<p> The purpose of this research was to identify limitations people with arm amputations face completing daily living tasks and to design a new prosthesis which alleviates these deficiencies. State of the art prosthetic devices can mimic many of the motions of an intact limb but are controlled by a limited number of signals from the muscles in the residual limb. The majority of current research is focused on improving the control of these devices by increasing the number of inputs or using software to interpret the limited inputs in a more meaningful way. This research instead determined that the mechanics of the prosthesis could be simplified while maintaining functionality and a simple control system. Specifically, this research tested the hypothesis that the three degrees of freedom in the wrist (flexion-extension, radial-ulnar deviation, and rotation), could be combined into a single degree of freedom, known as the Dart Thrower&rsquo;s Motion, in a way that preserves most of the wrist&rsquo;s motion and functionality and could be controlled with a simple input method. There are currently no commercially available wrist flexion devices which utilize this motion. The studies presented in this dissertation surveyed people with upper limb amputations and found that they are less satisfied performing tasks that utilize the Dart Thrower&rsquo;s Motion with their prosthesis. The major angle of the Dart Thrower&rsquo;s Motion was identified in able-bodied individuals to be 22 degrees offset from the anatomical flexion-extension plane. Finally, a new prosthetic wrist device was developed based on this angle. This new prosthesis improved functionality over a traditional flexion wrist and was no more difficult to use than a device without a wrist. This research helps to alleviate many of the barriers to inclusion which people living with upper limb deficiency regularly face.</p><p>

<p> The objective of this research was to quantify and better understand the mechanisms of performance in constricting snakes. Many non-venomous snakes use constriction to subdue and kill different types, sizes, and quantities of prey. Using eastern kingsnakes (<i>Lampropeltis getula</i>), I measured the effects of prey size and repeated feeding on constriction performance. I found that prey size alone did not affect constriction performance, but when kingsnakes encountered additional prey of medium and large sizes, they experienced significant reductions in the length of the body used and peak constriction pressure. In addition to feeding on a variety of different mammalian prey, kingsnakes (<i>Lampropeltis spp.</i>) are known to feed on other snakes, including other constrictors (<i>Pantherophis ssp.</i>). To begin addressing how this is possible, I studied the scaling of muscle cross-sectional area, pulling force as an indicator of escape performance, and constriction pressure as a measure of predation performance across the ontogeny of six species of snakes (three kingsnake and three ratsnake species). Muscle cross-sectional area and pulling force scaled similarly for all snakes, but all kingsnakes were able to exert significantly higher peak constriction pressures on their prey than ratsnakes. The ability to exert higher pressures suggests that kingsnakes may have differences in muscle anatomy and physiology that have gone untested. In another experiment, I described and quantified nine different muscles in speckled kingsnakes (<i>L. holbrooki</i>) and western ratsnakes (<i>P. obsoletus</i>) in order to better compare their anatomy. There were no significant differences in quantitative measures of musculature between these two species. Finally, I compared individual muscle performance between kingsnakes and ratsnakes by testing <i>in vivo</i> muscle force production and endurance. There was no difference between muscle force and endurance in our sample of kingsnakes and ratsnakes. The results from all chapters together indicate that kingsnakes are able to produce significantly higher constriction pressures because of their consistent coil posture (behavior) and not because of differences in their muscle anatomy or physiology. Integrated studies of behavior and its underlying mechanisms, such as in these chapters, are critical to making strong inferences about relationships in predator&ndash;prey interactions and their outcomes.</p><p>

Introduction: Claims that foot orthoses can resolve low-back pain are common in the marketing of these devices. The claims are based on the notion that wearing the orthoses will limit excess pronation at the subtalar joint thus reducing excessive internal tibial and femoral rotations. Excess leg rotations increase the anterior tilt of the pelvis and subsequently the degree of lumbar lordosis. Since lumbar lordosis has been suggested as a cause of low-back pain, it is speculated that foot orthoses could be used to treat and prevent pain to the low-back by reducing the forward curvature of the spine. This mechanical link between foot function and the low-back has not been investigated by experimental studies. Purpose: The purpose of this thesis was to investigate whether increased internal rotation of the femur induced an anterior tilt of the pelvis thus increasing the degree of lumbar lordosis and if external rotation induced a posterior pelvic tilt thus decreasing the degree of lumbar lordosis. Methods: In order to internally and externally rotate the femur, participants placed their feet in 18 different foot positions. Seven of these positions ranged from 15 degrees of foot eversion to 15 degrees of foot inversion and 11 positions ranged from 40 degrees of external foot rotation to 40 degrees of internal foot rotation. Six cameras surrounded the motion capture area and angles of pelvic tilt and lumbar lordosis were calculated. Results: Foot eversion and inversion did not have a statistically significant effect on pelvic tilt and lumbar lordosis. In-toeing had a statistically significant linear relationship with anterior pelvic tilt (R2=0.35, F1,131=69.79, p=0.00). Internally and externally rotating the feet had no effect on lumbar lordosis (R2=0.001, F1,153=0.09, p=0.77). Conclusion: Internally rotating the legs caused the pelvis to tilt anteriorly but only at extreme ranges of motion, much greater than what would normally be seen during gait. At which point, lumbar angles remained unaffected. This study does not dispute the effectiveness of foot orthoses to treat low-back pain but the results do not support the mechanical link proposed as the mechanism by which they work. / Education, Faculty of / Kinesiology, School of / Graduate

Many animals are able to scale smooth surfaces using adhesive structures on their feet. These organs are either soft pads with a relatively smooth surface or dense arrays of microscopic adhesive hairs with both designs having independently evolved in diverse taxa of arthropods and vertebrates. Biological adhesive pads out-perform conventional adhesives in many respects, making them important models for biomimetics. Hairy pads have attracted particular attention, because it has become feasible to fabricate similar synthetic microstructures. Nevertheless, the detailed performance and functional properties have not been characterised for any natural fibrillar adhesive system, and many fundamental aspects are still not understood. The aim of this thesis was therefore to investigate the fibrillar adhesive system of leaf beetles as a model. To investigate the functional implications of hairy pad design, the attachment performance between hairy pads of the leaf beetle Gastrophysa viridula and smooth pads of stick insects (Carausius morosus) was compared. Adhesive and frictional stresses were found to be similar in smooth and hairy pads, inconsistent with contact splitting theory, which predicts higher adhesive stresses for fibrillar adhesives. Hairy pads showed a greater direction-dependence of friction forces than smooth pads, confirming the importance of the asymmetric design of individual setae for effortless detachment. Experiments with contaminating particles also showed that hairy pads removed contamination more rapidly and efficiently than smooth pads. Self-cleaning ability had not been previously documented for adhesive organs of insects. To investigate to what extent the hairy system is able to compensate for surface roughness, whole-body attachment forces were measured for varying roughness levels. Attachment was reduced for all length scales of surface roughness, but in particular for asperity sizes smaller than the diameter of individual seta tips. Leaf beetles possess adhesive pads on three tarsal segments, which vary in setal morphology. However, the functional implications of this variation are unknown. The mechanical and adhesive properties of individual pads were therefore tested and their use during climbing observed. Proximal pads were shown to be stiffer than distal pads, conferring stability during pushing. In contrast, the softer distal pads allowed better attachment to rough surfaces. Hence the morphological variation is explained by an effective division of labour between the pads. To investigate an extreme example of pushing in a hairy system, pad use was studied during jumping in flea beetles. The pushing forces needed during take-off were exclusively produced by the proximal pads, again confirming the division of labour. To characterise the effects of different hair morphologies and to understand how individual setae contribute to array and whole-animal performance, single hair forces were measured using a glass capillary cantilever. Male-specific discoidal hairs were shown to be both stiffer and more adhesive than pointed and spatula-tipped setae, likely affecting overall pad stability and attachment. This thesis has shown that hairy pads are similar to smooth pads in the magnitude of adhesive stress supported yet outperform them in detachability and self-cleaning. It was also demonstrated that there are considerable differences in design and performance even within setal arrays of the same insect, indicating the limitations of general models of fibrillar adhesion and underlining the importance of specialised adaptations.

Abstract not available.

his study investigated the lower limb biomechanics during downhill and uphill running in habitual forefoot strike and habitual rearfoot strike runners. Fifteen habitual forefoot strike and fifteen habitual rearfoot strike recreational male runners ran at 3 m/s ± 5% during level, uphill and downhill overground running on a ramp mounted at 6° and 9°. Results showed that hill running had similar impacts on joint angles in rearfoot strike and forefoot strike runners, causing a decrease in hip flexion at initial contact during downhill running, an increase in knee flexion angle at initial contact during uphill running and a decrease in peak hip flexion angle. In addition to differences in ankle joint angle due to landing pattern difference between rearfoot strike and forefoot strike runners, forefoot strike runners had a more flexed hip angle during downhill running. Forefoot strike runners had an absent impact peak in all running conditions, while the impact peaks only decreased during the uphill conditions in rearfoot strike runners. Active peaks decreased during the downhill conditions in forefoot strike runners while active loading rates increased during downhill conditions in rearfoot strike runners. Compared to the level condition, parallel braking peaks were larger during downhill conditions and parallel propulsive peaks were larger during uphill conditions. Peak hip flexion moment was significantly greater while peak knee flexion moment was significantly lower in both groups during the downhill 9° condition. Forefoot strike runners had larger peak plantar flexion moments and peak ankle power absorption compared to rearfoot strike runners during all conditions. Forefoot strike runners had decreased peak power absorption at the knee joint during downhill and level running conditions. Combined with previous biomechanics studies, our findings of no impact peak in forefoot strike runners suggests that this landing pattern may have potential in reducing overuse running injuries. Forefoot strike running reduces loading at the knee joint and can be used as an effective strategy to reduce stress at the knee joint experienced with rearfoot strike running.

The effect of striking compliance in ice hockey impacts, and its influence on dynamic response and brain tissue strain was investigated in this study. In hockey, players can experience a broad range of striking/surface compliance during a head impact, from the stiff ice surface to highly compliant player collisions. An increase in striking compliance has been shown to extend the duration of an impact that is associated with an increase in risk of sustaining brain injuries. Three striking caps of low, medium, and high compliance were used to impact a helmeted 50th percentile Hybrid III male headform attached to an unbiased neckform. Each level of compliance was used to impact five high risk locations at three different velocities, representative of head impact scenarios in ice hockey. The dependent variables, peak resultant linear accelerations and peak resultant rotational acceleration as well as MPS, were analyzed using a multivariate analysis of variance (MANOVA) to determine if there were significant differences between the three controlled variables. The results demonstrate a significant effect of compliance, over the influence of velocity and acceleration. Conditions of low impact compliance resulted in higher response values compared to impacts of increased compliance. That being said, high compliance conditions remained in the range of concussion risk, even at the lowest velocity. The use of brain tissue modeling, compared to dynamic response alone, demonstrated an elevated risk of brain injury as a result of extended impact durations. Impact compliance in hockey is a factor that has not been considered when designing and testing helmet technology. The results of this study demonstrate that compliance is a determining factor in producing brain injury, and should be incorporated into helmet standard testing to mitigate risk. The results of this study have implications on brain injury risk that extend beyond the impacting scenarios of ice hockey. The results can be extrapolated to any contact sport that includes impacting scenarios against varied impacting compliances such as football and rugby.

Although frogs are recognized as accomplished swimmers, no detailed biomechanical study has been done. The hydrodynamics and mechanics of swimming, in the frog, Hymenochirus boettgeri, are investigated in this thesis. Hydrodynamic drag, of the body and splayed hind limbs of preserved H. boettgeri, was assessed by drop-tank experiments. Drag tests were also performed with the semi-terrestrial Rana pipiens. A comparison of their drag coefficients (CD) under dynamically similar conditions, suggests that jumping performance may not compromise the swimming ability of R. pipiens. Drag of the expanded foot of H. boettgeri, and acetate models thereof, was investigated by free fall drop-tank experiments, and a subtraction technique. The results of these methods and flow visualization experiments support the assumption that animal paddles can be treated as three dimensional flat plates, oriented normal to the direction of flow. Cine films were used to study swimming during the near-vertical breathing excursions of H. boettgeri. The acceleration of frogs throughout hind limb extension (power stroke), is distinct from other drag-based paddlers (eg. angelfish and water boatman), which accelerate and decelerate within the power stroke phase. The propulsive force generated during the power stroke of a single sequence (sequence 1) is calculated from quasi-steady drag (static-body drag measurements, see Chapter I) and inertial considerations. Additional components of the forcebalance, including the net effect of gravity and buoyancy, and the longitudinal added mass forces associated with the frog's body, are integrated to establish upper and lower bounds of the propulsive force. The propulsive force remains positive throughout extension. The validity of using static drag estimates to describe dynamic resistance is explored. Results from Chapter II suggest that simple drag-based models may not be sufficient to explain the swimming patterns observed. The right hind limb of the sequence 1 animal was modelled as a series of linked circular cylinders (the femur, tibiofibula, and metatarsal-phalangeal segments) and a flat plate (the foot). A blade-element approach was used to calculate the instantaneous drag-based and accelerative force components (parallel to the direction of motion) generated by hind limb flexion and extension. The negative thrust, generated by hind limb flexion, is probably responsible for the observed deceleration of the sequence 1 animal. Positive thrust is generated only during the initial stages of extension, almost exclusively by the feet. The impulse of the accelerative-based thrust far exceedes the impulse of the drag-based thrust. Negative thrust is initiated midway, and continues thoughout extension, despite the acceleration of the animal. Hind limb interaction, is thought to provide propulsive thrust for the latter half of the extension phase. A jet and/or ground effect may be involved. It is suggested that a combination of reactive, resistive and interactive forces are required to explain propulsion in H. boettgeri, and probably other anurans. / Science, Faculty of / Zoology, Department of / Graduate

<p>Underwater blasts travel further and injury more easily than blasts in air. However, because of a relative lack of data and study dedicated to the subject, the tolerances of personnel in the water to blast exposures have historically been poorly quantified. This dissertation presents an analysis of underwater blast exposures that have resulted in injuries and fatalities. Previously known standards for risk were evaluated and determined to be insufficient. Historical medical reports of exposed divers in the water were then evaluated and reconstructed to form the first known curves to prescribe a quantitative risk of injury or fatality.</p> <p>The mystery of the submarine HL Hunley is an historical underwater blast exposure that has puzzled generations of enthusiasts. The tools for evaluating blast transmission through the water were applied to this puzzle, and data were gathered to support a theory of why the famous submarine sank.</p> / Dissertation

The relationship between cells and their environment is one of dynamic reciprocity, whereby cells can influence their surrounding and the surroundings can influence the cells. One example of this relationship arises from the effect of the mechanical properties of an environment on a cell and of a cell on its environment. Inspired by this relationship, we investigate (1) the local environment of biological materials, both native and synthetic, and (2) the forces that cell sheets exert on surfaces. We do this by developing techniques that focus on local mechanical properties and experimental strategies that provide insight into intercellular mechanics. We first focus on determining local mechanical properties of hydrogel materials by developing the Cavitation Rheology technique. This process involves inducing a cavitation event at the tip of a syringe needle. We develop theory to show that the critical pressure to cavitate can be directly related to the modulus of the material (Chapter 2). This allows us to experimentally determine the mechanical properties at arbitrary locations throughout a material scaffold over a range of length scales defined by the needle radius (Chapter 3). We then demonstrate that we can viturally elminate the energy contribution from the creation of new surface area to the critical pressure by cavitating with a media of lower surface energy (Chapter 4). In chapter 5, we show that Cavitation Rheology can be used on native biological tissues and we go on to demonstrate the importance of measuring the mechanical properties in vivo. We then focus on understanding the force development of cells as they grow to confluency on a dynamic substrate (Chapter 6). We demonstrate the method of living microlenses to measure the collective strains cell sheets attain by growing cells on a thin polystyrene film supported by a surface of microwells. The cells cause the film to buckle and the resultant buckling can be directly related to the strain. We use this technique to study the strains exerted by various cell types and to determine the importance of the cell-cell junctions on the strain development.