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- Heintz, Sofia, 1972-
(författare)
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Muscular forces from static optimization
- 2006
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- At every joint there is a redundant set of muscle activated during movement or loading of the system. Optimization techniques are needed to evaluate individual forces in every muscle. The objective in this thesis was to use static optimization techniques to calculate individual muscle forces in the human extremities. A cost function based on a performance criterion of the involved muscular forces was set to be minimized together with constraints on the muscle forces, restraining negative and excessive values. Load-sharing, load capacity and optimal forces of a system can be evaluated, based on a description of the muscle architectural properties, such as moment arm, physiological cross-sectional area, and peak isometric force. The upper and lower extremities were modelled in two separate studies. The upper extremity was modelled as a two link-segment with fixed configurations. Load-sharing properties in a simplified model were analyzed. In a more complex model of the elbow and shoulder joint system of muscular forces, the overall total loading capacity was evaluated. A lower limb model was then used and optimal forces during gait were evaluated. Gait analysis was performed with simultaneous electromyography (EMG). Gait kinematics and kinetics were used in the static optimization to evaluate of optimal individual muscle forces. EMG recordings measure muscle activation. The raw EMG data was processed and a linear envelope of the signal was used to view the activation profile. A method described as the EMG-to-force method which scales and transforms subject specific EMG data is used to compare the evaluated optimal forces. Reasonably good correlation between calculated muscle forces from static optimization and EMG profiles was shown. Also, the possibility to view load-sharing properties of a musculoskeletal system demonstrate a promising complement to traditional motion analysis techniques. However, validation of the accurate muscular forces are needed but not possible. Future work is focused on adding more accurate settings in the muscle architectural properties such as moment arms and physiological cross-sectional areas. Further perspectives with this mathematic modelling technique include analyzing pathological movement, such as cerebral palsy and rheumatoid arthritis where muscular weakness, pain and joint deformities are common. In these, better understanding of muscular action and function are needed for better treatment.
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| 2. |
- Liljedahl, Johanna
(författare)
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Towards evidence-based classification in para-cycling
- 2022
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The aim of classification in Paralympic sport is to minimize the impact of impairment on the outcome of competition. The aim of this thesis was to investigate the impact of different types of impairments on para-cycling performance to develop an evidence-based classification system in the para-cycling C (bicycling) and T (tricycling) divisions.This thesis is based on four articles. The first article examined differences in race performance between para-cycling classes by comparing track race results. The second article evaluated leg strength measures in para-cyclists with musculoskeletal impairments. The third article investigated leg coordination and leg strength and the association with para-cycling performance in para-cyclists with hypertonia, ataxia, or athetosis. The fourth article aimed to gather consensus on para-cycling classification issues and to identify research priorities within para-cycling, by consulting a panel with expertise within para-cycling and para-sport.This thesis has identified performance characteristics in para-cyclists with musculoskeletal and coordination impairments, and suggested tests with potential to be used in para-cycling classification to assess muscle strength and coordination. The results indicate that the classes for athletes with the least impairments, as well as the classes for athletes with impaired coordination, need to be further investigated.
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| 3. |
- Rosén, Johanna
(författare)
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Performance determinants and classification in paracanoe
- 2021
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Valid classification systems are vital for Paralympic sports in order to minimise the impact of impairment on sports performance. To achieve valid classification, each Paralympic sport must develop evidence-based classification systems by examining the impact of impairment on key performance determinants. The aim of this thesis was to examine the impact of impairment on key performance determinants in para va’a and para kayak. Additional aims were to examine the reliability of the para va’a classification system and the validity of the para kayak classification system.In studies I and III, three-dimensional (3D) kinematic data from the arms, trunk and legs as well as force from the paddle was collected. Ten non-impaired va’a and 44 para va’a athletes participated in study I and 10 non-impaired kayak and 41 para kayak athletes participated in study III. In study II, three international classifier teams, each comprised of a medical and technical classifier, classified 12 para va’a athletes using the new trunk, leg and on-water classification test batteries and class allocation for para va’a. In study IV, 3D kinematics of the trunk, legs and paddle as well as forces at the footrest, seat and paddle were measured in 17 para kayak athletes with above knee (AK) (n=11) or below knee (BK) (n=6) amputation.The main findings were:If para va'a athletes have full trunk function, the level of leg impairment does not affect the performance in terms of paddling force (Study I).The inter-rater reliability of the evidence-based classification system for para va’a was excellent with no discrepancies between the classifier teams in class allocation and minor discrepancies in individual tests (Study II).The differences between the three para kayak classes were in line with the definition of the classes in the new evidence-based classification system for para kayak. In addition, no significant correlations were seen between power output and joint variables in trunk or legs for two of the three classes indicating that these classes are valid (Study III).Differences between athletes with AK and BK amputation were seen for variables concerning the hip joint. No differences were however seen between the groups in paddle performance variables (Study IV).In conclusion, this thesis has described how athletes with different impairment differ in key performance determinants for para va’a and para kayak. The results of the thesis also gave indications that the new evidence-based classification system for para va’a is reliable and that the new evidence-based classification system for para kayak is valid in regard to two of the three classes.
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