No description available.

In sports, one might wish to test new ideas regarding player movement, tactics, or strategy without subjecting the athletes to possibly wasteful or even harmful habit formations. If a method of simulation of the athlete can be devised, experiments might reasonably be conducted to evaluate the ideas independently of actual training or trial in the field. Simulation of a complex system generally begins with a long period of analysis. During this time there may be mathematical and programming explorations and constructions to sharpen and examine different approaches. Meetings are usually held by the participants to try to define the task and explore alternatives. Ideas are amplified, possibly discarded as not feasible, or incorporated into the system package. Gradually there evolves a tighter and more acceptable formulation using logical and mathematical expressions (Preface, p. vii)

No description available.

Accurate perception and control of self-motion is vital for human survival. Most animals rely on vision for navigating through complex environments. In this thesis, I investigated how vision influence perception and guide self-motion from two aspects: (1) what visual information humans pick up from the environment to form their perception and guide their self-motion; (2) how the degeneration of the basal ganglia and cerebellum, the two largest subcortical nuclei connecting the visual and motor areas of the brain, affect the controller’s performance. Study 1 examined the condition under which optic-flow information beyond velocity field helps heading perception. I systematically varied the amount of information in velocity field through manipulations of field of view (FOV). The amount of optic-flow information beyond velocity field was manipulated by two types of displays. I found heading bias increased with the reduction of FOV only when optic-flow information beyond velocity field was not available. Study 2 investigated whether the information investigated in Study 1 is sufficient and necessary for active control of heading. I used the similar display simulations as study 1 with the exception that the vehicle orientation was perturbed pseudo-randomly. Participants used a joystick, under both velocity and acceleration control dynamics, to continuously rotate the vehicle orientation back to its heading direction. The results showed that participants’ accurate performance under condition that only provided velocity field information was further improved when optic-flow information beyond velocity field was available. Study 3 examined the relative contributions of three visual cues (i.e., heading from optic flow, bearing, and splay angle) for lane-keeping control. Observers controlled the car’s lateral movement to stay in the center of the lane while facing two random perturbations affecting the use of bearing or splay angle information. I found that performance improved with enriched flow information. In the presence of splay angles, participants ignored bearing angle information. Study 4 investigated the roles of the basal ganglia and cerebellum in motor control task using brain-damaged patients. Participant’s task was to use the joystick to keep a blob in the center of the display while the horizontal position of the blob was perturbed pseudo-randomly. This task is not a self-motion task but mimics real-world lane-keeping control. Both the Parkinson’s disease patients and cerebellar patients showed impaired motor control performance in comparison with the healthy controls. In conclusion, the visual information used for motor control in general depends on the task. For traveling along a curved path, the velocity field contains sufficient information for heading perception and heading control. Optic-flow information beyond velocity field improves heading perception when the velocity field does not contain sufficient information. It also helps heading control when available. For lane-keeping control, adding optic flow information improves participants’ performance. Splay angle information plays a more important role than does bearing angle information. The visual information used for motor control changes when certain brain areas are damaged. Parkinson’s disease patients and cerebellar patients show the inability to process visual input effectively for online motor control. / published_or_final_version / Psychology / Doctoral / Doctor of Philosophy

[Truncated astract] Talent Identification (TI) in sports begins by mass screening individuals' motor abilities. du Randt (2000) wrote that, as test items from one country might not necessarily suit another, appropriate basic motor skill test items are important for developing a TI mass screening instrument. Three hundred and thirty Malaysian adolescents aged from 12-15 years were tested on three motor skill test batteries: the McCarron Assessment of Neuromuscular Development (MAND, McCarron, 1982); the Australian Talent Identification Test (AIS, Australian Sports Commission, 1998); and a Balance and Movement Coordination Test which was specifically developed for this project. In the current research, the motor performance data recorded from the adolescents underwent several types of analyses. Principal Component analyses were conducted on the MAND, AIS and BMC motor skill instruments to understand what the three motor skill instruments were assessing globally in the Malaysian adolescents. Then, first-order and higher-order factor analyses were conducted on the 13 parameters making up the AIS+BMC motor skill instrument to examine the concept of general motor ability (GMA). After descriptive analyses of the adolescents' motor skill performances, age and gender differences were examined using two (gender) by four (age) ANOVAs. Finally, stepwise discriminant function analyses were conducted on a combined AIS+BMC motor skill instrument to determine the best sub-set of motor skills that reliably classified the Malaysian adolescents into three levels of motor performance.... Two stepwise discriminant analyses were undertaken to find the best set of motor skills for classifying Malaysian adolescents into three motor coordination groups based on scores on the MAND and three motor ability groups derived from scores on the motoric 'g'. The ability of a combined AIS+BMC motor skill instrument to classify Malaysian adolescents into the three groups was good for those classified as Normal, not so great for those adolescents classified as High, and poor for those adolescents classified as Low. The motor skills consistently reported across both sets of analyses were Balance-Eyes-Open, Balance-Eyes-Closed, Dynamic Balance, Hopping Speed, Quadrant Jump, Hopping-in-Square, Basketball Throw and Shuttle-Run-with-Object. Hence, motor skills assessing static balance, dynamic balance and postural control appeared to reliably discriminate the Malaysian adolescents into three motor performance groups. Finally, an examination of the misclassifications found in the discriminant analyses revealed two things. Those individuals being predicted into a lower group performed a large number of the motor skills to a lesser standard when compared with their correctly classified cohorts. Conversely, those predicted into a higher group performed a number of motor skills to a standard higher than their correctly classified cohorts. Thus, at a global level, certain individuals could be overlooked for further athletic development and is a concern when developing a rigorous TI program. Therefore, practitioners need to be cautious of any single ability score, and how that represents an individual's athletic potential. These results are discussed, limitations noted, and directions for future research provided.

Falls in the older population have devastating consequences on the psychological and physiological health of the individual. Due to the complexity of interacting factors associated with ageing, pathology and falling episodes, determination of a primary cause or set of causes has been difficult to establish. Deficits in components of neuromuscular control have been widely studied with the coordinated interaction of sensory and motor system components being presented as a fundamental factor in the reduction of falling episodes. A causal relationship between deficits in vitamin D status and falling episodes has also been suggested. Furthermore, a relationship between poor vitamin D status, falling episodes and poor neuromuscular performance has been reported. The aims of the current study were designed to advance understanding in three aspects of the problem of falls prevention. Firstly an examination of the reliability of testing procedures commonly used in assessment of falls risk was undertaken. The Physiological Profile Assessment (PPA) testing procedure was selected as a commonly used tool and the reliability of its various components (sensory, motor and balance) was undertaken as an independent assessment of this approach to assessing falls propensity. Secondly, a case control study of fallers and non fallers was undertaken in which the neuromuscular tests evaluated in the reliability study were used to assess differences in neuromuscular control. The influence of vitamin D status on these measures was also considered. Thirdly, a 12-month randomised controlled trial of vitamin D/calcium supplementation or placebo/calcium was undertaken to identify the effect on falls outcome and individual measures of neuromuscular control.