The pronation curve transitioned from a unimodal to a bimodal configuration and the bimodal tibial rotation curve experienced increases in the bimodal characteristics. Increasing impact forces resulted in increases of maximum pronation and maximum tibial internal rotation as well as decreasing the time to reach maximum knee flexion. However, the times to maximum pronation or maximum tibial rotation remained unaffected. This resulted in increases in the time differences between maximum pronation and maximum knee flexion. Therefore, the tibia may have been put under abnormal torsional stresses that were augmented with increasing impact forces as the proximal end began external rotation due to earlier knee flexion and the distal end maintained internal rotation due to unchanging pronation times. Future studies will focus in the measurement of these forces, as well as to justify these phenomena with additional perturbations

Biomechanical Locomotion Heterogeneity in Synthetic Crowds

Synthetic crowd simulation combines rule sets at different conceptual layers to represent the dynamic nature of crowds while adhering to basic principles of human steering, such as collision avoidance and goal completion. In this dissertation, I explore synthetic crowd simulation at the steering layer using a critical approach to define the central theme of the work, the impact of model representation and agent diversity in crowds. At the steering layer, simulated agents make regular decisions, or actions, related to steering which are often responsible for the emergent behaviours found in the macro-scale crowd. Because of this bottom-up impact of a steering model's defining rule-set, I postulate that biomechanics and diverse biomechanics may alter the outcomes of dynamic synthetic-crowds-based outcomes. This would mean that an assumption of normativity and/or homogeneity among simulated agents and their mobility would provide an inaccurate representation of a scenario. If these results are then used to make real world decisions, say via policy or design, then those populations not represented in the simulated scenario may experience a lack of representation in the actualization of those decisions. A focused literature review shows that applications of both biomechanics and diverse locomotion representation at this layer of modelling are very narrow and often not present. I respond to the narrowness of this representation by addressing both biomechanics and heterogeneity separately. To address the question of performance and importance of locomotion biomechanics in crowd simulation, I use a large scale comparative approach. The industry standard synthetic crowd models are tested under a battery of benchmarks derived from prior work in comparative analysis of synthetic crowds as well as new scenarios derived from built environments. To address the question of the importance of heterogeneity in locomotion biomechanics, I define tiers of impact in the multi-agent crowds model at the steering layer--from the action space, to the agent space, to the crowds space. To this end, additional models and layers are developed to address the modelling and application of heterogeneous locomotion biomechanics in synthetic crowds. The results of both studies form a research arc which shows that the biomechanics in steering models provides important fidelity in several applications and that heterogeneity in the model of locomotion biomechanics directly impacts both qualitative and quantitative synthetic crowds outcomes. As well, systems, approaches, and pitfalls regarding the analysis of steering model and human mobility diversity are described

Effects of Direction Time Constraints and Walking Speed on Turn Strategies and Gait Adaptations in Healthy Older and Young Adults

Hip fractures can be life-threatening, debilitating, and costly. The odds for hip fracture increases from impact of sideways falls. While turning has been strongly associated with hip fracture & sideways falls, the distinction between the risks for walking-turns as opposed to low-velocity in-place turning is not clear. The present study sought to fill a gap as previous research had not compared walking-turn performance in young & healthy older adults at low-fall risk within the same study and response-conditions of speed interacting with direction-cue time constraints. Spatial-temporal variables representative of AP braking/propulsion (i.e. stride-length & speed) & ML stability (left/right H-H BOS) were collected with the Gaitrite upon approach of a turning zone whose entrance width was just 73 cm; and turn-strategy categorical data for stable wide-BOS step-turns, biomechanically challenging narrow-BOS spin-turns, and combined subtypes of mixed-turns either of the “extra-step” variety representative of an AP stability/braking issue or “small-amplitude” variety representative of a ML stability/balance issue were captured on video. Mixed-ANOVA of gait measures for AP propulsion/braking revealed no age-group differences in speed despite a trend for less of a fast-pace increase in elderly stride-length, yet similar anticipatory slowing and shorter strides approaching turns. Measures of ML stability revealed similar anticipatory widening of right BOS approaching turns, and a three-way interaction showed both had similar anticipatory narrowing of left BOS when approaching turns at fast-pace and similar reactive narrowing of left BOS following an unexpected turn-cue at preferred pace. Loglinear analysis of turn-strategies revealed no age-related associations as both preferred mixed-turns the least. At fast speeds preference for spin-turns decreased, yet when late-cued preference for both step-turns and spin-turns decreased 5.5-fold & 4.0-fold, respectively, indicating other factors besides biomechanical. Furthermore, the standardized residual reached significance for the elderly mixed-turns cell at the most constrained fast-speed*late-cue response-condition, with the “extra-step” sub-type contributing greatest possibly implying an AP rather than ML stability issue. The findings suggest that when approaching turns across an interaction of response-time conditions, healthy older adults show similar anticipatory/reactive gait adaptations and turn-strategy preferences with regards to AP propulsion/deceleration and ML stability/balance. In conclusion, within study limits, fall-prevention gait-training for healthy elderly with low-fall-risk and no age-related speed declines, in addition to addressing important ML stability issues of turn execution, are best served by not losing sight of the fundamental prerequisite to arrest forward momentum upon approach, and being inclusive of spin-turns for their ML space-efficiency

Effects of Direction Time Constraints and Walking Speed on Turn Strategies and Gait Adaptations in Healthy Older and Young Adults

Hip fractures can be life-threatening, debilitating, and costly. The odds for hip fracture increases from impact of sideways falls. While turning has been strongly associated with hip fracture & sideways falls, the distinction between the risks for walking-turns as opposed to low-velocity in-place turning is not clear. The present study sought to fill a gap as previous research had not compared walking-turn performance in young & healthy older adults at low-fall risk within the same study and response-conditions of speed interacting with direction-cue time constraints. Spatial-temporal variables representative of AP braking/propulsion (i.e. stride-length & speed) & ML stability (left/right H-H BOS) were collected with the Gaitrite upon approach of a turning zone whose entrance width was just 73 cm; and turn-strategy categorical data for stable wide-BOS step-turns, biomechanically challenging narrow-BOS spin-turns, and combined subtypes of mixed-turns either of the “extra-step” variety representative of an AP stability/braking issue or “small-amplitude” variety representative of a ML stability/balance issue were captured on video. Mixed-ANOVA of gait measures for AP propulsion/braking revealed no age-group differences in speed despite a trend for less of a fast-pace increase in elderly stride-length, yet similar anticipatory slowing and shorter strides approaching turns. Measures of ML stability revealed similar anticipatory widening of right BOS approaching turns, and a three-way interaction showed both had similar anticipatory narrowing of left BOS when approaching turns at fast-pace and similar reactive narrowing of left BOS following an unexpected turn-cue at preferred pace. Loglinear analysis of turn-strategies revealed no age-related associations as both preferred mixed-turns the least. At fast speeds preference for spin-turns decreased, yet when late-cued preference for both step-turns and spin-turns decreased 5.5-fold & 4.0-fold, respectively, indicating other factors besides biomechanical. Furthermore, the standardized residual reached significance for the elderly mixed-turns cell at the most constrained fast-speed*late-cue response-condition, with the “extra-step” sub-type contributing greatest possibly implying an AP rather than ML stability issue. The findings suggest that when approaching turns across an interaction of response-time conditions, healthy older adults show similar anticipatory/reactive gait adaptations and turn-strategy preferences with regards to AP propulsion/deceleration and ML stability/balance. In conclusion, within study limits, fall-prevention gait-training for healthy elderly with low-fall-risk and no age-related speed declines, in addition to addressing important ML stability issues of turn execution, are best served by not losing sight of the fundamental prerequisite to arrest forward momentum upon approach, and being inclusive of spin-turns for their ML space-efficiency

Biomechanical Assessment of Ertl and Burgess Transtibial Amputation Techniques

In this dissertation, a model was developed to predict the inertial properties of the shank and foot of persons with TTA and functional differences between Ertl and Burgess amputees during curb negotiation and the sit-to-stand tasks were evaluated. The developed inertial model was able to predict the shank and foot segment mass, COM location, and MOI more accurately than using the intact limb inertial properties. Used as inputs into inverse dynamics equations, the general model predictions produced joint moments which were also similar to the subject-specific measures. Thus, this model is a better predictor than the current method of using the intact limb inertial measures for the amputated limb. The second and third studies showed differences between the Ertl and Burgess amputated limbs in functional ability. During curb negotiation the Ertl amputated limb produced net limb work (sum of ankle, knee, and hip work) similar to that of the intact limbs of both groups on the curb step. This net limb work was produced by the hip early in stance phase as a compensatory mechanism to help propel the body forward. During the sit-to-stand task, the Ertl group was able to perform the task more quickly than the Burgess group. The faster performance time was due in part to larger ground reaction forces in the Ertl amputated limb compared to the Burgess amputated limb. This suggested the Ertl limb was able to bear higher loads overall during this task. While no other differences were found between the amputated limbs, the Ertl intact limb showed unexpected differences. Where the Burgess limbs and Ertl amputated limb adopted a hip strategy to complete the task, the Ertl intact limb adopted a knee strategy. This knee strategy is more similar to the way non-amputees complete the task. Both study 2 and 3 highlighted functional advantages of the Ertl procedure over the Burgess procedure for these tasks and is, to our knowledge, the first study of its kind. Based on these outcomes, it appears that the Ertl procedure does lead to better functional performance during prosthesis use, and further consideration should be given to using this procedure at the time of amputation. Future work needs to continue to focus on functional performance in both groups and begin to contrast the outcomes with post-operative risks following the amputation to better inform patients and clinicians about potential advantages of either technique

Development of human locomotion

Neural control of locomotion in human adults involves the generation of a small set of basic patterned commands directed to the leg muscles. The commands are generated sequentially in time during each step by neural networks located in the spinal cord, called Central Pattern Generators. This review outlines recent advances in understanding how motor commands are expressed at different stages of human development. Similar commands are found in several other vertebrates, indicating that locomotion development follows common principles of organization of the control networks. Movements show a high degree of flexibility at all stages of development, which is instrumental for learning and exploration of variable interactions with the environment

An Analysis of the Relationship Between Complexity and Gait Adaptability

The presented sequence of studies considers theoretical applications from Complexity Science and Chaos Theory for gait time-series analysis. The main goal of this research is to build on insights from a previous body of knowledge, which have identified measures derived from Complexity Science and Chaos Theory as critical markers of gait control. Specifically, the studies presented in this dissertation attempt to directly test whether characterizing gait complexity relates to an ability to flexibly adjust gait. The broader impact of this research is utilizing measures of complexity to characterize gait control, and as a tool for rehabilitation which have both gained momentum in fall prevention research. Through a series of four studies, this dissertation was designed to test the theoretical viewpoint that complexity is related to gait control, particularly gait adaptability. Firstly, I sought to develop a paradigm for reliably entraining gait complexity with the use of several auditory fluctuating timing imperatives which, differed based on specified fractal characteristics. I also sought to quantify the duration of the retention of gait complexity, following entrainment. Thirdly, I assessed whether attentional demands required during entrainment were affected by the fractal characteristics of a fluctuating timing imperative. Lastly, I applied the developed paradigm to evaluate the theoretical relationship between gait complexity and stepping performance. The findings from this dissertation have developed a framework for assessing gait control. This series of projects has determined that a fluctuating timing imperative can reliably prescribe the gait pattern of healthy individuals towards a particular complexity. The use of a fluctuating timing imperative leads to entrainment of the stimulus complexity. Furthermore, once the timing imperative has ceased, there is a brief period of complexity retention in the walking pattern. This dissertation has also confirmed that entraining complexity to a fluctuating timing imperative does not alter the attentional demands associated with entrainment. However, entraining gait to fluctuating timing imperatives of different complexities alters the stepping strategy that is adopted. Lastly, this dissertation has shown that synchronizing gait to a fixed-interval stimulus following entrainment, depends on the complexities of the gait pattern

Virtual obstacle crossing and the clinical implications for rehabilitation

Fall risk is a concern for a variety of clinical populations, especially in lower-limb amputees. The risk of falling during walking is increased by an individual with pathology’s diminished ability for obstacle negotiation. Virtual obstacle crossing environments offer a rehabilitation technique that is space and material efficient and may enhance obstacle crossing skill acquisition and retention though the use of task specificity, repetition, and feedback; while presenting an engaging and motivating challenge for participants. Current literature has not determined the response of an individual to virtual obstacle crossing in comparison to real environment over-ground obstacle crossing, nor whether aging influences this behavior. In a first step to determine the clinical viability of a virtual reality obstacle crossing environment, this task was tested using healthy able-bodied individuals (20 younger adults and 20 older adults) to determine an individual’s expected crossing behavior during a single session of training. The purpose of this study was to (1) determine the biomechanical obstacle-crossing behavior of an able-bodied individual within a virtual environment, (2) determine if a learning effect exists with virtual obstacle crossing, and (3) determine if the learning effect will transfer to over-ground obstacle crossing and create performance changes. Dependent variables measured were foot placement before and after the obstacles for the both the lead and trail limbs, toe/heel clearance for both limbs in the vertical and radial directions, and the peak toe and heel elevation. The hypotheses were: (1) a training effect would be observed at the end of the virtual obstacle crossing training in the form of the adoption of a safer obstacle crossing strategy in the virtual environment, (2) a safer obstacle crossing strategy in the real environment would be adopted in the post-test relative to the pre-test, and (3) the performance changes in the virtual environment would be correlated with the performance changes in the real environment, suggesting an association between motor learning in a virtual environment and transfer to a real environment task. It was also postulated that each hypothesized finding would be affected by age, with older adults showing less learning and transfer (albeit still significant) compared to the younger adults. Results indicate that participants learned to cross the virtual obstacle more safely and that change in behavior was transfer to the real environment. Further, while both age groups showed transfer to the real environment task, they differed on which limb their transfer effects applied to. The data suggest it is plausible to use virtual reality training as a way to enhance gait characteristics in the context of obstacle avoidance, potentially a leading to a novel way to reduce fall risk

Fall prevention strategy for an active orthotic system

Dissertação de mestrado integrado em Engenharia Biomédica (especialização em Eletrónica Médica)Todos os anos, são reportadas cerca de 684,000 quedas fatais e 37.3 milhões de quedas não fatais que requerem atenção médica, afetando principalmente a população idosa. Assim, é necessário identificar eficientemente indivíduos com alto risco de queda, a partir da população alvo idosa, e prepará los para superar perturbações da marcha inesperadas. Uma estratégia de prevenção de queda capaz de eficientemente e atempadamente detetar e contrariar os eventos de perdas de equilíbrio (PDE) mais frequentes pode reduzir o risco de queda. Como slips foram identificados como a causa mais prevalente de quedas, estes eventos devem ser abordados como foco principal da estratégia. No entanto, há falta de estratégias de prevenção de quedas por slip. Esta dissertação tem como objetivo o design de uma estratégia de prevenção de quedas de slips baseada na conceção das etapas de atuação e deteção. A estratégia de atuação foi delineada com base na resposta biomecânica humana a slips, onde o joelho da perna perturbada (leading) apresenta um papel proeminente para contrariar LOBs induzidas por slips. Quando uma slip é detetada, a estratégia destaca uma ortótese de joelho que providencia um torque assisstivo para prevenir a queda. A estratégia de deteção considerou as propriedades atrativas dos controladores Central Pattern Generator (CPG) para prever parâmetros da marcha. Algoritmos baseados em threshold monitorizam o erro de previsão do CPG, que aumenta após uma perturbação inesperada na marcha, para a deteção de slips. O ângulo do joelho e a velocidade angular da canela foram selecionados como os parâmetros de monitorização da marcha. Um protocolo experimental concebido para provocar perturbações de slip a sujeitos humanos permitiu a recolha de dados destas variáveis para posteriormente validar o algoritmo de deteção de perturbações. Algoritmos CPG foram capazes de produzir aproximações aceitáveis dos sinais de marcha em estado estacionário do ângulo do joelho e da velocidade angular da canela com sucesso. Além disso, o algoritmo de threshold adaptativo detetou LOBs induzidas por slips eficientemente. A melhor performance global foi obtida usando este algoritmo para monitorizar o ângulo do joelho, que detetou quase 80% (78.261%) do total de perturbações com um tempo médio de deteção (TMD) de 250 ms. Além disso, uma média de 0.652 falsas perturbações foram detetadas por cada perturbação corretamente identificada. Estes resultados sugerem uma performance aceitável de deteção de perturbações do algoritmo, de acordo com os requisitos especificados para a deteção.Every year, an estimated 684,000 fatal falls and 37.3 million non-fatal falls requiring medical attention are reported, mostly affecting the older population. Thus, it is necessary to effectively screen high fall risk individuals from targeted elderly populations and prepare them to successfully overcome unexpected gait perturbations. A fall prevention strategy capable of effectively and timely detect and counteract the most frequent loss of balance (LOB) events may reduce the fall risk. Since slips were identified as the main contributors to falls, these events should be addressed as a main focus of the strategy. Nonetheless, there is a lack of slip-induced fall prevention strategies. This dissertation aims the design of a slip-related fall prevention strategy based on the conception of an actuation and a detection stage. The actuation strategy was delineated based on the human biomechanical reactions to slips, where the perturbed (leading) leg’s knee joint presents a prominent role to counteract slip-induced LOBs. Thereby, upon the detection of a slip, this strategy highlighted a knee orthotic device that provides an assistive torque to prevent the falls. The detection strategy considered the attractive properties of biological-inspired Central Pattern Generator (CPG) controllers to predict gait parameters. Threshold-based algorithms monitored the CPG’s prediction error produced, which increases upon an unexpected gait perturbation, to perform slip detection. The knee angle and shank angular velocity were selected as the monitoring gait parameters. An experimental protocol designed to provoke slip perturbations to human subjects allowed to collect data from these variables to further validate the perturbation detection algorithm. CPG algorithms were able to successfully produce acceptable estimations of the knee angle and shank angular velocity signals during steady-state walking. Furthermore, an adaptive threshold algorithm effectively detected slip-induced LOBs. The best overall performance was obtained using this algorithm to monitor the knee angle from the perturbed leg, which detected almost 80% (78.261%) of the total perturbations with a mean detection time (MDT) of 250 ms. In addition, a mean of 0.652 false perturbations were detected for each correct perturbation identified. These results suggest an acceptable perturbation detection performance of the algorithm implemented in light of the detection requirements specified