▼ textabstractIn this thesis, the influence of prosthetic inertial properties (mass, mass distribution and moment of inertia) on the gait of transtibial amputation (TTA) subjects is studied. Chapter 1 introduces the present ideas on prosthetic mass. It describes that the general design effort has always been, and still is, to reduce prosthetic mass. However, as far as we know, lightweight design has never been advocated in the present literature. The Chapter introduces the opposite view, found in a relatively large body of literature, that lightweight design might not be beneficial for prosthetic gait. The aim of this thesis, therefore, is to determine the optimal inertial properties of the prosthetic leg.

▼ Based on World Health Organization (WHO) report, between 250,000 and 500,000 people suffer from disabilities caused by spinal cord injuries each year. The result of this study is development of a medical device to restore walking in such patients using Functional Electrical Stimulation (FES). We selected dogs as our animal subject. This device uses FES to prevent an affected dog with limited walking abilities from falling during walking. The final version of the device includes a sensing core consisted of four Inertial Measurement Units (IMUs) attached to the hip, femur, tibia and metatarsus of our test subject. Using this sensory system, the device tracks and measures the hip, knee and hock joint angles in real time. We use a commercial microcontroller as our analytical core to provide suitable stimulation commands and provide appropriate voltage/current for delivery to target muscles. Data from IMUs are received by microcontroller using I2C bus communication. An advanced embedded C code is developed to program the microcontroller. We discuss a method to recognize the swing and stance phases of the dog gait during walking and propose several balancing strategies to be used for gait control during the stance and swing phase before falling occurs. We design and build a robodog to be compatible with the medical device. We use this robot to program and test the different cores of the device. We test our balancing strategies on our bionic test-bed before applying them on an actual animal subject. Results show the device can provide suitable sensing and stimulation control to balance the body of a dog that has limited ambulation abilities.

▼ The aim of this study was to investigate the effects of arm motion and surface slope on postural strategies and gait stability. We hypothesized that active arm swing would increase postural control compared to walking with arms held and normal arm swing, and that holding the arms would lead to an increasing number of compensatory gait strategies with the aim of increasing balance, both uphill and downhill. We tested fifteen healthy, young adults (age 23.4 ± 2.8 years) using the Computer- Assisted Rehabilitation ENvironment (CAREN) using a simulated rolling-hills condition under 3 arm swing conditions: held, normal, and active. Outcome measures included spatiotemporal gait parameters and postural stability measures in the 3 planes of motion (anterior-posterior, medial- lateral, and vertical). No significant interaction effects between arm swing and surface slope were found. However, results showed main effect for arms (held, normal, active) and slope (uphill versus level walking, downhill versus level walking) conditions. Stepping and postural strategies when walking uphill compared to level were opposite to those used in downhill walking compared to level. Participants adopted an overall more cautious strategy when walking downhill, as seen by a combination of decreased cadence and increased double-support time, while the opposite strategies were seen in uphill walking. Effects of arm swing remained relatively consistent for both uphill and downhill walking conditions. Both uphill and downhill, holding the arms led to stability-seeking measures in the form of increasing base of support (double-support time), and increased control (decreased vertical accelerations of the head and trunk compared to normal and active arm swing). These results substantiate the destabilizing effects of walking without arm swing and the usefulness of active arm swing for enhancing gait stability on minor slopes. This research also provides insight into the control mechanisms regulating dynamic balance in healthy young adults, which can be used to inform protocols and develop models aimed at preventing occupational health and safety hazards in challenging environments (e.g. construction workers).

▼ This thesis examines the medio-lateral body motion during single steps in an attempt to understand how balance is controlled in human stepping and gait. During a step the body's centre of mass (CoM) is not over the base of support. The body is unstable and falls sideways, but is 'held together' such that it moves approximately as a single unit. Over a range of step directions, there is a close relationship at the end of the step between stepping foot position and CoM position and velocity. This may be in order that the stepping limb can catch and redirect the fall of the body securely. A freely- falling model of the body closely predicts body motion during the step. This suggests that the position and velocity of the CoM at the end of the step are determined by the values at the start. Subjects are found to vary these starting values systematically with step direction and duration, and also to take into account initial posture. Together with evidence that the duration of the single-support phase is determined in advance, this suggests that the body motion during the step could be controlled ballistically. This strategy may be used because body motion is difficult to influence appreciably once the step is under way. In responding to a cue to change step direction 'midflight', subjects are able to alter body motion but 1) are more able to increase than to decrease the rate of the sideways fall, and 2) appear to have to resort to a multi-segment strategy. In contrast, responses appearing in the swing limb at short latency suggest that ordinarily swing limb motion may be subject to 'on-line' control. Thus inaccuracies in the ballistic control of the body mass may be compensated for by mid-step alterations in swing limb motion.

▼ Human gait identification has become an active area of research due to increased security requirements. Human gait identification is a potential new tool for identifying individuals beyond traditional methods. The emergence of motion capture techniques provided a chance of high accuracy in identification because completely recorded gait information can be recorded compared with security cameras. The aim of this research was to build a practical method of gait identification and investigate the individual characteristics of gait. For this purpose, a gait identification approach was proposed, identification results were compared by different methods, and several studies about the individual characteristics of gait were performed. This research included the following: (1) a novel, effective set of gait features were proposed; (2) gait signatures were extracted by three different methods: statistical method, principal component analysis, and Fourier expansion method; (3) gait identification results were compared by these different methods; (4) two indicators were proposed to evaluate gait features for identification; (5) novel and clear definitions of gait phases and gait cycle were proposed; (6) gait features were investigated by gait phases; (7) principal component analysis and the fixing root method were used to elucidate which features were used to represent gait and why; (8) gait similarity was investigated; (9) gait attractiveness was investigated. This research proposed an efficient framework for identifying individuals from gait via a novel feature set based on 3D motion capture data. A novel evaluating method of gait signatures for identification was proposed. Three different gait signature extraction methods were applied and compared. The average identification rate was over 93%, with the best result close to 100%. This research also proposed a novel dividing method of gait phases, and the different appearances of gait features in eight gait phases were investigated. This research identified the similarities and asymmetric appearances between left body movement and right body movement in gait based on the proposed gait phase dividing method. This research also initiated an analysing method for gait features extraction by the fixing root method. A prediction model of gait attractiveness was built with reasonable accuracy by principal component analysis and linear regression of natural logarithm of parameters. A systematic relationship was observed between the motions of individual markers and the attractiveness ratings. The lower legs and feet were extracted as features of attractiveness by the fixing root method. As an extension of gait research, human seated motion was also investigated.

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A two dimensional, seven segment biped transfemoral amputee swing phase model was developed at four walking speeds as an evaluation tool for variable cadence swing phase controllers. Torques at each joint were modelled as a function of tracking error and a forward dynamic optimization was performed to produce joint torques to match four sets of reference amputee kinematics. A prosthetic knee’s swing phase was simulated across four speeds (0.5, 1, 1.5, 2 m/s) and compared to experimental data. The knee performance RMSE ranged from 1.42° - 37° with increasing errors at higher walking speeds. The introduction of absolute hip motion measured from the affected side increased errors across all walking speeds. Additional modelling and optimization strategies to improve the model’s accuracy are discussed.

M.H.Sc.

Advisors/Committee Members: Andrysek, Jan, Biomedical Engineering.

▼ The functional role of arm swing during walking has been hypothesized to reduce net angular momentum and moment about the vertical axis, and to minimize metabolic costs of locomotion. Arm swing follows a specific timing pattern, with peak flexion occurring at the midpoint of stride. Recent studies have proposed that arm swing arises passively from driving forces imparted on the arm by thorax rotation and derived from energy input from the lower body. However, the passively driven hypothesis does not account for changes in arm swing timing that would occur with changes in stride frequency or inertia properties of the segments, or for measured muscle activity in the shoulder and trunk. Here I present a passively driven forward dynamic model of the upper body with rotational springs in the shoulder joints and in the trunk. To account for the constant timing of arm swing across different speeds and the presence of muscle activity in the upper body I propose an Actively Tuned Hypothesis: The dynamics of arm swing and thorax rotation are derived from the lower body and act like a passively driven spring-mass-pendular system, with muscles in the shoulder and trunk actively tuning the spring parameters to phase-lock arm swing in-phase with thorax rotation and anti-phase with ipsilateral heel strike. Eight male subjects participated in three walking experiments testing the ability of the model to reproduce in vivo kinematics and the actively tuned hypothesis. A Speed Experiment varied stride frequency, an Arm Inertia Experiment added inertia to both arms, and a Thorax Inertia Experiment added inertia to the thorax. The passively driven model was able to reproduce the experimentally measured kinematics of the subjects. Spring stiffness at the shoulder and trunk varied with experimental manipulations, and the result was maintenance of the natural frequency of the arms below the driving frequency of the stride. Tuning of the spring parameters cause phase-locking between thoracic rotation and arm swing in an in-phase manner, and thoracic rotation and ipsilateral heel strike in an anti-phase manner. Muscle activity in the posterior deltoid and erector spinae group showed timing similar to a spring. The tuning mechanism in the upper body was proposed to be active muscular contraction. Through active tuning of the system the timing of arm swing is controlled in order to produce the hypothesized functions during gait.

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Mulheres submetidas à mastectomia, apresentam assimetrias posturais, assim como alterações na cinemática do movimento do ombro e tronco. O objetivo deste estudo foi avaliar o equilíbrio estático bem como a marcha em mulheres submetidas à cirurgia de mastectomia unilateral. Para tanto, foram analisadas 42 mulheres, divididas em dois grupos: mulheres submetidas à mastectomia unilateral (GM), com idade média de 53,77±7,24 anos, e mulheres sem a doença como controle (GC), com idade média de 54,70±6,31 anos. As análises do equilíbrio estático e da marcha foram efetuadas com sistema Vicon System (VICON-MX-T40S, Oxford, Inglaterra). Foi avaliado o equilíbrio estático com olhos abertos e olhos fechados, com e sem o uso da prótese mamária externa, por meio da área e do deslocamento do centro de massa projetado no chão, assim como o ângulo da coluna. Na marcha, foram avaliados os parâmetros espaço-temporal com e sem o uso da prótese mamária externa, e a oscilação dos membros superiores e do tronco. Foi aplicado o teste de normalidade de Shapiro-Wilk, diante de uma distribuição normal e relacionada, aplicou-se o teste T relacionado, e para amostras independentes, teste T independente, em distribuição não paramétrica, foi aplicado Wilcoxon para variáveis relacionadas e Mann-Whitney, para variáveis independentes. Foi fixado o nível crítico de 5% (p<0,05), o processamento dos dados efetuado pelo software SPSS, versão 17.0. A análise do equilíbrio estático apontou aumento significativo na área e no deslocamento do centro de massa projetado no chão, e deslocamento médio-lateral do ângulo da coluna. Na marcha, houve piora dos parâmetros espaço-temporal e menor oscilção do membro superior homolateral à cirurgia para movimentos de flexão/extensão e abdução/adução, o tronco apresentou menor oscilação médio-lateral. A prótese parece não ter influenciado no equilíbrio e na marcha. Os resultados sugerem que a mastectomia unilateral pode afetar o equilíbrio e a marcha.

Women undergoing mastectomy, have postural asymmetries as well as changes in the kinematics of the movement of the shoulder and spine. The objective of this study was to evaluate static balance and gait in women undergoing unilateral mastectomy surgery. Therefore, 42 women were analyzed, divided into two groups: women who underwent unilateral mastectomy (GM) with a mean age of 53.77 ± 7.24 years, and women without the disease as control (GC) with a mean age of 54.70 ± 6.31 years. Analyses of static equilibrium and gait was performed with Vicon System (MX-T40S-VICON, Oxford, England). We evaluated the static balance with eyes open and eyes closed, with and without the use of external breast prosthesis through the area and the center of mass displacement designed on the floor, as well as the angle of the spine. On the gait were evaluated spatiotemporal parameters with and without the use of external breast prosthesis and the oscillation of the upper limbs and trunk during walking. The functionality of the upper limbs was measured by the DASH questionnaire, and the…

Advisors/Committee Members: Elaine Caldeira de Oliveira Guirro, Renato de Moraes, Marislei Sanches Panobianco.

▼ The first topic of this thesis is a practical load-optimized VCO design for low-jitter 5V 500 MHz digital phase-locked loop. Besides the low jitter advantage, the design also possesses another feature, i.e., fast locked time. The second topic is the half-swing PLA circuit. An additional 1/2 VDD voltage source and buffering transmission gates are inserted between the NOR planes of PLAs to erase the racing problem and shorten the rise delay as well as the fall delay of the output response such that the speed is enhanced and the dynamic power is reduced. The third topic is a novel design of a the 1.0 GHz pipelining 8-bit CLA based on the architecture we mentioned in the second topic. The operating clock frequency is 1.0 GHz and the output of the addition of two 8-bit binary numbers is done in 2 cycles ( 2.0 ns ). Advisors/Committee Members: Chau-Chin Wang (committee member), Sying-Jyan Wang (chair), Yau-Hwang Kuo (chair).

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The objectives of this study were to adopt the automatic stance-phase lock (ASPL) technology to a paediatric prosthetic knee, optimize and incorporate the extension assist to the proposed design, structurally and clinically validate the prototype of the knee in a structural testing and single subject pilot study, and use a questionnaire to evaluate its efficacy. Biomechanical models were used to analyze the gait characteristics of the participant with the proposed knee and the conventional knee joint used by the participant in the clinical pilot study. A questionnaire pertaining to the functions and characteristics of the proposed knee joint was administered to the participant. The results of the clinical study indicated that the stance phase performance of the proposed design is comparable to the conventional knee. Questionnaire results revealed participant was very confident with the design, and was able to participate in many activities such as running and playing dodge ball.

M.Sc.

Advisors/Committee Members: Andrysek, Jan, Biomedical Engineering.

▼ There are millions of fall-related injuries worldwide requiring medical attention on a yearly basis. These falls place a financial burden on the healthcare system. These falls can occur in the event of disruption in the postural control system and/or a loss of balance while walking. Previously, most gait studies have focused on the assessment of the lower extremities while neglecting the contribution of arm swing as it was believed to be a passive motion. However, it has been shown that there is an active component to arm swing. Moreover, these arm movements have been shown to affect the motion of the center of mass when walking. Therefore, arm swing could mitigate the destabilizing effects of perturbations caused by challenging surfaces. Additionally, no studies have examined the effect of arm swing when walking on a rocky surface. This type of surface causes perturbations in the anteroposterior and mediolateral directions simultaneously, leading to uneven center of mass displacement and spatiotemporal modifications. Hence, the present study assessed the effect of normal arm swing, held arm swing and active arm swing on postural control and dynamic stability when walking on regular and rocky surface. We hypothesized that active arm swing will have a negative impact on postural control and gait dynamics on a regular surface, while rocky surface walking will decrease stability and increase spatiotemporal variability. Additionally, we expect active arm swing to attenuate the negative effects of the rocky surface. Fifteen healthy young adults from the University of Ottawa community (mean age 23.4 ± 2.8 years) were recruited to participate in this study. They were asked to walk using three different arm conditions (normal, held and active arm swing) on the dual-belt CAREN-Extended System (Motek Medical, Amsterdam, NL) on simulated regular and rocky surface. This last is generated using the “Rumble” module (maximum range of ±2 cm at 0.6 Hz vertically, ±1° at 1 Hz pitch, and ±1° at 1.2 Hz roll). Mean, standard deviation and maximal values of trunk linear and angular velocity were calculated in all three planes. Moreover, step length, time and width mean and coefficient of variation as well as margin of stability mean and standard deviation were calculated. A mixed linear model was performed to compare the effects of the arm swing motions and surface types. The arm and surface conditions were set as fixed effects, while the walking speed was set as a covariate. Active arm swing increased trunk linear and angular velocity variability and peak values compared to normal and held arm conditions. Active arm swing also increased participants’ step length and step time, as well as the variability of margin of stability. Similarly, rocky surface walking increased trunk kinematics variability and peak values compared to regular surface walking. Furthermore, rocky surface increased the average step width while reducing the average step time. The spatiotemporal adaptations show the use of “cautious” gait to mitigate the… Advisors/Committee Members: Nantel, Julie (supervisor).

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Gait event detection allows for insight into one’s gait pattern, an invaluable aid in rehabilitation. Current methods often rely on measured acceleration and rarely on position measurements [3]–[6]. In this paper we propose 4 novel gait detection methods based on the position of the Center of Mass (one approach being causal and thus suitable for real-time use) and compare them to 4 existing state-of-the-art acceleration- based methods. All algorithms are benchmarked on an existing data set (overground walking, 23 participants, 1772 steps), comparing the detection rate, false positive rate and the mean and (intra- and interparticipant) standard deviation of the timing error for Heel Strikes and Toe-Offs. We show that position-based algorithms give well-balanced results and are able to outperform the acceleration-based algorithms in all five metrics. Additionally, we propose and compare several methods for detecting left and right steps, thereby enabling quantification of the full gait cycle.

Biomechanical Design | BioRobotics

Advisors/Committee Members: Vallery, H. (mentor), Reijne, M.M. (graduation committee), Kok, M. (graduation committee), Delft University of Technology (degree granting institution).

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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES

This work proposes two techniques for the detection of power swings and blocking of distance relays on transmission lines to prevent undue shutdowns. If a fault occurs during power swing, it must be immediately detected and removed. One of the major challenges for the detectors is to distinguish power swing from symmetrical fault near to electrical center (power angle δ near to 180º, since both are balanced phenomena. First technique is inspired by the fact that the frequency with which the signal of active power oscillates is proportional to the swing frequency of power system. Thus, the swing frequency of the active power derivate (dP/dt); the estimated frequency behavior is monitored by the slope angle between samples with the objective of detecting power swing (soft tendency – low angle values) from others events (abrupt tendency – high angle values). This technique was designed to be easy to ajust without extensive studies or evaluations of all possible scenarios in order to get the best setting. A second technique that uses of the asymmetry of the waveform in the stage of detection of short-circuit during power swing is proposed, and its main advantage is the ability to identify three-phase faults during power swing near the electrical center up to δ ≤ 120º. This technique calculates the mean square erros comparing the input signal with periodic functions with the objective of detecting power swing, this technique has predefined settings facilitating the adjustment process. The results show that the approaches provide satisfactory performance for stable power swing, unstable power swing and short-circuit during power swing. The highlights of proposed techniques are the simplicity of mathematical operations used, besides the speed in its operations.

Este trabalho propõe duas técnicas para a detecção de oscilações de potência e bloqueio dos relés de distância em linhas de transmissão, prevenindo desligamentos indevidos. Caso uma falta ocorra durante uma oscilação de potência, a mesma deve ser imediatamente detectada e removida. Um dos maiores desafios para os detectores é distinguir oscilação de potência de falta simétrica perto do centro elétrico, isto é, com ângulo de potência δ próximo a 180o, já que ambos são fenômenos balanceados. A primeira técnica é inspirada no fato de que a frequência com que o sinal da potência ativa oscila é proporcional à frequência de oscilação do sistema elétrico. Assim, estima-se a frequência de oscilação sobre a derivada da potência ativa (dP/dt); o comportamento da frequência estimada é monitorado através do ângulo de inclinação entre amostras de modo a discriminar oscilação de potência (tendência suave - valores de ângulos baixos) de outros eventos (tendência abrupta - valores de ângulos altos). Esta técnica foi projetada para ser de fácil ajuste, evitando extensos estudos e avaliações de todos os cenários possíveis de modo a obter o melhor ajuste. Uma segunda técnica que faz…

Advisors/Committee Members: Cardoso Junior, Ghendy, Oliveira, Aécio de Lima, Ferreira, Gustavo Dorneles, Marchesan, Gustavo, Moreto, Miguel.

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Bioengineering

Locomotion is essential to survival in most animals. Studies have shown that animals, including humans, choose a gait that minimizes the risk of injury and maximizes energetic efficiency. Individuals often encounter obstacles and perturbations during normal locomotion, from which they must recover. Despite the importance of understanding the mechanisms that enable recovery from perturbations, ethical and experimental challenges have prevented full exploration of these in legged systems. A powerful paradigm with which to tackle this difficulty would be the application of external and internal manipulation of the nervous system. These perturbations could target how gait is regulated and how the neural systems process sensory information to control locomotion during an unexpected perturbation. Here we present data on the response of female mice to rapid, precisely timed, and spatially confined mechanical perturbations applied by a treadmill system. Our data elucidate that after the mechanical perturbation, the mouse gait response is anisotropic, preferring deviations away from the trot towards bounding, over those towards other gaits, such as walk or pace. We quantified this shift by projecting the observed gait onto the line between trot and bound, in the space of quadrupedal gaits. We call this projection λ. For λ=0, the gait is the ideal trot; for λ=±π, it is the ideal bound. We found that the substrate perturbation caused a significant shift in λ towards bound during the stride in which the perturbation occurred and the following stride (linear mixed effects model: Δλ=0.26±0.07 and Δλ=0.21±0.07, respectively; random effect for animal, p<0.05 for both strides, n = 8 mice). We hypothesize that this is because the bounding gait is better suited to rapid acceleration or deceleration, and an exploratory analysis of jerk showed that it was significantly correlated with λ (p<0.05). To evaluate whether the same structure of gait controller exists when undergoing an entirely different class of manipulation, we applied an internal, neuromuscular perturbation. We directly stimulated the lateral gastrocnemius muscle of mice using implanted electrodes and a custom magnetic headstage. We found that the electrical muscle stimulation caused a significant shift in λ towards bound in trials where the stimulation occurred during the swing phase (linear mixed effects model: Δλ=0.23±0.06 and Δλ=0.28±0.06; for the stride during and after the stimulation, respectively; random effect for animal, p<0.05 for both, n = 7 mice). Understanding how gait is controlled under perturbations can give insight into the neuromechanical basis of locomotion, aid in diagnosing gait pathologies, and aid the design of more agile robots.

Temple University – Theses

Advisors/Committee Members: Spence, Andrew;, Lemay, Michel A., Smith, George, Hsieh, Tonia;.

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Bioengineering

Locomotion is essential to survival in most animals. Studies have shown that animals, including humans, choose a gait that minimizes the risk of injury and maximizes energetic efficiency. Individuals often encounter obstacles and perturbations during normal locomotion, from which they must recover. Despite the importance of understanding the mechanisms that enable recovery from perturbations, ethical and experimental challenges have prevented full exploration of these in legged systems. A powerful paradigm with which to tackle this difficulty would be the application of external and internal manipulation of the nervous system. These perturbations could target how gait is regulated and how the neural systems process sensory information to control locomotion during an unexpected perturbation. Here we present data on the response of female mice to rapid, precisely timed, and spatially confined mechanical perturbations applied by a treadmill system. Our data elucidate that after the mechanical perturbation, the mouse gait response is anisotropic, preferring deviations away from the trot towards bounding, over those towards other gaits, such as walk or pace. We quantified this shift by projecting the observed gait onto the line between trot and bound, in the space of quadrupedal gaits. We call this projection λ. For λ=0, the gait is the ideal trot; for λ=±π, it is the ideal bound. We found that the substrate perturbation caused a significant shift in λ towards bound during the stride in which the perturbation occurred and the following stride (linear mixed effects model: Δλ=0.26±0.07 and Δλ=0.21±0.07, respectively; random effect for animal, p<0.05 for both strides, n = 8 mice). We hypothesize that this is because the bounding gait is better suited to rapid acceleration or deceleration, and an exploratory analysis of jerk showed that it was significantly correlated with λ (p<0.05). To evaluate whether the same structure of gait controller exists when undergoing an entirely different class of manipulation, we applied an internal, neuromuscular perturbation. We directly stimulated the lateral gastrocnemius muscle of mice using implanted electrodes and a custom magnetic headstage. We found that the electrical muscle stimulation caused a significant shift in λ towards bound in trials where the stimulation occurred during the swing phase (linear mixed effects model: Δλ=0.23±0.06 and Δλ=0.28±0.06; for the stride during and after the stimulation, respectively; random effect for animal, p<0.05 for both, n = 7 mice). Understanding how gait is controlled under perturbations can give insight into the neuromechanical basis of locomotion, aid in diagnosing gait pathologies, and aid the design of more agile robots.

Temple University – Theses

Advisors/Committee Members: Spence, Andrew;, Lemay, Michel A., Smith, George, Hsieh, Tonia;.

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Bioengineering

Locomotion is essential to survival in most animals. Studies have shown that animals, including humans, choose a gait that minimizes the risk of injury and maximizes energetic efficiency. Individuals often encounter obstacles and perturbations during normal locomotion, from which they must recover. Despite the importance of understanding the mechanisms that enable recovery from perturbations, ethical and experimental challenges have prevented full exploration of these in legged systems. A powerful paradigm with which to tackle this difficulty would be the application of external and internal manipulation of the nervous system. These perturbations could target how gait is regulated and how the neural systems process sensory information to control locomotion during an unexpected perturbation. Here we present data on the response of female mice to rapid, precisely timed, and spatially confined mechanical perturbations applied by a treadmill system. Our data elucidate that after the mechanical perturbation, the mouse gait response is anisotropic, preferring deviations away from the trot towards bounding, over those towards other gaits, such as walk or pace. We quantified this shift by projecting the observed gait onto the line between trot and bound, in the space of quadrupedal gaits. We call this projection λ. For λ=0, the gait is the ideal trot; for λ=±π, it is the ideal bound. We found that the substrate perturbation caused a significant shift in λ towards bound during the stride in which the perturbation occurred and the following stride (linear mixed effects model: Δλ=0.26±0.07 and Δλ=0.21±0.07, respectively; random effect for animal, p<0.05 for both strides, n = 8 mice). We hypothesize that this is because the bounding gait is better suited to rapid acceleration or deceleration, and an exploratory analysis of jerk showed that it was significantly correlated with λ (p<0.05). To evaluate whether the same structure of gait controller exists when undergoing an entirely different class of manipulation, we applied an internal, neuromuscular perturbation. We directly stimulated the lateral gastrocnemius muscle of mice using implanted electrodes and a custom magnetic headstage. We found that the electrical muscle stimulation caused a significant shift in λ towards bound in trials where the stimulation occurred during the swing phase (linear mixed effects model: Δλ=0.23±0.06 and Δλ=0.28±0.06; for the stride during and after the stimulation, respectively; random effect for animal, p<0.05 for both, n = 7 mice). Understanding how gait is controlled under perturbations can give insight into the neuromechanical basis of locomotion, aid in diagnosing gait pathologies, and aid the design of more agile robots.

Temple University – Theses

Advisors/Committee Members: Spence, Andrew;, Lemay, Michel A., Smith, George, Hsieh, Tonia;.

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Bioengineering

Locomotion is essential to survival in most animals. Studies have shown that animals, including humans, choose a gait that minimizes the risk of injury and maximizes energetic efficiency. Individuals often encounter obstacles and perturbations during normal locomotion, from which they must recover. Despite the importance of understanding the mechanisms that enable recovery from perturbations, ethical and experimental challenges have prevented full exploration of these in legged systems. A powerful paradigm with which to tackle this difficulty would be the application of external and internal manipulation of the nervous system. These perturbations could target how gait is regulated and how the neural systems process sensory information to control locomotion during an unexpected perturbation. Here we present data on the response of female mice to rapid, precisely timed, and spatially confined mechanical perturbations applied by a treadmill system. Our data elucidate that after the mechanical perturbation, the mouse gait response is anisotropic, preferring deviations away from the trot towards bounding, over those towards other gaits, such as walk or pace. We quantified this shift by projecting the observed gait onto the line between trot and bound, in the space of quadrupedal gaits. We call this projection λ. For λ=0, the gait is the ideal trot; for λ=±π, it is the ideal bound. We found that the substrate perturbation caused a significant shift in λ towards bound during the stride in which the perturbation occurred and the following stride (linear mixed effects model: Δλ=0.26±0.07 and Δλ=0.21±0.07, respectively; random effect for animal, p<0.05 for both strides, n = 8 mice). We hypothesize that this is because the bounding gait is better suited to rapid acceleration or deceleration, and an exploratory analysis of jerk showed that it was significantly correlated with λ (p<0.05). To evaluate whether the same structure of gait controller exists when undergoing an entirely different class of manipulation, we applied an internal, neuromuscular perturbation. We directly stimulated the lateral gastrocnemius muscle of mice using implanted electrodes and a custom magnetic headstage. We found that the electrical muscle stimulation caused a significant shift in λ towards bound in trials where the stimulation occurred during the swing phase (linear mixed effects model: Δλ=0.23±0.06 and Δλ=0.28±0.06; for the stride during and after the stimulation, respectively; random effect for animal, p<0.05 for both, n = 7 mice). Understanding how gait is controlled under perturbations can give insight into the neuromechanical basis of locomotion, aid in diagnosing gait pathologies, and aid the design of more agile robots.

Temple University – Theses

Advisors/Committee Members: Spence, Andrew;, Lemay, Michel A., Smith, George, Hsieh, Tonia;.

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Bioengineering

Locomotion is essential to survival in most animals. Studies have shown that animals, including humans, choose a gait that minimizes the risk of injury and maximizes energetic efficiency. Individuals often encounter obstacles and perturbations during normal locomotion, from which they must recover. Despite the importance of understanding the mechanisms that enable recovery from perturbations, ethical and experimental challenges have prevented full exploration of these in legged systems. A powerful paradigm with which to tackle this difficulty would be the application of external and internal manipulation of the nervous system. These perturbations could target how gait is regulated and how the neural systems process sensory information to control locomotion during an unexpected perturbation. Here we present data on the response of female mice to rapid, precisely timed, and spatially confined mechanical perturbations applied by a treadmill system. Our data elucidate that after the mechanical perturbation, the mouse gait response is anisotropic, preferring deviations away from the trot towards bounding, over those towards other gaits, such as walk or pace. We quantified this shift by projecting the observed gait onto the line between trot and bound, in the space of quadrupedal gaits. We call this projection λ. For λ=0, the gait is the ideal trot; for λ=±π, it is the ideal bound. We found that the substrate perturbation caused a significant shift in λ towards bound during the stride in which the perturbation occurred and the following stride (linear mixed effects model: Δλ=0.26±0.07 and Δλ=0.21±0.07, respectively; random effect for animal, p<0.05 for both strides, n = 8 mice). We hypothesize that this is because the bounding gait is better suited to rapid acceleration or deceleration, and an exploratory analysis of jerk showed that it was significantly correlated with λ (p<0.05). To evaluate whether the same structure of gait controller exists when undergoing an entirely different class of manipulation, we applied an internal, neuromuscular perturbation. We directly stimulated the lateral gastrocnemius muscle of mice using implanted electrodes and a custom magnetic headstage. We found that the electrical muscle stimulation caused a significant shift in λ towards bound in trials where the stimulation occurred during the swing phase (linear mixed effects model: Δλ=0.23±0.06 and Δλ=0.28±0.06; for the stride during and after the stimulation, respectively; random effect for animal, p<0.05 for both, n = 7 mice). Understanding how gait is controlled under perturbations can give insight into the neuromechanical basis of locomotion, aid in diagnosing gait pathologies, and aid the design of more agile robots.

Temple University – Theses

Advisors/Committee Members: Spence, Andrew;, Lemay, Michel A., Smith, George, Hsieh, Tonia;.

▼ 

Bioengineering

Locomotion is essential to survival in most animals. Studies have shown that animals, including humans, choose a gait that minimizes the risk of injury and maximizes energetic efficiency. Individuals often encounter obstacles and perturbations during normal locomotion, from which they must recover. Despite the importance of understanding the mechanisms that enable recovery from perturbations, ethical and experimental challenges have prevented full exploration of these in legged systems. A powerful paradigm with which to tackle this difficulty would be the application of external and internal manipulation of the nervous system. These perturbations could target how gait is regulated and how the neural systems process sensory information to control locomotion during an unexpected perturbation. Here we present data on the response of female mice to rapid, precisely timed, and spatially confined mechanical perturbations applied by a treadmill system. Our data elucidate that after the mechanical perturbation, the mouse gait response is anisotropic, preferring deviations away from the trot towards bounding, over those towards other gaits, such as walk or pace. We quantified this shift by projecting the observed gait onto the line between trot and bound, in the space of quadrupedal gaits. We call this projection λ. For λ=0, the gait is the ideal trot; for λ=±π, it is the ideal bound. We found that the substrate perturbation caused a significant shift in λ towards bound during the stride in which the perturbation occurred and the following stride (linear mixed effects model: Δλ=0.26±0.07 and Δλ=0.21±0.07, respectively; random effect for animal, p<0.05 for both strides, n = 8 mice). We hypothesize that this is because the bounding gait is better suited to rapid acceleration or deceleration, and an exploratory analysis of jerk showed that it was significantly correlated with λ (p<0.05). To evaluate whether the same structure of gait controller exists when undergoing an entirely different class of manipulation, we applied an internal, neuromuscular perturbation. We directly stimulated the lateral gastrocnemius muscle of mice using implanted electrodes and a custom magnetic headstage. We found that the electrical muscle stimulation caused a significant shift in λ towards bound in trials where the stimulation occurred during the swing phase (linear mixed effects model: Δλ=0.23±0.06 and Δλ=0.28±0.06; for the stride during and after the stimulation, respectively; random effect for animal, p<0.05 for both, n = 7 mice). Understanding how gait is controlled under perturbations can give insight into the neuromechanical basis of locomotion, aid in diagnosing gait pathologies, and aid the design of more agile robots.

Temple University – Theses

Advisors/Committee Members: Spence, Andrew;, Lemay, Michel A., Smith, George, Hsieh, Tonia;.

▼ 

Bioengineering

Locomotion is essential to survival in most animals. Studies have shown that animals, including humans, choose a gait that minimizes the risk of injury and maximizes energetic efficiency. Individuals often encounter obstacles and perturbations during normal locomotion, from which they must recover. Despite the importance of understanding the mechanisms that enable recovery from perturbations, ethical and experimental challenges have prevented full exploration of these in legged systems. A powerful paradigm with which to tackle this difficulty would be the application of external and internal manipulation of the nervous system. These perturbations could target how gait is regulated and how the neural systems process sensory information to control locomotion during an unexpected perturbation. Here we present data on the response of female mice to rapid, precisely timed, and spatially confined mechanical perturbations applied by a treadmill system. Our data elucidate that after the mechanical perturbation, the mouse gait response is anisotropic, preferring deviations away from the trot towards bounding, over those towards other gaits, such as walk or pace. We quantified this shift by projecting the observed gait onto the line between trot and bound, in the space of quadrupedal gaits. We call this projection λ. For λ=0, the gait is the ideal trot; for λ=±π, it is the ideal bound. We found that the substrate perturbation caused a significant shift in λ towards bound during the stride in which the perturbation occurred and the following stride (linear mixed effects model: Δλ=0.26±0.07 and Δλ=0.21±0.07, respectively; random effect for animal, p<0.05 for both strides, n = 8 mice). We hypothesize that this is because the bounding gait is better suited to rapid acceleration or deceleration, and an exploratory analysis of jerk showed that it was significantly correlated with λ (p<0.05). To evaluate whether the same structure of gait controller exists when undergoing an entirely different class of manipulation, we applied an internal, neuromuscular perturbation. We directly stimulated the lateral gastrocnemius muscle of mice using implanted electrodes and a custom magnetic headstage. We found that the electrical muscle stimulation caused a significant shift in λ towards bound in trials where the stimulation occurred during the swing phase (linear mixed effects model: Δλ=0.23±0.06 and Δλ=0.28±0.06; for the stride during and after the stimulation, respectively; random effect for animal, p<0.05 for both, n = 7 mice). Understanding how gait is controlled under perturbations can give insight into the neuromechanical basis of locomotion, aid in diagnosing gait pathologies, and aid the design of more agile robots.

Temple University – Theses

Advisors/Committee Members: Spence, Andrew;, Lemay, Michel A., Smith, George, Hsieh, Tonia;.

▼ 

Bioengineering

Locomotion is essential to survival in most animals. Studies have shown that animals, including humans, choose a gait that minimizes the risk of injury and maximizes energetic efficiency. Individuals often encounter obstacles and perturbations during normal locomotion, from which they must recover. Despite the importance of understanding the mechanisms that enable recovery from perturbations, ethical and experimental challenges have prevented full exploration of these in legged systems. A powerful paradigm with which to tackle this difficulty would be the application of external and internal manipulation of the nervous system. These perturbations could target how gait is regulated and how the neural systems process sensory information to control locomotion during an unexpected perturbation. Here we present data on the response of female mice to rapid, precisely timed, and spatially confined mechanical perturbations applied by a treadmill system. Our data elucidate that after the mechanical perturbation, the mouse gait response is anisotropic, preferring deviations away from the trot towards bounding, over those towards other gaits, such as walk or pace. We quantified this shift by projecting the observed gait onto the line between trot and bound, in the space of quadrupedal gaits. We call this projection λ. For λ=0, the gait is the ideal trot; for λ=±π, it is the ideal bound. We found that the substrate perturbation caused a significant shift in λ towards bound during the stride in which the perturbation occurred and the following stride (linear mixed effects model: Δλ=0.26±0.07 and Δλ=0.21±0.07, respectively; random effect for animal, p<0.05 for both strides, n = 8 mice). We hypothesize that this is because the bounding gait is better suited to rapid acceleration or deceleration, and an exploratory analysis of jerk showed that it was significantly correlated with λ (p<0.05). To evaluate whether the same structure of gait controller exists when undergoing an entirely different class of manipulation, we applied an internal, neuromuscular perturbation. We directly stimulated the lateral gastrocnemius muscle of mice using implanted electrodes and a custom magnetic headstage. We found that the electrical muscle stimulation caused a significant shift in λ towards bound in trials where the stimulation occurred during the swing phase (linear mixed effects model: Δλ=0.23±0.06 and Δλ=0.28±0.06; for the stride during and after the stimulation, respectively; random effect for animal, p<0.05 for both, n = 7 mice). Understanding how gait is controlled under perturbations can give insight into the neuromechanical basis of locomotion, aid in diagnosing gait pathologies, and aid the design of more agile robots.

Temple University – Theses

Advisors/Committee Members: Spence, Andrew;, Lemay, Michel A., Smith, George, Hsieh, Tonia;.

▼ 

Bioengineering

Locomotion is essential to survival in most animals. Studies have shown that animals, including humans, choose a gait that minimizes the risk of injury and maximizes energetic efficiency. Individuals often encounter obstacles and perturbations during normal locomotion, from which they must recover. Despite the importance of understanding the mechanisms that enable recovery from perturbations, ethical and experimental challenges have prevented full exploration of these in legged systems. A powerful paradigm with which to tackle this difficulty would be the application of external and internal manipulation of the nervous system. These perturbations could target how gait is regulated and how the neural systems process sensory information to control locomotion during an unexpected perturbation. Here we present data on the response of female mice to rapid, precisely timed, and spatially confined mechanical perturbations applied by a treadmill system. Our data elucidate that after the mechanical perturbation, the mouse gait response is anisotropic, preferring deviations away from the trot towards bounding, over those towards other gaits, such as walk or pace. We quantified this shift by projecting the observed gait onto the line between trot and bound, in the space of quadrupedal gaits. We call this projection λ. For λ=0, the gait is the ideal trot; for λ=±π, it is the ideal bound. We found that the substrate perturbation caused a significant shift in λ towards bound during the stride in which the perturbation occurred and the following stride (linear mixed effects model: Δλ=0.26±0.07 and Δλ=0.21±0.07, respectively; random effect for animal, p<0.05 for both strides, n = 8 mice). We hypothesize that this is because the bounding gait is better suited to rapid acceleration or deceleration, and an exploratory analysis of jerk showed that it was significantly correlated with λ (p<0.05). To evaluate whether the same structure of gait controller exists when undergoing an entirely different class of manipulation, we applied an internal, neuromuscular perturbation. We directly stimulated the lateral gastrocnemius muscle of mice using implanted electrodes and a custom magnetic headstage. We found that the electrical muscle stimulation caused a significant shift in λ towards bound in trials where the stimulation occurred during the swing phase (linear mixed effects model: Δλ=0.23±0.06 and Δλ=0.28±0.06; for the stride during and after the stimulation, respectively; random effect for animal, p<0.05 for both, n = 7 mice). Understanding how gait is controlled under perturbations can give insight into the neuromechanical basis of locomotion, aid in diagnosing gait pathologies, and aid the design of more agile robots.

Temple University – Theses

Advisors/Committee Members: Spence, Andrew;, Lemay, Michel A., Smith, George, Hsieh, Tonia;.

▼ 

Bioengineering

Locomotion is essential to survival in most animals. Studies have shown that animals, including humans, choose a gait that minimizes the risk of injury and maximizes energetic efficiency. Individuals often encounter obstacles and perturbations during normal locomotion, from which they must recover. Despite the importance of understanding the mechanisms that enable recovery from perturbations, ethical and experimental challenges have prevented full exploration of these in legged systems. A powerful paradigm with which to tackle this difficulty would be the application of external and internal manipulation of the nervous system. These perturbations could target how gait is regulated and how the neural systems process sensory information to control locomotion during an unexpected perturbation. Here we present data on the response of female mice to rapid, precisely timed, and spatially confined mechanical perturbations applied by a treadmill system. Our data elucidate that after the mechanical perturbation, the mouse gait response is anisotropic, preferring deviations away from the trot towards bounding, over those towards other gaits, such as walk or pace. We quantified this shift by projecting the observed gait onto the line between trot and bound, in the space of quadrupedal gaits. We call this projection λ. For λ=0, the gait is the ideal trot; for λ=±π, it is the ideal bound. We found that the substrate perturbation caused a significant shift in λ towards bound during the stride in which the perturbation occurred and the following stride (linear mixed effects model: Δλ=0.26±0.07 and Δλ=0.21±0.07, respectively; random effect for animal, p<0.05 for both strides, n = 8 mice). We hypothesize that this is because the bounding gait is better suited to rapid acceleration or deceleration, and an exploratory analysis of jerk showed that it was significantly correlated with λ (p<0.05). To evaluate whether the same structure of gait controller exists when undergoing an entirely different class of manipulation, we applied an internal, neuromuscular perturbation. We directly stimulated the lateral gastrocnemius muscle of mice using implanted electrodes and a custom magnetic headstage. We found that the electrical muscle stimulation caused a significant shift in λ towards bound in trials where the stimulation occurred during the swing phase (linear mixed effects model: Δλ=0.23±0.06 and Δλ=0.28±0.06; for the stride during and after the stimulation, respectively; random effect for animal, p<0.05 for both, n = 7 mice). Understanding how gait is controlled under perturbations can give insight into the neuromechanical basis of locomotion, aid in diagnosing gait pathologies, and aid the design of more agile robots.

Temple University – Theses

Advisors/Committee Members: Spence, Andrew;, Lemay, Michel A., Smith, George, Hsieh, Tonia;.

▼ 

Bioengineering

Locomotion is essential to survival in most animals. Studies have shown that animals, including humans, choose a gait that minimizes the risk of injury and maximizes energetic efficiency. Individuals often encounter obstacles and perturbations during normal locomotion, from which they must recover. Despite the importance of understanding the mechanisms that enable recovery from perturbations, ethical and experimental challenges have prevented full exploration of these in legged systems. A powerful paradigm with which to tackle this difficulty would be the application of external and internal manipulation of the nervous system. These perturbations could target how gait is regulated and how the neural systems process sensory information to control locomotion during an unexpected perturbation. Here we present data on the response of female mice to rapid, precisely timed, and spatially confined mechanical perturbations applied by a treadmill system. Our data elucidate that after the mechanical perturbation, the mouse gait response is anisotropic, preferring deviations away from the trot towards bounding, over those towards other gaits, such as walk or pace. We quantified this shift by projecting the observed gait onto the line between trot and bound, in the space of quadrupedal gaits. We call this projection λ. For λ=0, the gait is the ideal trot; for λ=±π, it is the ideal bound. We found that the substrate perturbation caused a significant shift in λ towards bound during the stride in which the perturbation occurred and the following stride (linear mixed effects model: Δλ=0.26±0.07 and Δλ=0.21±0.07, respectively; random effect for animal, p<0.05 for both strides, n = 8 mice). We hypothesize that this is because the bounding gait is better suited to rapid acceleration or deceleration, and an exploratory analysis of jerk showed that it was significantly correlated with λ (p<0.05). To evaluate whether the same structure of gait controller exists when undergoing an entirely different class of manipulation, we applied an internal, neuromuscular perturbation. We directly stimulated the lateral gastrocnemius muscle of mice using implanted electrodes and a custom magnetic headstage. We found that the electrical muscle stimulation caused a significant shift in λ towards bound in trials where the stimulation occurred during the swing phase (linear mixed effects model: Δλ=0.23±0.06 and Δλ=0.28±0.06; for the stride during and after the stimulation, respectively; random effect for animal, p<0.05 for both, n = 7 mice). Understanding how gait is controlled under perturbations can give insight into the neuromechanical basis of locomotion, aid in diagnosing gait pathologies, and aid the design of more agile robots.

Temple University – Theses

Advisors/Committee Members: Spence, Andrew;, Lemay, Michel A., Smith, George, Hsieh, Tonia;.

▼ 

Bioengineering

Locomotion is essential to survival in most animals. Studies have shown that animals, including humans, choose a gait that minimizes the risk of injury and maximizes energetic efficiency. Individuals often encounter obstacles and perturbations during normal locomotion, from which they must recover. Despite the importance of understanding the mechanisms that enable recovery from perturbations, ethical and experimental challenges have prevented full exploration of these in legged systems. A powerful paradigm with which to tackle this difficulty would be the application of external and internal manipulation of the nervous system. These perturbations could target how gait is regulated and how the neural systems process sensory information to control locomotion during an unexpected perturbation. Here we present data on the response of female mice to rapid, precisely timed, and spatially confined mechanical perturbations applied by a treadmill system. Our data elucidate that after the mechanical perturbation, the mouse gait response is anisotropic, preferring deviations away from the trot towards bounding, over those towards other gaits, such as walk or pace. We quantified this shift by projecting the observed gait onto the line between trot and bound, in the space of quadrupedal gaits. We call this projection λ. For λ=0, the gait is the ideal trot; for λ=±π, it is the ideal bound. We found that the substrate perturbation caused a significant shift in λ towards bound during the stride in which the perturbation occurred and the following stride (linear mixed effects model: Δλ=0.26±0.07 and Δλ=0.21±0.07, respectively; random effect for animal, p<0.05 for both strides, n = 8 mice). We hypothesize that this is because the bounding gait is better suited to rapid acceleration or deceleration, and an exploratory analysis of jerk showed that it was significantly correlated with λ (p<0.05). To evaluate whether the same structure of gait controller exists when undergoing an entirely different class of manipulation, we applied an internal, neuromuscular perturbation. We directly stimulated the lateral gastrocnemius muscle of mice using implanted electrodes and a custom magnetic headstage. We found that the electrical muscle stimulation caused a significant shift in λ towards bound in trials where the stimulation occurred during the swing phase (linear mixed effects model: Δλ=0.23±0.06 and Δλ=0.28±0.06; for the stride during and after the stimulation, respectively; random effect for animal, p<0.05 for both, n = 7 mice). Understanding how gait is controlled under perturbations can give insight into the neuromechanical basis of locomotion, aid in diagnosing gait pathologies, and aid the design of more agile robots.

Temple University – Theses

Advisors/Committee Members: Spence, Andrew;, Lemay, Michel A., Smith, George, Hsieh, Tonia;.

▼ Coordination indicates the ability to assemble and maintain a series of proper relations between joints or segments during motions. In Dynamical Systems Theory (DST), movement patterns are results of a synergistic organization of the neuromuscular system based on the constraints of anatomical structures, environmental factors, and movement tasks. Human gait requires the high level of neuromuscular control to regulate the initiation, intensity and adaptability of movements. To better understand how the neuromuscular system organizes and coordinates movements during walking, examination of single joint kinematics and kinetics alone may not be sufficient. Studying inter-joint coordination will provide insights into the essential timing and sequencing of neuromuscular control over biomechanical degrees of freedom, and the variability of inter-joint coordination would reflect the adaptability of such control. Previous studies assessing inter-joint coordination were mainly focused on neurological deficiencies, such as stroke or cerebral palsy. However, information on how inter-joint coordination is modulated with different constraints, such as walking speeds, aging, brain injury or joint dysfunctions, are limited. This knowledge could help us in identifying the potential risks during walking and improve the performance of individuals with movement impairments. The purpose of the present study was to investigate the properties of inter-joint coordination pattern and variability during walking with different levels of neuromuscular system perturbations using a DST approach, including an overall neuromuscular systemic degeneration, a direct insult to the brain, and a joint disease. We found that aging seemed to reduce the pattern adaptability of neuromuscular control. Isolated brain injury and joint disease altered the coordination pattern and exaggerated the variability, indicating a poor neuromuscular control. To improve gait performances for different populations, clinical rehabilitation should be carefully designed as different levels of neuromuscular system constraints would lead to different needs for facilitating appropriate coordinative movement. This dissertation includes both previously published/unpublished and coauthored material. Advisors/Committee Members: Chou, Li-Shan (advisor).

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Seven above-knee amputees were fitted with a low-cost prosthetic knee and different low-cost swing-phase setups were clinically assessed. Clinical testing included the 20-meter walk tests utilizing a mobile computer setup connected to a potentiometer and accelerometer mounted on the prosthetic limb. As hypothesized, incorporating friction and a spring system resulted in improved gait function. Of the two spring systems evaluated, the dual spring system performed better than the single spring system resulting in increased walking velocity with decreased maximum flexion and terminal impact. The dual spring system resulted in lower terminal impact because the deactivation of the stiff spring and activation of the less stiff spring during the last 25 degrees of swing-phase before extension allows the shank to decelerate and hit the bumper at a lower velocity. The swing-phase control mechanisms evaluated have the potential to improve prosthetic function and are ideal for use in low-cost and peadiatric prostheses.

MAST

Advisors/Committee Members: Cleghorn, William L., Andrysek, Jan, Biomedical Engineering.

▼ Alterations in gait patterns are commonly observed in individuals with transtibial amputation (TTA) who use a prosthesis. Current commercially available ankle-foot prostheses (AFP) offer very little range of motion (ROM) at the ankle joint. Previous researchers have hypothesized that lack of ankle ROM significantly contributes to alterations in TTA gait patterns. However, different patterns have been observed among TTA using the same AFP. Therefore it is unclear how restricted ankle ROM in current commercially available ankle-foot prostheses (AFP) contributes to observed changes in gait. Alterations in gait patterns have been shown to increase the incidence of low back pain and other musculoskeletal injuries. TTA have a greater incidence of low back pain and osteoarthritis of the knee and hip. Therefore it is important for researchers to understand the influence of different prosthetic components on gait in order to optimize gait patterns and minimize complications due to alterations in gait. The purpose of this study was to determine what compensatory alterations in gait patterns may occur as a result of imposed restricted ankle range of motion. Kinematic data was collected from 19 participants (9 men, 10 women) age 18-32 with no previous history of lower extremity injury or deformity in two conditions: level-ground walking with no restriction and level ground walking with the ankle restricted at 0 degrees plantarflexion by plaster casting. Results indicated that restricted ankle ROM contributes to decreased velocity and cadence and decrease in gait symmetry. A compensatory pattern was observed for pelvic obliquity, hip and knee flexion at toe-off and foot progression angle. Observed patterns did not resemble those observed in TTA. Results suggest that restricted ankle ROM contributes to some components of alterations in gait patterns observed in TTA. However a combination of other components, including loss of proprioception and power generation at the metatarsophalangeal (toe) joints may have a more significant contribution to TTA gait patterns than restricted ankle ROM alone. Advisors/Committee Members: Yun, Joonkoo (advisor), McCubbin, Jeff (committee member).