Yes / Although gaze during adaptive gait involving obstacle crossing is typically directed two or more steps ahead, visual information of the swinging lower-limb and its relative position in the environment (termed visual exproprioception) is available in the lower visual field (lvf). This study determined exactly when lvf exproprioceptive information is utilised to control/update lead-limb swing trajectory during obstacle negotiation. 12 young participants negotiated an obstacle wearing smart-glass goggles which unpredictably occluded the lvf for certain periods during obstacle approach and crossing. Trials were also completed with lvf occluded for the entirety of the trial. When lvf was occluded throughout, footplacement distance and toe-clearance became significantly increased; which is consistent with previous work that likewise used continuous lvf occlusion. Both variables were similarly affected by lvf occlusion from instant of penultimate-step contact, but both were unaffected when lvf was occluded from instant of final-step contact. These findings suggest that lvf (exproprioceptive) input is typically used in an online manner to control/update final foot-placement, and that without such control, uncertainty regarding foot placement causes toe-clearance to be increased. Also that lvf input is not normally exploited in an online manner to update toe-clearance during crossing: which is contrary to what previous research has suggested.

Undesirable landing area (e. g. , a hole, a fragment of glass, a water puddle, etc) creates the necessity for an alternate foot placement planning and execution. Previous study has proposed that three determinants are used by the central nervous system (CNS) for planning an alternate foot placement: minimum foot displacement, stability and maintenance of forward progression. However, validation of these determinants is lacking. Therefore, the general purpose of the series of studies presented here is to validate and test the generality of the decision algorithm of alternate foot placement selection developed previously. The first study was designed to validate the use of a virtual planar obstacle paradigm and the economy assumption behind minimum foot displacement determinant. Participants performed two blocks of trials. In one block, they were instructed to avoid stepping in a virtual planar obstacle projected in the screen of a LCD monitor embedded in the ground. In another block, they were instructed to avoid stepping in a real hole present in walkway. Behavioral response was unaffected by the presence of a real hole. In addition, it was suggested that minimum foot displacement results in minimum changes in EMG activity which validates the economy determinant. The second study was proposed to validate the stability determinant. Participants performed an avoidance task under two conditions: free and forced. In the free condition participants freely chose where to land in order to avoid stepping in a virtual obstacle. In the forced condition, a green arrow was projected over the obstacle indicating the direction of the alternate foot placement. The data from the free condition was used to determine the preferred alternate foot placement whereas the data from the forced condition was used to assess whole body stability. It was found that long and lateral foot placements are preferred because they result in a more stable behavior. The third study was designed to validate the alternate foot placement model in a more complex terrain. Participants were required to avoid stepping in two virtual planar obstacles placed in sequence. It was found that participants used the strategy of planning the avoidance movement globally and additional determinants were used. One of the additional determinants was implementation feasibility. In the third study, gaze behavior was also monitored and two behaviors emerged from this data. One sub-group of participants fixated on the area stepped during adaptive step, whereas another sub-group anchor their gaze in a spot ahead of the area-to-be avoided and used peripheral vision for controlling foot landing. In summary, this thesis validates the three determinants for the alternate foot placement planning model and extends the previous model to more complex terrains.

Walking around in dynamically changing environments require the integration of three of our sensory systems: visual, vestibular, and kinesethic. Vision is the only modality of these three sensory systems that provides information at a distance for proactively controlling locomotion (Gibson, 1958). The visual system provides information about self-motion, about body position and body segments relative to one another and the environment, and environmental information at a distance (Patla, 1998). Gibson (1979) developed the idea that everyday behaviour is controlled by perception-action coupling between an action and some specific information picked up from the optic flow that is generated by that action. Such that visual perception guides the action required to navigate safely through an environment and the action in turn alters perception. The objective of my thesis was to determine how well perception and action are coupled when approaching and walking through moving doors with dynamically changing apertures. My first two studies were grouped together and here I found that as the level of threat increased, the parameters of control changed and not the controlling mechanism. The two dominant action control parameters observed were a change in approach velocity and a change in posture (i. e. shoulder rotation). These findings add to previous work done in this area using a similar set-up in virtual reality, where after much practice participants increased success rate by decreasing velocity prior to crossing the doors. In my third study I found that visual fixation patterns and action parameters were similar when the location of the aperture was predictable and when it was not. Previous work from other researchers has shown that vision and a subsequent action are tightly coupled with a latency of about 1second. I have found that vision only tightly couples action when a specific action is required and the threat of a collision increases. My findings also point in the same direction as previous work that has shown that individuals look where they are going. My last study was designed to determine if we go where we are looking. Here I found that action does follow vision but is only loosely correlated. The most important and common finding from all the studies is that at 2 seconds prior to crossing the moving doors (any type of movement) vision seems to have the most profound effect on action. At this time variability in action is significantly lower than at prior times. I believe that my findings will help to understand how individuals use vision to modify actions in order to avoid colliding with other people or other moving objects within the environment. And this knowledge will help elderly individuals to be better able to cope with walking in cluttered environments and avoid contacting other objects.

Approved for public release, distribution is unlimited / This thesis investigates user interfaces for locomotion in virtual environments (VEs). It looks initially at virtual environments and user interfaces, then concentrates on locomotion interfaces, specifically on the Omni-Directional Treadmill (ODT) (Darken and Cockayne, 1997) and a new virtual walking device, LocoX, which was developed at the MOVES Institute, Naval Postgraduate School. It analyzes and compares the ODT and LocoX in terms of the application of human ability requirements (HARs). Afterwards, it compares the results of the analysis of the ODT and LocoX to real-world locomotion. The analysis indicates that LocoX, a new way of exploring virtual environments (VEs), provides a close match to real locomotion on some subtasks in VEs-- compared to the ODT--and produces relatively closer representation on some subtasks of real world locomotion. This thesis concludes that LocoX has great potential and that the locomotion provided is realistic enough to simulate certain kinds of movements inherent to real-world locomotion. LocoX still requires maturation and development, but is nonetheless a viable locomotion technique for VEs and future game-based simulations. / Lieutenant Junior Grade, Turkish Navy

4 Summary: Title: Intraindividual comparison of selected indicators of coordinating steps on the ice skating and in-line. Objective: Assessment of coordination relationship rate of the skating forward during ice hockey and inline skating. Methods: Surface electromyography combinated with kinematography analysis used synchronized video recording. Results: Kinesiological content of movement during ice skating and inline skating is not the same. The general stereotype of the skating step is significantly different from the walking stereotype. Key words: human locomotion, sport locomotion, phylogeny, ontogeny, surface electromyography, ice hockey skating, inline skating.

O pé torto congênito idiopático é a deformidade congênita de maior prevalência na ortopedia. Estudos da locomoção podem favorecer condutas na reabilitação de crianças com tal disfunção. Neste trabalho foram analisados parâmetros biomecânicos da marcha e do salto vertical com contra-movimento, além do estudo do limiar de percepção plantar de crianças com pé torto congênito, tratadas cirurgicamente. Para análise dos resultados, foram utilizados testes estatísticos não paramétricos. Não foram identificadas alterações na sensibilidade plantar. Apesar da semelhança das curvas médias de força, variação angular e eletromiografia, as variáveis biomecânicas mostraram diferenças. Na marcha, as crianças com pé torto mostraram maior taxa de crescimento para o primeiro pico da força vertical; no apoio médio, maiores flexão do joelho e dorsiflexão do tornozelo, e menor força vertical; na fase de propulsão, menores força ântero-posterior, segundo pico da força vertical e flexão plantar. Enquanto que as mesmas crianças mostraram na fase de preparação do salto vertical, menor dorsiflexão; na impulsão, maior flexão do joelho e menores flexão plantar, força vertical e atividade do músculo gastrocnêmio medial; e na aterrissagem, maior taxa de crescimento da força vertical, menor flexão plantar e maior flexão do joelho. O entendimento de como o sistema locomotor opera durante as atividades analisadas pode contribuir para direcionamentos relacionados com os estímulos adequados de atividades físicas para essas crianças / Idiopathic clubfoot is the most prevalent congenital deformity in orthopedics. Locomotion studies in children with such a deformity can help towards better rehabilitation. The aim of this study was to analyze the gait and countermovement jump biomechanics, and to describe the perception threshold in children with congenital clubfoot who have been surgically treated. For data analysis, non-parametric statistical tests were applied. Changes in plantar sensitivity were not found. Despite similar force, kinematics, and electromyography curves along groups, it was found differences for some biomechanical variables. For gait, children with clubfoot showed higher vertical force increase to the first peak. At midstance, they showed higher knee flexion and ankle dorsiflexion, and lower vertical force. At toe off, they presented lower anterior-posterior force, second vertical force peak, and plantar flexion. For jump, during the preparation phase, they presented smaller dorsiflexion; during propulsion, they showed larger knee flexion and smaller plantar flexion, vertical force and m medial gastrocnemius activity. In landing, there was a higher vertical force growth rate, less plantar flexion, and larger knee flexion. The understanding of how the locomotion system work contributes to choose the best stimuli to be applied during physical activity for those children

This thesis examines the use of motion detection and analysis systems to detect falls and repetitive motion patterns of at-risk individuals. Three classes of motion are examined: Activities of daily living (ADL), falls, and repetitive motion. This research exposes a simple relationship between ADL and non-ADL movement, and shows how to use Principal Component Analysis and a kNN classifier to tell the 2 classes of motion apart with 100% sensitivity and specificity. It also identifies a more complex relationship between falls and repetitive motion, which both produce bodily accelerations exceeding 3G but differ with regard to their periodicity. This simplifies the classification problem of falls versus repetitive motion when taking into account that their data representations are similar except that repetitive motion displays a high degree of periodicity as compared to falls. / by Clyde Carryl. / Thesis (M.S.C.S.)--Florida Atlantic University, 2013. / Includes bibliography. / Mode of access: World Wide Web. / System requirements: Adobe Reader.

Thesis. 1977. B.S.--Massachusetts Institute of Technology. Dept. of Mechanical Engineering. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND ENGINEERING. / Includes bibliographical references. / B.S.

Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1982. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND ENGINEERING. / Includes bibliographies. / by Erik Karl Antonsson. / Ph.D.

Thesis. 1977. M.S.--Massachusetts Institute of Technology. Dept. of Mechanical Engineering. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND ENGINEERING. / Bibliography: leaves 203-204. / by Frank C. Conati. / M.S.