Twelve children without intellectual disability and 12 children and adolescents with Down syndrome were administered a short form of Roy and Black's (1998) Apraxia Battery. Participants with Down syndrome also completed a free-recall dichotic listening test. While the mean laterality indices for the group with Down syndrome was negative, indicative of a left ear-right hemisphere specialization for speech perception, they were not significantly different from zero. There was a wide range of individual variability in laterality, and individuals with a left ear advantage for speech perception performed more poorly on the portions of the apraxia battery that involved verbal instruction. The possibility that individuals with Down syndrome who have apraxia may constitute an important subset of individuals with Down syndrome was considered. The results are discussed within the framework of Elliott, Weeks, and Elliott's (1987) biological dissociation model. / Thesis / Master of Science (MS)

In order to meet higher performance demands on brushless motor controllers, motor feedback signals must meet correspondingly higher standards. Brushless motor controllers require angular feedback for motor commutation, and generally for one or more of the following: torque, velocity or position regulation. These feedback categories impose different requirements on the control system. In many brushless motor applications, sinusoidal encoders have significant advantages over square-wave encoders. Signal processing techniques for sinusoidal encoder feedback signals are considered in the context of a brushless motor positioning system. In particular, a method is presented for correcting gain and offset measurement errors based on ellipse-fitting techniques. / Master of Science

<p>Two studies were conducted to examine the effects of learner-adapted practice on the self-efficacy beliefs, acquisition and retention of a motor task. Through a discovery process all participants learned to perform several keypress patterns, with the goal of completing each sequence as fast and accurate as possible. The first experiment had learners practice the keypress sequences in one of two adaptive schedules, which utilized either a ‘WinSwitch’ or ‘WinRepeat’ task switching algorithm, or follow a pre-determined order of tasks (two yoked-control groups). The purpose of this experiment was to determine if adaptive schedules were effective because they were tailored to a learner’s performance characteristics or due to the nature of the contextual interference employed by the switching algorithm when the 'winning' criterion was satisfied. To examine the psychological factors involved in adaptive practice, the second experiment had all groups practice in a ‘WinSwitch Adaptive’ schedule and manipulated the social-comparative feedback that was provided (positive, negative or control). Together these studies revealed that the effectiveness of adaptive schedules may not necessarily be due to the fact that they are tailored to a learner's performance characteristics. They also suggest that learning is facilitated by a switching algorithm that involves some blocked practice towards the beginning and mostly random practice towards the end of acquisition (WinRepeat schedule). However, providing positive social-comparative feedback can override the negative effects of the opposite schedule (WinSwitch) and result in more effective learning and increases in self-efficacy beliefs. These findings are discussed in reference to contextual interference effects and the self-efficacy framework.</p> / Master of Science in Kinesiology

Humans learn to interact with many complex dynamic systems such as helicopters, bicycles, and automobiles. This dissertation develops a subsystem identification method to model the control strategies that human subjects use in experiments where they interact with dynamic systems. This work provides new results on the control strategies that humans learn. We present a novel subsystem identification algorithm, which can identify unknown linear time-invariant feedback and feedforward subsystems interconnected with a known linear time-invariant subsystem. These subsystem identification algorithms are analyzed in the cases of noiseless and noisy data. We present results from human-in-the-loop experiments, where human subjects in- teract with a dynamic system multiple times over several days. Each subject’s control behavior is assumed to have feedforward (or anticipatory) and feedback (or reactive) components, and is modeled using experimental data and the new subsystem identifi- cation algorithms. The best-fit models of the subjects’ behavior suggest that humans learn to control dynamic systems by approximating the inverse of the dynamic system in feedforward. This observation supports the internal model hypothesis in neuro- science. We also examine the impact of system zeros on a human’s ability to control a dynamic system, and on the control strategies that humans employ.

Disability due to low back pain is common. While evidence exist that exercise is effective in reducing pain and disability, it is still largely undetermined which kind of exercises that are most effective. The overall aim of this thesis was to evaluate and compare the effects of a high-load lifting exercise and individualized low-load motor control exercises for patients with nociceptive mechanical low back pain. A secondary aim was to evaluate which patients benefit from training with a high-load lifting exercise. All four papers in this thesis were based on a randomized controlled trial including 70 participants with nociceptive mechanical low back pain as their dominating pain pattern. Participants were randomized into training with either a high-load lifting exercise (HLL), the deadlift, (n=35) or individualized low-load motor control exercises (LMC) (n=35). Both interventions included aspects of pain education. All participants were offered twelve sessions during an eight week period. The effects of the interventions were evaluated directly after and twelve months after the end of the intervention period. Outcome measures were pain intensity, activity, disability, physical performance, lumbo-pelvic alignment and lumbar multifidus muscle thickness. There was a significant between-group effect in favour of the LMC intervention regarding improvements in activity, movement control tests and some tests of trunk muscle endurance. For pain intensity there were no significant differences between groups. A majority of participants in both intervention groups showed clinically meaningful improvements from baseline to two and twelve month follow-up regarding pain intensity and activity. There were no significant differences between HLL and LMC regarding the effect on lumbo-pelvic alignment or lumbar multifidus thickness. The participants who benefit the most from the HLL intervention were those with a low pain intensity and high performance in the Biering-Sørensen test at baseline. The results of this thesis showed that the HLL intervention was not more effective than the LMC intervention. The LMC was in fact more effective in improving activity, performance in movement control tests and some tests of trunk muscle endurance, compared to the HLL intervention. The results imply that the deadlift, when combined with education, could be considered as an exercise to produce clinically relevant improvements on pain intensity in patients who prefer a high-load exercise. However, before considering deadlift training, the results suggest that pain intensity and performance in the Biering-Sørensen test should be evaluated.

Many children with developmental disabilities (DD) have physical impairments and limitations in their participation. Rehabilitation research often focuses on either physical impairments or participation restrictions, when both need to be investigated. The purposes of these two studies were to evaluate an at home therapist directed video game balance training intervention on balance, gait velocity (GV), hip strength and activities of children with DD. The pilot study was a single-subject non-concurrent multiple baseline design. Balance measures included: weight bearing symmetry; center of pressure area and velocity; time to boundary mean minima and standard deviation; and timed up and go. The participant’s enjoyment and perceived difficulty was also explored. Five children (7 to 10 years) with cerebral palsy (CP) participated in a 6 week, 30 minute intervention 3 times per week, with four preselected balance games. Minimal improvements were found in balance, GV, and hip strength, and participants reported the intervention enjoyable and challenging. Three of five participants had significant increases in activities, as measured by the Activities Scale for Kids (ASK). The second study expanded on pilot study results and included 5 children (5 to 10 years) with different diagnoses. Another non-concurrent multiple baseline design was utilized, and the same measures of balance were used except single leg stance time was substituted for timed up and go. No changes were made to the intensity of intervention, but two games were added to the repertoire. There were minimal changes in balance and hip strength; and no changes were found in the ASK. A majority of participants increased GV, and reported the intervention was enjoyable and challenging. Positive changes were found in the combined results for: center of pressure area with eyes open and closed; time to boundary mean minima with eyes closed in the anterior-posterior direction; and GV. These studies suggest this intervention was insufficient to make improvements in the majority of balance measurements and hip strength for children with DD. Increased activities in children with CP were found in the pilot study. These results suggest video game balance training alone for children with DD was insufficient to demonstrate clinically meaningful change. KEYWORDS: Balance, Developmental Disabilities, Gait Velocity, Hip Strength, Activities and Participation

In developing a method of quantifying stability in the lumbar spine Cholewicki and McGill (1996) have also broached the notion of sufficient stability, where too much stiffness (and stability) would hinder motion. Thus people highly skilled at maintaining stability may use different and optimal strategies, where <i>sufficient</i> stability is maintained. The purpose of this work was to explore the contributors to <i>sufficient</i> stability, how they coordinate and relate to injury mechanisms. This work represents a cascade of investigations where. 1) To explore the balance of various sources of stiffness and their effect on the critical load and post-buckling behaviour, simulations were undertaken where the buckled configuration of the spine was predicted and its stability in this new configuration was assessed. 2) The various sources of stiffness contributing to stability in the lumbar spine have been in some cases found to be deficient. The question of how these deficiencies place individuals at risk of instability, if at all, remains unresolved. A challenged breathing task was used to determine if there was a difference in stabilizing potential between healthy individuals and low back pain sufferers. Given that differences in stabilizing potential are apparent, several tasks which included a predetermined motor strategy, such as 3)pressurizing the abdomen and 4) abdominal hollowing vs. muscle bracing, were evaluated to determine if individuals can utilize motor strategies to augment stability. The stabilizing potential of abdominal pressure (IAP) and its interaction with muscle activation was evaluated. Some individuals are more skilled at stabilizing their lumbar spine than others. Some consciously controlled motor strategies are better stabilizers than others. These strategies highlight the relative contributions of various components (posture, passive tissue, muscle activation, and load) in that no single muscle dominates stability and IAP appears to augment stability beyond muscle activation alone. The margin of safety is considerable and depends on the task at hand, but it is possible to speculate on which tissues are at greatest risk of injury.

Knowing where and when to look is critical for effective performance of visually guided tasks. A gaze strategy termed the quiet eye (QE; the final gaze before the onset of a critical movement) is strongly associated with motor skill proficiency, with earlier and longer QE periods leading to improved visuomotor control. Children with poor motor proficiency, such as those with Developmental Coordination Disorder (DCD), have impairments in the pick-up and processing of visual information, translating into poorly coordinated movements. The purpose of this project therefore was to perform the first examination of the QE strategy in children of different motor coordination abilities and furthermore to investigate the efficacy of task-specific QE training (QET) to improve the skills of children with and without DCD beyond the effects of a standard coaching technique. Study 1 determined that children with low motor coordination had later, shorter QE durations in comparison to coordinated children and as a result, performed worse in a specified motor task (throwing and catching). Study 2 therefore performed two experiments aimed at developing an appropriate but brief QET protocol for children to improve their throwing and catching ability. These experiments found that typically developing children were able to increase their QE durations with QET and this was reflected in a durable improvement in their motor skill execution. The final study examined this QET intervention in children with DCD. This was the first application of QET in a clinical population, and found that children with DCD were able to improve their QE durations, and make robust changes to their visuomotor control. These studies associate a longer QE with motor skill proficiency in children, and provide an important adjunct to current therapeutic intervention for children with poorly developed motor skills.

One possible solution to common running related injuries is to transition runners from a rearfoot strike during initial contact to a midfoot strike. Natural rearfoot strike runners were studied to see if a modified elliptical trainer could be used to alter their running pattern to that of a midfoot strike runner. Their results were compared to subjects who ran on a non-modified elliptical trainer. After training on the modified elliptical trainer, subjects demonstrated a decrease in foot angle at initial contact when attempting to run with a midfoot strike. Training did not affect all kinetic metrics or stride frequency. However, the kinematic change suggests that there may be an impact on running energetics. Training on the modified elliptical trainer resulted in improved midfoot strike kinematics in natural rearstrike runners when they attempted run in a midfoot strike pattern.

Recent evidence suggests that when performing reach-and-grasp actions on day-to-day objects, lift-actions are faster to execute relative to use-actions, and that a “use-on-lift” interference occurs and produces switch costs when changing actions from using to then lifting (Jax & Buxbaum, 2010; Osiurak & Badets, 2016). Such findings result from paradigms that include the sudden appearance of objects, requiring participants to react quickly to the features of the object, independent of the functionality of the objects. Because of the importance this topic has to day-to-day interactions with objects, the following four experiments were executed with objects continuously visible to participants. When imitating images of hand actions on objects, participants showed no differences in the initiation time of use- and lift-actions, suggesting that no systematic differences exist between these two actions. Using this as a baseline, we compared a more generative approach, as when actions are instructed by auditory sentences. In this case, we see that switching actions is difficult, switching objects is even more difficult, and that use-actions are modestly faster than lift-actions; the reverse of what previous research shows. In a third experiment modelled after the paradigm used in studies producing rapid lift- and slowed use-actions, we showed that use-actions are actually facilitating lift-actions. Further, we demonstrate that having a use-action goal in mind provides the knowledge required to perform a lift-action, and that use-actions are again faster than lift-actions. These results are a critical addition to the task-switching literature on the cognitive control of motor processes associated with hand actions as distinctions are made between non-naturalistic and realistic settings relevant to day-to-day interactions with objects. We show that use-actions facilitate lift-actions and that, in realistic settings, both use- and lift-actions require access to stored knowledge. / Graduate / 0633 / hvanmook@uvic.ca