The learning and retention adaptations of muscle activity were studied during a novel multi-joint task. Electromyographic (EMG) signals were recorded from the posterior deltoid, long and lateral heads of the triceps, pectoralis major, biceps and brachioradialis muscles. These data were assayed in a pattern recognition analysis (SVD) to ascertain the minimum number of 'common features' or waveforms (W's) required to describe the set of input EMG patterns (IP). / Fifteen participants performed targeted arm movements, which incorporated the shoulder and elbow articulations, as fast and as accurately as possible in the horizontal plane. Both experimental (E) and control (C) groups were employed. The E group was trained (Day 1 to Day 4) and tested both pre- and post-learning. They were further re-tested during a retention period (RET) consisting of 1, 2, 4, 6 and 8 week post-learning sessions. The C group was tested before and after learning and at the end of the RET period. (Abstract shortened by UMI.)

Empirical and modelling studies are reported which explore ways in which the central nervous system might consider musculo-skeletal geometry when generating commands for single degree of freedom elbow flexion and extension movements. In a series of experiments it is shown that subjects do not perform rapid, goal-directed flexion and extension movements equally accurately in different parts of the elbow's workspace. In these experiments, movements of 10, 20 and 30 degrees in amplitude were tested using up to five different initial elbow angles. When performing flexions, subjects tended to overshoot targets when starting from extended positions, to undershoot targets when starting from more flexed positions, and to perform relatively accurate movements when starting from the centre of the workspace. Final position accuracy was more variable for extensions. When reliable differences existed for extensions, subjects tended to produce a pattern of results opposite to that of flexions: subjects overshot targets when starting from flexed positions and undershot targets when starting from more extended positions. A model of elbow movement based on the $ lambda$ version of the equilibrium-point hypothesis was used to assess the extent to which the pattern of errors obtained in the empirical studies could be reproduced by a control scheme that does not adjust commands in response to changing musculo-skeletal geometry, but rather uses one single invariant command throughout the workspace. The motivation for testing the invariant command notion was to explore the possibility that motion planning might be achieved without an explicit representation of musculo-skeletal geometry. Predicted patterns of final position errors across the workspace matched empirically obtained error patterns for flexions, but the model performed less well when predicting the pattern of errors observed for extension movements.

The present study investigated the patterns of interlimb organization during the concurrent performance of asymmetrical reaching movements. The inherent tendency towards interlimb synchronization often constrains activities requiring the two limbs to move over different distances or at different movement speeds. The study of bimanual coordination has shown that the amount of interlimb interference during bilateral performance of asymmetrical actions, is regulated according to the magnitude characteristics of the variable used to introduce the asymmetry between the limbs. The purpose of the present study was to examine the relationship between the degree of interlimb decoupling and the magnitude of the asymmetry between the limbs. Asymmetry was systematically manipulated by scaling the magnitude of the interlimb difference in final target distance, during bimanual performance of reaching movements. The degree of interlimb decoupling was reflected in the movement time, muscle activity onset and joint torque relationship between the limbs. / Decoupling of the asymmetrical limb movements was effected by an earlier onset of the antagonist muscles in the constrained limb which scaled the amount of muscle torque production and therefore the stiffness of the limb during the acceleration phase of the movement. Thus, the movement amplitude differentiation was achieved by an initial accelarative impulse attributed to the differential control of the muscle torque production at each joint. On the other hand, the interactive forces played a secondary role in the degree of decoupling process. Overall, the degree of decoupling scaled according to the magnitude of the interlimb difference in distance; the greater the asymmetry, the greater the differentiation between the limbs. However, systematic variations of the interlimb asymmetry in distance gave rise to a wide variety of individual decoupling trends. Bimanual practice of the asymmetrical reaching tasks did not result in the development of more independent limb movements. The results of the present study have implications to human factor design and ergonomics.

The present thesis investigated the process of gross motor skill acquisition in the context of how movement pattern characteristics are organized and modified as a result of learning. The process of multisegmental skill acquisition was studied using performance production measures as a window to explore stable and transient changes in the movement control process. Bernstein's principles of exploitation of motion dependent torques, and the minimization of the degree of freedom were tested. / Twenty male subjects performed a total of 240 trials, as fast and accurate as possible, over 4 sessions for two tasks with different level of complexity (10 subjects per task). Kinematic and EMG data were acquired for a two segment model of the arm using a lightweight, adjustable manipulandum, and surface EMG for the PDL, PEC, TRI, and BIC muscles. Movement organization characteristics were revealed by wave pattern analyses performed with a phase breakdown technique, CCCF on torque partitioning components, and the CFs on the muscle activation waveforms. / The experimental protocol allowed enough practice for the tasks to be learned resulting in PT decrease. Consistent adaptations in movement organization were revealed by all three levels of analysis. Improvement in the performance production measures were in the same direction for both learning conditions, and the rate of change within experimental sessions decreased over time. The significant adaptations in movement organization occurred at the critical phases of each task (i.e. the power absorption--phase simple task, and the reversal phase--complex task). The EMG and joint torque components demonstrated significant amplitude and profile changes particularly during the critical phases. The subjects learned to perform the tasks faster by compensating the motion dependent torques components with the muscle torques in time and amplitude. This finding was consistent with the principle of exploitation of motion dependent torques which was enhanced with learning. Significant task specific motor program adaptations were revealed by the SVD analysis. The minimization of the degree of freedom hypothesis is consistent with the increasing covariation observed over learning between the antagonists PEC and BIC in the simple task, and for both the agonists PDL and TRI and antagonists PEC and BIC in the complex task. In addition the results justified the use of waveform analysis on performance production measures, as a method that can reveal important adaptation details in the underlying control mechanisms for gross motor skill.

No description available.

The primary purpose of this study is to use three-dimensional motion analysis to determine and compare certain kinematic joint and segmental variables at defined events (bar off and knee passing) between the conventional and sumo styles of deadlifts. The secondary purpose of this study is to investigate bar path profiles and vertical bar velocity patterns (including attempting to determine a "sticking region") and compare these variables between the two styles and two sub-maximal loads (50% and 75%). Five subjects performed each style at each load. Each trial was filmed, digitized, and imported for 3-D reconstruction. This data was utilized to determine hip, knee, inter-thigh, trunk, thigh, and shank angles at bar off and knee passing; bar path profiles; and bar velocity values (including determining the "sticking region"). A two way ANOVA showed statistically significant differences between the two styles for most joint and segmental variables at both events and the range between the two events. There was a significant difference between the two styles for total time and horizontal and vertical bar displacement. Only one trial showed a sticking region. Based on the results of this study, it can be stated that kinematic differences do occur between the two styles of deadlifts at submaximal loads. A sticking region does not appear to occur at loads of 75% of a 1 rep maximum or less. / School of Physical Education

Practice and modeling are common approaches to teaching motor skills. Qualitative and quantitative feedback have also been used to improve complex skill learning. The purpose of this study is to determine if providing real-time kinematic feedback in addition to traditional training will enhance skill acquisition of unskilled dancers when compared to traditional dance instruction alone. Two groups of dancers participate in testing and training protocols including a traditional group and a biofeedback training group to examine differences between the two teaching methods. Significant differences were found due to time for knee flexion and hip rotation. Significant differences due to training group were found at one time point for knee flexion. The main finding of this study was that the addition of biofeedback had a limited effect on skill acquisition on beginning level dancers. / School of Physical Education, Sport, and Exercise Science

This work addresses the distortions in Functional Magnetic Resonance Images (FMRI) caused by subject motion. FMRI is a non-invasive technique which shows great promise in providing researchers and clinicians with neurological information both about healthy subjects and clinical patients by mapping functional activation within the brain using Echo Planar Imaging (EPI). If reliable information is to be obtained from these images, motion correction must be carried out in order to remove or suppress the artefacts arising from subject movement. This work begins by using exploratory data techniques to describe these artefacts so that they can be characterised according to their origin and spatio-temporal manifestation. Based on testing of the accuracy and consistency of existing rigid-body motion correction methods on FMRI data, a new registration algorithm Motion Correction using the FMRIB Linear Image Registration Tool (MCFLIRT) has been developed. It is shown that while MCFLIRT is both more accurate and more robust than previous methods, rigid-body registration schemes in general cannot completely remove the distortions associated with motion and so subsequent analysis of the images may still be inaccurate. Furthermore, it is demonstrated that failure to use a sufficiently detailed model of subject motion in FMRI can in fact lead to degradation of the images through the use of existing motion correction algorithms. Based on these findings, alternative schemes including non-rigid registration and adaptive real-time methods are evaluated. Leading on from this investigation, a framework for Temporally-Integrated Geometric EPI Realignment (TIGER), incorporating both spatial and temporal information about the images, is proposed. An implementation based on this novel modality-specific model is developed and tested against existing rigid-body registration methods. Results show that this new approach is able to achieve significantly more accurate results than previous methods. The quality of correction provided by this new approach brings more subtle artefacts in the data to the fore, suggesting a number of avenues of further research in this area. These are outlined in the final chapter of the thesis.

The purpose of this dissertation was to determine if the CNS produces relatively simple alterations in muscle activity to accomplish goal-directed reaching motions of the upper limb under a variety of movement conditions. / To this end, six subjects performed goal-directed arm movements in the horizontal plane. Two movement amplitudes (300 mm and 400 mm) were completed at a moderate speed (1050 mm/s) and as-fast-as possible. The speed and amplitude conditions were repeated for the 45$ sp circ$ and 90$ sp circ$ movement directions. Finally, each of the movement conditions mentioned thus far, were performed within the right and left sections of the work-space. Surface electro-myographic activity was recorded from the pectoralis major, posterior deltoid, biceps brachii short head, brachioradialis, triceps brachii long head, and triceps brachii lateral head. Motion recordings were obtained with a spatial imaging system that monitored the positions of infrared emitting diodes attached to the subject's upper arm and forearm-hand complex. / Several simplification schemes were found to be operative at the level of the electro-myogram. These include: (a) simple timing relationships for agonists between joints and agonist/antagonist intermuscle latencies within each joint; (b) tightly coupled timing between agonists within a single joint; (c) for a particular movement direction, the form and shape of EMG burst activity followed a strategy associated with modulation of pulse height and width; (d) the slope, duration, and onset were further affected by the direction of hand movement which resulted in the greatest RMS-EMG signal amplitude, changing in a predictable manner, and finally (e) there was tuning in which elbow muscles were activated earlier for goal-directed arm movements in the left area of the work-space.

Thesis (Ph.D.)--McMaster University, 2002. / Adviser: Digby Elliott. Includes bibliographical references (leaves 239-240). Also available via World Wide Web.