Walking pigeons display a characteristic behaviour: head-bobbing. Head-bobbing consists of two phases, the hold phase during which the head is kept stable in space, and the thrust phase during which the head is quickly moved forward. But why do pigeons and so many other birds head-bob? Two theories have been developed to answer this question. First, head-bobbing may have a visual function, namely object detection during the hold phase and depth perception during the thrust phase. Second, head-bobbing may have the biomechanical function of increasing the stability. The present study aimed to gain further insight into why pigeons head-bob. A gait cycle analysis of walking pigeons revealed that the hold phase starts at a specific point in the gait cycle and is not dependent on the walking speed. The point in the gait cycle at which the hold phase starts indicates a potential increase in stability during the single stance phase, as it leads to a longer period of time during which the center of mass is above the base of support. The end of the hold phase, however, is dependent on the walking speed, specifically the step length for a given walking speed. I found that the thrust phase duration is constant for all walking speeds and the distance the head travels during that time is equal to the step length. With increasing walking speed the head moves faster during the thrust phase and the hold phase duration is decreased leading to a higher head-bobbing frequency. With fast enough walking speed the hold phase is eventually eliminated, marking the transition point from walking with head-bobbing to fast walking without head-bobbing. The exact velocity of this transition point was predicted for each individual and was dependent on the maximal step length of each pigeon. All head-bobbing parameters could be described with the step-frequency, the thrust phase duration, and the maximal step length, indicating that head-bobbing behavior is individual for every pigeon and depends on its body size. / Thesis (Master, Biology) -- Queen's University, 2013-07-22 23:11:41.557

Objective: To develop modular software to assess angular impulse and to determine the effect of a reduced dataset on the net angular impulse acting at the L5/S1 joint. Background. With the prevalence and incidence of lower back pain increasing annually, accurate assessment of physical job demands is needed. Many lab based approaches exist to measure the moments acting on the lower back, but require advanced and sensitive testing equipment. Of the methodologies currently used in industrial settings, most require significant contributions of time or money to be implemented. There is a need for cost and time effective methods to record a worker’s kinematic data over their whole shift. Methods: Twelve participants performed 12 consecutive lifts under five lifting conditions: SQ00 (squat 0kg); SQ04 (squat 4kg); SQ10 (squat 10kg); FP04 (fast squat 4kg); ST04 (stoop 4kg). Kinematic data of the upper limbs, head, and trunk was recorded with external load data and kinetic analysis was performed by implementing an extension of the Hof (1992) method called the lined-segment engine (LSE) to calculate the angular impulse (N•m•s) acting on the L5/S1 joint. Results: The LSE was sensitive to changes in load, lifting speed, and lifting posture (p < 0.05). There was no difference in dynamic, quasi-static, or static models when calculating angular impulse, but there was a difference in the L5/S1 angular impulse when the upper limbs were removed from the dynamic LSE model (p < 0.05). Conclusion: The LSE requires further refinement, but could be a generic approach to kinetic calculations. A scaled no-arms model for calculating the angular impulse acting on the low back could be used to assess field based lifting studies with 5.8% error. / Thesis (Master, Kinesiology & Health Studies) -- Queen's University, 2013-08-03 15:05:03.257

The majority of stroke survivors return to living in the community; however, muscle weakness and cardiovascular deconditioning can restrict mobility, limit community access and independence, particularly when challenging activities like stair negotiation are involved. A “step-by-step” (SBS) strategy (both feet per step) may be adopted in lieu of a “step-over-step” (SOS) method (one foot per step) to increase stability and off-load the paretic limb though the physical demands of the two methods are unknown. The main objective of this thesis was to investigate the strength and energy demands of the two stair-stepping strategies in chronic stroke compared to healthy adults. The first study identified the relative strength and aerobic demands of both strategies. The results showed that the stroke group produced similar peak joint moments compared to controls, despite their slower cadence suggesting that the stroke group exerts comparable ‘effort’ to move more slowly. The SBS method was associated with lower strength costs (relative to individuals’ maximum strength output) than SOS, however aerobic cost was significantly higher. The second study identified the mechanical energy expenditures (MEEs) and transfers related to both strategies. The MEEs were found to be lower when the SBS strategy was used. Though expenditures were similar between groups, the stroke group had higher expenditures associated with the work of the less affected knee extensors (lead limb) during ascent and descent and controls exhibited higher expenditures for the plantarflexors during ascent. The reduced output of the trail (affected) limb plantarflexors likely resulted in the increased workload of the knee extensors. Overall, the aerobic cost per step was higher in stroke, particularly during descent, suggesting that in addition to reducing cadence, persons with stroke may be co-contracting to increase stabilization during descent, thus increasing oxygen demands. This thesis provides novel information on the physical demands associated with two methods of stair negotiation demonstrating that the SBS strategy might be better suited to persons with chronic stroke by minimizing the strength demands on the paretic side, but the benefit comes at an elevated aerobic cost. This information is valuable to rehabilitation professionals engaged in retraining mobility to facilitate community reintegration. / Thesis (Master, Rehabilitation Science) -- Queen's University, 2013-09-30 13:42:08.209

With the popularity of outdoor activities like hiking, the demands of certain types of employment, or being a student, an individual’s ability to carry a load is an important mobility consideration. By understanding the changes to an individual’s gait when supporting a backpack load, an individual’s ability to carry heavy loads for prolonged periods could be improved. Most biomechanical studies have examined the changes in able-bodied gait when carrying a load. However, research is lacking on the effect of backpack loads on amputee gait patterns. This project examined the effects of a backpack load on the gait patterns of unilateral transtibial amputees. Ten participants performed walking trials on four surfaces (level ground, uneven ground, walking up an incline, and walking down an incline), without a pack and with a pack. A total of 40 trials were collected per subject, with 10 trials collected on each surface. Three-dimensional motion data were collected with an eight-camera Vicon Motion Analysis system to describe limb motion as well as compare kinematic outcomes between tasks and conditions. Force platform data were collected during the level ground trials and used to calculate kinetic measures for both limbs. With the addition of the pack changes were seen on each surface, with different changes occurring to each limb. The ramp up surface created the most changes when comparing the two conditions. The only change seen across all four surfaces was a decrease in ankle dorsiflexion before push-off on the prosthetic limb. The two next most common changes were increases in knee and hip flexion during weight-acceptance.

A major function of the central nervous system (CNS) during locomotion is the ability to maintain dynamic stability during threats to balance. The CNS uses reactive, predictive, and anticipatory mechanisms in order to accomplish this. Previously, stability has been estimated using single measures. Since the entire body works as a system, dynamic stability should be examined by integrating kinematic, kinetic, and electromyographical measures of the whole body. This thesis examines three threats to stability (recovery from a frontal plane surface translation, stepping onto and walking on a compliant surface, and obstacle clearance on a compliant surface). These threats to stability would enable a full body stability analysis for reactive, predictive, and anticipatory CNS control mechanisms. From the results in this study, observing various biomechanical variables provides a more precise evaluation of dynamic stability and how it is achieved. Observations showed that different methods of increasing stability (eg. Lowering full body COM, increasing step width) were controlled by differing CNS mechanisms during a task. This provides evidence that a single measure cannot determine dynamic stability during a locomotion task and the body must be observed entirely to determine methods used in the maintenance of dynamic stability.

No description available.

Les joueurs de tennis sont confrontés à un problème fondamental : comment améliorer la vitesse de leur service tout en limitant le plus possible les risques de pathologies chroniques ? L’objectif de ce travail est d’analyser, d’identifier et de comprendre les facteurs biomécaniques responsables de l’amélioration de la performance et de l’apparition des blessures articulaires chroniques lors de la réalisation du service au tennis. A partir de captures de mouvement en 3D chez des joueurs professionnels, la première étude s’attache à analyser les relations entre les valeurs de moments cinétiques segmentaires et la vitesse de balle au service. Grâce à une approche combinant captures de mouvement en laboratoire et suivi épidémiologique, la seconde étude explore l’influence du niveau d’expertise sur les contraintes articulaires du membre supérieur lors de la réalisation du service et sur l’apparition de blessures articulaires chroniques. La troisième étude identifie des facteurs "pathomécaniques" du service en comparant les mouvements de joueurs "sains" avec ceux de joueurs "blessés". La quatrième étude s’intéresse aux relations pouvant exister entre la vitesse de balle, les contraintes articulaires et le transfert de l’énergie mécanique lors du service. Enfin, la dernière étude porte sur l’influence de la fatigue musculaire sur la biomécanique, les risques de blessures et la performance du service lors d’un match de tennis prolongé. L’ensemble de ce travail démontre qu’il est à la fois possible d’améliorer la performance sportive et de limiter les risques de blessures grâce à la réalisation d’un geste de service "juste" sur le plan biomécanique / Tennis players are confronted with a crucial problem : how being more efficient by increasing serve’s ball velocity and limiting risks of overuse injuries ? The aim of this work is to analyze, identify and understand the biomechanical determinants of the tennis serve responsible for the performance’s enhancement and the arrival of overuse upper limb joint injuries. From motion captures in professional tennis players, the first study aims to analyze the relationships between segmental angular momentum values and serve’s ball velocity. By coupling motion capture with a prospective registration of injuries, the second study investigates the influence of two different levels of expertise on upper limb joint kinetics during thetennis serve and on the occurrence of overuse upper limb joint injuries. The third study aims to identify pathomechanical factors during the tennis serve by comparing injured and non-injured tennis players. The purpose of the fourth study is to investigate the relationships between the mechanical energy flow, the ball velocity and the peaks of upper limb joint kinetics. Finally, the last study evaluates the effects of muscular fatigue on serve biomechanics, upper limb injury risks and serve performance during a prolonged tennis match. These works imply that using proper mechanics during the tennis serve can enhance serve performance and possibly decrease injury risks

Purpose: We evaluate solutions for an applanating surface modification to the Goldmann tonometer prism, which substantially negates the errors due to patient variability in biomechanics. Methods: A modified Goldmann or correcting applanation tonometry surface (CATS) prism is presented which was optimized to minimize the intraocular pressure (lOP) error due to corneal thickness, stiffness, curvature, and tear film. Mathematical modeling with finite element analysis (FEA) and manometric lOP referenced cadaver eyes were used to optimize and validate the design. Results: Mathematical modeling of the optimized CATS prism indicates an approximate 50% reduction in each of the corneal biomechanical and tear film errors. Manometric lOP referenced pressure in cadaveric eyes demonstrates substantial equivalence to GAT in nominal eyes with the CATS prism as predicted by modeling theory. Conclusion: A CATS modified Goldmann prism is theoretically able to significantly improve the accuracy of lOP measurement without changing Goldmann measurement technique or interpretation. Clinical validation is needed but the analysis indicates a reduction in CCT error alone to less than +/- 2 mm Hg using the CATS prism in 100% of a standard population compared to only 54% less than +/- 2 mm Hg error with the present Goldmann prism. Translational Relevance: This article presents an easily adopted novel approach and critical design parameters to improve the accuracy of a Goldmann applanating tonometer.

O bobsled é um esporte desenvolvido para prática de inverno e tem como objetivo principal, percorrer uma pista de gelo inclinada de aproximadamente 1500m no menor tempo possível. A atividade é iniciada com o trenó parado, sem movimento. Existem duas modalidades, o bobsled para quatro pessoas e bobsled para duas pessoas. O movimento inicial do bobsled é conhecido como o momento de propulsão do trenó ou da largada, já teve sua importância demonstrada para a obtenção de um bom desempenho final em estudos anteriores, é executado na modalidade de dois atletas pelo atleta piloto e pelo atleta breakman. Os objetivos deste trabalho se preocuparam em investigar a existência de um padrão cinemático adotado pelos atletas piloto e atletas breakman durante o momento de propulsão do trenó das 15 melhores equipes participantes do campeonato, assim como a existência da relação entre o tempo de largada e o tempo final da prova e a variação do desempenho obtido entre todas as equipes participantes. As imagens utilizadas neste trabalho foram adquiridas durante o XIV Campeonato Mundial de Bobsled masculino na modalidade de dois atletas, realizado na cidade de Koonigssee (Alemanha) em 2004. Para se investigar o padrão cinemático foram utilizadas variáveis relacionadas a angulação do ombro, cotovelo, tronco e joelho; variações do deslocamento e altura do centro de gravidade; além do comprimento do passo dos atletas piloto e breakman. Foi possível identificar um padrão cinemático típico adotado pelos atletas piloto e breakman durante o momento da largada, além de se identificar semelhanças entre o comportamento adotado pelos atletas piloto e breakman durante o instante da largada e o comportamento adotado pelos atletas de atletismo. O coeficiente de correlação encontrado neste estudo se assemelhou aos coeficientes encontrados nos estudos anteriores (aproximadamente r2=0,5), assim como pode se verificar a pequena variação do desempenho entre as equipes participantes (inferior a 4%) / Bobsled is a sport developed for practiced in winter time and has as main objective cover an inclined ice track of approximately 1500 m in less time as possible. The activity is initiated with the sleigh stopped, without movement. There are two modalities, the bobsled for four persons and for two persons. The initial movement of the bobsled is known as the propulsion moment and its importance for a good final performance had already been demonstrated in preview studies. This moment is executed in the modality for two persons by the pilot athlete and by the breakman athlete. The purpose of this study was to investigate the existence of a kinematic pattern adopted by the pilot athlete and the breakman athlete during the propulsion moment of the sleigh of the 15 best teams of the championship, as well as the existence of a relation between the propulsion moment and the final time of the test and the variation of the performance gotten by all the participant teams. The imagesm used in this study had been acquired during the XIV Word-Wide Championship of male bobsled in the modality for two persons, carried through in the city of Koonigsee (Germany) in 2004. To investigate the kinematic pattern it was used variables related to the shoulder, elbow, trunk and knee angles; variations of the center of gravity displacement and height; and the length of the step of the pilot and breakman athletes. It was possible to identify a typical kinematic pattern adopted by the pilot and breakman athletes during the propulsion moment, beyond identifying similarities between the behavior adopted by the pilot and breakman athletes during the propulsion moment and the behavior adopted by the track and fields athletes. The correlation coefficient found in this study was similar to those found in the previous studies (around r2=0,5) as well as the small variation verified in the performance between the participant teams (less than 4%)

Pesquisas sobre próteses ativas e exoesqueletos têm se intensificado nas últimas décadas. Seu uso para reabilitação, aumento de força ou substituição de um membro debilitado já está sendo utilizado comercialmente. Porém, um dos desafios para o controle deste tipo de dispositivo é a identificação dos parâmetros das articulações humanas para que o equipamento simule o mesmo comportamento e a interface homem máquina seja mais eficaz e confortável. Este trabalho apresenta o desenvolvimento, construção e validação de um exoesqueleto que é um dispositivo para estudo da marcha. Em outras palavras, o exoesqueleto apresentado é capaz de medir a força de interação com o corpo humano bem como a posição angular das articulações do joelho e tornozelo durante a marcha. Com essas medições é possível calcular os parâmetros de impedâncias dessas articulações. A revisão bibliográfica sobre exoesqueletos foi necessária para a definição dos requisitos do projeto. O projeto do exoesqueleto desenvolvido pela autora durante o trabalho de conclusão de curso foi revisto de acordo com os requisitos estabelecidos. Assim, o novo projeto, chamado de Protótipo II ou ExoLoLi, é capaz de suprir as deficiências do primeiro projeto e atender a todos os requisitos para ser uma ferramenta de estudo da marcha. O ExoLoLi foi construído e experimentos preliminares foram realizados para a sua validação como ferramenta de estudo da marcha. Foi possível confirmar que o exoesqueleto faz as medições de força de interação e de posição corretamente. Também foi possível verificar que o exoesqueleto interfere no padrão natural da marcha. De qualquer forma, o exoesqueleto poderá ser usado, não apenas para o cálculo dos parâmetros de impedância, mas também para estudo de consumo energético com diferentes tipos de controle e para diferentes aplicações (como reabilitação e aumento de força), dependendo do controle programado para o seu funcionamento. / Research on active prosthetics and exoskeletons has been intensified in recent decades. Its use for rehabilitation, strength increase or replacement of a disabled member is already being used commercially. But one of the challenges for the control of this type of device is the identification of the human joint\'s parameters so the machine is able to simulate the same behavior and the man-machine interface is more effective and comfortable. This dissertation presents the development, construction and validation of an exoskeleton which is a device for gait study. In other words, the presented exoskeleton is capable of measuring the interaction force with the human body as well as the angular position of the knee and ankle joints during gait. With these measurements it is possible to calculate the impedance parameters of these joints. The literature review about exoskeletons was necessary to define the project requirements. The exoskeleton developed by the author to obtain the engineering degree (undergraduate paper) has been reviewed in accordance with the established requirements. So the new exoskeleton design, called as Prototype II or ExoLoLi, is able to address the weaknesses of the first project and meet all the requirements to be a gait study tool. The ExoLoLi was built and preliminary experiments were performed to validate it as gait study tool. It was confirmed that the exoskeleton is able to measure the interaction forces and the angular position correctly. It was also observed that the exoskeleton interferes at the natural gait pattern. Anyway, the exoskeleton can be used not only for calculating the human impedance parameters, but also to analyze the energy consumption using different control strategies and to be used in different applications (such as rehabilitation or strength increase) depending on the programmed control for its operation.