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- Truong, Minh, 1994-
(author)
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Quantifying Gait Characteristics and Neurological Effects in people with Spinal Cord Injury using Data-Driven Techniques
- 2024
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Licentiate thesis (other academic/artistic)abstract
- Spinal cord injury, whether traumatic or nontraumatic, can partially or completely damage sensorimotor pathways between the brain and the body, leading to heterogeneous gait abnormalities. Mobility impairments also depend on other factors such as age, weight, time since injury, pain, and walking aids used. The ASIA Impairment Scale is recommended to classify injury severity, but is not designed to characterize individual ambulatory capacity. Other standardized tests based on subjective or timing/distance assessments also have only limited ability to determine an individual's capacity. Data-driven techniques have demonstrated effectiveness in analysing complexity in many domains and may provide additional perspectives on the complexity of gait performance in persons with spinal cord injury. The studies in this thesis aimed to address the complexity of gait and functional abilities after spinal cord injury using data-driven approaches.The aim of the first manuscript was to characterize the heterogeneous gait patterns in persons with incomplete spinal cord injury. Dissimilarities among gait patterns in the study population were quantified with multivariate dynamic time warping. Gait patterns were classified into six distinct clusters using hierarchical agglomerative clustering. Through random forest classifiers with explainable AI, peak ankle plantarflexion during swing was identified as the feature that most often distinguished most clusters from the controls. By combining clinical evaluation with the proposed methods, it was possible to provide comprehensive analyses of the six gait clusters. The aim of the second manuscript was to quantify sensorimotor effects on walking performance in persons with spinal cord injury. The relationships between 11 input features and 2 walking outcome measures - distance walked in 6 minutes and net energy cost of transport - were captured using 2 Gaussian process regression models. Explainable AI revealed the importance of muscle strength on both outcome measures. Use of walking aids also influenced distance walked, and cardiovascular capacity influenced energy cost. Analyses for each person also gave useful insights into individual performance. The findings from these studies demonstrate the large potential of advanced machine learning and explainable AI to address the complexity of gait function in persons with spinal cord injury.
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| 2. |
- Sjöberg, Maria
(author)
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Biomechanical analyses of flywheel resistance exercise : From a space- and ground-based perspective
- 2020
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Doctoral thesis (other academic/artistic)abstract
- Astronauts suffer degradation of postural muscles and weight-bearing bones during long-duration spaceflight. Resistance exercise is used as a primary countermeasure against these degradations. However, it has proven difficult to predict appropriate exercise loads, and the countermeasure regimens in current use are not fully preventing bone and muscle loss. It is likely that gravity-independent exercise devices, based on flywheel inertial resistance, will be implemented in future musculoskeletal countermeasure regimens.In this thesis, biomechanical analyses of external and internal exercise loads during flywheel leg resistance exercises, were performed through experimental data collection and musculoskeletal modelling. The thesis is based on four separate studies with the collective aim to provide knowledge that can be implemented when designing flywheel-based strength-training regimens to be used both in terrestrial settings and as countermeasures against musculoskeletal deconditioning in weightlessness.The first study analyzed computed joint kinematics and kinetics, and relative muscle forces in the lower limb during maximal effort flywheel leg press (FWLP) and flywheel squat (FWS) exercises. Results showed that total exercise load was slightly higher during FWS than FWLP, whereas relative muscle force did not differ between the two exercises, suggesting that they may have similar strength training effects.The second study investigated the effect of gravity on internal joint load distribution during leg resistance exercise. This was done in two steps: 1) by comparing joint kinetics during FWLP and FWS at a given submaximal exercise load (80% of the isometric maximum load in FWLP), and 2) by simulating both FWLP and FWS in zero gravity and studying changes in joint loads. The first step revealed greater hip extension moment and lumbar joint-contact forces in FWLP than in FWS, indicating a notable effect of the direction of motion relative to the gravity vector, on body load distribution. Step two showed similar, or lower, joint loads in FWLP when gravity was removed, whereas in FWS, removal of gravity resulted in increased hip extension moment and lumbar force. Collectively, the results suggest that FWLP is a better ground-based analogue than FWS for leg-resistance exercise in space.The third study examined the accuracy of a pressure insole system regarding measurements of centre of pressure and ground reaction force during resistance exercises. The results showed that insoles are capable of accurately measuring centre of pressure at loads higher than 250 N and that force measurements are accurate in exercises involving mainly vertical ground reaction forces, but appears to overestimate ground reaction force for exercises involving greater portions of shear force.The fourth study analyzed low-back loads during FWLP, FWS and barbell back squat. Lumbar compression forces were high and similar in the three exercises, suggesting that the flywheel exercises are capable of stimulating vertebral bone regeneration without inflicting risk of vertebral fractures. Muscle engagement in the investigated back extensors were lower in FWLP than in the other two exercises, although presumed high enough to counteract space-induced atrophy if implemented in countermeasure training regimens.
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