Twisting movements are categorised into three mechanical types, named as DIRECT, COUNTER-ROTATION and TILT TWIST. Twisting techniques are studied using mathematical models. A mathematical inertia model is constructed to enable the determination of segmental inertia parameters from anthropometric measurements. A film analysis program is developed so that the angles, which specify the orientation and configuration of the body, may be derived from digitised film data. A computer simulation model, comprising 11 segments and 17 degrees of freedom, is constructed to represent the human body in free fall. The combined use of the three computer programs results in maximum errors of 3% for somersault and 9% for twist in ten filmed movements. The mechanics of twisting techniques are explained using simple mathematical models. An analysis of rigid body motions shows that there are two distinct modes of motion, named as the ROD MODE and the DISC MODE. It is shown that it is possible to change from one mode to the other by varying the angle of pike and this permits the twist to be increased or stopped or even reversed. The capacities of twisting techniques are determined using simulations. For twists from a piked position, delaying the extension from the pike can increase the twist rate although this does depend upon the particular technique used and the initial direction of somersault. The contributions of twisting techniques used in the filmed movements are determined using simulations based upon modifications of the film data. It is found that counter-rotation techniques made small contributions and that aerial techniques, which increased the angle of tilt, were the major contributors, even in movements where the twist was apparent at take off. Using the simulation model it is shown that the build up of twist in the unstable double layout somersault may be controlled by means of small asymmetrical arm movements during flight.

This thesis investigated the relationship between the three-dimensional kinematics of the human back and spinal pathology. This required the development of a system capable of the in vivo measurement of spinal movement non-invasively and in three-dimensions. The opto-electronic CODA-3 Scanner proved unsatisfactory in this respect. The electro-magnetic 3SPACE Isotrak, however, was found to be an accurate and reliable system during a study of twisting in flexed postures. Available axial rotation was significantly increased in some degree of sagittal flexion suggesting that this may be a mechanism for intervertebral disc injury. At high degrees of sagittal flexion a reduction in available axial rotation was noted. In vitro tests on isolated lumbar motion segments confirmed the increase in axial rotation available in flexed postures shown in vivo, this was presumed to be due to an opening of the lumbar zygapophysial joints. Mechanical testing of lumbar interspinous and supraspinous ligaments showed them to be active only in the extremes of sagittal flexion and hence that they could be responsible for the reduction in axial rotation seen in vivo. The 3SPACE Isotrak was used in a clinical study of 80 normal and 43 pathologic subjects. In the normals ranges of motion were, in general, reduced with increasing age in both males and females although a significant increase in sagittal flexion occurred with increasing age in females. Male mobility significantly exceeded female in sagittal flexion but female tended to exceed male in extension, lateral bend and axial rotation. Opposite axial rotation occurred consistently upon lateral bend and vice versa, flexion also occurred on lateral bend but not axial rotation. There was widespread disruption to the primary and coupled movements of the back pain patients when compared to normal movement patterns but there was no clear distinction between the kinematic movement patterns of discrete patient groups. The small numbers in these patient groups warrant a further, more detailed, clinical study.

This thesis investigated some of the eye movement factors related to the development and use of eye pointing devices with three dimensional displays (stereoscopic and linear perspective). In order for eye pointing to be used as a successful device for input-control of a 3D display it is necessary to characterise the accuracy and speed with which the binocular point of foveation can locate a particular point in 3D space. Linear perspective was found to be insufficient to elicit a change in the depth of the binocular point of fixation except under optimal conditions (monocular viewing, accommodative loop open and constant display paradigm). Comparison of the oculomotor responses made between a stereoscopic 'virtual' and a 'real' display showed there were no differences with regards to target fixational accuracy. With one exception, subjects showed the same degree of fixational accuracy with respect to target direction and depth. However, close target proximity (in terms of direction) affected the accuracy of fixation with respect to depth (but not direction). No differences were found between fixational accuracy of large and small targets under either display conditions. The visual conditions eliciting fast changes in the location of the binocular point of foveation, i.e. saccade disconjugacy, were investigated. Target-directed saccade disconjugacy was confirmed, in some cases, between targets presented at different depths on a stereoscopic display. However, in general the direction of saccade disconjugacy was best predicted by the horizontal direction of the target. Leftward saccade disconjugacy was more divergent than rightward. This asymmetry was overlaid on a disconjugacy response, which when considered in relative terms, was appropriated for the level of vergence demand. Linear perspective depth cues did not elicit target-directed disconjugate saccades.

These studies examined motion trajectories and electromyographic (EMG) activity patterns during human horizontal reaching movements towards single- and double-step visual targets. These data were used to test and elaborate a model of two-joint planar arm movement based on the equilibrium point (EP) hypothesis or $ lambda$ model of motor control. This work aims to understand how reaching movements are planned and controlled by the nervous system. To this end, simulated trajectories and EMG patterns, generated with hypothetical central commands, were compared to empirical trajectories and EMG patterns. In general, the model was able to predict trajectories but was less successful in predicting EMG patterns. The results indicated that, in general, motions to both single- and double-step targets are generated by shifting the EP of the hand in a straight line towards the present target. Thus, a common control strategy underlying movements to single-step targets and trajectory modifications to double-step targets is proposed. Whereas the direction of shift of the EP is specified at the level of the hand, the rate of shift may be limited at the joint level.

Thesis (MAppSc in Physiotherapy) -- University of South Australia

Grinding is integral to tacking and gybing manoeuvres in America’s Cup sailing. Grinding is a standing position cyclic upper body task requiring manual arm cranking of winches, which control movement of the mast and sails. Limited information exists on biomechanical factors involved in grinding performance. This thesis determined technique and muscular performance characteristics of sailors related to grinding performance, and effects of a training intervention on grinding performance. Reliability of grinding ergometer performance testing was evaluated across direction, load and heel conditions. In all conditions relative performance between individuals was consistent (r = 0.84-0.99) and the grinding performance test differentiated well between individuals. External work had lower overall variation (1.6-3.9%) than peak power (1.3-5.4%), especially when grinding against greater loads. Grinding performance was less consistent in heeled conditions (4.6-6.9%) than on the flat, but grinding direction did not affect reliability. Performance changes over 4% could be interpreted with confidence. Peak torque occurred at 95° (77 N m) and 35° (69 N m) for forward and backward grinding respectively (0° = grinding crank vertically up). Torque of >50 N m was maintained through 72% of the cycle during forward grinding but only 47% for backward grinding. Differences were attributed to a greater spread of active muscles throughout the cycle for forward grinding, and contrasting movements contributing most to torque – upper body push for forward grinding and pull for backward grinding. Variant characteristics of the two grinding directions provide some explanation for the significant advantage (+8.0%, p<0.001) when grinding in pairs with an anterior-posterior heel compared to a medio-lateral heel. Movement characteristics did not readily explain why an anterior-posterior heel may be more advantageous under higher grinding loads (1.0%, p = 0.254), while medio-lateral heel is better at lower loads (2.0%, p = 0.017). Muscular performance of sailors, examined using an instrumented Smith machine, showed force and 1RM strength were greater in the bench press by ~17%. Velocity and power output were greater for the bench pull across the range of loads with the difference increasing exponentially as load increased to over 400% higher at 1RM load. Bench press 1RM and maximum force capability demonstrated strongest correlations with forward grinding performance (r = 0.88-0.99 and 0.87-0.99 respectively) with the relationship increasing with grinding load. There was a strong relationship for backward grinding with bench pull maximum power (r = 0.85-0.98) in addition to 1RM (r = 0.90-0.95) and maximum force (r = 0.87-0.95). Backward grinding performance showed greater improvements in the power-focussed training group than the control group for moderate (+1.8%) and heavy load (+6.0%) grinding in the intervention study. Changes in maximum power output and power at 1RM had large correlations (r = 0.56-0.61) with changes in both moderate and heavy load grinding performance. Time to peak force explained 70% of the change in heavy load grinding performance. Performance benefits from the training intervention were not entirely clear, but the likelihood of a detrimental effect was low (<5%), therefore further training intervention was recommended.

Thesis (M.A.)--Cincinnati Bible Seminary, 1988. / Bibliography: leaves [144]-152.

Thesis (M.A.)--University of Akron, School of Dance, Theatre and Arts Administration, 2007. / "December, 2007." Title from electronic thesis title page (viewed 02/22/2008) Advisor, James Slowiak; Committee member, Chris Hariasz; School Director, Neil Sapienza; Dean of the College, James Lynn; Dean of the Graduate School, George R. Newkome. Includes bibliographical references.

Thesis (M.A.)--Cincinnati Christian Seminary, 1986. / Abstract (untitled). Includes bibliographical references (leaves [161-171]).

Thesis (M.A.)--Cincinnati Christian Seminary, 1986. / Abstract. Includes bibliographical references (leaves [174]-178).