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A meniscal tear is an injury that often occurs as a result of a varus or valgus rotation of the femur on the tibia coupled with axial rotation while the knee is partially flexed, thus creating preferential loading of the posterior horn and shear forces on the meniscus. Such injuries can be repaired surgically, either with standard suturing techniques or with commercially available all-inside meniscal repair devices, which are designed to make the repair surgery faster, easier, and potentially safer. Many prior biomechanical studies have loaded an excised, repaired meniscus in tension and found that the repaired meniscus performs similarly to an uninjured sample. However, it is more appropriate to apply shear forces to the tissue in order to simulate the mechanism of injury. To date, three prior studies have investigated the biomechanical properties of meniscal repairs in shear, all of which used isolated meniscal tissue samples. The present study used an in situ bovine model to investigate the strength of commercially available meniscal repair systems under a shear loading regime. Medial menisci were torn and subsequently repaired using one of three techniques: standard inside-out vertical mattress sutures, Depuy Mitek Omnispan, or Smith & Nephew Fast-Fix. A control group was left unrepaired. Samples were subjected to a battery of cyclic side loading to create shear forces within the knee. Statistical analysis (ANOVA) demonstrated no significant difference in the stiffness, shear force, or subsidence between groups. The conclusion that the repair techniques perform similarly is consistent with tensile and in situ testing. Pathological observations showed no significant differences between repair devices, but all repaired samples demonstrated less wear than unrepaired samples, indicating that the experimental model is an effective method for creating wear within the knee. This result indicates that the flexible all-inside devices are mechanically comparable to the more commonly performed conventional suturing techniques. It is concluded that the mechanical performance may not be the best indicator of success of the surgical repair, as long as the device is able to anatomically reduce the tear. / Bioengineering

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<p>A dynamic ballistic elbow extension task was chosen to investigate the mechanisms responsible for achieving a high final velocity during this type of movement. After a screening process of one hundred male participants, thirty-two were chosen to be further investigated who fell into the extremes of the strength and speed continuums. The main investigation involved having participants ballistically extend their elbows against external relative loads of 0%, 20%, 40%, 60% and 80% of their maximum isometric force and two absolute loads of 1.1 kg and 2.2 kg. External torque and angular displacement measurements were recorded as well as triceps and biceps electrical activity. EMG modeling, which employed the characteristics of muscle mechanics, was used to determine the differences in performance. Isometric strength did not produce a 1:1 mapping with maximum velocity. Individuals existed that were relatively strong but not fast. Additionally, there were subjects that were quite strong but not appreciably fast. Peak instantaneous power, however, produced the best correlations with peak final velocity. To determine why certain individuals were capable of producing more power, each subject's triceps EMG was modeled in order to predict the actual muscle torque. The model predicted torques with a mean correlation of 0.957 and a mean RMSerror value of 5.8 Nm for the 224 trials. As a result of the good predictions, a forward-dynamics approach was used to manipulate weaknesses in one performance with another individual's superior attributes. Performance improvements were noted as a result. These findings demonstrate that peak instantaneous power best predicts peak terminal velocity. Furthermore, this study has developed a model capable of identifying neuro-muscular weaknesses in performance and suggesting how improvements in those areas would change the maximum velocity attained. The next stage is to determine the proper training stimuli that would make these specific neuro-muscular improvements possible.</p> / Doctor of Philosophy (PhD)

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<p>The purpose of this study was to investigate leaning behaviours when completing tasks with constrained reaches. A logistic regression was developed, with the input of individual subject anthropometry and specific task characteristics, and the resulting model was able to provide a very accurate prediction of when an individual would lean. The inputs to this model give insight into what factors are important in the decision making process when a worker chooses whether lean. The task hand locations with the longest reaches resulted in the most frequent choice to lean. Leaning appears to be particularly common, and important, with long reaching and pulling tasks that can reduce task hand shoulder and trunk loads and improve balance, while allowing the worker to get closer to the task. Leaning hand forces were highest during pulling tasks. These findings are very important to document, as current ergonomic tools neglect to consider that different task characteristics may change how, and when, a worker leans. Even when only the direction of the task hand force was changed, leaning hand forces differed significantly. In this study, leaning hand height was slightly higher for the shoulder height, when compared to the umbilical height, task hand locations. The average height of the leaning hand did not vary considerably and ranged between 106.6cm to 116.3cm, depending on the condition. The leaning hand force magnitude changed as task hand location, force direction and force level changed. Leaning hand forces increased with increasing task hand load. Task hand forces in the push direction were higher compared to push and down exertions, regardless of task hand location or task hand load. The findings from this study are of particular use to industry as ergonomists now have representative forces and heights, to help guide leaning estimates during proactive risk assessments.</p> / Master of Science (MSc)

<p> Recent motor control literature has demonstrated that using verbal cues to direct a performer&rsquo;s attention externally (i.e. toward movement outcome) enhances motor skill performance. The purpose of this study was to investigate how an athlete&rsquo;s focus of attention impacts kinematic performance of the snatch. 12 competitively trained athletes performed blocks of 3 snatch repetitions at 80% 1RM following internal and external instructions. The results indicated that athletes adopting an internal focus increased elbow velocity relative to an external, while an external focus increased horizontal barbell velocity. Internal cues resulted in larger BCH angles at the max height (MH), relative to external, indicating that the athletes are squatting under the barbell too soon. This information adds to the literature suggesting small changes in coaching cues can impact performance significantly. It is recommended that coaches use cues that direct an athlete&rsquo;s attention externally, toward the movement outcome, rather than the action itself. </p>

Asymmetry of weight-bearing and impaired ability to maintain centre of pressure in midline contribute to an increased fall risk during sit-to-stand in people with stroke. The main objective of this thesis was to investigate the effect of constraint-induced movement strategies on affected limb weight-bearing and measures of balance in people with stroke. Four studies were conducted to achieve this objective. Study one and two investigated the methodology for describing sit-to-stand performance in people with stroke and reliability of measures of sit-to-stand performance. Findings from study one demonstrated that methods for describing sit-to-stand performance in healthy adults are not feasible in people with stroke and established a method for describing sit-to-stand performance in subsequent studies. Findings from the second study demonstrated within and between day reliability of temporal, weight-bearing and displacement measures of sit-to-stand performance in both groups. The third study of this thesis described impairments of sit-to-stand performance in people with stroke when compared with healthy age and sex matched adults. The findings confirmed results from previous studies and further described sit-to-stand performance by demonstrating a shift in the frontal plane centre of pressure and centre of mass position toward the unaffected limb at seat-off in people with stroke. The final study investigated the effect of three constraint-induced movement strategies on sit-to-stand performance in people with stroke. The results demonstrated increased affected limb weight-bearing and a shift of the centre of pressure and centre of mass toward midline with all of the strategies. Only two of the strategies altered centre of pressure and centre of mass displacement in the sagittal plane. Findings from this body of research provide new information regarding the methodology of describing sit-to-stand performance in people with stroke and the reliability of measures of sit-to-stand performance. The results also provide an advanced understanding of sit-to-stand performance in people with stroke and the effect of constraint-induced movement strategies on sit-to-stand performance. Additional research using constraint-induced movement strategies in a randomized controlled trial will inform clinical practice and may reduce the fall risk in people with stroke. / Thesis (Ph.D, Rehabilitation Science) -- Queen's University, 2013-07-24 13:30:53.585

The purpose of this study was to study the essential• factors involved in the execution of the parallel arm downswing in the sequence of the backward giant swing on the still rings. Comparisons were made among gymnasts who had had different amounts of experience in the use of the parallel arm downswing technique.The subjects were four male American collegiate gymnasts. Selected as the experienced performers were an Olympic gymnast from Indiana State University, Terre Haute, Indiana, and. a specialist on the still rings from Ball State University, Muncie, Indiana. Selected as the less experienced performers were two all around gymnasts from the Ball State University men's gymnastic team.The cinematographic method was used to collect the data. In order to identify the biomechanical differences between the subjects, seven categories were considered to be the essential factors possibly involved in the execution of the parallel arm downswing. The horizontal and linear velocities of the wrist, the body angles, the angular velocity of the body segments, and the total body's tangential forces were graphed and studied. Plots of the trajectory of the center of gravity and plots of the loci of the body joints were compared and interpreted. The performance times of the subjects were compared in terms of the time elapsed during the whole and a part of the downswing.It was concluded that for these subjects, the successful parallel arm downswing should be accomplished by using the following factors: a faster push of the rings, a lean of the shoulders, a straighter body, a stronger beat action of the trunk, a proper timing (after the bottom of the downswing) of the legs and. a closer trajectory of the center of gravity throughout the downswing. The total body's tangential force and the performance time, appeared to be essential factors for the successful parallel arm downswing. However, it was not determined whether a greater amount of force or a shorter execution time is necessary for the ideal execution of the reverse giant swing on the still rings.