No description available.

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

An underactuated exoskeleton design for walking assistance is presented and evaluated. The exoskeleton uses one motor per leg and makes use of a pantograph to reduce the overall profile and allow the exoskeleton to closely follow the shape of the user's leg. Support is provided between the ball of the user's foot and their waist by compressing a spring in parallel with the user's leg during Stance Phase. The exoskeleton has a mass of 14.0 kg (30.8 lbs) and was tested up to a supplied spring force of 323.6 N (72.75 lbf) which equates to around 161.8 N (36.38 lbf) of assistive force at the waist. Range of motion tests showed minimal restriction at the knee and ankle, but some restriction of the hip. Human subject experiments using a simple gait detection method based on GRF at walking speeds from 0.45 m/s to 1.12 m/s (1.0 mph to 2.5 mph) were performed and showed an increase in the time between actual heel strike and predicted heel strike of approximately 0.05 seconds to 0.1 seconds. Lastly, calculations are presented examining the effect of exoskeleton assistance on the biological joint moments and optimizing the actuator design to reduce power consumption. The actual performance of the exoskeleton is compared with the calculations based on the joint angles during a typical walking cycle. / Master of Science / A design for an exoskeleton capable of providing walking assistance without requiring a motor for every joint is presented and evaluated. The exoskeleton uses one motor per leg and makes use of a pantograph to reduce the required size and allow the exoskeleton to closely follow the shape of the user's leg. Support is provided between the ball of the user's foot and their waist by compressing a spring attached beside the user's leg while the user's foot is on the ground. The exoskeleton weighs 14.0 kg (30.8 lbs) and was tested up to a supplied spring force of 323.6 N (72.75 lbf) which equates to around 161.8 N (36.38 lbf) of assistive force at the waist. Range of motion tests showed minimal restriction at the knee and ankle, but some at the hip. Testing with a human participant using a simple method for determining when to apply support and remove it based on the forces measured at the user's foot were performed at walking speeds of 0.45 m/s to 1.12 m/s (1.0 mph to 2.5 mph). These tests showed an increase in the time between when the heel of the foot initially hits the ground and when the exoskeleton code determined that it occurred of approximately 0.05 seconds to 0.1 seconds. Lastly, calculations are presented examining how exoskeleton assistance affects what is felt at the joints of the user and determining what spring stiffness would best reduce the power required from the motors. The actual performance of the exoskeleton is compared with the calculations based on the joint angles during normal human walking.

This research has investigated the influence of gait cycle, malalignment and overweight on total knee replacements using a finite element method. Dynamic and finite element models of fixed- and mobile-bearing implants have been created and solved; the fixed- and mobile-bearing implants demonstrated different performance on movement and contact pressure distribution in the tibio-femoral contact surfaces. More contact areas were found in the mobilebearing implant than in the fixed-bearing implant, but the maximum contact pressures were almost the same in both. The thickness of the tibial bearing component influenced the fixed- and mobile-bearing implants differently. A dynamic model of an implanted knee joint has been developed using MSC/ADAMS and MSC/MARC software. Stress shielding was found in the distal femur in the implanted knee joint. The stresses and strains in the distal femur were found to increase with body weight, especially during the stance phase. Serious stress shielding and more bone loss appear in condition of overweight. The increase of bone loss rate and stress in the distal femur with increase of body weight will result in a higher risk of migration of femoral component after total knee replacement. The peg size effect has been studied using this dynamic model; a longer peg with smaller diameter was found to be the best. Varus/valgus malalignment redistributed the tibio-femoral contact force and stress/strain distribution in the distal femur. The difference between contact forces on the medial and lateral condyle decreased in the valgus malalignment condition. Contact pressure increased in the varus/valgus malalignment condition in the dynamic models of both the fixed- and mobile-bearing implant. However, the mobile-bearing implant performed better in conditions of malalignment, especially malrotation. Body weight had less influence on the maximum contact pressure in the mobile-bearing implant.

No description available.

The work performed in this thesis involves the study of human hip joint kinematics and load analysis. Such analyses are very useful for investigating mobility and natural functionality as well as the variation in motion due to replacement implants. The objective of this study is to design, build and testing of a universal human joint simulator that is configurable to hold several human joints and easily programmable to create the required motion. This was performed by creating a Stewart Platform, which is capable of moving in all six degrees of freedom; the maximum number needed by any human joint. Many specific human joint simulators are available on the market for simulating all major human limbs. These are used for wear testing replacement joints by using high load repetitive motion. These systems have a predetermined limit degree of movement and are very expensive; if one wanted to emulate another joint, one would have to purchase a whole new system. This novel system compromises of a three-phase power supply, Control Area Network with six actuators and drivers, a force reading clamp with strain gauges and data logger. A user friendly computer program was developed that is able to derive joint movement data from two inputs and replicating the movement by driving the platform, as well as recording force and displacement data from the joint. The product would be marketed towards biomechanical researchers and implant designers. Verification of this system was performed by simulating the human hip joint. A known combination of kinematic and force data were inputted into the system for nine different types of activities. The resultant force and joint centre displacement was then compared to see how well the system perform in comparison to the inputted data from a previous study. The outcome of this project is a fully functional machine and configurable program that can create movement data at varying speeds and body weights; which is also able to drive the human joint simulator. The design also costs a fraction of any industrial joint simulator. It is hoped that the simulator will allow easier study of both the kinematics and load analysis within the human joints, with the intent on aiding investigation into mobility and functionality; as well as variation in motion caused by a replacement implant.

Försvarsmakten gav KTH:s omgivningsfysiologiavdelning i uppdrag att studera energiåtgången vid gång med night vision goggles. För att ta reda på om rörelsemönstret påverkades av night vision goggles och därmed skulle ha inverkan på energiåtgången så samlades data in med inertial measurement units (IMU), men någon fullständig analys på datan gjordes inte. För att undersöka datan från IMU skapades en mjukvara i Python. Gångcykelns karaktäristik identifierades från datan för vinkelhastighet och acceleration från en IMU på vänster ankel. Position beräknades stegvis med dubbelintegration, på så vis analyserades rörelsen för varje individuellt steg. Träffsäkerheten för gångcyklarnas medelfrekvens med nämnda metod hamnade inom 5% mot tidigare validerad data med analys av motion capture system i inomhusförsök. Andra stegparametrar som steglängd och steghöjd antar dock helt orimliga värden. Vi tror att denna orimlighet till stor del beror på tekniska fel vid insamlingen av rådatan som orsakat dataförlust då liknande metoder med framgång använts av andra inom området. Rapporten beskriver utöver metoden för själva analysen även metoden för att skapa ett användarvänligt gränssnitt för forskare att utföra den med. / The Swedish Armed Forces asked the Division of Environmental Physiology at KTH to study the energy demand whilst walking with night vision goggles. To explore whether the patterns of movement changed and hence impacted energy use, data was gathered with inertial measurement units (IMU). However, no complete analysis of the collected data was performed. To study this data, software was created in Python. The gait cycle characteristics were identified from angular velocity and acceleration data from an IMU attached to the left ankle. Position was calculated stepwise by double integration, allowing for analysis of each individual step. Mean step frequency was calculated within 5% accuracy of earlier results validated by analysis with a motion capture system indoors. Other step parameters like stride length and height on the other hand take on completely unreasonable values. We believe this to largely be due to technical errors during the collection of the data leading to data loss, since similar methods have successfully been used by others in the field. The report also discusses the production of software with a user-friendly interface to be used by the scientists performing the final analysis.

This report presents the design and manufacturing process of a bionic signal messagebroker (BSMB), intended to allow communication between implanted electrodes andprosthetic legs designed by Ossur. The BSMB processes and analyses the data intorelevant information to control the bionic device. The intention is to carry out eventdetection in the BSMB, where events in the muscle signal are matched to the events ofthe gait cycle (toe-o, stance, swing).The whole system is designed to detect muscle contraction via sensors implantedin residual muscles and transmit the signals wireless to a control unit that activatesassociated functions of a prosthetic leg. Two users, one transtibial and one transfemoral,underwent surgery in order to get electrodes implantable into their residual leg muscles.They are among the rst users in the world to get this kind of implanted sensors.A prototype of the BSMB was manufactured. The process took more time thanexpected, mainly due to the fact that it was decided to use a ball grid array (BGA)microprocessor in order to save space. That meant more complicated routing and higherstandards for the manufacturing of the board. The results of the event detection indicatethat the data from the implanted electrodes can be used in order to get sucient controlover prosthetic legs. These are positive ndings for users of prosthetic legs and shouldincrease their security and quality of life.It is important to keep in mind when the results of this report are evaluated that allthe testing carried out were only done on one user each.

Bibliographic record SVOBODOVÁ, Jaroslava. The influence of the level and type of postural load on parameters of dynamic plantography during standing and walking. Prague: Charles University, 2nd Faculty of Medicine, Department of Rehabilitation and Sports Medicine, 2018, 124 p. Supervisor Mgr. Michaela Opálková. Abstract The thesis deals with the reaction of body to postural loading during stance and walking. The theoretical part of this thesis is focused on postural control and postural reaction during stance and walking. Particular attention is paid to gait cycle, dynamic plantography and Zebris FDM-T Rehawalk system, which has been used in the practical part of this thesis. Two chapter deal with postural loading, the first is focused on symmetrical loading (e.g. backpack) and second on asymmetrical loading (laptop back - ipsilateral, contralateral and held in hand). The practical part presents the examination of 32 volunteers who were either standing or walking on a dynamic plantograph. The volunteers were exposed to either symmetrical or asymemtrical 5 or 10 kg load. Subsequently, statistical tests were used to search for any change of dynamic plantography parameters depending on the level of loading, on the type of loading and in the comparison of the situation with and without loading. The results...

Abstract Primary hallmark of osteoarthritis (OA) is the progressive degeneration of articular cartilage. An accurate estimation of cartilage mechanics is important when analyzing the subject-specific function of the knee joint and risks for the onset and development of OA due to cartilage damage. Finite element (FE) modeling can help to estimate peak joint stresses and strains and explain how they could lead to OA. FE models of the knee joint during simplified gait were developed to define the level of material complexity required for 3D FE modeling of the knee joint in estimation of reliable tissue stresses and strains within articular cartilage of the knee joint; and to investigate the predictive value of FE modeling of the knee joint on the development and progression of radiographic OA within obese and normal weight subjects. It was found that maximum principal stresses and strains within articular cartilage in the knee joint during walking are highly sensitive to the material parameters of cartilage. It was not possible to match simultaneously stresses, strains and contact pressures between simplified (non-fibrillar) and advanced (fibrillar) models. Though, it was possible to find parameters for transversely isotropic models that enable the estimation of stresses and strains throughout the depth of cartilage similarly to more advanced fibril reinforced models. Locations of peak cumulative stresses in obese subjects at the baseline without radiographic OA showed a good agreement with the locations of cartilage loss and magnetic resonance imaging (MRI) based scoring in four year follow-up when they had developed OA. Simulated weight loss in obese subjects significantly reduced the highest cumulative stresses in cartilage to the level of normal weight subjects. The cartilage degeneration algorithm was able to predict subject-specific progression of OA similarly with MRI follow-up data and separate subjects with radiographic OA from healthy subjects. The computational FE models developed in this thesis represent useful tools to identify possible risk locations within the knee joint and how they relate to OA onset and progression. The presented methods have clinical potential in the diagnostics of knee joint OA in a subject-specific manner and in simulating the effect of interventions on the progression of OA thus helping with an effective treatment planning. / Tiivistelmä Nivelrikon tunnusomaisin piirre on nivelrustokudoksen rappeutuminen ja kuluminen. Nivelruston tehtävänä on tasata niveliin kohdistuvaa kuormitusta. Rustokudoksen mekaanisten ominaisuuksien määrittäminen on tärkeässä roolissa, kun halutaan arvioida tarkemmin polvinivelen toimintakykyä sekä rustokudoksen rappeutumista. Magneettikuvantamisen pohjalta tehtävä polvinivelen biomekaaninen tietokonemallinnus mahdollistaa rustokudoksen jännitys- ja puristusjakauman arvioinnin simuloidun kuormituksen aikana, mikä edelleen voi antaa vastauksia siihen, kehittyykö niveleen tulevaisuudessa nivelrikko, tai miten tietyn nivelrikkopotilaan sairaus etenee. Tämän tutkimuksen päätavoitteena oli kehittää kolmiulotteisia polvinivelen biomekaanisia tietokonemalleja, joiden perusteella simuloitiin normaalia kävelyä. Polvinivelen kolmiulotteinen geometria luotiin terveiden koehenkilöiden sekä nivelrikkopotilaiden magneettikuvista. Malleilla selvitettiin aluksi, miten monimutkaisena materiaalina nivelrusto tulee mallintaa, jotta mallin ennustama jännitys- ja puristusjakauma on silti realistinen. Tämän jälkeen tutkittiin, miten hyvin tietokonemallinnus ennustaa polvinivelrikon kehittymistä ja etenemistä sekä nivelruston rappeutumista ylipainoisilla potilailla. Tutkimuksessa havaittiin, että tietokonemallin ennustamat jännitys- ja puristusjakaumat nivelrustossa kävelyn aikana riippuvat merkittävästi nivelrustolle valitusta materiaalimallista ja sen parametreista. Tietokonemallien ennustamat nivelruston jännityskeskittymien sekä ruston rappeutumisen sijainnit vastasivat erittäin hyvin nivelrustokudoksen todellisen kulumisen sijainteja magneettikuvasta arvioituna neljän vuoden seuranta-ajan jälkeen. Tietokonemalleilla oli myös mahdollista simuloida painon pudotuksen vaikutusta, jolloin nivelrustokudoksen jännitys- ja puristusjakaumat palautuivat normaalien koehenkilöiden tasolle. Tässä tutkimuksessa kehitetyt polvinivelen tietokonemallit tarjoavat tutkijoille uuden työkalun paikallistaa sellaiset kohdat nivelpinnalta, joissa kuormituksen aiheuttama mekaaninen jännitys on suurta; nämä kohdat ovat kaikista riskialtteimpia nivelrikon kehittymiselle. Kehitettyjä malleja voidaan perustutkimuksen lisäksi jatkokehittää edelleen kohti kliinistä sovellusta, jolloin niitä voitaisiin hyödyntää esimerkiksi simuloitaessa erilaisten hoitojen vaikutusta kuormitusjakaumiin ja rustokudoksen rappeutumiseen.