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No description available.

Locomotion is essential to survival in most animals. Studies have shown that animals, including humans, choose a gait that minimizes the risk of injury and maximizes energetic efficiency. Individuals often encounter obstacles and perturbations during normal locomotion, from which they must recover. Despite the importance of understanding the mechanisms that enable recovery from perturbations, ethical and experimental challenges have prevented full exploration of these in legged systems. A powerful paradigm with which to tackle this difficulty would be the application of external and internal manipulation of the nervous system. These perturbations could target how gait is regulated and how the neural systems process sensory information to control locomotion during an unexpected perturbation. Here we present data on the response of female mice to rapid, precisely timed, and spatially confined mechanical perturbations applied by a treadmill system. Our data elucidate that after the mechanical perturbation, the mouse gait response is anisotropic, preferring deviations away from the trot towards bounding, over those towards other gaits, such as walk or pace. We quantified this shift by projecting the observed gait onto the line between trot and bound, in the space of quadrupedal gaits. We call this projection λ. For λ=0, the gait is the ideal trot; for λ=±π, it is the ideal bound. We found that the substrate perturbation caused a significant shift in λ towards bound during the stride in which the perturbation occurred and the following stride (linear mixed effects model: Δλ=0.26±0.07 and Δλ=0.21±0.07, respectively; random effect for animal, p<0.05 for both strides, n = 8 mice). We hypothesize that this is because the bounding gait is better suited to rapid acceleration or deceleration, and an exploratory analysis of jerk showed that it was significantly correlated with λ (p<0.05). To evaluate whether the same structure of gait controller exists when undergoing an entirely different class of manipulation, we applied an internal, neuromuscular perturbation. We directly stimulated the lateral gastrocnemius muscle of mice using implanted electrodes and a custom magnetic headstage. We found that the electrical muscle stimulation caused a significant shift in λ towards bound in trials where the stimulation occurred during the swing phase (linear mixed effects model: Δλ=0.23±0.06 and Δλ=0.28±0.06; for the stride during and after the stimulation, respectively; random effect for animal, p<0.05 for both, n = 7 mice). Understanding how gait is controlled under perturbations can give insight into the neuromechanical basis of locomotion, aid in diagnosing gait pathologies, and aid the design of more agile robots. / Bioengineering / Accompanied by eleven .mpeg4 files.

<p> The motor driven treadmill is often used in research as a convenient tool for simulating overground running. There has been varied opinion in the literature regarding the accuracy of this assumption. The major difference that has been quantified is the variation in treadmill belt speed as a result of the forces applied by a runner. In comparison, the earth does not vary its speed during overground running. The aim of the present study was to more clearly define the causes of treadmill belt-speed variation and to elucidate its effects on running mechanics. </p> <p> An in-lab fabricated tachometer was used to determine accurate treadmill belt speed while the treadmill was challenged by five subjects weighing 55.2 to 99.6 kg running at four speeds of 2.6, 3.1, 3.5 and 4.0 m/s. The actual running velocity was found on average to be 0.62% higher than the treadmill display setting. The intra-step belt-speed variation ranged from 4.2 to 8.6 % of average belt velocity. Linear regression analysis showed that 86 % of the variance in intra-step belt-speed variation was attributed to total body mass and a further 10 % attributed to running speed. </p> <p> The effect that this variation had on running mechanics was determined from the power transfer between the foot and belt, as calculated from the product of the change in belt speed and the horizontal ground reaction force. The horizontal force, as calculated using a segmental acceleration approach, did not show complete agreement with simultaneously recorded forceplate data. It was found that an average of 4.49 J flowed to the treadmill during the eccentric phase of running and 3.37 J of energy flowed to the runner during the concentric phase of running. Despite inaccuracies in the calculation, the mathematical approach used in this study permitted insight into the theoretical benefit of belt-speed variation in treadmill running. </p> / Thesis / Candidate in Philosophy

Skeletal muscle is the primary site of glucose disposal in the body, and consequently plays a predominant role in the regulation of blood glucose levels after the ingestion of a meal. Following spinal cord injury (SCI), skeletal muscles below the level of an upper motor neuron lesion undergo marked changes in muscular properties that affect glucose tolerance. Recent studies on individuals with a SCI have reported improved glucose tolerance following periods of electrically-stimulated training. This appears to result from improved muscle morphology and post-exercise insulin sensitivity, and increased GLUT 4 content, enzyme activity, and muscle fiber capillary number. It might be expected that the weight-bearing and greater muscular involvement associated with body-weight support treadmill training (BWSTT) would have an even more profound effect on previously observed responses. The purpose of this study was to investigate whether 6 months of BWSTT improved whole-body glucose tolerance and some of the muscular parameters that are expected to influence glucose metabolism, in a group of 9 individuals with an incomplete SCI. A leg biopsy and a resting, 3 hour oral glucose tolerance test (OGTT) were performed on each subject before and after 6 months of training. Analysis of the muscle biopsy revealed significant increases in post-training muscle fiber size for type I (P=0.01) and type IIa (P=0.05) fibers in comparison to pre-training values. A significant increase in type IIa fiber proportion (P=0.03) and a significant decrease in type IIx fiber proportion (P<0.01) were found following training. In addition, significant increases in post-training GLUT 4 protein content (P<0.01), citrate synthase protein content (P<0.01), and citrate synthase activity (P=0.01) were found in comparison with pre-training values. No change was found in the number of capillaries per fiber after training. Plasma insulin area under the time curve (AUC) during the post-training OGTT significantly decreased (P=0.04) in the subjects as a result of BWSTT. Despite the large decrease in plasma insulin concentration, blood glucose AUC also showed a significant decrease (P<0.01) during the post-training OGTT, indicating a training-induced increase in insulin sensitivity occurred in the subjects. According to the findings, we can speculate that the increase in insulin sensitivity was a result of the increase in muscle GLUT 4 content in the exercised muscles, possibly in combination with an increase in leg muscle mass, as indicated by an increased muscle fiber cross-sectional area. The results are the first in this field to provide evidence that BWSTT leads to beneficial morphological and metabolic changes in skeletal muscle fibers that improve glucose tolerance. / Thesis / Master of Science (MSc)

The purpose of this study was to determine the effects of cessation of a 12-month thrice-weekly body-weight supported treadmill training (BWSTT) program on functional ambulation and aspects of health-related quality of life (HRQL) in individuals with incomplete SCI. Twelve men and women (aged 22-55) with chronic (> 1 year post-injury) incomplete SCI (ASIA B or C) returned for follow-up (FOL) testing 37 weeks (SD 2.1) following their final scheduled BWSTT session. Functional ambulation was compared based on: i) required percentage of body-weight support (%BWS) on the treadmill, ii) preferred treadmill speed and iii) overground walking. Evaluation of HRQL included measures of: i) satisfaction with life, ii) perceived ability to perform activities of daily living (ADL), iii) perceptions of health, and iv) depressive symptomology. Participants were invited to participate in once-weekly BWSTT and twice-weekly fitness training during the FOL period (37 sessions); the actual number of BWSTT sessions attended was only 11.6 (range 0-29) and the total days of exercise was 29.1 (range 0-75). The 12-month BWSTT program resulted in a decrease in the required %BWS (73±10% to 19±12%; p<.01), an increase in treadmill speed (0.5±0.3 to 1.4±0.8 km/h; p<.01), improved overground walking in 4 individuals, and improved group satisfaction with life (p<.05). At FOL, %BWS increased to 35±14% (p<.01), but was still less than at pre-training (p<.01). There were no differences between 12-month and FOL scores on any HRQL-related measures. High exercise adherence during the FOL period had a strong correlation with a positive percent change in perceived ability to perform ADL (r = .70; p<.05), as well as non-significant trends with positive percent change in perceptions of health and negative percent change in depressive symptomology (r = .49; p=.13 and r = .51; p=.ll, respectively). Therefore, even with very limited access to the BWS treadmill, much of the improvement in treadmill walking ability and satisfaction with life following long-term BWSTT in individuals with incomplete SCI can be retained for at least 8 months. Continued exercise participation, however, may contribute to maintain or further improve aspects of HRQL in this population. / Thesis / Master of Science (MS)

Body weight supported treadmill training (BWSTT) is being promoted as an effective means of restoring ambulatory abilities among individuals with incomplete spinal cord injuries. The emphasis of this thesis is on the description of the metabolic demands and the EMG profiles of able-bodied persons and individuals with a spinal cord injury (SCI) while walking under the identical conditions on a body weight support (BWS) treadmill. The secondary purpose was to contrast the metabolic and muscular responses between the two groups. Two separate chapters describing the metabolic demands and EMG profiles respectively follow the review of the literature. The metabolic results indicate that raising the speed and/or decreasing the amount of BWS increase the intensity of BWS treadmill walking, with speed having a more profound effect. The SCI group was less efficient and they had greater metabolic rates of oxygen consumption than the controls for all conditions examined. This led to the conclusion that walking on the treadmill, for the SCI group can provide an effective aerobic exercise stimulus. The EMG profiles suggest that speed and BWS affect the phasic characteristics of the muscular activity while walking for both groups. Furthermore, abnormalities, omissions and inappropriate levels of activity were observed in the SCI group when compared to the controls. These irregularities suggest that the SCI participants have adopted altered motor strategies while walking, relative to the control group. Nonetheless, the SCI participants showed evidence of appropriate modulations in their EMG activity to meet the demands of the task as they changed from one condition to the next. / Thesis / Master of Science (MSc)

Patients with severe heart failure (HF) are often excluded from exercise training studies due to their potentially unstable nature and severe exercise intolerance. Steady state cycling and walking have been the most common interventions and it is unknown whether these training modalities are appropriate and safe for patients with severe HF as they can produce significant cardiovascular stress. Body-weight supported treadmill (BWST) training may be beneficial in patients with severe HF by improving the periphery while minimizing cardiac loading. The purpose of this study was to: 1) assess the safety and feasibility of BWST training in severe HF patients and 2) to evaluate the effect of BWST training on functional capacity, health-related quality of life (HRQL ), cardiopulmonary function, and blood vessel function. Three male patients with severe HF participated in the study. On study entry and at the end of 24 sessions of physician supervised BWST training, patients completed a cardiopulmonary exercise test, two HRQL questionnaires, a 6-Minute Walk Test (6-MWT), and a Doppler ultrasound study. Although there were no study-related adverse events, only one subject (Patient 1) was able to complete post-testing. However, all three patients seemed to demonstrate a general trend towards increased exercise tolerance. By the seventeenth exercise session, the BWS was reduced to zero for Patient 1. In addition, Patient 1 achieved an average walking speed of2.0 km/hr and was completing 34 minutes ofwalking with minimal rest periods by the end of the training program. Patients 2 and 3 also responded to the training as evidenced by a slight increase in exercise duration. However due to fluctuations in their health status, they did not have any substantial improvement. Patient 1 experienced substantial increases in functional capacity: a 64% increase in V02 peak (7.2 to 11.7 ml/kg/min); a 33% increase in peak power output (300 to 400 kpm/min); a 37% increase in VE peak (28 to 39 L/min); and a 28% increase in 6-MWT distance (223. 5 to 286m). In addition, Patient 1 's NYHA-FC improved after training from class III to II. A significant training effect was also evident by reductions in HR at rest (96 to 79 bpm) and during submaximal exercise (100 kpm/min) (105 to 84 bpm). HRQL also tended to improve for Patient 1. Based on these findings and observations, two conclusions can be made. First, patients with severe HF can safely participate in BWST training and may derive considerable benefits. Second, the feasibility of training patients with severe HF is highly dependent on their cardiac condition and other co-morbidities remaining stable enough to allow consistent training. / Thesis / Master of Science (MS)