The ability to safely and efficiently negotiate stairs is an essential skill for independent ambulation. To date, basic research to identify biomechanical and physical costs is limited in older adults. In persons with stroke, this aspect of mobility is virtually unexplored. The main objective of this thesis was to investigate biomechanical alterations during stair negotiation and to evaluate the physical costs of the task in older adults and persons with stroke. This was approached by conducting four studies. The first study identified age-related alterations in joint kinetics during stair negotiation. The results showed age-related differences in moment magnitudes, an exaggerated net support moment and sustained abductor moments through stance. To gain insight into these adaptive changes with respect to mechanical efficiency, the second study evaluated age-related changes in mechanical energy transfers during stair negotiation. During ascent, older adults achieve similar efficiencies as young adults by slowing their cadence. During descent, age-related differences in mechanical energy expenditures and related variances in mechanical energy compensation coefficients reflect a loss in mechanical efficiency. The impact was likely the provision of enhanced extensor support and stability. The results also highlight a functional role for concentric energy expenditures during descent. The third study provided a detailed biomechanical description of stair negotiation in people with stroke, revealing important differences in how stroke survivors manage stairs and how handrail use modifies the magnitudes of lower limb joint moments. The fourth study evaluated the strength and aerobic requirement of stair ambulation in persons with stroke. The findings reveal increased costs of the task, primarily due to reduced neuromuscular and aerobic capacities and serve to identify factors that may be limiting during stair negotiation. This thesis provides new information regarding movement control in older adults during stair negotiation, providing a normative benchmark of age-related alterations in movement patterns. In persons with stroke, this work is the first to quantify the biomechanical patterns and physical requirements of stair negotiation. Future work may extend these findings to explore mobility challenges in persons with greater levels of impairment as well as guide the development of targeted and task oriented rehabilitation programs. / Thesis (Ph.D, Rehabilitation Science) -- Queen's University, 2011-08-25 09:24:26.106

The predominant model of the human hip is a mechanical ball-and-socket joint. This description has two key implications: that the motion of the hip is purely rotational, and that the rigid articulating geometry of the hip is a sphere-on-sphere contact. Since the widespread adoption of this model, in the late 1960s, there has however been a persistent thread of literature suggesting that the articulating geometry of the hip is aspherical. The recent widespread availability of three-dimensional medical imaging now makes it possible to empirically assess the applicability of the predominant model. For this research dissertation, two arthritic groups were examined: patients either had primary early-life osteoarthritis of the hip, or hip dysplasia with secondary osteoarthritis. Computed tomography scans, taken as part of routine preoperative preparation, served as the source data for this work. The scans were manually segmented to produce 3D models of the bones of the hip, which were further refined to isolate the bony articular surfaces. These surfaces were fit to general ellipsoids and to spheres, the latter being the ball-and-socket model. The arthritic hips examined had comparable fitting accuracy for both ellipsoids and spheres; however, sixteen of nineteen hips formed geometrically incompatible ball-and-socket joints. The dysplastic hips examined had a notable difference in fitting accuracy, with ellipsoids being a statistically significantly better fit to the hip geometry. The ellipsoid shapes in all cases were aspherical, and in each population formed a statistically significantly aspherical group. There were no trends relating the ellipsoid shapes of bones of an individual joint, nor were there practical differences between the ellipsoid shapes between the two populations. Despite patient groups not being controlled for age, sex, or race, and accounting for typical manual segmentation errors, these results suggest that the hip is aspherically shaped. Thus, the geometric foundation of the ball-and-socket motion may be unsupported, and the conventional kinematic description of the hip may be called into question. / Thesis (Master, Mechanical and Materials Engineering) -- Queen's University, 2011-09-28 09:41:29.114

Reverse shoulder arthroplasty is a relatively new procedure that is used to treat shoulders with massive rotator cuff tears combined with arthritis, a condition that is not well managed using conventional shoulder arthroplasty. By reversing the ‘ball-and-socket’ anatomy of the shoulder, the constraint of the joint can be increased. Despite the success of this prosthesis in improving pain and function, complication rates remain high and instability is often reported as the most commonly occurring complication. The mechanism of dislocation as well as factors that can be modified to decrease the risk of dislocation are not well understood for reverse shoulder arthroplasty. Therefore, the purpose of this study was to create a platform for examining the stability of reverse shoulder arthroplasty and use this to investigate factors affecting stability, including shoulder orientation (abduction and abduction plane angles), loading direction, glenosphere eccentricity and diameter, and humeral socket constraint. An anatomical shoulder simulator was developed using a synthetic bone model and pneumatically actuated cables to represent the three heads of the deltoid. A displacing force was applied to the humeral head by a material testing machine in an anterior, posterior, superior, or inferior direction. The force required to dislocate the joint was used as a measure of stability and the identified factors and the interactions between factors were examined using a half-fraction factorial design experiment. Increases in glenohumeral abduction or inferior-offset of the glenosphere were found to improve the stability of the prosthesis. Additionally, increased humeral socket depth resulted in greater stability for all loading directions, with the exception of inferior loading. Abduction plane angle and glenosphere diameter had no effect on the stability of reverse shoulder arthroplasty. / Thesis (Master, Mechanical and Materials Engineering) -- Queen's University, 2011-12-23 11:42:21.592

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<p> The screwdriver is a tool that has been among the most widely used hand tools for decades and continues to be used in the workplace to perform a variety of fastening tasks. Advancements in fastener technology have been complemented by the development of new types of screwdriver bits. While designs may vary, so do the force application requirements placed on the tool user. The primary objective of this experiment is to analyze the relationship between user torque and screwdriver bit design. A further objective is to utilize the results to develop an effort metric by which bits of different designs can be compared. In this experiment, three types of screwdriver bit designs (straight, Phillips, and combination of straight/Phillips (ECX)) were tested to determine how the design affects the amount and type of force applied by the user when performing a fastening task. The designs were tested to simulate fastener tightening and loosening operations. Sixteen participants were tested in this study. Although there was no significant effect, the data suggest that the Phillips bit design allow subjects to exert the maximum torque and the minimum axial force. This divergence suggests that the Phillips bit may have a higher biomechanical effort ratio, which is greater torque for the same or lower axial force. Finally, the data suggest there is little difference in user torque exertion between the ECX bit and the straight bit designs. Subjective assessment indicated that users overwhelmingly preferred the Phillips bit design. Bit designs requiring less axial force for the same torque exertion level reduce the overall muscular effort of the user, allowing work to be completed more efficiently and may reduce the risk of musculoskeletal disorder affecting the wrist, elbow, and shoulder. Results may also assist designers by allowing them to select fasteners that provide sufficient mechanical integrity of the design while maximizing user effectiveness.</p>

A four segment model of the crawl arm stroke is developed and validated. The construction of a theoretical model is discussed in a number of progressive stages. First, discussion is focussed on a basic two segment model; second, on a linearly configured simple three segment model; third, on the same model extended by introducing hand angle changes: then fourth, on modification of the forearm-hand configuration and on the effects of progressive lateral displacements changing as a functionofnormalised cycle time. Validation is sought from the start in a step-by-step process in which a physical model of the arm, first as a one and then a two segment system, is designed. built and tested in parallel. Thus, during the early stages of development, the behaviour of the physical model can be used to check the computer simulation of the theoretical model. Subsequently, as the theoretical model is extended to a four segment system, its validation is achieved by comparison with a series of experimental observations of five highly skilled competitive crawl-stroke swimmers. Film analysis procedures are developed to establish the velocities, lift, drag and total propulsive forces acting on, or generated from the arm and body segments. These parameters are obtained from an analysis of the digitized coordinates of eight body landmarks from two camera views. The two cameras are used with the aid of specially designed open plan periscopes for underwater filming. The initial values of the measured parameters from film are then incorporated into the model and the output values of the simulation are compared with the swimmers actual performances to establish the accuracy of the theoretical model. The comparison use of the theoretical model and the physical model results in a range of error between 6% and 30% for the total force and 6% and 11% for the body velocity. The comparison of the theoretical model and film analysis results in maximum error of 12% for the body velocity and 18% for the total propulsive force. Simulations of the crawl arm stroke during the underwater phase provide examples of the procedure. The examples illustrate the value of such simulations in that quantitative results are obtained which can be used to alter and improve performance. Considerable changes in the total force occur when the force acting on the hand is related to the angle of attack and to the rate at which the angle is altered. A maximum increase of 18% in the total force is obtained when the hand isorientated at 20 degrees to the horizontal on entry compared with an increase of only 14% at 40 degrees. During mid-stroke an entty angle of 10 degrees inaeases total force by 16%. The difference between maximum and minimum peak velocity is 19% when angles increase from 10 to 40 degrees on entry. The body velocity is found to increase by 25% if the input power is increased by 30%. The hand is able to deliver about 46% to 63% of the total propulsive force, the forearm is found to contribute by 28%. and the upper arm by about 2O%. Within limits a 5% change in hand size results in about a 1.6% change in velocity. A maximumin increase of 0.15% in body velocity is obtained as a result of a gradual increase followed by a gradual decreases of the hand angle of pitch, 0.72% as a result of modifying the forearm lateral movement and 2.6% as a result of combined modification.