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1
Koirala, Binu. "THE RELATIONSHIP BETWEEN EDUCATIONAL ATTAINMENT AND REASONS FOR LABOR FORCE PARTICIPATION AMONG ADULTS AGED 45 TO 74 YEARS." Miami University / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=miami1470402305.
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Aillon, Gomez Tania Leda. "L' évolution du travail au cours de la restructuration productive : l'enjeu entre efficacité productive et contrôle au sein de l’automatisation croissante : Deux études de cas dans l’industrie pétrolière en Bolivie." Paris 10, 2011. http://www.theses.fr/2011PA100057.
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Le cadre général où s’inscrit cette thèse est celui de la restructuration productive qui a introduit l’innovation technologique et de nouvelles formes de gestion et de mobilisation de la force de travail dans le cadre d’un nouveau rapport de force entre capital et travail à partir de la crise structurelle des années soixante dix. Plus précisément, le sujet de la recherche est celui de la tension entre efficacité productive et contrôle hiérarchique dans le cadre d’une automatisation croissante. Pour bien saisir cette tension, nous avons étudié avec une méthodologie ethnographique, l’organisation et les stratégies de mobilisation et de contrôle de la force de travail de deux entreprises pétroliers en Bolivie. Sur la base des résultats de notre recherche, nous avons trouvé que la tendance de la division technique du travail a suivi un processus contradictoire qui illustre la tension entre les exigences de l’efficacité technique dans les automatismes, tel que l’intégration du travail et les rapports de dominations et de hiérarchie qui sont essentiels au sein de l’entreprise capitaliste. Le processus contradictoire, qui d’un coté incite à l’intégration du travail, et d’un autre coté met en œuvre des contraintes à l’intégration. Par conséquent, si on introduit une approche d’ensemble du processus et, dans un même sens, on considère non seulement, la forme mais le contenu des rapports sociaux de production ; on trouve l’aspect inégal et contradictoire d’un processus qui, à la fois, cherche l’exploitation et la subordination de la force de travail et ouvre des espaces à de nouvelles sources de productivité à partir de l’implication des ouvriersThe general context, in which this thesis is located, is the situation of the productive restructuring that has introduced innovative technology and new forms of management and mobilization of the workforce as part of a new balance of power between capital and labour from the structural crisis of seventies. Specifically, the research subject is the tension between efficiency and hierarchical control through increasing automation. To understand this tension we have studied with ethnographic methodology, organization and ways of controlling the labour force of two companies working oil in Bolivia. Based on the results of our research, we found that the trend of the technical division of labour has taken a contradictory process that illustrates the tension between the demands of technical efficiency in automation, such as the integration of work and relations of domination and hierarchy that are essential within the capitalist enterprise. The process, one side encourages the integration of work and elsewhere implements constraints to integration. Consequently, if we introduce a comprehensive approach to the process and, in the same direction, we consider not only the form but the content of social relations of production, abut and adversarial process that while looking for the exploitation and subordination of the labour force, opens spaces for new sources of productivity from the involvement of workers
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Daastøl, Arno M. [Verfasser], Helge [Akademischer Betreuer] Peukert, and Jürgen [Akademischer Betreuer] Backhaus. "Friedrich List’s Heart, Wit and Will : Mental Capital as the Productive Force of Progress / Arno M. Daastøl. Betreuer: Helge Peukert ; Jürgen Backhaus." Erfurt : Universitätsbibliothek Erfurt, 2014. http://d-nb.info/1052020461/34.
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Daastøl, Arno Mong [Verfasser], Helge [Akademischer Betreuer] Peukert, and Jürgen G. [Akademischer Betreuer] Backhaus. "Friedrich List’s Heart, Wit and Will : Mental Capital as the Productive Force of Progress / Arno M. Daastøl. Betreuer: Helge Peukert ; Jürgen Backhaus." Erfurt : Universitätsbibliothek Erfurt, 2014. http://nbn-resolving.de/urn:nbn:de:gbv:547-201300317.
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Daastøl, Arno Mong [Verfasser], Helge [Akademischer Betreuer] Peukert, and Jürgen [Akademischer Betreuer] Backhaus. "Friedrich List’s Heart, Wit and Will : Mental Capital as the Productive Force of Progress / Arno M. Daastøl. Betreuer: Helge Peukert ; Jürgen Backhaus." Erfurt : Universitätsbibliothek Erfurt, 2014. http://d-nb.info/1052020461/34.
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Čejka, Libor. "Produktivní obrábění titanových slitin." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2013. http://www.nusl.cz/ntk/nusl-230589.
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The aim of the thesis is to analyze the production costs and optimize cutting conditions for high-feed face milling of titanium alloy Ti6Al4V. In the experiment were changed cutting conditions, such as cutting speed vc and feed speed vf. During the experiment were checked cutting forces by dynamometr. Furthermore, surface roughness and tool wear is observed.
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Yaman, Ibrahim. "Effects Of Instructions Based On Cognitive Bridging And Cognitive Conflict On 9th Grade Students." Phd thesis, METU, 2013. http://etd.lib.metu.edu.tr/upload/12615734/index.pdf.
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The aim of this study is to compare the effects of the instructions based on cognitive bridging and cognitive conflict approaches and gender on 9th grade students&lsquoconceptual understanding of force and motion, self-efficacy, and epistemological beliefs. The study was conducted with a sample of 206 students in two different schools. The instructional method (traditional, cognitive conflict, and cognitive bridging) and students&lsquo
gender were used as independent variables in a 3x2 factorial design. Within this design, three treatment groups were constructed, one was control group with no researcher intervention and the other two were used as experimental groups. In one of the experimental groups, students received cognitive bridging instruction and students in the other group received cognitive conflict instruction. Pretests and posttests were administered to assess students&lsquo
conceptual understanding of force and motion, self-efficacy, and epistemological beliefs. Multivariate Analysis of Covariance (MANCOVA) was used to explore the main effects of teaching methods and gender, and possible interactions between them. The results showed that teaching method had a significant effect on students&lsquo
conceptual understanding of force and motion in favor of experimental groups. Nevertheless, no significant difference was detected between the effects of cognitive conflict and cognitive bridging. There was no significant difference between male and female students either on the dependent variables of conceptual understandings of force and motion, self-efficacy, and epistemological beliefs. Finally, the present study couldn&lsquo
t capture any significant interaction between teaching method and gender on the combined dependent variables.
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Tremblay, Stéphanie. "Force field adaptation in speech production." Thesis, McGill University, 2006. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=103014.
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Although audition may appear to be the dominant sensory modality in speech production, the capacity for intelligible speech following severe hearing loss suggests that other sensory information - for example, somatosensory feedback - may also contribute to the achievement of speech targets. The aim of this thesis is to explore the role of somatosensory feedback in speech produced by healthy adults.The first study aimed at providing a test of whether somatosensory feedback plays a role in speech production beyond the language acquisition period in early childhood. In order to achieve this goal, we designed a pattern of forces that affects jaw movements during speech production, but at the same time has no measurable acoustic effect. We found that subjects compensated for such a distortion in speech movement trajectories, even though it had no impact on the sounds. In contrast, no adaptation was observed in matched non-speech jaw movements, indicating that this was not an inevitable consequence of exposing the orofacial apparatus to this pattern of forces. This is the first demonstration that somatosensory information on its own drives the achievement of articulator positions in speech.
In study one, it was observed that subjects only adapted to the loads in the opening phase of the jaw movement. In order to elucidate this somewhat unexpected finding, we carried out experiments in which we manipulated the linguistic content of the training utterance. We found that subjects compensated for the perturbations only in portions of the movement that contained a vowel-to-vowel transition. It was suggested that the required kinematic precision during a transition between two vocal tract shapes associated with vowels is higher than during transitions between a consonant and a vowel. It also points to the speech-like nature of the observed adaptation.
The third study aimed at investigating the extent to which speech motor learning generalizes across acoustic contexts. We trained subjects to produce utterances while exposed to a velocity dependent force field. After learning, the subjects were tested with new utterances, matched on dynamics to the ones used in training. Note that even if the acoustic contents of the test and the training utterances were different, the loads had a similar effect on both speech movements. We showed that learning did not transfer to the test utterances; therefore adaptation was restricted to the specific training context. These results point to the specificity of speech motor learning.
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Heaton, Richard Charles. "Factors affecting the uterine force production." Thesis, University of Liverpool, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.283042.
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Lycke, Liselott. "Implementing total productive maintenance : driving forces and obstacles." Licentiate thesis, Luleå tekniska universitet, 2000. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-18583.
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The global marketplace is highly competitive and organisations who want to survive long-term, have to continuously improve, change and adapt in response to market demands. Improvements in a company's performance should focus on cost cutting, increasing productivity levels, quality and guaranteeing deliveries in order to satisfy customers. Total Productive Maintenance (TPM) is one method, which can be used to achieve these goals. TPM is an approach to equipment management that involves employees from both production and maintenance departments. Its purpose is to eliminate major production losses by introducing a program of continuous and systematic improvements to production equipment. TPM should be developed and expanded to embrace the whole organisation and all employees should be involved in the process as members of improvement teams. This thesis describes the development of TPM and the TPM implementation process. Research is focused on the implementation process of TPM. The author has had the opportunity of both monitoring and steering a company through part of its TPM implementation program and has conducted a longitudinal study. The implementation process takes several years and this thesis focuses on the initial three years of the process. This study demonstrates that driving forces, obstacles and difficulties often are dependent on the organisation, its managers and the individual employees. It also shows that the TPM implementation process has many similarities to the implementation of other improvement concepts. The analysis of these findings forms the basis for recommendations and guidance for organisations, who intend to implement TPM.Godkänd; 2000; 20070318 (ysko)
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Kokotilo, Kristen J. "Reorganization of brain function during force production after stroke." Thesis, University of British Columbia, 2008. http://hdl.handle.net/2429/2723.
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Damage to motor areas of the brain, caused by stroke, can produce devastating motor deficits, including aberrant control of force. After stroke, reorganization of the brain’s motor system has been identified as one of the fundamental mechanisms involved in recovery of motor control after stroke. Yet, few studies have investigated how force production and modulation are encoded in the brain after stroke and how this relates to motor outcome. Thus, the purpose of this study was to (1) understand how past neuroimaging literature has contributed to establishing common patterns of brain reorganization during both relative and absolute force production after stroke, (2) examine how brain function is reorganized during force production and modulation in individuals with stroke, and (3) relate this task-related reorganization of brain function to the amount of paretic arm use after stroke. In the second chapter, we systematically reviewed all relevant literature examining brain activation during force production after stroke. The following chapters (chapters 3 and 4) applied functional magnetic resonance imaging (fMRI) to examine the neural correlates of force production and modulation after stroke. Chapter 2 supports differences in task-related brain activation dependent on features of stroke, such as severity and chronicity, as well as influence of rehabilitation. In addition, results suggest that activation of common motor areas of the brain during force production can be identified in relation to functional outcome after stroke. Results from the subsequent two chapters (3 and 4), demonstrate that brain function reorganizes in terms of absolute, and not relative force production after stroke. Specifically, stroke participants exhibit greater activation of motor areas than healthy controls when matched for absolute force production. Moreover, there is a relationship between paretic arm usage and brain activation, where stroke participants having less paretic arm use, as measured using wrist accelerometers, exhibit higher brain activation. Results of this thesis suggest that during absolute force production, brain activation may approach near maximal levels in stroke participants at lower forces than healthy controls. Furthermore, this effect may be amplified even further in subjects with less paretic arm usage, as increased activation in motor areas occurs in participants with less arm use after stroke. Ultimately, the results from this thesis will contribute to research relevant to brain reorganization in individuals with stroke and may lead to the development of new, beneficial therapeutic interventions that optimize brain reorganization and improve functional recovery after stroke.
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Bailey, Christopher A. "Force Production Symmetry During Static, Isometric, and Dynamic Tasks." Digital Commons @ East Tennessee State University, 2014. https://dc.etsu.edu/etd/2388.
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The purpose of this dissertation was to examine the existence of force production and strength symmetry while concentrating on its role with performance. Specifically, in this dissertation I sought to determine if differences in symmetry exist between male and female athletes as well as between athletes of different strength levels. Various symmetry assessments were used and the amount of carryover between tests was also evaluated. Furthermore, the relationship between asymmetry magnitude and various aspects of jump performance was also assessed.
The results showed that female athletes were more asymmetrical than their male counterparts for most assessments. Interestingly, weaker athletes regardless of gender were more asymmetrical than stronger athletes for all assessments. Symmetry characteristics appeared to carryover between all tests and conditions with the exception of the bilateral strength assessment. When separated by strength level, good carryover of explosive strength symmetry characteristics was noted. A trend of negative relationships was noted between jump performance and kinetic asymmetry, measured during jumps and weight distribution. Isometric mid-thigh pull force production asymmetry did not relate to jump performance as it had previously. Kinetic asymmetry was shown to influence the direction of center of mass displacement (COMd). Specifically, asymmetrical rate of force development showed the most ability to differentiate between values of COMd in the mediolateral direction.
The finding that female athletes are more likely to produce force asymmetrically may indicate that they are more susceptible to the performance detriments that accompany force production asymmetry. This may also indicate that female athletes are more susceptible to injury if force asymmetry is an injury predictor. However, differences in asymmetry magnitude between the sexes may be due to differences in strength level between the sexes in the current study, as weaker athletes were shown to be more asymmetrical than their stronger counterparts. Thus, it may be inadequate strength level that is a risk factor to performance detriments and possible injury. It also appears that force production asymmetry can both alter and hinder optimal jump performance. In order to optimize performance and possibly reduce injury risk, it is recommended that weaker athletes focus on bilateral strengthening exercises.
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Kollimada, Aiyappa Somanna. "Study of the factors regulating traction force production by cells." Thesis, Université Grenoble Alpes, 2020. http://www.theses.fr/2020GRALY050.
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La production de forces mécaniques est impliquée dans de nombreux processus physiologiques incluant la morphogénèse, la migration, la division ou encore la différentiation. Tous ces évènements requièrent une régulation précise de la magnitude des forces et de leur distribution spatiale à l’échelle de la cellule et du tissu. Bien que la production de ces forces au niveau moléculaire repose sur l’interaction complexe d’un petit nombre de protéines bien identifiées, la régulation de ces forces aussi bien que leur mécanisme de transmission à l’échelle de la cellule entière demeure encore mal compris. D’autre part, prédire la magnitude des forces exercées par les cellules sur leur matrice extracellulaire ou leur variation s’avère impossible, en particulier à cause de la difficulté à caractériser précisément comment la composition des réseaux intracellulaires d’acto-myosine et celle des adhésions est reliée de manière individuelle ou combinée, à ces dernières. Dans ce contexte, l’objectif de ma thèse a été d’investiguer comment des paramètres biologiques clés sont impliqués précisément dans les processus de génération des forces et leur régulation.La première partie de mon étude s’est portée sur l’effet de la progression dans le cycle cellulaire sur l’hétérogénéité des forces développées par les cellules. J’y ai ainsi démontré que le statut des cellules dans le cycle cellulaire, bien qu’ayant un impact majeur sur la magnitude des forces exercées par les cellules, n’impactait pas la variation des forces intercellulaires. J’ai par la suite examiné la possibilité qu’une partie des efforts contractiles internes/sub-cellulaires soit dissipée au lieu d’être transmise aux ancrages cellulaires en étudiant l’interconnexion entre la dynamique de l’actine et les forces de traction. L’analyse du renouvellement dynamique de l’actine dans les fibres de stress a ainsi montré que bien que le turnover de l’actine variait en relation avec les modulations de forces, ces variations n’étaient pas suffisamment significatives pour expliquer l’hétérogénéité des forces mesurées entre les cellules. Pour finir, j’ai conduit une étude dédiée à la caractérisation de la composition biochimique du réseau d’actine et des adhésions en relation avec la force exercée et transmise par les cellules. Pour se faire, j’ai tout d’abord implémenté la technique classique de TFM en y incorporant une étape intermédiaire d’immunomarquage afin de pouvoir suivre simultanément les forces exercées par les cellules ainsi que leur composition biochimique. Cet essai a ensuite été appliqué à la caractérisation du lien entre le contenu intracellulaire de plusieurs protéines du cytosquelette d’actomyosine et des adhésions, seules ou combinées entre elles, avec la force. Ces travaux ont tout d’abord démontré que le contenu en vinculine, mesuré à l’échelle de la cellule entière, et l’aire des adhésions, constituaient de bons prédicteurs des forces cellulaires. J’ai par ailleurs pu montrer que l’actine et la myosine exhibaient quant à elles des déviations plus larges dans leur relation linéaire avec l’énergie mécanique des cellules, et représentaient ainsi des prédicteurs moins directs des forces. Au contraire, les données obtenues suggèrent que c’est leur composition relative dans la cellule qui détermine la magnitude des forces exercées par les cellules. J’ai enfin pu mettre en évidence que la quantité d’alpha-actinine cellulaire seule ne corrélait pas du tout avec les forces, mais que sa quantité relative par rapport à l’actine jouait un rôle clé pour réguler la production des forces.En conclusion, ces résultats ont permis d’identifier la composition biochimique des adhésions, ainsi que le contenu relatif des moteurs moléculaires et crosslinkers par rapport à l’actine comme des paramètres essentiels de la régulation de la production des forcesMechanical forces are involved in many physiological processes including morphogenesis, migration, division and differentiation. All these events involve a tight regulation of both the magnitude and spatial distribution of the contractile forces at the cell and tissue-level. Although we know that at the molecular level, the regulation of force production and transmission relies on the complex interplay between a well-conserved set of proteins of the cytoskeleton, we still do not have a comprehensive understanding of the mechanisms supporting force generation at the entire cell level. In addition, the magnitude of the traction forces exerted by cells on their underlying extracellular matrix in culture and as such the cell to cell variation of theses forces remain difficult to predict, largely because of the difficulty to characterize precisely how molecular components forming the actomyosin and adhesion networks, individually or via their specific interplay, are related to the force magnitude exerted by these cells. In this context, the aim of my PhD project was to investigate how key biological parameters are precisely related to force generation and regulation process.The first part of my study thereby focused on looking into the effect of the progression of the cell cycle on cell to cell heterogeneity in traction forces. I demonstrated that although the cell cycle status of the cells had a major impact on the magnitude of forces exerted by cells, it was not impacting the overall cell to cell variability in the traction force exerted. I also examined next the possibility that some internal/subcellular contractile efforts could be dissipated instead of being transmitted to cell anchorages by looking at the interplay between actin dynamics and traction forces. The analysis of actin turnover in stress fibers showed that although variations in strain energies were associated to variations in actin dynamics, they were not significant enough to explain the large cell to cell heterogeneities measured in traction force. Finally, I conducted a study dedicated to the characterization of the biochemical composition of the actomyosin network and adhesion pattern of cells in relationship with the force generated and transmitted by cells. To that end, I implemented the standard TFM assay in order to introduce an intermediate labeling step allowing for simultaneous measurement of traction forces and intracellular protein contents. This assay was then used to characterize the content of molecules of the actomyosin cytoskeleton and of the adhesions, either alone or in combination, and force. This work first demonstrated that the vinculin content measured at the level of the entire cell and the area of the focal adhesions, represented good predictors of force. I then showed that actin and myosin displayed broader deviations in their linear relationship to the strain energies, and thus appeared as less reliable predictors of force. Instead, my data suggested that their relative cellular amount plays a key role in setting the magnitude of force exerted by cells. I finally demonstrated that although the alpha-actinin content was not correlated at all with force magnitude, the relative amount of alpha-actinin as compared to actin content was of key importance to regulate force production.In conclusion, these results identified the biochemical contant of focal adhesion and the relative amounts of molecular motors and crosslinkers per actin as key parameters involved in setting the magnitude of force exerted by cells and thereby shed new light on the mechanisms supporting force generation at the entire cell level
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Comfort, Paul, Thomas Dos'Santos, Paul A. Jones, John J. McMahon, Timothy J. Suchomel, Caleb D. Bazyler, and Michael H. Stone. "Normalisation of Early Isometric Force Production as a Percentage of Peak Force, During Multi-Joint Isometric Assessment." Digital Commons @ East Tennessee State University, 2019. https://dc.etsu.edu/etsu-works/5787.
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Purpose: To determine the reliability of early force production (50, 100, 150, 200, and 250 ms) relative to peak force (PF) during an isometric mid-thigh pull and to assess the relationships between these variables. Methods:: Male collegiate athletes (N = 29; age 21.1 [2.9] y, height 1.71 [0.07] m, body mass 71.3 [13.6] kg) performed isometric mid-thigh pulls during 2 separate testing sessions. Net PF and net force produced at each epoch were calculated. Within- and between-session reliabilities were determined using intraclass correlation coefficients and coefficient of variation percentages. In addition, Pearson correlation coefficients and coefficient of determination were calculated to examine the relationships between PF and time-specific force production. Results:: Net PF and time-specific force demonstrated very high to almost perfect reliability both within and between sessions (intraclass correlation coefficients .82–.97; coefficient of variation percentages 0.35%–1.23%). Similarly, time-specific force expressed as a percentage of PF demonstrated very high to almost perfect reliability both within and between sessions (intraclass correlation coefficients .76–.86; coefficient of variation percentages 0.32%–2.51%). Strong to nearly perfect relationships (r = .615–.881) exist between net PF and time-specific net force, with relationships improving over longer epochs. Conclusion:: Based on the smallest detectable difference, a change in force at 50 milliseconds expressed relative to PF > 10% and early force production (100, 150, 200, and 250 ms) expressed relative to PF of >2% should be considered meaningful. Expressing early force production as a percentage of PF is reliable and may provide greater insight into the adaptations to the previous training phase than PF alone.
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Mansouri, Yassine. "La localisation des activités productives : les tensions entre forces centrifuges et forces centripètes." Phd thesis, Université du Sud Toulon Var, 2008. http://tel.archives-ouvertes.fr/tel-00326119.
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Nous nous interrogeons, dans le cadre de la NEG, sur la validité empirique d'un certain nombre de grands facteurs explicatifs de la répartition spatiale des activités (le coût du travail local, les coûts de la concurrence, localisation de la demande finale, le coût de transport etc). Nos résultats, trouvés à l'aide de différentes simulations dans un contexte de processus d'intégration régionale au sein des PVD, suggèrent que les firmes semblent réaliser un arbitrage entre s'agglomérer pour bénéficier de rendements croissants dus à l'effet taille du marché et se disperser pour bénéficier des coûts du travail plus faibles. Nous modélisons, en particulier, l'avantage des régions côtières par rapport aux régions intérieures dans le commerce avec le reste du monde. Ce constat est particulièrement vrai dans le bassin méditerranéen qui est caractérisé par une littoralisation excessive de l'activité économique et démographique. Il apparaît qu'au-delà des politiques d'ouverture internationale mises en évidence par Krugman et Elizondo (1996), la dotation régionale en terme d'infrastructures de transport a un impact certain sur le degré et l'efficacité de la concentration spatiale au sein des PVD. Le second grand enseignement de cette étude est que la tendance au redéploiement des activités des grands pôles urbains vers les zones de moindre densité se confirme avec la considération des forces centrifuges. En effet, cette extension influence directement la fonction de production des firmes et conduit à une répartition plus égale de l'activité économique entre deux régions. De ce fait, les possibilités d'équilibres de long terme sont plus larges avec la prise en compte des coûts de congestion.
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Mansouri, Yassine Gilles Philippe Boismery Hervé. "La localisation des activités productives Les tentions entre forces centrifuges et forces centripètes /." [S.l.] : [s.n.], 2008. http://tel.archives-ouvertes.fr/tel-00326119/fr.
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Fogelson, Benjamin Marc Feder. "Mechanical Models in Single-Cell Locomotion, Adhesion, and Force Production." Thesis, New York University, 2016. http://pqdtopen.proquest.com/#viewpdf?dispub=10190369.
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Here we present the results of two distinct projects in the field of cellular mechanics. In the first project, we describe a non-monotonicity in the scaling of force production in actomyosin stress fibers. We develop a continuum mechanical model to explain that non-monotonicity and, using both analytical and numerical techniques, conclude that the scaling is due to an interaction between different physical lengthscales inherent in the actomyosin force-production system. Using singular perturbation methods, we study the model further to make predictions about the physical conditions under which a cell can break symmetry. In the second project, we explore how lipid flow in the plane of the plasma membrane contributes to membrane translocation during cell migration. By numerically solving the Stokes equations, we quantify the magnitude of the force necessary to generate this flow, and analyze how the presence of transmembrane protein obstacles influences the resulting front-to-rear membrane tension gradient. We make several analytic estimates of the mechanical importance of this membrane tension for cell motility.
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Bailey, Chris A., Kimitake Sato, Ryan Alexander, Chieh-Ying Chiang, and Michael H. Stone. "Isometric Force Production Symmetry and Jumping Performance in Collegiate Athletes." Digital Commons @ East Tennessee State University, 2013. https://dc.etsu.edu/etsu-works/4617.
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Objectives: The purpose of this study was to identify the relationship between isometric force production symmetry and jumping performance in weighted and un-weighted static and countermovement jumps (SJ and CMJ). Design: Bivariate correlation between isometric force production symmetry and vertical jump performance variables. Methods: Collegiate athletes were evaluated for this study (n=36). Subjects performed SJ, CMJ, and isometric mid-thigh pulls (IMTP). Jumps were analyzed for jump height (JH) and peak power (PP). IMTP was analyzed for peak force (PF) for left and right sides, and values were calculated to produce a peak force symmetry index (PF-SI) score. Correlational statistics were performed examining the relationship between PF-SI and jump variables. Results: Moderate statistically significant negative correlations were observed between PF-SI and all jump variables, indicating that as asymmetry increases jump performance decreases. SJ correlations weakened in weighted conditions (JH r=-0.52 @ 0 kg/r=-0.39 @ 20 kg, PP r=-0.43 @ 0 kg/r=-0.34 @ 20 kg), but CMJ produced similar correlations for both conditions (JH r=-0.47 @ 0 kg/r=-0.49 @ 20 kg, PP r=-0.28 @ 0 kg/r=-0.34 @ 20 kg). Unlike the SJ, which only contains the propulsive or concentric portion of the jump, the CMJ also contains the eccentric portion and performance contributions of the stretch-shortening cycle (SSC). The addition of the SSC may play a role in the maintaining the magnitude of asymmetry in the CMJ weighted condition. Conclusions: The results indicate that force production asymmetry may be detrimental to bilateral vertical jumping performance. The findings should be considered for further investigation on sport-specific tasks.
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Kim, Junghoon. "The influence of force production and eccentric exercise on growth hormone." Virtual Press, 1997. http://liblink.bsu.edu/uhtbin/catkey/1048386.
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The main purpose of this study was to investigate the relationship between human growth hormone (hGH) and two separate components of resistance exercise. Eight non-weight-trained subjects (23.33 ± 0.3 yrs) performed three force production trials (FPT), at different concentric workloads, and an 120% eccentric exercise trial (EET) on the Cybex 6000. Blood samples (3 mls) were taken pre- and post-exercise and analyzed for lactate, creatine kinase (CK) and hGH. Electromyographic (EMG) activity of the quadriceps muscle was recorded during each trial. The mean peak torque produced during the FPTs increased as work intensity increased but was the highest in the EET. The data for total work showed a proportional relationship with the intensity of the three concentric work loads but not the 120% EET. EMG activity of vastus medialis (VM) and rectus femoris (RF) measured during EET was 26% less than RF of 50% and 15% less than VL of 70% in FPT, respectively. The highest hormonal response occurred following the 120% EET. The hormonal response following the FPTs was highest in the 90% FPT with the two lower work intensity trials (50 and 70%) showing no clear hormonal response. Although the hGH response was the highest in the 120% EET, the post-exercise lactic acid levels in EET were 24% less than that of the 90% FPT. Creatine kinase (CK) activity was significantly elevated 36 hours after the last bout of EET which suggests that the eccentric exercise resulted in muscle damage. The results from concentric trials showed that muscle force generation, EMG, and lactic acid of the three different concentric trials were well correlated to the pattern of hGH secretion. However, only peak torque was consistent with the hGH response of the EET. The highest peak torque and hGH levels were achieved with eccentric exercise. The highest levels of fatigue, as a result of the combination of longer exercise time and overloading of the muscle during EET, may explain the higher hGH output. The muscle damage caused by the eccentric trial was enough to induce delayed onset of muscle soreness and may be the stimulus for the higher hGH output. The hGH response may facilitate repair of the muscular damage induced by eccentric exercise by promoting protein synthesis.School of Physical Education
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Elliott, Kirsty. "The influence of reproductive hormones on maximum force production in females." Thesis, Liverpool John Moores University, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.247473.
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Kosterina, Natalia. "Muscular force production during non-isometric contractions : towards numerical muscle modeling /." Licentiate thesis, Stockholm : Skolan för teknikvetenskap, Kungliga Tekniska högskolan, 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-10672.
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Casanova, Antoine. "Forces productives, peuple corse et Révolution française : 1770-1815." Paris 1, 1988. http://www.theses.fr/1988PA010565.
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Notre travail se propose d'étudier les interactions complexes qui ont pu exister dans les campagnes corses entre le mouvement des forces productives (envisagées sous leur aspect matériel comme sous l'aspect des aptitudes et savoir-faire humains) et celui des structures sociales depuis les années de la conquête française jusque vers 1815. La première et la deuxième partie de l'ouvrage s'efforcent d'analyser le milieu technique insulaire et les capacités opératoires humaines dans leurs diverses composantes et leurs traits d'ensemble. Cette étude est menée dans un constant essai de réflexion comparative. Les rapports entre forces productives et mouvement des structures sociales propres à l'ile de 1770 à 1789 sont examinés dans la troisième partie. Les caractères originaux des antagonismes et enjeux qui marquent les campagnes corses de 1789 à 1815 en même temps que les modalités propres de leur articulation sur le conflit national et global entre révolution et contrerévolution sont étudiés dans la quatrième partie. C'est également ici que sont examinés les modes sous lesquels les processus des années 1789-1815 vont en partie transformer les bases sociales de la communauté ethnique corse ainsi que les références symboliques où s'exprime son identité. La conclusion générale se propose de réfléchir sur quelques problèmes théoriques que soulève l'étude ici menée de l'évolution de la Corse de 1770 à 1815.
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Walther, Mario. "Entwicklung und Evaluierung eines systematischen Vorgehens zur Erfassung von Aktionskräften in der Automobilproduktion." Doctoral thesis, Universitätsbibliothek Chemnitz, 2016. http://nbn-resolving.de/urn:nbn:de:bsz:ch1-qucosa-199247.
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Aktionskräfte stellen wesentliche Risikofaktoren für die Entstehung von Erkrankungen im Finger-, Hand- und Armbereich dar. Daher ist die Erfassung und Analyse von Aktionskräften ein wichtiger Bestandteil der ergonomischen Bewertung von Arbeitsplätzen. Zur Erfassung von Aktionskräften, insbesondere in der Automobilproduktion, existiert bisher jedoch weder eine einheitliche noch eine systematische Vorgehensweise. Es mangelt an konkreten Forschungserkenntnissen über den Messaufbau, die Messdurchführung und die Messauswertung von Kraftfällen. In der vorliegenden Arbeit wird deshalb ein erster Schritt unternommen, um die Erfassung von Aktionskräften auf Basis wissenschaftlich gestützter Erkenntnisse zu standardisieren. Hierzu werden insgesamt vier empirische Untersuchungen (zwei Vorstudien und zwei empirische Laborstudien) durchgeführt. In der ersten Studie (Kapitel 4) erfolgt eine Identifizierung der vorhandenen Arten von Kraftaufwendungen in verschiedenen Fertigungsbereichen der Automobilproduktion im Rahmen einer Dokumentenanalyse. In der zweiten Studie (Kapitel 5) wird der bedeutendste Fertigungsbereich ausgewählt, um darin eine Auszählung der Kraftaufwendungen anhand einer standardisierten Beobachtung definierter Arbeitsprozesse durchzuführen. Die dritte Untersuchung (Kapitel 6) ist als empirische Laborstudie konzipiert. Darin wird die technische Erfassung von Aktionskräften unter idealisierten Bedingungen ohne menschlichen Einfluss erprobt. In der vierten Untersuchung (Kapitel 7), ebenfalls als empirische Laborstudie konzipiert, werden spezifische Kraftaufwendungen im Labor systematisch durch Probanden nachgestellt und gemessen. Dabei wird das Vorgehen zur Durchführung und Auswertung von praxisnahen Kraftmessungen unter menschlichem Einfluss evaluiert. Die Erkenntnisse der Arbeit helfen dabei, bestehende Forschungsdefizite aufzuarbeiten und zu beheben. Sie stellen ferner eine Handlungshilfe für betriebliche Kraftanalysen sowie eine Orientierung für zukünftige Forschungsarbeiten darAction forces have been identified as risk factors. Therefore, the collection and analysis of action forces is an essential part of the ergonomic evaluation. Up to now, there was a lack of a standardized and systematic approach to evaluate action forces, especially in the automotive production. Thus, in the present thesis a methodical approach is described to evaluate action forces systematically. The thesis is divided into four studies. The first study contains the identification of the variety of action forces in the different manufacturing areas of automotive production. The second study describes the detailed analysis of action forces in the assembly shop, which is the manufacturing area with the highest count of action forces in the automotive production. The third study describes the direct measurement of action forces in laboratory conditions. The action forces are applied by a testing machine. The fourth study consists of the direct measurement of action forces, which are applied by subjects. Thereby, the methodical approach to perform direct measurements has been evaluated. The findings of the thesis can be used as a guideline, to evaluate action forces in the automotive production. Also the findings highlight the potential for further research projects
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Enebo, Brian A. "Contact force production accuracy and consistency: Generalizations to a simulated clinical task." Diss., Connect to online resource, 2006. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:3239423.
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Marley, Mathias Huuse. "Modelling and Robust Control of Production Force of a Wave Energy Converter." Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for marin teknikk, 2014. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-26357.
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Lifesaver is a point-absorber wave energy converter developed by Fred. Olsen. She is currently deployed off the coast of England for pre-commercial testing. Lifesaver consists of a toroidal floater supporting three Power-Take Off (PTO) units moored separately to the seabed. The mooring lines are kept taut by electrical generators.Large force oscillations have been encountered in the mooring lines during testing. The source of force oscillations is identified as velocity fluctuations in the PTO drive train due to sudden saturation of generator torque. The unfavorable transient response is a result of low stiffness in the mooring line combined with large inertia in the drive train. A numerical model of the mooring line and PTO unit is developed for use in control system development. The system dynamics are identified through a frequency analysis of a linearized model. Based on these findings a Kalman filter observer is developed to estimate force and force gradient from the angular velocity of the electrical generator. Three different controllers are proposed to mitigate the undesirable force oscillations. The first prevents sudden saturation by limiting the generator force gradient, and should be straight-forward to implement. Proportional-derivative (PD) feedback of the rope force is enabled by the Kalman filter, and is shown to effectively mitigate the unwanted behavior. However, PD feedback reduces the stability margin of the controller and must be implemented with care. A control algorithm using hysteresis is explored. The hysteretic controller behaves in a predictable and similar manner independent of the incoming wave, and has the potential of increasing robustness during high sea states. Real-time optimization of the main control parameter using extremum seeking is explored. The algorithm may be used to track a time-varying optimum due to changes in sea state. The adaptation rate is limited by the high peak-to-average power ratio of Lifesaver.
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Beckham, George K., Kimitake Sato, Hugo A. P. Santana, Satoshi Mizuguchi, G. Gregory Haff, and Michael H. Stone. "Effect of Body Position on Force Production During the Isometric Midthigh Pull." Digital Commons @ East Tennessee State University, 2018. https://dc.etsu.edu/etsu-works/4652.
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Various body positions have been used in the scientific literature when performing the isometric midthigh pull resulting in divergent results. We evaluated force production in the isometric midthigh pull in bent (125° knee and 125° hip angles) and upright (125° knee, 145° hip angle) positions in subjects with (>6 months) and without (<6 months) substantial experience using weightlifting derivatives. A mixed-design ANOVA was used to evaluate the effect of pull position and weightlifting experience on peak force, force at 50, 90, 200, and 250 ms. There were statistically significant main effects for weightlifting experience and pull position for all variables tested, and statistically significant interaction effects for peak force, allometrically scaled peak force, force at 200 ms, and force at 250 ms. Calculated effect sizes were small to large for all variables in subjects with weightlifting experience, and were small to moderate between positions for all variables in subjects without weightlifting experience. A central finding of the study is that the upright body position (125° knee and 145° hip) should be used given that forces generated are highest in that position. Actual joint angles during maximum effort pulling should be measured to ensure body position is close to the position intended.
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Bailey, Christopher A., Kimitake Sato, Angus Burnett, and Michael H. Stone. "Carry-Over of Force Production Symmetry in Athletes of Differing Strength Levels." Digital Commons @ East Tennessee State University, 2015. https://dc.etsu.edu/etsu-works/4634.
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Carry-over of force production symmetry in athletes of differing strength levels. J Strength Cond Res 29(11): 3188–3196, 2015—This study sought to determine the level of association between bilateral force production symmetry assessment methods (standing weight distribution [WtD], unloaded and lightly loaded jumps, and isometric strength) and to determine whether the amount of symmetry carry-over between these tasks differs for strong and weak athletes. Subjects for this study included male (n = 31) and female (n = 32) athletes from National Collegiate Athletic Association Division I sports. Athletes performed WtD, unloaded and lightly loaded (20 kg) static and countermovement jumps, and isometric midthigh pull (IMTP) assessments on 2 adjacent force plates. Ground reaction force data were used to calculate symmetry variables and performance-related variables. Using Pearson zero order correlations, evaluations of the amount of symmetry carry-over were made. Weight distribution correlated strongly with jump peak force (PF) (r = 0.628–0.664). Strong relationships were also observed between loading conditions for jump variables (r = 0.568–0.957) as were the relationships between jump types for PF, peak power, and net impulse (r = 0.506–0.834). Based on the pooled sample, there was a lack of association between IMTP and WtD for jump symmetry variables. However, when examining strong and weak groups, rate of force development showed moderate to strong symmetry carry-over in the strongest athletes (r = 0.416–0.589). Stronger athletes appear to display similar explosive strength symmetry characteristics in dynamic and isometric assessments, unlike weaker athletes. Strength seems to influence the amount of force production symmetry carry-over between bilateral assessments. There may be optimal loads and variables for symmetry assessment, but these may differ based on population characteristics.
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Bailey, Christopher A., Kimitake Sato, Angus Burnett, and Michael H. Stone. "Force-Production Asymmetry in Male and Female Athletes of Differing Strength Levels." Digital Commons @ East Tennessee State University, 2015. https://dc.etsu.edu/etsu-works/4628.
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The purpose of this investigation was to determine the existence of bilateral strength and force-production asymmetry and evaluate possible differences based on sex, as well as strength level. Asymmetry was assessed during weight-distribution (WtD) testing, unloaded and lightly loaded static- (SJ) and countermovement-jump (CMJ) testing, and isometric midthigh-pull (IMTP) strength testing. Subjects included 63 athletes (31 male, 32 female) for WtD, SJ, and CMJ tests, while 129 athletes (64 male, 65 female) participated in IMTP testing. Independent-samples t tests were used to determine possible differences in asymmetry magnitude between males and females, as well as between strong and weak athletes. Cohen d effect-size (ES) estimates were also used to estimate difference magnitudes. Statistically different asymmetry levels with moderate to strong ESs were seen between males and females in WtD, 0-kg SJ (peak force [PF]), 20-kg SJ (peak power [PP]), 0-kg CMJ (PF, PP, net impulse), and 20-kg CMJ (PF), but no statistical differences were observed in IMTP variables. Dividing the sample into strong and weak groups produced statistically significant differences with strong ES estimates in IMTP PF and rate of force development, and many ESs in jump symmetry variables increased. The results of this investigation indicate that females may be more prone to producing forces asymmetrically than males during WtD and jumping tasks. Similarly, weaker athletes displayed more asymmetry than stronger athletes. This may indicate that absolute strength may play a larger role in influencing asymmetry magnitude than sex.
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Teo, Wei Peng. "The effects of circadian rhythmicity of salivary cortisol and testosterone on maximal isometric force, maximal dynamic force production and power output." Thesis, Edith Cowan University, Research Online, Perth, Western Australia, 2009. https://ro.ecu.edu.au/theses/1872.
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The purpose of the study was to investigate the effects of circadian rhythm (CR) of salivary cortisol (C) and testosterone (T) on maximal isometric and dynamic force production (Fpeak), and power output (Ppeak). Twenty male university students (mean age= 23.8 ± 3.6, mean± standard deviation; height= 177.5 ± 6.4cm, weight= 78.9 ± 11.2kg) with at least 1 year of resistance training experience were recruited as subjects. Session one was used for the collection of subject's physical data (ie. height, weight and aural temperature [Taural). An evaluation of morningness-eveningness was also performed using the Home and Ostberg questionnaire (1976). Saliva samples were collected at 4 different times of the day (0800 hours, 1200 hours, 1600 hours, and 2000 hours) to assess C and T levels at those times. The second testing session was used as a familiarisation session for subjects and also to establish baseline strength and power measurements. Subjects performed a battery of 4 different tests for the assessment of strength and power in the following order; 3 trials of counter-movement jumps (CMJ), 3 trials of squat jumps (SJ), 3 trials of isometric mid-thigh pull (IMTP), and a 1RM squat. After the session ended, subjects were requested to sit quietly for 15 minutes to 30 minutes before a session rating of perceived exertion (RPE) score was collected based on a Borg's CR-10 RPE scale. Sessions 3 to 6 were kept identical to the familiarisation session with the exception of randomised start times. The results showed that Fpeak and peak rate of force development (RFDpeak) presented a clear CR in CMJ, IMTP, but not significant in SJ. A distinct CR in P peak and jump height (HT max) was also clearly present in CMJ, but not significant in SJ. One repetition max squat did not show any fluctuations in weight lifted with the exception of values obtained at 0800 hours. Ratings of perceived exertion collected at 0800 hours and 2000 hours were found to be higher with 1200 hours and 1600 hours being significantly (p:≤0.05) lower. Salivary T and C also showed clear CR elevated highest values at 0800 hours and lowest values at 2000 hours, however, TIC ratios did not seem to display any variations with the exception of 0800 hours being elevated. The results, however, did show a very strong correlation between Taural with Fpeak and Ppeak (r=0.86 and r=0.8, p:≤0.001). The study showed the existence of a CR in isometric Fpeak dynamic Fpeak and Ppeak in certain testing modalities. Stretch-shortening cycle component seemed to be more sensitive to a time-of-day variation. The findings do show an increase in physical performance was concomitant with an increase in body temperature, suggesting that it would be a better indicator of physical performance.
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Франів, І. А. "Розміщення продуктивних сил: теоретичний підхід." Thesis, Видавництво СумДУ, 2012. http://essuir.sumdu.edu.ua/handle/123456789/26744.
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Casanova, Antoine. "Forces productives rurales, peuple corse et Révolution française, 1770-1815." Lille 3 : ANRT, 1989. http://catalogue.bnf.fr/ark:/12148/cb37612494b.
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Planelles, Herrero Vicente José. "Bases mécanistiques et structurales de la régulation de l'activité des myosines." Thesis, Paris 6, 2017. http://www.theses.fr/2017PA066465.
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Les moteurs moléculaires sont des protéines capables de produire une force : elles transforment l'énergie chimique de l'hydrolyse de l'ATP en énergie mécanique. Cette thèse se focalise sur l'étude d'une famille de moteurs moléculaires, les myosines, qui se déplacent le long des filaments d'actine et assurent d'importantes fonctions cellulaires.La myosine VI est une myosine très particulière car elle est la seule à se déplacer vers l'extrémité négative des filaments d'actine. Elle est produite dans la cellule sous forme auto-inhibée, inactive. Dans la cellule, son activité est également régulée par plusieurs protéines interagissant avec la queue C-terminale de la myosine VI. Ces protéines, présentes à des endroits précis de la cellule, recrutent la myosine VI et dictent l'action qu'elle doit effectuer. Des analyses de SAXS, de dispersion de la lumière, de microscopie, d'interaction et de mutagénèse ont permis de mieux comprendre le mécanisme régulant l'adoption de l'état auto-inhibé, ainsi que son activation par le calcium. L'interaction avec différents partenaires a été caractérisée. GIPC1, le partenaire le plus étudié, promeut de façon indirecte la dimérisation et l'activation de la myosine VI.Pendant ma thèse, j'ai également été impliqué dans deux autres projets qui s'inscrivent dans la logique du projet de thèse et qui ont mené à la publication de quatre articles. Deux chapitres, plus brefs, sont donc dédiés à ces projets. Le deuxième chapitre porte sur la régulation de l'activité de la myosine VII par ses partenaires cellulaires. Finalement, le troisième chapitre est dédié à l'étude de la modification allostérique de l'activité des myosines par des petites moléculesMolecular motors are essential agents of force production in the cells: they convert the chemical energy released by the hydrolysis of ATP into mechanical work. This thesis focuses on myosins, a family of molecular motors responsible for actin-based motility. Myosin VI is unique among all of the myosin superfamily members in that it moves in the opposite direction of all other known myosins. Previous work revealed myosin VI tail ability to fold back, constituting a potential auto-inhibited state that prevents motor activity. Several myosin VI partners, binding to the C-terminal tail of the myosin, have been identified and shown to recruit the motor for different functions. In the first chapter of this thesis, the mechanism allowing the regulation of myosin VI activity has been studied using biochemical and biophysical analysis (SAXS, light scattering, microscopy, binding assays and mutagenesis). GIPC1, the most studied myosin VI partners, promotes myosin dimerization and activation. During my PhD, I have been also involved in two other projects, in line with my thesis project, that have led to the publication of four articles. Two shorter chapters are therefore devoted to these projects. The second chapter of my thesis explores myosin VII activity regulation by its cellular partners. Finally, the third chapter is devoted to the allosteric regulation of myosins activity by small molecules
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Birch, Cai Owain. "How does mental and physical fatigue affect a rugby player’s force production during scrummaging?" Thesis, Gymnastik- och idrottshögskolan, GIH, Institutionen för idrotts- och hälsovetenskap, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:gih:diva-4610.
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Aims: This study investigates the effects of physical fatigue, mental fatigue and their combinations on the ability of rugby players to produce force during rugby scrummaging. Method: 10 male subjects (Mean age = 27.4 ± 3.92, Weight =102.9kg ± 10.96) were recruited from local rugby union football clubs in the Stockholm area. Scrummaging force measurements were collected following and before treatments (control), after a 30-min mental task and after a physical fatigue protocol. The mean peak force was calculated by averaging the force data 1 second around the highest peak of force during a 5 second sustained push. Results: Mean force decreased significantly after the physical fatigue (PF) protocol compared to the control (CON) (PF = 1740 ± 342 N vs. CON = 2007.5 ± 359 N. P= 0.0009) and combinations of physical and mental fatigue (PMF) or mental and physical fatigue (MPF) were also found to significantly decrease compared to the control (PMF = 1750 ± 348N vs. CON = 2007.5 ± 359N. P=0.0014 and MPF = 1818 ± 335N vs. CON = 2007.5 ± 359N. P=0.026). Mental fatigue did not significantly decrease mean peak force during the sustained push of a rugby scrum (MF = 1912 ± 321N vs. CON = 2007.5 ± 359N. P=0.52). Conclusion: Physical fatigue reduces the ability of rugby players to produce force during rugby scrummaging, however mental fatigue does not. Furthermore, mental fatigue does not exacerbate the effects of physical fatigue on scrummaging performance.
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Korkmaz, Lale. "Static Force Production Analysis in a 3D Musculoskeletal Model of the Cat Hindlimb." Thesis, Georgia Institute of Technology, 2004. http://hdl.handle.net/1853/5193.
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To understand control strategies employed by the central nervous system (CNS) control movement or force generation in a limb, a seven degree of freedom cat hindlimb was modeled. In this study, the biomechanical constraints affecting force generation for balance and postural control were investigated. Due to the redundancies at the muscular and joint levels in the musculoskeletal system, even the muscle coordination pattern to statically produce a certain amount of force/torque at the ground is not straightforward.
A 3D musculoskeletal model of the cat hindlimb was created from cat cadaver measurements using Software for Interactive Musculoskeletal Systems (SIMM, Musculographics, Inc.). Six kinematic degrees of freedom and 31 individual hindlimb muscles were modeled. The moment arms of the muscles were extracted from the software model to be used in a linear transformation between muscle activation, and end effector force and moment. The Jacobian matrix that establishes the relationship between joint torques and end effector wrench was calculated. Maximal muscle forces were estimated from the literature. A feasible set of forces that can be generated at the toe was constructed using combination of maximally activated muscle excitations. Because the endpoint torque is typically small in a cat, an optimization algorithm was also performed to maximize the force generation at the end effector while constraining the magnitude of the endpoint torque. The results are compared with the measured force magnitude and direction data from an acute cat hindlimb preparation for different postures. This static model is applicable for understanding muscle coordination during postural responses to small balance perturbations.
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MacKenzie, Mary B. "The relationship between blood lactate and force production in elite cross country skiers." Thesis, University of Ottawa (Canada), 1989. http://hdl.handle.net/10393/5750.
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Krantz, Frida. "Building Information Modeling : In the production phase of civil works." Thesis, KTH, Fastigheter och byggande, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-101091.
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Building Information Modeling, abbreviated BIM, is a process of information sharing which enhances communication and which helps in visualizing complex problems in the building industry. BIM has not been used in a larger extent in the production phase of civil works. The purpose of the study is therefore to investigate driving forces behind the use of BIM and the resistors against it and to investigate in what ways BIM could be used in the production phase. The theoretical framework is based on one licentiate thesis, two degree projects, three research papers and three books. A qualitative method with semi-structured interviews was used. The interviews were made with a calculator, a supervisor and a CAD planner from Skanska, a constructor and project manager from ELU, a Project Information Officer from Tyréns and a VDC coordinator and VDC business developer from Veidekke who all have been working with BIM. This was to get a good representation from different actors and people with different professional roles. The study shows that the driving forces behind a use of BIM are that it enhances collaboration and communication between the actors, it makes it easier to visualize the project and the scope, and it provides a higher degree of accuracy of coordination’s. BIM also makes the work more effective and results in fewer errors. Above all, BIM give a possibility for a shorter production phase, shorter total project duration and a lower total cost. The study also shows that the resistors against the use of BIM are employee’s negative attitude against administrative work, that it is hard to measure profitability of using BIM, the uncertainty of who has the legal ownership of the data, and who has the responsibility of the accuracy of it. 3 That the implementation cost and the design phase are more expensive is also a resistor against a use of BIM. BIM could be used in visualization with 3D models in collision controls and co-reviews in meetings, work preparations and at site. A workplace outline could also be printed from the 3D model to be placed on the site for visualization. 4D scheduling and 4D animations could be used for visualization in meetings, work preparations and at site. The study showed that quantity takeoff and cost estimation with 5D is only reconciled in the meetings in the production phase and that the programs for it are not needed in this phase. RFID tags could be used at site for logistics and tracking materials, and field verifications could be used to verify that a work task is executed according to exact coordination’s in the 3D model. Furthermore tablet computers could be used for bringing the technique of BIM to the site which enables a better understanding of complex work tasks for the workers. A BIM coordinator who understands the process of working with BIM and who could work as a bridge between the users and the technical development team is important in a successful implementation. The study also shows that the focus of BIM should lie on how to make use of the technique. The examples of how BIM could be used in the production phase of civil works have to be useful and meet the needs and demands of the users. The processes of using 3D models, 4D scheduling, 4D animations, RFID tags, field verifications and tablet computers should therefore be studied thoroughly to find how the technique could be applicable at site, in meetings and work preparations and how it could enhance the daily activities and work tasks. If the demands are met it will be accepted by both the user and the organization. Further research should therefore lie on how 3D models, 4D scheduling, 4D animations, RFID tags, field verifications and tablet computers could be useful in the production phase. These BIM techniques should then be tested on a real project to investigate how the processes could be useful at site, in meetings and in work preparations. Further research should also be made on how countries like Norway, Finland and USA have made use of BIM in the production of civil works.
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Laspas, Theodoros. "Closed Force Loop Evaluation of Machining Systems." Licentiate thesis, KTH, Maskin- och processteknologi, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-227664.
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Machine tools accuracy has been a cornerstone in defining machining system capability and directly affecting dimensional and geometrical tolerance of machined parts. The effort for achieving higher precision and accuracy can be distinguished in two general ideas. One is to improve performance of machine tools by designing better, stiffer and more accurate machine tools. The other is to develop tools and methods for evaluating and measuring their behaviour and gain knowledge of their performance. In order to properly control the machine tool characteristics that can affect and improve their accuracy such as static stiffness and static accuracy.This thesis is aiming at establishing and further advancing the idea of loaded testing of machining systems and the concept of Elastically Linked Systems as a framework for measuring, identifying and characterising quasi-static stiffness of machine tools under loaded conditions. This will allow the creation of an improved capability profile of machining system accuracy. The focus is on the implementation of Elastically Linked Systems concept (ELS) through the Loaded Double Bar system, a measurement method that can partly simulate the process-machine interaction by reproducing forces exerted on the machine tool structure for the evaluation of system characteristics under loaded condition. This allows the qualitative and quantitative evaluation and comparison of machine tools for the purpose of accuracy enhancement, identification of weak directions with potential utilization in process planning, machine procurement and maintenance.Through two case studies, the capability to identify the effect of machine components and structure behaviour is shown.QC 20180514
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Lameu, Paula Cristina. "Education ICT assemblage : encounters of discourses, emotions, affects, subjects, and their productive forces." Thesis, University of Birmingham, 2017. http://etheses.bham.ac.uk//id/eprint/7629/.
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Information and Communication Technology (ICT) is part of everyday life. It is not different in the education field. However, its use has implications for what it means to teach and learn effectively in contemporary education. When ICT is used in the classroom, things happen through divergent forces, components, and mechanisms, according to different contexts, and evidencing a complex environment. The purpose of this study is to show how complex the use of ICT in education is by analysing different components and their productive forces. Assemblage ethnography is the methodology adopted and a range of data collection tools are used. The thesis explores five case studies generated from different settings: Primary, Secondary and Post-secondary education. The analysis offered shows how discourse, policy-making, budget, and CPD are not enough to account for all of the ICT-related situations that happen on a daily basis inside schools. ICT in education evidences a diverse and fragmented field of policy, money, and practice, pedagogy and many other elements. This study concludes that there are three main productive forces emerging from the education ICT assemblage which: evidenced unsolved issues of the schooling process, enhanced or made emotions emerge; opened possibilities for other subjectivities to happen.
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Fleenor, Bradley S. "The effects of policosanol on reaction time, force production, and the blood lipid profile." Virtual Press, 2002. http://liblink.bsu.edu/uhtbin/catkey/1231340.
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Thirty recreationally active individuals, 16 males and 14 females, participated in the study to examine the effects of policosanol supplementation on reaction time, force production and the blood lipid profile. The subjects were matched based on height, weight. gender, current physical activity level and body fat percentage. The matched subjects where randomly assigned to either the policosanol or placebo group. Supplementation period lasted 8 weeks with reaction and decision time measurements taken at baseline, weeks 2, 4, 6 and 8. Force production was evaluated with the Cybex Dynamometer at speeds of 60, 120, 180 and 240 degrees/second at baseline, weeks 2, 4, 6 and 8. Blood was drawn and analyzed at baseline, weeks 4 and 8. A two way repeated analysis of variance was used to analyze differences between pre and post measurement at a significance level of p <_ .05. There were no significant changes in reaction ordecision time between groups. Force production significantly increased in both groups however, there was no significance between groups. The blood analysis demonstrated significant changes in total cholesterol and triglycerides. No differences were found in high-density lipoprotein cholesterol, low-density lipoprotein cholesterol or liver function measurements. It was concluded that further research in needed to examine the effects of reaction time in older individuals with possibly slower reaction times. The increase in force was due to a training effect and not from policosanol supplementation. However, future research with policosanol and strength needs to incorporate a training protocol. The trend observed with the blood parameters was concluded be a normalizing effect rather than a lowering effect.School of Physical Education
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Bailey, Christopher A., Caleb D. Bazyler, Chieh-Ying Chiang, Kimitake Sato, and Michael H. Stone. "The Relationship of Force Production Asymmetry and Performance in Athletes of Different Strength Levels." Digital Commons @ East Tennessee State University, 2014. https://dc.etsu.edu/etsu-works/3825.
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The purpose of this study was to evaluate the relationship between force production asymmetry and performance of athletes with differing strength levels in males and females. Collegiate athletes (n=129) from various sports were ranked according to isometric mid-thigh pull peak force and the top (‘strong’) and bottom (‘weak’) 25% were used for analysis. Symmetry index (SI) scores were calculated and correlated with their respective force-time characteristics using bivariate correlations. For the weaker males, several negative moderate correlations were observed; however, no statistically significant correlations were observed for the females in either group. These findings indicate that force production asymmetry is inversely related to performance in weaker male athletes during isometric strength testing; however, similar to previous findings, this relationship is not apparent in stronger males.
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Bazyler, Caleb D., Christopher A. Bailey, Chieh-Ying Chiang, Kimitake Sato, and Michael H. Stone. "The Effects of Strength Training on Isometric Force Production Symmetry in Recreationally Trained Males." Digital Commons @ East Tennessee State University, 2014. https://dc.etsu.edu/etsu-works/3785.
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Objectives: The purpose of this investigation was to determine what effect a bilateral strength training regimen has on isometric force production symmetry and if changes in force production symmetry can be accounted for by differences in pre-intervention strength levels. Design: Sixteen recreationally trained males (1-RM squat: 146.8 ± 23.0 kg.) were assigned to two groups for the 7-week training intervention: strong (S) and weak (W) based on pre-training squat isometric peak force allometrically scaled (IPFa) at 120° knee angle. Methods: Subjects completed a 7-week training intervention following a block-periodized model and were tested on measures of dynamic (1RM squat) and isometric (isometric squat at 90° and 120° knee angle) strength pre- and post-intervention. The degree of bilateral lower limb asymmetry was calculated as a percentage where 0% symmetry index (SI) indicates perfect symmetry on the isometric squat.Results: ANCOVA results showed no statistical difference between groups for all dependent variables when pre-intervention IPFa 120° scores were used as the covariate. Paired t-tests results showed both groups statistically improved 1RM squat and IPFa 120° (p < 0.05). IPFa 120° SI decreased statistically from pre-training in the W group (p = 0.03). Independent t-test results showed the W group had statistically larger pre-intervention SI scores for IPFa 90° (p = 0.045) and IPFa 120° (p = 0.007); however this difference was no longer present following strength training. There was a strong inverse relationship between pooled IPFa 120° and IPFa 120° SI (r = -0.64, p = 0.004). Conclusions: The findings of the current study support the notion that weaker individuals can augment lower limb symmetry with strength training. The same does not seem to be true for stronger individuals who already have a low symmetry index score. These findings indicate that strength training improves force production symmetry in relatively weak males, which may be important for bilateral tasks and injury potential reduction.
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Alahmari, Sami Khaloufah M. "Muscle force production and neuromuscular fatigue responses to neuromuscular electrical stimulation and tendon vibration." Thesis, Queensland University of Technology, 2022. https://eprints.qut.edu.au/236174/1/Sami_Alahmari_Thesis.pdf.
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Neuromuscular electrical stimulation is an intervention that produces artificial muscle contractions and is used to rehabilitate people with motor impairments. However, a typical problem is the occurrence of rapid fatigue, which limits the training stimulus. This thesis investigated whether the addition of tendon vibration and concurrent activation of upper limb muscles could minimise fatigue and maximise torque produced by the calf muscles during neuromuscular electrical stimulation. The experiments in this thesis showed that superimposition of tendon vibration can increase the amount of torque produced by calf muscles, and that the addition of sustained handgrip contraction could further increase this torque.
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Павлов, Р. А., Євген Олегович Балацький, Евгений Олегович Балацкий, and Yevhen Olehovych Balatskyi. "Вплив науково-технічного прогресу на розвиток продуктивних сил." Thesis, Українська академія банківської справи Національного банку України, 2010. http://essuir.sumdu.edu.ua/handle/123456789/61579.
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Зміни в технології та організації виробництва, якщо вони мають
кардинальний характер, можуть істотно вплинути на розміщення
продуктивних сил. На території деяких країн і регіонів може виникнути
виробництво, яке раніше тут було неефективним.
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Massacand, Christophe Maurice Jean-Baptiste. "Particle production by tidal forces and the energy-momentum tensor /." [S.l.] : [s.n.], 1993. http://e-collection.ethbib.ethz.ch/show?type=diss&nr=10359.
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Garcia, Stéphane. "Production d’hydrogène solide sous forme de films de taille micronique." Thesis, Université Grenoble Alpes (ComUE), 2015. http://www.theses.fr/2015GREAY050/document.
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Le développement des lasers de fortes puissances réalisé au cours des dix dernières années a ouvert de nouveaux champs de recherche dans de nombreux domaines tels que la production de faisceaux de particules chargées. Lors de l'interaction d'un faisceau laser avec une cible, il est en effet possible de générer un faisceau d'ions ou d'électrons d'une large gamme énergétique dépendant de la puissance du laser et de la nature de la cible.Les physiciens qui étudient les interactions laser-matière montrent un grand intérêt à pouvoir réaliser des expériences avec une cible d'hydrogène pure de l'ordre d'une dizaine de micromètres d'épaisseur. Lors d'une telle interaction, un faisceau constitué uniquement de protons accélérés est produit. La protonthérapie est l'une des applications phares qui utilise les propriétés particulières des protons accélérés pour détruire des tumeurs cancéreuses. Cette technique, plus légère et moins coûteuse, pourrait remplacer dans les années à venir les gros accélérateurs de particules, situés en sous-sol des hôpitaux. Les travaux menés durant cette thèse ont permis de développer un moyen d'obtenir et de caractériser de telles cibles, et ce en utilisant un nouveau procédé d'extrusion.L'extrusion d'hydrogène solide requiert des fortes pressions (100 à 400 bar) et des basses températures (inférieures à 13 K). Les fortes pressions sont obtenues à l'aide des propriétés thermodynamiques du fluide. Dans un premier temps, de l'hydrogène est introduit puis solidifié dans la cellule expérimentale jusqu'à remplir celle-ci. La cellule est alors fermée et chauffée en partie haute afin de liquéfier l'hydrogène qui s'y trouve. La dilatation qui résulte du changement de phase, génère une pression sur l'hydrogène solide qui est situé sous le liquide. Cette pression permet d'obtenir la force nécessaire à l'extrusion qui est réalisée au travers d'une buse se situant à l'extrémité basse de la cellule. La principale différence avec un procédé classique d'extrusion est l'absence de parties mobiles.Des premiers rubans d'hydrogène d'une largeur de 1 mm et d'une épaisseur de 100 µm ont été obtenus et ont donné lieu à publication en mars 2014. Une évolution de la cellule et du cryostat a ensuite été réalisée dans le but d'atteindre des épaisseurs de rubans plus faibles (25 et 50 µm).Une buse cylindrique d'un diamètre de 140 µm a également permis d'obtenir de longs cylindres d'hydrogène solide et de comprendre le comportement de l'écoulement dans des géométries simples. En parallèle, de nombreuses simulations numériques ont été réalisées dans le but de caractériser ce comportement. Un modèle dédié a ainsi été établi, pour lequel les résultats expérimentaux et les simulations sont en bon accord.Un algorithme de mesure de vitesses d'écoulement, basé sur le suivi de défauts présents dans le film d'hydrogène a également été développé. Celui-ci est basé sur une technique d'inter-corrélation d'images. L'épaisseur du ruban est également obtenue par analyse d'images acquises. Ces résultats sont en adéquation avec la mesure du débit d'hydrogène pompé, réalisée en aval du cryostat.De nombreux laseristes ont alors manifesté leur intérêt autour de ce nouveau procédé et une collaboration a été mise en place avec l'équipe du laser PALS, à Prague, dans le but d'installer une nouvelle version du cryostat, capable de se fixer sur la chambre à vide de leur laser. Cette équipe, qui sera la première à tirer sur des cibles d'hydrogène solide courant novembre 2015, souhaite valider certaines théories et accélérer des protons en utilisant le principe de la TNSA (Target Normal Shealth Acceleration). Les laseristes du LULI (situés à Palaiseau, en France) sont également intéressés pour utiliser de telles cibles et une installation sur leur chambre laser a été planifiée au mois de janvier 2016. En parallèle, des physiciens de l'Institut Lumière Matière du CNRS de Lyon souhaitent également utiliser ces cibles pour générer des rayons X-UVThe development of very high power lasers in the latest decade opened up new horizons in a various field, such as the production of accelerated ion beams. When a laser beam interacts with a target, the generated beam can contain energetic ions or electrons with a large energy spectrum (1–200 MeV). This energy distribution depends on the laser power and the nature of the target.Physicists studying the interaction between laser and materials are really interested in having very thin (10 µm) ribbons of solid hydrogen that could be used as a target. Indeed, during the interaction between a laser and such a target, a pure proton beam can be created. Protontherapy is one of the main potential applications which uses the special properties of accelerated protons to destroy cancerous tumor. This technique, lighter and cheaper, could replace in the next years huge particle accelerators situated underground the equipped hospitals. This PhD thesis was about developing a way to get and characterize such ribbons, using a new extrusion process.Extrusion of solid hydrogen requires a high pressure (10 MPa to 40 MPa) and a low temperature (below 13K). This is achieved by using the thermodynamic properties of the fluid. First, the cell is filled in with solid H2, then closed. Afterward, the upper part is heated to liquefy the solid. The expansion, resulting from the phase change creates a pressure on the solid hydrogen, located below the liquid. The extrusion is realized through a micron-sized hole at the bottom of the cell. The main difference with a classic extrusion process is the absence of moving parts.First solid hydrogen ribbons (1mm large and 100 microns of thickness) have been obtained in March 2014, leading to an article in a peer review (laser and particle beams (2014) 32,569-575, Continuous production of a thin ribbon of solid hydrogen). The use of a 50 micron nozzle was satisfying but it showed the limitation in the design of the cell, leading to an upgraded one, which will enable to extrude thinner ribbons.A cylindrical nozzle (140 microns diameter) has also been used to obtain long cylinders of solid hydrogen and to be able to understand the solid hydrogen flow in simple geometries. In parallel, several numerical simulations have been carried out to establish the flow behavior of solid hydrogen during the extrusion process. An “home made” model has been developed for which experimental results and numerical calculations fit quite well for different nozzles' geometries.Using small ribbon defaults as velocity tracers, cross-correlation algorithm has also been developed to measure the velocity during the extrusion process. The ribbon thickness is also extracted from image analysis. These results are also correlated by flowmeter measurements and appeared to be accurate.Several laser teams have shown a great interest for these results and a collaboration contract has been signed with the laser PALS team (Prague) to install an updated version of this cryostat, able to be plugged in their vacuum chamber. The team wants to shoot the solid hydrogen target to understand the laser/matter interaction and accelerate proton through the TNSA (Target Normal Sheath Acceleration) principle. It will be the first time such target will be shot. The installation of the cryostat is scheduled by the end of august and the first experiments are planned during november 2015. LULI's laser team at Palaiseau in France is also interested in using these targets and is planning to shoot them in January 2016. In parallel, CNRS physicists of the ILM (Institut Lumière Matière de Lyon) would like to use these targets to generate X-UV radiation
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Viström, Magnus. "Customised information on packaging : driving forces and logistical aspects." Licentiate thesis, KTH, Numerical Analysis and Computer Science, NADA, 2004. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-168.
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This thesis work is divided into two parts that relate to each other. The first part investigates driving forces and limiting factors in the customisation of information on packaging and the second part focuses on how the customisation task should be performed in order to obtain high productivity and efficient logistics. Opportunities with hybrid printing solutions where conventional technology is combined with digital printing are discussed.The first of the included papers talks about the driving forces and limiting factors in the customisation of information on packaging and focuses on marketing aspects and consumer value. The second paper investigates the logistical aspects of using digital printing to add information on pre-printed packaging, with the primary focus on the opportunities to reduce changeover time and printing form costs. The third paper investigates how digital printing can be integrated into a packaging line and identifies critical productivity related parameters. These three papers are analysed together in this report, giving input to conclusions about the driving forces and limiting factors in the customisation of information on packaging and how the customisation task should be performed to obtain high productivity and efficient logistics. Hence, this thesis work does not originate solely in one discipline. Digital printing technology, logistics and marketing aspects are all considered to draw conclusions.
It is shown that it is possible to obtain marketing advantages, fulfill market demands better, get increased consumer value and reduced costs by using a hybrid printing solution. There exists at the same time a number of limiting factors, such as print quality demands, additional costs and reliability issues that are crucial to consider before concluding whether or not customisation of information on packaging would be successful in any given business scenario.
Different scenarios for where the customisation task can be inserted into a value chain are defined and discussed. Explicit studies of one of the scenarios are made. This scenario is defined as having a customisation task inline in a packaging line. The other scenarios, customisation at the packaging producer and customisation at the wholesaler/retailer, are not explicitly investigated, but it has been possible to discuss these scenarios as well through the research results obtained. The results show that there are factors that point towards the scenario where digital printing is performed at the producer as being the most beneficial. A number of critical productivity related factors for this scenario are identified in paper III, which gives guidelines on how to obtain high productivity when a digital printing task is integrated into a packaging line. It is finally shown that it is possible to obtain high delivery service and efficient logistics by using a hybrid printing solution. It is, however, of crucial importance that possible drawbacks be considered in order to accurately conclude whether a hybrid printing solution will be successful or not.
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Fry, Adam. "A neurophysiological examination of voluntary isometric contractions : modulations in sensorimotor oscillatory dynamics with contraction force and physical fatigue, and peripheral contributions to maximal force production." Thesis, Loughborough University, 2016. https://dspace.lboro.ac.uk/2134/20392.
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Human motor control is a complex process involving both central and peripheral components of the nervous system. Type Ia afferent input contributes to both motor unit recruitment and firing frequency, however, whether maximal force production is dependent on this input is unclear. Therefore, chapter 2 examined maximal and explosive force production of the knee extensors following prolonged infrapatellar tendon vibration; designed to attenuate the efficacy of the homonymous Ia afferent-α-motoneuron pathway. Despite a marked decrease in H-reflex amplitude, indicating an attenuated efficacy of the Ia afferent-α-motoneuron pathway, both maximal and explosive force production were unaffected after vibration. This suggested that maximal and explosive isometric quadriceps force production was not dependent upon Ia afferent input to the homonymous motor unit pool. Voluntary movements are linked with various modulations in ongoing neural oscillations within the supraspinal sensorimotor system. Despite considerable interest in the oscillatory responses to movements per se, the influence of the motor parameters that define these movements is poorly understood. Subsequently, chapters 3 and 4 investigated how the motor parameters of voluntary contractions modulated the oscillatory amplitude. Chapter 3 recorded electroencephalography from the leg area of the primary sensorimotor cortex in order to investigate the oscillatory responses to isometric unilateral contractions of the knee-extensors at four torque levels (15, 30, 45 and 60% max.). An increase in movement-related gamma (30-50 Hz) activity was observed with increments in knee-extension torque, whereas oscillatory power within the delta (0.5-3 Hz), theta (3-7 Hz), alpha (7-13 Hz) and beta (13-30 Hz) bands were unaffected. Chapter 4 examined the link between the motor parameters of voluntary contraction and modulations in beta (15-30 Hz) oscillations; specifically, movement-related beta decrease (MRBD) and post-movement beta rebound (PMBR). Magnetoencephalography (MEG) was recorded during isometric ramp and constant-force wrist-flexor contractions at distinct rates of force development (10.4, 28.9 and 86.7% max./s) and force output (5, 15, 35 and 60%max.), respectively. MRBD was unaffected by RFD or force output, whereas systematic modulation of PMBR by both contraction force and RFD was identified for the first time. Specifically, increments in isometric contraction force increased PMBR amplitude, and increments in RFD increased PMBR amplitude but decreased PMBR duration. Physical fatigue arises not only from peripheral processes within the active skeletal muscles but also from supraspinal mechanisms within the brain. However, exactly how cortical activity is modulated during fatigue has received a paucity of attention. Chapter 5 investigated whether oscillatory activity within the primary sensorimotor cortex was modulated when contractions were performed in a state of physical fatigue. MEG was recorded during submaximal isometric contractions of the wrist-flexors performed both before and after a fatiguing series of isometric wrist-flexions or a time matched control intervention. Physical fatigue offset the attenuation in MRBD observed during the control trial, whereas PMBR was increased when submaximal contractions were performed in a fatigued state.
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Gibbs, A. P. "Characterising the influence of pre-drive lung volume on force and power production during rowing." Thesis, Brunel University, 2007. http://bura.brunel.ac.uk/handle/2438/3637.
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Purpose: This study evaluated the effect of lung volume at the catch position to force and power outputs during single maximal effort strokes in rowing. Responses were compared when the participants were ‘fresh’ and following specific inspiratory muscle fatigue (IMF). In addition, a single subject pilot study was performed to characterise the changes in intra-thoracic (ITP), intra-abdominal (IAP) and trans-diaphragmatic (Pdi) pressures during a 30 second maximal effort piece on a rowing ergometer. Methods: Nine male rowers of international standard participated in the research. Static force, as well as the power produced during a single stroke were assessed at residual volume (RV), 25%TLC, 50%TLC, 75%TLC, total lung capacity (TLC), and a self-selected lung volume (S-S). Lung volumes were derived from maximal flow-volume loops (MFVLs) and achieved using online real-time feedback. Inspiratory muscle fatigue (IMF) was induced by breathing against an inspiratory load equivalent to 80% baseline maximal inspiratory pressure (MIP), at a breathing frequency (fB) of 15 breaths per minute, and a duty cycle of 0.6. Expiration was unimpeded. The single subject pilot study was undertaken using balloon catheters to measure ITP, IAP, and Pdi during a 30 second maximal effort free-rating piece on the ergometer. Results: There was no significant effect of lung volume upon either force or power production. The RMF protocol induced a significant reduction in MIP (159.9 ± 70.8 vs. 106.8 ± 58.7 cmH2O; p = 0.000), but not maximal expiratory pressure (MEP; 159.9 ± 79.2 vs. 166.6 ± 53.0 cmH2O; p = 0.376). RMF induced a significant reduction in force output with increasing lung volume, across all lung volumes (mean force 1313.4 ± 31.9 vs. 1209.6 ± 45.0N; p < 0.008), but not power (mean power 598.6 ± 31.9 vs. 592.7 ± 45.0W; p > 0.05). Self-selected lung volumes were consistent across all tests for force and power (mean 38.1 ± 6.9% [Force] vs. 28.2 ± 0.6% [Power]; p > 0.017). The pilot study indicated that internal pressures fluctuate markedly during maximal effort rowing (pressure, [max, min, average] cmH2O; IAP [144.69, 7.46, 73.59], ITP [75, -22.65, 15.34], Pdi [111.84, 7.09, 58.83]), suggesting that the trunk muscles play an active role in power production during rowing. Conclusion: The present study suggests that there is no significant effect of lung volume on force or power when athletes are in a fresh condition. However, a decrement in force production is present with inspiratory muscle fatigue. Combined with evidence of high internal pressures during maximal effort rowing, these data may indicate a role for the inspiratory muscles in force production during rowing.
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Cáceres, Rodrigo. "Role of acto-myosin based force production in cell invasion during development in Caenorhabditis elegans." Thesis, Sorbonne Paris Cité, 2017. http://www.theses.fr/2017USPCB027/document.
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La membrane basale (MB) est une feuille dense de matrice extracellulaire spécialisée qui sépare l'épithélium du tissu sous-adjacent. La pénétration des cellules à travers les barrières des MB, c’est appelée «invasion», est un processus important pour le développement normal des tissus et dans la métastase du cancer. Beaucoup a été compris sur la génétique et la signalisation sur comment les trous sont formés dans le MB pendant de l'invasion ont été compris. Cependant, les forces physiques impliquées sont moins comprises: comment la contractilité de la myosine participe à l'élimination de la MB et comment les différents facteurs de polymérisation de l’actine et les protéines de réticulation contribuent au processus invasif. Pour répondre à ces questions, nous avons étudié un événement d'invasion dans un processus de développement, l’invasion de la cellule anchre (AC) chez Caenorhabditis elegans. La rupture de la MB par l’AC est connue pour dépendre d'une protrusion riche en actine et de l'activité des métalloprotéases (MMP), similaire à l'invasion de cellules cancéreuses. Inactivation génique par RNAi de différents activateurs et nucléateurs de la polymérisation d'actine, et l'expression spécifiquement dans l'AC d'une forme négative dominante d'un activateur du complexe Arp2/3 a montré que l'invasion de l’AC dépendes fortement des filaments ramifiés formés via l'activation WASP / WSP-1 du complexe Arp2/3. La microscopie à haute résolution a indiqué que la protrusion invasive de l’AC était densément assemblée, en accord avec l'idée que la protrusion invasive était fortement ramifiée. Nous avons également montré qu'un autre activateur du complexe Arp2/3, WAVE / WVE-1, pouvait permettre une invasion lorsque WASP / WSP-1 était absent. Les formines semblaient ne pas de jouer un rôle majeur et les protéines de réticulation d'actine étaient également dispensables pour l’invasion de l’AC. Dans les vers de type normaux, nous avons observé que l'activité de la myosine n'était pas nécessaire pour l'invasion. Cependant, il a été rapporté que les cellules cancéreuses augmentent la contractilité de la myosine pour envahir en l'absence de protéases, nous avons donc utilisé un ver sans les cinq principales MMPs du génome du ver pour tester le rôle de la myosine dans ce contexte. L'invasion de l’AC a eu lieu dans en l’absence des MMPs, mais avec un retard. L’inactivation génique par RNAi de différents composants lies à l’activité de la myosine n'a pas amélioré le défaut d'invasion. En plus, la visualisation du cytosquelette d'actine dans les vers sans MMPs a révélé que l'actine était concentrée dans la protrusion de l’AC et à peine détectable dans le cortex, ce qui rendait improbable que la contraction de la myosine du cortex aiderait la compression cellulaire à travers de la MB comme il a été reporté dans les cellules cancéreuses en l'absence de protéases. Tous ces résultats ensemble, ont montré que la cellule invasive a adapté sa polymérisation de filaments d'actine ramifiée pour maintenir l'invasion dans différents contextes biochimiques et environnementaux. Cette plasticité est un point crucial qui doit être mieux compris pour développer de futurs traitements visant l'invasion de cellules cancéreusesBasement membrane (BM) is a dense sheet of specialized extracellular matrix that separates epithelia from underlying tissue. The penetration of cells through BM barriers, called “invasion”, is an important process during normal tissue development and in cancer metastasis. Much has been understood concerning the genetics and signaling of how holes are formed in the BM during invasion. However less is clear about the physical forces involved: how myosin contractility participates in BM removal and how different actin polymerization factors and crosslinkers contribute to the invasive process. To address these questions, we studied an invasion event in a developmental process, anchor cell (AC) invasion in Caenorhabditis elegans. AC breaching of the BM is known to depend on an actin-rich protrusion and the activity of matrix metalloproteases (MMPs), similar to cancer cell invasion. RNAi knockdown of different actin polymerization activators and nucleators, and expression of a dominant negative form of an Arp2/3 complex activator specifically in the AC showed that AC invasion depended strongly on branched filaments formed via WASP/WSP-1 activation of the Arp2/3 complex. Super-resolution microscopy indicated that the AC invasive protrusion was densely packed with filaments, in keeping with the idea that the invasive protrusion was highly branched. We further showed that another Arp2/3 complex activator, WAVE/WVE-1, could enable invasion when WASP/WSP-1 was absent. Formins appeared not to play a major role and actin cross-linking proteins were likewise dispensable for AC invasion. In wild type worms, we observed that myosin activity was not needed for invasion. However it has been reported that cancer cells upregulate myosin contractility to invade in the absence of proteases, so we used a worm deleted for the five main MMPs of the worm genome to test the role of myosin in this context. AC invasion took place in MMP- worms, but with a time delay. RNAi knockdown of different components of the myosin machinery gave no enhancement of the invasion defect. In addition visualization of the actin cytoskeleton in MMP- worms revealed that actin was concentrated in the AC protrusion and barely detectable in the cortex, making it unlikely that myosin contraction of the cortex was helping the cell squeeze through the BM as reported in cancer cells in the absence of proteases. All together these results showed that the invasive cell adapted its branched actin filament polymerization to maintain invasion in different biochemical and environmental contexts. This plasticity is a crucial point that needs to be better understood in order to develop future treatments targeting cancer cell invasion
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Wilson, Cody J. "Mechanisms underpinning an improvement in dynamic muscle force production following a high-intensity warm-up." Thesis, Edith Cowan University, Research Online, Perth, Western Australia, 2020. https://ro.ecu.edu.au/theses/2537.
Full textAbstract:
The present research explored the mechanisms underpinning the enhancement of voluntary knee extensor torque after (1) extensive task-specific practice, and then (2) brief, intense warm-up exercise (conditioning activity; CA) as part of a complete warm-up routine. The same warm-up was completed in two Experiments (detailed below). In Experiment 1, voluntary (180⁰·s-1; T180) and electrically-evoked (isometric) knee extensor torques and electromyogram (EMG) and muscle temperature (Tm) data were recorded before and after (1) extensive task-specific practice where peak voluntary knee extensor performance was achieved, and (2) two isokinetic CAs matched for total concentric contraction time (CA60: 5 repetitions at 60⁰·s-1 vs. CA300: 25 repetitions at 300⁰·s-1; 7.5 s).
In Experiment 1, nineteen healthy adults (13 male, 6 female) completed the study. T180 increased after task-practice in both conditions (CA60: 6.2 ± 8.5% vs. CA300: 8.4 ± 8.0%). After the CA, T180 decreased at 1 min (-7.0 ± 8.6%) but then returned to post-TP values at 9 min post-CA (0.2 ± 9.8%) in CA60, while T180 did not change at any post-CA time point compared to immediately post-TP (1-3%) but remained significantly elevated (~9-12%) compared to baseline in CA300. Tm increased from baseline to post-TP (CA60: 0.6 ± 0.3°C vs. CA300: 0.4 ± 0.2°C) in both conditions and then increased further from post-TP (by 0.5 ± 0.2°C in CA60 and 0.8 ± 0.3°C in CA300). The 20 Hz torque measured with versus without shortinterval “double pulse” at stimulation onset (i.e. VFT:20 ratio) was decreased (-50-90%) after the CA. Further, peak twitch torque (Ttw,peak) increased from baseline to post-TP in both conditions (CA60: 13.5 ± 9.1% vs. CA300: 16.0 ± 7.2%), but did not increase further after the CAs ( < 2%) in either condition (9-14% above baseline), indicating that calcium sensitivity of the acto-myosin complex may have been enhanced. M-wave normalised VL EMG (EMGVL,40ms/M) increased from baseline to post-TP (CA60: 68.9 ± 105.7% vs. CA300: 116.4 ± 170.5%) then decreased from post-TP to 1 min post-CA (-22.0 ± 48.2%) in CA60, but remained elevated at all post-CA tests in CA300. Ttw,peak (r = 0.53), Tm (r = 0.63), VFT:20 ratio (r = 0.32) and EMGVL,40ms/M (r = 0.30) were all moderately-strongly correlated with T180 in CA300, but not CA60 ( < r = 0.15). EMG was the only variable that was associated with T180 in both conditions (r = 0.3-0.5). Therefore, EMG was included in a model with Tm (i.e. ‘EMGVL,T180/M + Tm’) and observed a moderate correlation with T180 in CA60 (r = 0.38) and a strong correlation in CA300 (r = 0.60). This suggests that muscle activation capacity mediates the effect of muscle temperature on voluntary muscle performance.
In Experiment 2, exercise-induced muscle fluid shifts after warm-up (identical to Experiment 1) were estimated on 19 healthy adults (13 male, 6 female) through assessments of muscle blood content (total haemoglobin concentration; THb), size (VL muscle thickness) and stiffness (VL passive stiffness). THb increased at post-TP (CA60: 55.5 ± 133.7% vs. CA300: 156.2 ± 267.5%) and continued to increase in both conditions to 9 min (CA60: 261.0 ± 226.5% vs. CA300: 759.8 ± 1141.8%). VL muscle thickness increased statistically from post-TP to all post-CA tests (1.8-2.4%) in CA60 but not CA300 (0.6-1.2%), while passive muscle stiffness increased from baseline to 1 min post-CA (3.8 ± 5.0%) in CA300 but not CA60 (~1%). THb was moderately correlated with VL muscle thickness (CA60: r = 0.31 vs. CA300: r = 0.34) and passive muscle stiffness (CA300: r = 0.48). Further, VL muscle thickness showed a small correlation with passive muscle stiffness (r = 0.28) in CA300 only.
Collectively, the present data support the hypothesis that significant enhancement of voluntary muscle performance can be achieved with sufficient task-specific practice, and that this enhancement was associated with enhanced muscle activation capacity (i.e. increased early-burst EMG), possibly indicating motor pattern optimisation as well as increased Tm (and other related variables). Furthermore, including brief, intense warmup exercise (CA) did not enhance voluntary muscle performance beyond the level achieved by task-specific practice, despite inducing a greater increase in numerous physiological markers (i.e. Tm, muscle water/blood, Ca2+ sensitivity, etc.) that could influence voluntary muscle performance. However, the most intriguing finding was that the performance of an under-speed (high force) CA (commonly utilised in the literature) resulted in a decrease in voluntary muscle performance after the task practice period (i.e. back to baseline levels) and that this was associated with decreased muscle activity (peak and early EMG). Therefore, voluntary muscle performance after warm-up is strongly associated with changes in both peak and early EMG; muscle activation capacity may therefore be a mediating variable that affects the normal relationship between changes in Tm and changes in dynamic muscle function.