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This thesis addresses some of the issues involved in the synthesis of swingthrough gait by functional electrical stimulation (FES). A general introduction is given to paraplegic gait, then the following areas are reviewed in detail: previous production of FES swing-through gait; biomechanical and energetics analyses of swing-through gait; general techniques for controlling FES gait; and the use of machine-learning techniques. Trained, non-impaired subjects wearing adjustable braces are used to model the movement patterns of FES swing-through gait. It is found that flexing the knees during the body-swing phase of swing-through gait reduces the energy cost of the gait. Hardware and software are developed to allow the production of FES swing-through gait in paraplegics with mid and low thoracic lesions of the spinal cord. The kinematic parameters of the resulting gait are assessed. It is found that the gait is faster than both knee-ankle-foot-orthosis (non FES) gait and reciprocal FES gait. This constitutes the first demonstration of FES free-knee swing-through gait in a spinal cord injured population. A symbolic inductive learning program, Empiric, is described. This program uses 'fuzzy' weighting to cope with uncertainty in the training data. This technique is found to offer improved classification performance (on artificially generated data) over both the orthodox (non-weighted) approach and an alternative weighting strategy. The fuzzy inductive learning technique is compared with a multi-layer perceptron type neural network for identifying the invariants (rules) that describe muscle activation during normal human gait. Both techniques are found to successfully model the muscular activation; the inductive learning technique has the advantage of producing explicit rules which are easily understood. The fuzzy inductive learning technique is applied to data obtained from the (previously mentioned) model of swing-through gait, in an attempt to mimic the control strategies used by the unimpaired subjects. It is found that the gait is best modelled with simple rule-sets, based on only one sensor. It is argued that this technique allows the automatic derivation of control strategies for FES gait: in particular, it allows the subjects' movement intentions to be determined. It is suggested that this 'intention detection' provides a more natural interface between a paraplegic subject and an FES control system than the techniques which are currently used.

The object of the present study was to investigate the three-dimensional kinematic and dynamic behaviour of the human ankle joint during walking and in particular to calculate joint and muscle forces. A review of the relevant literature is presented. In the analysis, the ankle is treated as consisting of two joints: the talocrural (Tc.) and the Talocalcaneonavicular (Tcn.). Five cadaveric legs were dissected to ascertain the joint axes, the lines of action of the relevant tendons, and the positions of the ligaments. Seven adult male subjects were studied during barefoot level locomotion, and on planes sloping sideways at + 10 . Observations were made with a force plate, and with three orthogonally placed cine-cameras. Stance phase forces were estimated as follows: inertia forces were neglected; anthropometric data from the cadavers were scaled to fit the walking subjects; the number of unknown forces was reduced to match the available equations by (a) combining muscles into four groups, and (b) assuming no antagonistic activity. Two free bodies were used: the hindfoot plus the talus alone. The Mark 1 solution excludes the Peroneal and Posterior Tibial groups; the Mark 11 solution includes them. The Mark 11 model gave a peak resultant Tc. joint force of 3.9 Body Weight (B.W.) mean, for normal locomotion. The Tcn. joint anterior and posterior facet peak resultants are 2.4 and 2.8 B.W. respectively. The Anterior Tibial/Calf group peak forces are 1.0/2.5 B.W. mean. The Peroneal/Posterior Tibial group peak forces are 0.7/1.1 B.W. mean. Side slope walking is shown to require greater Peroneal/Posterior Tibial muscle group activity than in normal locomotion. A Mark III model, including ligamentous constraint, is presented and recommendations made for its development. The relationship between the results of the study and clinical problems such as joint replacement is considered.

<p> Though many who walk along roadside cambers and hill edges may have an interest in making their travels sure and effective, those most concerned may be soldiers in the infantry. They need to be injury free and have as much energy as possible when they march into battle.</p><p> Walking on uneven ground without being injured by falling down (particularly with a heavy backpack) is generally accomplished by maintaining stability. This present study was conducted to determine an individual&rsquo;s most stable position (using a stability formula which compares dynamic center of mass with center of pressure) when wearing a backpack under differing load positions - low back, middle back or high back &ndash; and differing walking angles: level, as well as along a cross-sloped surface.</p><p> Furthermore, this study investigated the stability of persons walking along a cross-slope without a load.</p><p> Finally, this study attempted to determine which combination of backpack load location and slope tilt best conserved metabolic energy.</p><p> To carry out this backpack stability research, a group of 15 participants were asked to walk along an indoor track under the varying conditions mentioned (i.e., low to high backpack load positions and level to 10 degree tilted cross-slopes). The trials of their walks were performed randomly. The participants were recorded in a motion capture system and force plates documented their stepping times and locations.</p><p> Again, the same 15 participants walked along the track under the same conditions, but without the loads to determine the effect of different cross-slope angles on their stability.</p><p> Lastly, the same participants walked the track under the various conditions wearing portable oxygen sensors to analyze their energy expenditure. </p><p> The results of these limited tests indicate no significant stability differences between 0, 5 or 10 degree angles in cross-slope walking loaded or unloaded. Nor was any significant stability differences noted between the various load locations of the backpacks. Nor was there a significant energy difference between the conditions.</p>

<p> A living cell is a complex soft matter system far from equilibrium. While its components have definite mechanical properties such as stiffness and viscosity, cells consume energy to generate force and exhibit adaptation by modulating their mechanical properties through regulatory pathways. In this dissertation, we explore cell mechanics by stretching single fibroblast cells and simultaneously measuring their traction stresses. Upon stretch, there is a sudden, drastic increase in traction stresses, often followed by a relaxation over a time scale of about 1 minute. Upon release of stretch, traction stresses initially drop and often recover on a similar time scale of about 1 minute. We show that a minimal active linear viscoelastic model captures essential features of cell response to stretch. This model is most successful in describing the response of cells within the first 30 seconds of stretch. While perturbations of myosin and vinculin change quiescent traction stresses, they surprisingly have no significant impact on the stiffness or viscoelastic timescale of the cells. On longer time scales, cells may show an adaptive response to stretch that contradicts the minimal mechanical model. The probability of an adaptive response is significantly reduced by myosin de-activation and vinculin knockout. Therefore, we find that while vinculin and myosin are not important in determining passive mechanical properties of cells, such as stiffness and viscosity, they play a significant role in the adaptive mechanisms of cell response to stretch. To perform this work, we have built a novel micro stretching device compatible with live cell microscopy and developed a computational tool to analyze data from large traction stresses. Therefore, this dissertation's contribution is two-fold: (1) a novel experimental approach to explore the mechanics of living cells, and (2) a new model and framework for understanding the mechanical response of cells to stretch.</p>

<p> Deviations in foot posture, such as pes cavus or pes planus, may be a risk factor for lower limb injury due to compensatory motion of the lower extremity. Due to these compensatory motions dynamic balance has been reported to decline; with decreased dynamic balance risk of injury is increased. Assessing athletes to determine if they present characteristics related to higher risk of injury could potentially reduce the amount of athletes enduring injuries. Therefore, the purpose of the current study was to investigate if history of lower limb injury in the athletic population has a stronger association with foot posture or dynamic balance. A secondary purpose was to determine if foot posture relates to dynamic balance performance. Sixty collegiate athletes participated. Data analyses concluded female athletes had increased injury frequency and severity with severely pronated foot posture while male athletes had increased injury frequency and severity with moderately pronated foot posture.</p>

<p>Osteoarthritis is one of the most common, debilitating, musculoskeletal diseases in the world. Currently, there is no cure. It is well-known that a traumatic, joint injury increases the risk of developing post-traumatic osteoarthritis (PTOA). Therefore, in order to improve clinical treatment and prevention strategies for post-traumatic osteoarthritis (PTOA), a series of translational studies were conducted to develop research models to evaluate the effects of impact injury. </p><p> The first section of this dissertation (Ch. 1&ndash;2) provides a comprehensive introduction and literature review related to both clinical PTOA as well as previous research investigations of PTOA. The second section of this dissertation (Ch. 3&ndash;6) describes the methodology of optimizing a servo-hydraulic test machine to deliver a controlled impact injury (Ch. 3) as well as subsequent studies using this device to injure articular cartilage (Ch. 4) and cartilage-bone explants (Ch. 5&ndash;6). Further, the effects of dynamic, compressive loading to mimic walking after impact injury of cartilage-bone explants was investigated (Ch. 6). The third section of this dissertation (Ch. 7&ndash;8) details the development of an impactor device that may be used for pre-clinical, animal models. </p><p> Many significant findings were discovered through this dissertation work. Specifically, by using the proportional-integral-derivative (40, 0, 0) values, a large (25kN) servo-hydraulic test machine may be used to deliver a controlled impact injury to explants (Ch. 3). Biomarkers glycosaminoglycan (GAG) and prostaglandin E2 (PGE₂) were elevated after cartilage impact injury with PGE2 having the highest mechanosensitivity than any other biomarker (Ch. 4). Energy absorbed during cartilage-bone injury is dependent upon trauma severity; PGE₂ and monocyte attractant protein (MCP-1) were elevated following cartilage-bone injury (Ch. 5). Dynamic, compressive loading retained cell viability in non-impacted cartilage-bone explants and mitigated GAG release in impacted explants; GAG and PGE₂ were elevated due to cartilage-bone injury whereas matrix metalloproteinase-2 (MMP-2) and interleukin-8 (IL-8) were elevated due to injury plus dynamic, compressive loading (Ch. 6). The development of a 8mm diameter impactor does create articular cartilage damage (Ch. 7), albeit a smaller, 2mm diameter impactor creates higher impact stresses and may be used arthroscopically for pre-clinical animal models (Ch. 8). </p>

Hamstring injury is common in sprinting sports and injury recurrence remains a major concern. The aim of this thesis is to explore the biomechanical characteristics of athletes following sprint related hamstring injury. We conducted 1) An examination of already published research on biomechanical deficits following hamstring injury in athletes who had returned to sport by means of a systematic review and meta-analysis; 2) A detailed examination of sprinting following hamstring injury in athletes who had returned to sport muscle activity using 3D motion capture and surface EMG; 3) An examination of high intensity eccentric loading performance in previously injured athletes using low density, high surface area surface EMG and measures of force; 4) An analysis of hamstring muscle recovery until return to sport following hamstring injury using low density, high surface area surface EMG and measures of force via case reports in two elite athletes. Previous research indicates that athletes who had returned to sport following hamstring injury continue to display deficits in force production, especially during slow eccentric contractions. The observational studies indicate that athletes run with significantly asymmetric movements about the pelvis and hip that would place their hamstrings under increased length during the terminal swing phase of sprinting. Furthermore, significant alterations in late swing EMG ratios suggest relatively reduced activity in the previously injured biceps femoris. Spatial activation of the hamstring appears altered in previously injured athletes, with reduced relative activation of the proximal muscle and reduced median frequency values in the medial muscle compared to control limbs. Asymmetries in activation patterns are also noted in the pre-return to sport phase. Previous hamstring injury is associated with significant alterations in force production, movement symmetry and muscle activation patterns following return to sport highlighting the complexity of this injury and the need for advanced rehabilitation screening approaches.

Background Patellofemoral pain (PFP) is a common musculoskeletal complaint with inadequate long term outcomes. We aimed to review current evidence relating to tailored interventions, address knowledge gaps concerning how tailoring should best be delivered and establish whether such interventions are feasible. This thesis investigated whether the interaction of hip and foot biomechanics better explains PFP presentation and management, and could be used to inform feasibility studies of delivering tailored interventions for individuals with this recalcitrant condition. Methods Two systematic reviews with meta-analysis identified predictors of conservative management outcomes and the effects and mechanisms of proximal rehabilitation interventions. A reliability study tested a battery of clinical measures, designed to identify biomechanical deficits common in individuals with PFP. An observational study of individuals with PFP investigated possible biomechanical mechanisms of effect for in shoe foot orthoses. A case control study design explored the electromyographic activity of the gluteal region during common rehabilitation exercises. A randomised intervention trial implemented a tailored intervention to determine feasibility. Results Outcome predictors for conservative management are currently at a derivation stage of development. A clinical battery of 14 measures showed good intra and inter rater reliability for the assessment of lower limb biomechanics. Proximal rehabilitation, combined with quadriceps, achieves favourable outcomes in the short and medium term. Gluteal muscle electromyographic activity is comparable between symptomatic and asymptomatic individuals, with specific exercises achieving desired activation patterns. Tailored intervention using biomechanical characteristics, within a randomised trial, is feasible for recruitment and retention. Conclusion Interventions directed proximal and distal to the patellofemoral joint are effective in the management of PFP. Indicators of treatment success are at a derivation stage,with findings from this thesis providing a comprehensive clinical test battery for lower limb biomechanical assessment. Feasibility of a biomechanically determined tailored intervention has been established.with findings from this thesis providing a comprehensive clinical test battery for lower limb biomechanical assessment. Feasibility of a biomechanically determined tailored intervention has been established.