Tesis sobre el tema "Muscles"

Thesis (Ph. D.)--West Virginia University, 2007.<br>Title from document title page. Document formatted into pages; contains xii, 270 p. : ill. (some col.). Includes abstract. Includes bibliographical references.

Thèse de doctorat : Sciences de la vie et de la santé : Paris 12 : 2006.<br>Version électronique uniquement consultable au sein de l'Université Paris 12 (Intranet). Titre provenant de l'écran-titre. Bibliogr. : 410 réf.

Thesis (Ph.D.)--University of Florida, 2005.<br>Typescript. Title from title page of source document. Document formatted into pages; contains 171 pages. Includes Vita. Includes bibliographical references.

Le but de cette dissertation doctorale était de mieux comprendre les mécanismes de contrôle tant centraux que périphériques qui sont à l’origine de la régulation neuromusculaire lors de mouvement impliquant des contractions de type excentrique. Lors d’une première étude réalisée sur le muscle jambier antérieur, nous avons montré qu’un exercice utilisant des contractions excentriques présentait une meilleure résistance à la fatigue que lorsque des contractions concentriques étaient impliquées puisque celui-ci conduit à une moindre diminution du couple de force et de l’activité électromyographique. L’absence de fatigue nerveuse centrale et l’observation d’un comportement spécifique du couple de force et de l’activité électromyographique lors de ces épreuves de fatigue semblait traduire la mise en jeu de processus périphériques différents. La plus grande fatigue observée lors de l’épreuve concentrique suggérait une activation plus importante que pour l’épreuve excentrique, dont les conséquences métaboliques renforcent les altérations du couplage excitation-contraction. Dans un second temps, nous avons étudié l’effet des modifications de longueur de fascicule du muscle jambier antérieur sur le comportement spécifique des unités motrices (ordre, fréquence et seuil de recrutement) lors de contractions isométriques. Nous avons ensuite analysé le comportement d’unités motrices selon les différentes modalités de contractions (concentrique vs. excentrique) sur ce même muscle. Pour y répondre, différentes techniques d’analyse ont été utilisées dont l’enregistrement électromyographique intramusculaire et l’ultrasonographie. Enfin, nous avons cherché à analyser l’évolution des différents mécanismes de régulation d’origine périphérique et /ou central susceptible de modifier l’excitabilité du pool de motoneurone lors de contractions concentriques et excentriques. Pour y répondre, les modulations d’une part, du réflexe de Hoffmann (réflexe H) par stimulation électrique et d’autre part, celles du potentiel moteur évoqué (MEP) par stimulation magnétique transcorticale, ont été investiguées. Ces réponses ont été enregistrées à différents angles de la plage articulaires étudiée lors des contractions concentriques et excentriques, ainsi qu’aux deux extrémités angulaires lors de contraction isométriques. Notre travail indique que l’ordre de recrutement des unités motrices entre les contractions concentriques et excentriques étant identique, le système nerveux n’utilise qu’une seule et même stratégie d’activation liée à la taille des motoneurones impliqués dans ces deux types de contractions. En outre, les contractions excentriques lorsqu’elles sont réalisées à vitesse constante, sont associées à une modulation spécifique de la fréquence de décharge des unités motrices. Ce comportement diffère de celui observé lors de contractions concentriques, malgré une modification linéaire et similaire de la longueur des fascicules et du couple de force au cours de ces deux tâches. Les modulations du recrutement des unités motrices semblent davantage dépendre de la longueur musculaire tandis que les modulations de fréquence prédominent pendant les contractions en raccourcissement. Ce comportement spécifique semble dépendant de mécanismes de régulation principalement localisés au niveau spinal. Ainsi, le degré d’inhibition des afférences fusoriales affectant le pool de motoneurones du muscle tibial antérieur lors de sollicitations actives du muscle, dépend davantage de l’angle articulaire et donc de la longueur du muscle plutôt que du mode de contraction. Lors de sollicitations isométriques, le retour sensoriel Ia est principalement contrôlé au niveau présynaptique en fonction de la longueur du muscle. Lors de sollicitations concentriques et excentriques, ces mécanismes présynaptiques réguleraient l'excitabilité spinale de manière similaire entre les deux modes. Néanmoins, bien que l'inhibition présynaptique soit probablement plus marquée lors des sollicitations excentriques, ce mode de contraction semble également régulé par des mécanismes d'inhibition intervenant au niveau postsynaptique tel que l'inhibition récurrente de Renshaw. Ce mécanisme localisé au niveau postsynaptique permettrait de réguler la fréquence de pulsation des unités motrices lors de sollicitations excentriques dans le but le faciliter l'exécution du mouvement. L'originalité de notre travail a été d’étudier le comportement d’une même unité dans les deux modes de contractions alors que la méthode d’analyse généralement adoptée consistait à comparer des populations d’unités motrices entre-elles. De plus, les changements de la longueur du muscle au cours du mouvement ainsi que les vitesses de raccourcissement ou d'allongement ont été estimés à partir de la mesure directe de la longueur des fascicules musculaires. Cette dernière présente l’avantage de fournir une information de longueur et de vitesse sur la portion de muscle à partir de laquelle les enregistrements d’unités motrices ont été obtenus. Enfin, étant donné les modulations possibles tant au niveau spinal que supraspinal des mécanismes nerveux mis en jeu, il semblait important d’analyser celles-ci pendant le mouvement et aux différents angles investigués. Cette précision méthodologique a permis d'élargir la discussion concernant les possibles modifications de la balance "excitation-inhibition" lors de sollicitations excentriques, qui, jusqu’à présent, n'avaient été analysées que pour un angle articulaire donné.<br>Doctorat en Sciences de la motricité<br>info:eu-repo/semantics/nonPublished

Le but de ce travail de thèse était d'étudier chez le rat, la vitessse et la qualité de regenérescence d'un muscle squelettique de type lent, après différents mode lésionnels. Pour ce faire, nous avons analysé l'évolution des marqueurs du phenotype contractile [distribution des différentes isoformes des chaînes lourdes de la myosine (MHC)] et du phénotype métabolique [isoformes de la créatine-kinase (CK) et de la lactate-deshydrogénase (LDH)] au cours de la régénérescence. Ce travail peut être décliné en trois grandes étapes : 1) dans un premier temps, nous avons établi la cinétique de récupération du phénotype musculaire après une lésion induite par écrasement (lésions associées à de graves désordres anatomiques et avec une altération neuro-vasculaire), puis nous l'avons comparée à celle observée après une lésion induite par injection de notexine (dégénérescence étendue des fibres musculaires, mais sans graves desordres anatomiques). Nos résultats ont montré que le type de lésion n'affecte que faiblement la vitesse de récupération des isoformes de MHC et le retour à un phénotype contractile normal. . .<br>The aim of this thesis was to study kinetic and quality of regeneration in a slow type skeletal muscle of the rat, after different kinds of injury. Therefore, we analyzed the evolution of contractile phentype markers[distribution of the different myosin heavy chain isoforms (MHC)] and of metabolic phenotype markers [creatine-kinase (CK) and lactate-dehydrogenase (LDH) isoforms] during regeneration. This work can be declined in into three main steps : 1) initially, we established the time course recovery of the muscular phenotype after a crash injury (associated with serious anatomical disorders and with neuro-vascular alterations), then we compared it with that observed after an injury induced by a notexin injection (wide myofibres degeneration, but without serious anatomical disorders). Our results showed that the type of injury affects only slightly the recovery of the MHC isoforms and the return to a normal contractile phenotype. On the other hand, the recovery of the oxydative capacities and the return to a mature metabolic phenotype are slower than the recovery of contractile proteins. Moreover, the recovery of the oxydative capacities is much slower in the crush-injured muscles. . .

Les hydrogels de Polyacrylamide (PAAM) hydrolysés sont des matériaux électroactifs biocompatibles non biodégradables. Ils possèdent des propriétés très proches de celles du muscle naturel et leur mode opérationnel basé sur la diffusion d’ions est similaire à celui existant dans les tissus musculaires naturels. Compte tenu de ces caractéristiques, ces hydrogels sont de bons candidats pour la conception de nouveaux muscles artificiels. Le problème qui limite leur utilisation réside dans leur temps de réponse qui reste encore inférieur à celui du système de fibres musculaires naturelles. Leur fonction actuatrice est limitée par le phénomène de diffusion en raison de leur structure massique qui est à l’origine de cycles de fonctionnement relativement lents. Dans le but de développer un nouveau système artificiel mimant le comportement du muscle squelettique naturel cette étude se divise en deux grandes étapes. La première étape vise le développement d’une étude de la synthèse de l’hydrogel de PAAM et de son mode de fonctionnement. Dans cette étude les effets des paramètres gouvernant la polymérisation sur les propriétés des hydrogels sont évalués. Les propriétés électrochimiques et le mécanisme d’activation des actuateurs soumis à une excitation électrique sont étudiés et le mode de fonctionnement des actuateurs est caractérisé et expliqué. La seconde étape est la proposition et le développement d’une nouvelle architecture de muscle artificiel à base de PAAM. Cette architecture consiste en une structure fibreuse du gel encapsulée par une couche en gel conducteur jouant le rôle d’électrodes. La structure fibreuse permet au système d’exhiber une réponse rapide et la couche en gel améliore ses propriétés mécaniques. Comme un premier pas dans la réalisation du modèle nous avons mis en place un nouveau procédé basé sur la technique d’électrofilage qui permet la génération de fibres linéairement disposées. En utilisant ce processus nous avons réussi à fabriquer des microfibres de PAAM réticulées, électroactives montrant des réponses rapides<br>Hydrolyzed Polyacrylamide (PAAM) hydrogels are electroactive, biocompatible and non-biodegradable materials. Their main attractive characteristic is their operative similarity with biological muscles and particularly their life-like movement. They suit better the artificial muscle fabrication despite their response time which stays low compared to natural human muscle due to their bulky structure and due to the kinetics of the size dependence of their volume change. In order to copy the natural skeletal muscle design into a new artificial muscle system this study is divided into two steps. The first step is the development of a comprehensive study of the hydrogel itself in order to obtain the elementary background needed for the design of actuating devices based on this material. The effect of polymerization parameter on the hydrogel properties is investigated. The electrochemical properties and actuation mechanisms of the hydrogel is studied, the bending of PAAM actuators induced by electric field is discussed and a mechanism for the bending phenomenon is proposed. The second step is the proposition of a new artificial muscle architecture based on PAAM hydrogel. The model consists on a fiber like elements of hydrolyzed PAAM, working in parallel, embedded in a thin conducting gel layer which plays the role of electrodes. The fiber-like elements enable the system to exhibit relatively rapid response and the gel layers enhance their mechanical properties. Aiming to realize the model we have put in place a new electrospinning setup which is a modified process for the production of micro to nanofibers via electrostatic fiber spinning of polymer solutions. The main advantage of this technology is to produce aligned electrospun fibers over large areas by simple and a low cost process making it possible to produce fiberbased devices efficiently and economically. Using this setup, we succeeded in the fabrication of electroactive crosslinked hydrogel microfibers that can achieve fast electroactive response

There is a dearth of knowledge on the functional organization of the anatomically complex human masseter muscle. Limited physiological studies suggest a functional organization which may differ significantly from human limb muscles. The present studies aimed to examine the putative relationship between structure and function in the human masseter muscle as a basis for understanding function and dysfunction in human jaw muscles. In the first experiment single motor unit (SMU) activity was recorded from pairs of recording sites distributed throughout the masseter muscle. In each case SMU activity at a chosen location was used as a reference to search for synchronized SMU activity at another selected site. The locations of the needle tips were estimated in 3-dimensions (3-D) by means of an optical system, then transferred to 3-D reconstructions derived from Magnetic Resonance images. This approach permitted calculation of the linear distances between verified muscle recording sites. The mean separation of the sites from which synchronous SMU activity could be recorded was 8.8±3.4mm. The putative territories had a preferred orientation in the antero-posterior axis. Motor unit territories were larger than described previously, and appeared to be related to anatomical compartments. The second experiment involved recording activity from stereotactically mapped masseter SMUs. In each case, the lowest sustainable firing frequency (LSFF) was reached by slow increases and decreases in voluntary firing rate, followed by sustained firing at the lowest possible rate. Pulse-discrimination and digital sampling of consecutive inter-spike intervals (ISIs) were then used to measure LSFF for 2-6 separate occlusal and postural tasks to which each unit contributed. There were significant differences between mean ISIs for the tasks performed by most units, which suggests descending drive to masseter units is highly task-dependent. There were also regional differences in unit task specificities. In the third paradigm, reflex SMU activity was recorded from units in the masseter muscle and the inferior head of the lateral pterygoid muscle. Bipolar electrodes fixed to the gingiva near the maxillary canine delivered single pulses of 1ms duration at sub-noxious levels of intensity. At constrained firing frequencies (10, 15Hz), pulses were injected sequentially, with increasing delays, after preselected spikes. More profound inhibition occurred in units firing at 10 than 15Hz. There were significant differences in masseter inhibitory responses when the unit task varied. Reflex inhibition in masseter and lateral pterygoid SMUs is highly frequency-dependent, and also task-dependent in masseter units. The fourth study involved recording activity from SMUs in the masseter muscle. A midline load cell was fixed to the incisor teeth and aligned either perpendicular (P) or 30 degrees anterior (A) to the occlusal plane, without altering jaw position. A rigid spike-triggered averaging (STA) paradigm was used to extract the contribution of individual SMUs to the overall force at load cell orientations P and A. Spikes preceded or followed by an interval of less than 100ms were rejected prior to averaging. At background bite forces from 0.06-8N, the isometric forces apparently developed by individual units varied randomly with load cell orientations, (P range 36.2±19.6mN; A range 38.2±28.4mN). All units could be fired slowly with varying degrees of muscle coactivation, in some instances without contact on the load cell. The use of STA as a method for determining SMU tension in the masseter muscle appears to be task-dependent and in the presence of coactivation may be inappropriate. The findings collectively indicate the heterogeneous nature of SMU behaviour in the human masseter muscle which is consistent with internal muscle compartments based on anatomical features and functional behaviour. There thus appear to be both physiological and anatomical substrates for differential motor control of selected regions of the human masseter muscle.<br>Dentistry, Faculty of<br>Graduate

Thesis (M.S.)--California Polytechnic State University, 2008.<br>"July 2008." "In partial fulfillment of the requirements for the degree [of] Master of Science in Engineering with a specialization in Biomedical Engineering." "Presented to the faculty of California Polytechnic State University, San Luis Obispo." Major professor: Trevor Cardinal, Ph.D. Includes bibliographical references (leaves 96-101). Also available on microfiche and online.

Thesis (M.S.)--West Virginia University, 1999.<br>Title from document title page. Document formatted into pages; contains viii, 81 p. : ill. Vita. Includes abstract. Includes bibliographical references.

The investigation of motor-unit fatigability in reduced-animal models has been dominated by a single fatigue test, one fatigue index, and an emphasis on changes in the magnitude of (usually peak) force. Although the standard fatigue test has been reported to elicit changes in the dynamic phases of an isometric tetanus, this has not been systematically studied in single motor units. Furthermore, changes in the profile of individual tetani during the fatigue test have led some investigators to suggest that other force parameters (i.e., integrated force) or fatigue indices may provide additional information about motor-unit performance during the test. The purposes of this project were to: (1) evaluate the time courses of a variety of force parameters characterizing both the magnitude of force and the dynamic aspects of force during a 4-min fatigue test of functionally isolated cat, tibialis posterior motor units; and (2) determine if motor units could be classified into the conventional motor-unit types based on these new parameters. There was considerable variability in the average time course of the magnitude of force during the fatigue test. The variability within the type FR and F(int) motor-unit groups resulted in several units whose characteristics bordered those which, by definition, separate unit types. The classification of these units depended on the force parameter and fatigue index used to quantify their fatigability. The time course of the magnitude of force also revealed differences in the behavior of potentiating and non-potentiating groups. There were many differences between motor-unit types in terms of dynamic-force parameters before, during and after the fatigue test. Comparison of initial and 2-min values revealed a preferential effect of stimulation on force development in type S and FR units (i.e., increased rate) and on force decay in type F(int) and FF units (i.e., prolonged duration and decreased rate). The time courses of these effects further revealed qualitative differences between different combinations of motor-unit types. Groups of units (or lack thereof) revealed by dynamic-force parameters were compared to conventional motor-unit types by discriminant analysis. The results were not always consistent with conventional types.

It is well established that unilateral exercise can produce contralateral effects. However, it is unclear whether unilateral exercise that leads to muscle injury and inflammation also affects the homologous contralateral muscles. To test the hypothesis that unilateral muscle injury causes contralateral muscle changes, an experimental rabbit model with unilateral muscle overuse caused by a combination of electrical muscle stimulation and exercise (EMS/E) was used. The soleus and gastrocnemius muscles of both exercised and non-exercised legs were analyzed with enzyme-and immunohistochemical methods after 1, 3 and 6 weeks of repeated EMS/E. After 1 w of unilateral EMS/E there were structural muscle changes such as increased variability in fiber size, fiber splitting, internal myonuclei, necrotic fibers, expression of developmental MyHCs, fibrosis and inflammation in the exercised soleus muscle. Only limited changes were found in the exercised gastrocnemius muscle and in both non-exercised contralateral muscles. After 3 w of EMS/E, muscle fiber changes, presence of developmental MyHCs, inflammation, fibrosis and affections of nerve axons and AChE production were observed bilaterally in both the soleus and gastrocnemius muscles. At 6 w of EMS/E, the severity of these changes significantly increased in the soleus muscles and infiltration of fat was observed bilaterally in both the soleus and the gastrocnemius muscles. The affections of the muscles were in all three experimental groups restricted to focal regions of the muscle samples. We conclude that repetitive unilateral muscle overuse caused by EMS/E overtime leads to both degenerative and regenerative tissue changes and myositis not only in the exercised muscles, but also in the homologous non-exercised muscles of the contralateral leg. Although the mechanism behind the contralateral changes is unclear, we suggest that the nervous system is involved in the cross-transfer effects.

Le travail de thèse a porté sur l'étude de la 0- N-acétylglucosaminylation (0-GlcNAc) dans le muscle squelettique et son implication dans la physiologie musculaire. Nous avons identifié par approche protéomique des protéines musculaires modifiées par la O-GlcNAc, jouant un rôle clé dans tous les moyens de régénération d'énergie du muscle squelettique ainsi que dans le processus contractile. Nous mettons également en évidence la possible implication de la O-GlcNAc dans l'atrophie fonctionnelle induite par le modèle d'hypodynamie-hypokinésie, les taux de O-GlcNAc étant corrélés au degré d'atrophie du muscle après hypodynamie-hypokinésie. Enfin, l'analyse du rôle de la O-GlcNAc sur l'activité contractile, et sur la sensibilité calcique des fibres musculaires, démontre que cette glycosylation pourrait jouer un rôle clé dans le processus contractile. Nos résultats suggèrent que la O-GlcNAc pourrait intervenir dans les interactions protéine-protéine qui régissent la contraction musculaire.

L’asthme est un désordre respiratoire obstructif qui affecte plus de 330 millions de personnes à travers le monde. Les symptômes de cette pathologie comprennent de l’essoufflement, de l’oppression thoracique, de la sibilance et de la toux, et surviennent suivant l’inhalation de facteurs déclencheurs (virus, allergène, pollution…). La pathologie de l’asthme est caractérisée par une inflammation chronique et variable au sein du système respiratoire, un remodelage des voies aériennes ainsi qu’une hyperréactivité bronchique. L’équipe de recherche du Dr Ynuk Bossé travaille sur la physiologie du muscle lisse des voies aériennes, et plus spécifiquement sur l’augmentation des capacités contractiles du muscle lisse en réponse à un tonus (i.e. contraction soutenue). Ce phénomène nommé le gain de force du muscle lisse a été observé avant mon arrivée dans ce laboratoire sur des trachées de moutons et de souris montées en bain d’organe, ainsi qu’in vivo chez la souris. Des travaux antérieurs ont démontré que la présence d’un tonus augmentait la réactivité bronchique de souris en réponse à l’inhalation d’une forte dose de métacholine. Le but de cette thèse était d’explorer dans une dynamique translationnelle, les rouages moléculaires de ce phénomène et d’en définir les impacts sur la fonction respiratoire in vivo. Dans une première étude réalisée au début de mon doctorat, nous avons étudié les conséquences du tonus sur la réactivité bronchique in vivo chez l’humain. Nous avons ainsi observé que l’augmentation du tonus, provoquée par l’inhalation répétée de faibles doses de métacholine durant une période de 30 minutes, augmentait la réactivité bronchique en réponse à l’inhalation d’une forte dose de métacholine. De plus, nous avons également observé grâce à l’utilisation de la technique des oscillations forcées que cette augmentation de la réactivité bronchique était liée à une augmentation de la résistance des voies périphériques. Nous avons donc confirmé dans cette étude que la présence d’un tonus augmente la réactivité bronchique chez de jeunes humains en santé. Dans une seconde étude, conduite tout au long de mon doctorat, nous avons étudié les mécanismes moléculaires responsables du gain de force du muscle lisse en réponse à un tonus. Nous avons ainsi observé que ce phénomène n’était pas lié à une potentialisation de la phosphorylation de la chaîne légère de myosine, mais plutôt provoqué par une augmentation de la filamentogénèse d’actine. Nous avons également déterminé que cette augmentation de la filamentogénèse d’actine était en partie provoquée par une inhibition de la dépolymérisation des filaments d’actine suite à l’inhibition de la protéine cofiline. Nous avons donc démontré que le tonus augmente la filamentogénèse d’actine au sein des cellules musculaires lisses, ce qui pourrait contribuer à une augmentation des capacités contractiles. Finalement, dans une troisième étude entreprise durant la dernière partie de mon doctorat, nous tentons de comprendre les liens entre le phénomène du gain de force du muscle lisse et l’inflammation présente dans l’asthme. Il semblerait que la présence d’une inflammation provoquée par de la poudre d’acariens chez la souris augmente la réactivité bronchique, mais empêche le développement du gain de force du muscle lisse. En revanche, les résultats obtenus sont encore préliminaires. Il est actuellement impossible de tirer des conclusions fermes. Ainsi, nous nous interrogeons toujours à l’égard du rôle de l’inflammation sur le gain de force du muscle lisse des voies aériennes. Dans sa globalité, cette thèse démontre que le gain de force du muscle lisse des voies aériennes est provoqué par un remodelage du cytosquelette d’actine, et que ce phénomène augmente la réactivité bronchique in vivo chez l’humain. De plus, cette thèse ouvre des voies de recherche afin de déterminer si ce phénomène pourrait être impliqué dans l’hyperréactivité bronchique dans l’asthme.<br>L’asthme est un désordre respiratoire obstructif qui affecte plus de 330 millions de personnes à travers le monde. Les symptômes de cette pathologie comprennent de l’essoufflement, de l’oppression thoracique, de la sibilance et de la toux, et surviennent suivant l’inhalation de facteurs déclencheurs (virus, allergène, pollution…). La pathologie de l’asthme est caractérisée par une inflammation chronique et variable au sein du système respiratoire, un remodelage des voies aériennes ainsi qu’une hyperréactivité bronchique. L’équipe de recherche du Dr Ynuk Bossé travaille sur la physiologie du muscle lisse des voies aériennes, et plus spécifiquement sur l’augmentation des capacités contractiles du muscle lisse en réponse à un tonus (i.e. contraction soutenue). Ce phénomène nommé le gain de force du muscle lisse a été observé avant mon arrivée dans ce laboratoire sur des trachées de moutons et de souris montées en bain d’organe, ainsi qu’in vivo chez la souris. Des travaux antérieurs ont démontré que la présence d’un tonus augmentait la réactivité bronchique de souris en réponse à l’inhalation d’une forte dose de métacholine. Le but de cette thèse était d’explorer dans une dynamique translationnelle, les rouages moléculaires de ce phénomène et d’en définir les impacts sur la fonction respiratoire in vivo. Dans une première étude réalisée au début de mon doctorat, nous avons étudié les conséquences du tonus sur la réactivité bronchique in vivo chez l’humain. Nous avons ainsi observé que l’augmentation du tonus, provoquée par l’inhalation répétée de faibles doses de métacholine durant une période de 30 minutes, augmentait la réactivité bronchique en réponse à l’inhalation d’une forte dose de métacholine. De plus, nous avons également observé grâce à l’utilisation de la technique des oscillations forcées que cette augmentation de la réactivité bronchique était liée à une augmentation de la résistance des voies périphériques. Nous avons donc confirmé dans cette étude que la présence d’un tonus augmente la réactivité bronchique chez de jeunes humains en santé. Dans une seconde étude, conduite tout au long de mon doctorat, nous avons étudié les mécanismes moléculaires responsables du gain de force du muscle lisse en réponse à un tonus. Nous avons ainsi observé que ce phénomène n’était pas lié à une potentialisation de la phosphorylation de la chaîne légère de myosine, mais plutôt provoqué par une augmentation de la filamentogénèse d’actine. Nous avons également déterminé que cette augmentation de la filamentogénèse d’actine était en partie provoquée par une inhibition de la dépolymérisation des filaments d’actine suite à l’inhibition de la protéine cofiline. Nous avons donc démontré que le tonus augmente la filamentogénèse d’actine au sein des cellules musculaires lisses, ce qui pourrait contribuer à une augmentation des capacités contractiles. Finalement, dans une troisième étude entreprise durant la dernière partie de mon doctorat, nous tentons de comprendre les liens entre le phénomène du gain de force du muscle lisse et l’inflammation présente dans l’asthme. Il semblerait que la présence d’une inflammation provoquée par de la poudre d’acariens chez la souris augmente la réactivité bronchique, mais empêche le développement du gain de force du muscle lisse. En revanche, les résultats obtenus sont encore préliminaires. Il est actuellement impossible de tirer des conclusions fermes. Ainsi, nous nous interrogeons toujours à l’égard du rôle de l’inflammation sur le gain de force du muscle lisse des voies aériennes. Dans sa globalité, cette thèse démontre que le gain de force du muscle lisse des voies aériennes est provoqué par un remodelage du cytosquelette d’actine, et que ce phénomène augmente la réactivité bronchique in vivo chez l’humain. De plus, cette thèse ouvre des voies de recherche afin de déterminer si ce phénomène pourrait être impliqué dans l’hyperréactivité bronchique dans l’asthme.<br>Asthma is an obstructive respiratory disorder affecting more than 330 million people worldwide. The symptoms include breathlessness, chest oppression, wheezing and cough. The symptoms are variable in nature and severity and generally coincide with the inhalation of environmental factors (viruses, allergens, pollution…). The pathology of asthma is characterized by several typical features, such as airway inflammation, airway remodeling and airway hyperresponsiveness. The research team of Dr Ynuk Bossé is specialized in the study of lung physiology and airway smooth muscle mechanics. Of particular interest is a phenomenon called ‘force adaptation’. Force adaptation is a time-dependent gain in the contractile capacity of airway smooth muscle in response to tone (i.e., a sustained contraction). This phenomenon was observed in vitro in isolated ovine and murine tissues, as well as in vivo in mice. Previous work has demonstrated that the presence of tone, provoked by repeated exposures to low doses of methacholine during 20 min, increases airway responsiveness to the inhalation of a high dose of methacholine. The aim of this thesis was to decipher the molecular mechanisms of force adaptation in vitro and to explore the impact of this phenomenon on respiratory function in vivo. In a first study, which was conducted at the beginning of my PhD, we assessed the effect of tone on airway responsiveness in young healthy adults. We demonstrated that tone, which was generated by repeated inhalations of low doses of methacholine during 30 min, enhances airway responsiveness to a high dose of methacholine. Moreover, with the use of the force oscillation technique, we demonstrated that this effect was predominant in the peripheral airways. Therefore, this study confirmed that airway smooth muscle tone increases airway responsiveness in young healthy adults. In a second study, conducted over the entire course of my PhD, we investigated the molecular mechanisms responsible for the gain in contractile capacity induced by tone. We observed that force adaptation does not rely on molecular mechanisms enhancing the phosphorylation of the myosin light chain but rather occurs in conjunction with an increase in actin filamentogenesis. We further demonstrated that this increase in actin filamentogenesis may stem not only from actin polymerization but also from the inhibition of actin filament depolymerization via the inhibition of the protein cofilin. Therefore, the results of this study suggested that tone increase the contractile capacity of airway smooth muscle by fostering actin filamentogenesis. Finally, in a third study started at the end of my PhD, we are trying to understand the links between the gain in contractile capacity induced by tone and airway inflammation in asthma. We are using a mouse model of allergic airway inflammation induced by repeated exposures to house dust mite. While allergic inflammation increases airway responsiveness, it seems to diminish the phenomenon of force adaptation. However, the results obtained so far will require further investigations. It is currently impossible to reach authoritative conclusions. We are still left wondering whether airway inflammation alters the gain in contractile capacity induced by tone. Overall, this thesis is demonstrated that force adaptation increases airway responsiveness in vivo in human and, at the molecular level, the phenomenon seems to rely on an active remodeling of the actin cytoskeleton. Moreover, this thesis opens new research areas, which will need to be further explored in order to determine whether the gain in contractile capacity induced by tone is implicated in airway hyperresponsiveness in asthma<br>Asthma is an obstructive respiratory disorder affecting more than 330 million people worldwide. The symptoms include breathlessness, chest oppression, wheezing and cough. The symptoms are variable in nature and severity and generally coincide with the inhalation of environmental factors (viruses, allergens, pollution…). The pathology of asthma is characterized by several typical features, such as airway inflammation, airway remodeling and airway hyperresponsiveness. The research team of Dr Ynuk Bossé is specialized in the study of lung physiology and airway smooth muscle mechanics. Of particular interest is a phenomenon called ‘force adaptation’. Force adaptation is a time-dependent gain in the contractile capacity of airway smooth muscle in response to tone (i.e., a sustained contraction). This phenomenon was observed in vitro in isolated ovine and murine tissues, as well as in vivo in mice. Previous work has demonstrated that the presence of tone, provoked by repeated exposures to low doses of methacholine during 20 min, increases airway responsiveness to the inhalation of a high dose of methacholine. The aim of this thesis was to decipher the molecular mechanisms of force adaptation in vitro and to explore the impact of this phenomenon on respiratory function in vivo. In a first study, which was conducted at the beginning of my PhD, we assessed the effect of tone on airway responsiveness in young healthy adults. We demonstrated that tone, which was generated by repeated inhalations of low doses of methacholine during 30 min, enhances airway responsiveness to a high dose of methacholine. Moreover, with the use of the force oscillation technique, we demonstrated that this effect was predominant in the peripheral airways. Therefore, this study confirmed that airway smooth muscle tone increases airway responsiveness in young healthy adults. In a second study, conducted over the entire course of my PhD, we investigated the molecular mechanisms responsible for the gain in contractile capacity induced by tone. We observed that force adaptation does not rely on molecular mechanisms enhancing the phosphorylation of the myosin light chain but rather occurs in conjunction with an increase in actin filamentogenesis. We further demonstrated that this increase in actin filamentogenesis may stem not only from actin polymerization but also from the inhibition of actin filament depolymerization via the inhibition of the protein cofilin. Therefore, the results of this study suggested that tone increase the contractile capacity of airway smooth muscle by fostering actin filamentogenesis. Finally, in a third study started at the end of my PhD, we are trying to understand the links between the gain in contractile capacity induced by tone and airway inflammation in asthma. We are using a mouse model of allergic airway inflammation induced by repeated exposures to house dust mite. While allergic inflammation increases airway responsiveness, it seems to diminish the phenomenon of force adaptation. However, the results obtained so far will require further investigations. It is currently impossible to reach authoritative conclusions. We are still left wondering whether airway inflammation alters the gain in contractile capacity induced by tone. Overall, this thesis is demonstrated that force adaptation increases airway responsiveness in vivo in human and, at the molecular level, the phenomenon seems to rely on an active remodeling of the actin cytoskeleton. Moreover, this thesis opens new research areas, which will need to be further explored in order to determine whether the gain in contractile capacity induced by tone is implicated in airway hyperresponsiveness in asthma

Although traditional prevention and management strategies for hamstring injuries have focussed on optimising muscle strength, flexibility and endurance, incidence and/or recurrence rates of these injuries remains high. A theoretical framework was developed considering additional factors that increase the stabilising demand of the hamstrings. These factors included loss of related stability at the knee and lumbopelvic regions and extrinsic factors during functional and sporting activities. The aims of this research were to determine whether electromyographic (EMG) derived hamstrings, quadriceps and gluteal muscle activation patterns as well as isokinetic torque generation patterns could differentiate athletes who had incurred a hamstring injury from uninjured control athletes. It was hypothesised that the EMG activity of the injured participants would be decreased compared to uninjured control participants during maximal activities, but increased during weight bearing activities. The research included the identification of laboratory-based tasks relevant to the function of the hamstring muscles; test-retest reliability of EMG variables recorded during these tasks; and a comparative cross-sectional study of hamstring-injured (hamstring group, HG) and control athletes (control group, CG). Electromyographic activation patterns were determined during assessment of concentric and eccentric isokinetic strength of the thigh muscles, during transition from double- to single-leg stance, and forward lunging. Isokinetic and EMG onset and amplitude variables were compared both within- and between-groups. Despite no significant differences for peak torque, the HG injured limb generated lower average eccentric flexor torque towards the outer range of motion in comparison to the HG uninjured limb (P = 0.034) and the CG bilateral average (P = 0.025). Furthermore, the EMG root mean square (RMS) decrease from the start to the end range of the eccentric flexor contraction was greater for the HG injured limb hamstrings than the CG bilateral average. During the transition from double- to single-leg stance, the EMG onsets of the HG injured limb (biceps femoris [BF] P < 0.001, medial hamstrings [MH] P = 0.001), and the HG uninjured limb (BF P = 0.023, MH P = 0.011) were earlier in comparison to the CG bilateral average. The transition normalised EMG RMS was significantly higher for the HG injured side BF (P = 0.032), MH (P = 0.039) and vastus lateralis (VL, P = 0.037) in comparison to the CG bilateral average. During the forward lunge, no significant differences were observed within- and between-groups for the normalised EMG amplitude prior to and following initial foot contact. These results suggest that during maximal isokinetic eccentric flexor contractions, the average torque and EMG activity is decreased towards the lengthened position of the hamstring-injured limb. This may be due to structural changes or neurophysiological inhibitory mechanisms. During the static weight bearing task an earlier onset of the HG hamstring muscles was evident in comparison to controls. The hamstrings and the VL of the injured limbs were activated at greater normalised amplitude. The increased muscle activation in the hamstring-injured limbs during the support phase may indicate a greater demand towards stability of the kinetic chain or changes in proprioceptive function. Future research should consider the mechanisms and clinical implications underlying a loss of eccentric flexor torque towards the outer range of contraction, and investigate why increased activation of thigh muscles occurs during the static weight bearing task in hamstring-injured athletes.

Thesis (Ph. D.)--State University of New York at Binghamton, Thomas J. Watson School of Engineering and Applied Science, Department of Bioengineering, Biomedical Engineering, 2009.<br>Includes bibliographical references.

Objectif : Proposer une alternative fiable, et plus proche de la réalité fonctionnelle, en utilisant une approche isocinétique sectorielle représentée par le calcul de ratios agonistes/antagonistes par plage angulaire de 10°. Matériel et Méthode : Trois études ont été menées, chaque étude portant sur des sites articulaires particulièrement impliqués dans la motricité humaine, et également très concernés par la survenue de blessure en lien avec la balance musculaire des principaux groupes stabilisateurs. Il s'agit respectivement de l'articulation scapulo-humérale (muscles rotateurs interne/externe), de l'articulation fémoro-tibiale (muscles fléchisseurs/extenseurs), et du rachis lombaire (muscles fléchisseurs/extenseurs). Les sujets étaient des volontaires sains, non spécialistes d'une pratique sportive. Les ratios par plage angulaire de 10° étaient comparés entre les plages angulaires et également par rapport aux ratios classiques associés aux valeurs "pic". La reproductibilité était évaluée pour l'ensemble des ratios. Résultats : Nos études ont montré que les ratios par plage angulaire étaient évolutifs au cours du mouvement et significativement différents des ratios classiques. De plus, nos résultats ont mis en exergue une bonne reproductibilité absolue des ratios associés aux plages angulaires de 10°. Conclusion : La méthode sectorielle associée aux plages angulaires de 10° permet une évaluation fiable et pertinente de la balance musculaire<br>Objective : The general objective was to propose a reliable alternative to assess agonists-antagonists muscle balance in dynamic perspective by using a sector approach: the angular range method. Material and method : Three studies were conducted, each study involving joint particularly involved in human motion, and also in injury occurence related to the muscle balance between the main joint stabilizers. These are respectively scapulohumeral joint (internal ans external rotator muscles), femoro-tibial joint (flexor and extensor muscles), and lumbar spine (flexor and extensor muscles). Subjects were healthy volunteers, not specialists in a sport. The ratios by angular range of 10° were compared between the angular ranges and also compared to the classical ratios associated with the peak torques. Reliability was evaluated for all ratios. Results : All studies have shown that angular range ratios were signicantly different between angular ranges and also significantly different to the classical peak torque ratios. In addition, the results have highlighted a good absolute reliability of the ratios associated with the angular ranges of 10°. Conclusion : The sector method associated with angular ranges of 10° allows a reliable and relevant assessment of the muscle balance by a finer analysis of a major parameter of muscle function involved in physiopathology and motor performance

Le système musculaire joue un rôle primordial dans l’homéostasie de l’organisme. Il est impliqué dans différentes fonctions indispensables aux activités de la vie quotidienne telles que la production de mouvement, la locomotion, le maintien postural et l’équilibre. La qualité du tissu musculaire est donc primordiale dans le maintien de la qualité de vie et, à long terme, à la longévité. L'hypoactivité et le vieillissement sont deux situations qui entraînent le déconditionnement musculaire, et qui partagent une caractéristique commune: une perte de force musculaire, une atrophie et la modification du typage musculaire, ainsi que l'accumulation de tissu adipeux intramusculaire. Aujourd'hui, il existe de nombreuses données dans la littérature indiquant un lien entre le stress oxydant et le déconditionnement musculaire. Le but de cette thèse était d'évaluer l'impact de la modulation des défenses antioxydantes sur la prévention du déconditionnement musculaire. Cela a été étudié sous deux angles, l'un dans le contexte du vieillissement, et le second dans un contexte d'hypoactivité. La première étude avait pour but d'évaluer la fragilité chez un modèle souris âgées, utilisant un groupe de souris WT et un groupe de souris transgéniques sur-exprimant l'enzyme G6PD. Nous avons évalué des paramètres de qualité musculaire et de stress oxydant et avons réalisé une analyse transcriptomique à partir d'échantillons musculaires des souris de chacun des deux groupes. La seconde étude a été conduite dans le but d'évaluer les effets d'un cocktail enrichi en composés anti-oxydants et anti-inflammatoires, durant deux mois d'hypoactivité (modèle Bedrest). Nos résultats ont démontré l’inefficacité de cette supplémentation sur la prévention de la perte de masse et de force musculaire. De plus, les données concernant les mécanismes moléculaires ont démontré une altération des processus de récupération chez les sujets supplémentés.Les conclusions de nos études donnent des pistes sur les stratégies anti-oxydantes les plus appropriées contre le déconditionnement musculaire. Il semble préférable de intéresser à la stimulation des systèmes de défenses endogènes, plutôt que de se centrer sur une supplémentation nutritionnelle exogène. Néanmoins, la complexité des voies de signalisation redox requièrent une meilleure compréhension pour optimiser les mesures de prévention afin de limiter la perte de fonction musculaire<br>Musculoskeletal system plays a key role in organism’s well-functioning and is responsible for a large variety of functions such as posture, locomotion, balance, and activities of daily life. The quality of the skeletal muscle is therefore capital to maintain quality of life and, in the long term, survival. Hypoactivity and aging are two situations that cause skeletal muscle deconditioning, therefore sharing common characteristics: loss of muscle strength, muscular atrophy and MyHC redistribution, as well as IMAT accumulation. To date, there is plenty of evidence supporting a causative link between oxidative stress phenomenon and muscle deconditioning.The general aim of this PhD thesis was to evaluate the impact of the modulation of the antioxidant defenses on the prevention of muscle deconditioning. It has been studied from two perspectives, the first one in the context of aging and the second in the context of hypoactivity.The first study aimed to evaluate frailty in old female animals, using WT and G6PD-overexpressing mice. We evaluated muscle quality parameters and oxidative stress markers. Finally, we performed a transcriptomic analysis of muscle samples and highlighted differentially expressed genes in both groups of mice.The second study was conducted to evaluate the effects of a cocktail enriched in antioxidant/anti-inflammatory molecules in a 2-month hypoactivity experiment (Bedrest model). Our results clearly demonstrate the ineffectiveness of this type of supplementation in the prevention of muscle mass and strength loss. Moreover, data regarding muscle molecular mechanisms highlight an alteration of recovery processes in the supplemented subjects.Finally, the conclusions of our two studies gave clues on the suitable antioxidant modulation strategy for the prevention of skeletal muscle deconditioning. It seems preferable to focus on the stimulation of endogenous defense system whether than towards exogenous supply of nutritional antioxidants. Nevertheless, the complexity of redox signaling requires better understanding to optimize countermeasures in muscle wasting situations

This thesis investigated the effect of knee angle position on the electrical signal of two hamstring muscles using a traditional technique (bipolar electromyography) and a modern technique (high-density electromyography). The results suggest that changes in knee position affect the electrical activity on bipolar electromyography and these changes are associated with the rotation of muscle fibers under the pair of electrodes. However, using high-density electromyography, there was no difference between different knee positions. These findings suggest that high-density electromyography has different responses compared to bipolar electromyography. Hence, studies using bipolar montages need to be interpreted with caution to avoid wrong conclusions.

Thesis (M.S. in animal science)--Washington State University, May 2009.<br>Title from PDF title page (viewed on Apr. 7, 2010). "Department of Animal Sciences." Includes bibliographical references (p. 61-74).

The present study was undertaken to determine the relationship between perinatal complications and subsequent development of Attention Deficit Hyperactivity Disorder (ADHD) and other behavioral characteristics. The biological mothers of 74 children diagnosed with ADHD and 77 children displaying no characteristics of the disorder completed the Maternal Perinatal Scale (MPS), the Behavior Assessment System for Children-Parent Rating Scales (BASC-PRS), and a demographic survey. In addition, the biological mothers of 120 children with no characteristics of ADHD or any other behavior disorders completed only the MPS so that exploratory factor analysis of the MPS could be completed.Following factor analysis, stepwise discriminant analysis of the resulting five factors was utilized to explore the nature of the relationship between such perinatal factors and ADHD. Results of this analysis indicated that emotional factors, or the amount of stress encountered during pregnancy and the degree to Relationship Between Perinatal Complications 3 was planned, were the items that maximized the separation between the ADHD and Non-ADHD groups. Additional discrimination between the groups was attributed to the extent of insult or trauma to the developing fetus and the outcome of prior pregnancies. ADHD children were also found to have experienced twice as many behavioral, social, or medical problems, and were more likely to reach developmental milestones with delays.Stepwise discriminant analysis also revealed the Attention Problems and Hyperactivity scales of the BASC-PRS were most significant in differentiating between the ADHD and Non-ADHD subjects. Using the BASC-PRS resulted in approximately 90% of the total sample being correctly classified as ADHD or Non-ADHD. Canonical correlation analysis indicated that emotional factors and the general health of both the mother and the developing fetus were the best predictors of later behavioral patterns reported on the BASC-PRS.<br>Human Performance Laboratory

The aims of this thesis were to 1) investigate the effect of SB431542 <i>in vitro</i> and <i>ex vivo</i> as a novel approach towards promoting the functional hypertrophy of skeletal muscle by inhibiting the myostatin-Smad pathway, 2) to investigate the expression and function of the Yes-associated protein (Yap) in skeletal muscle and C2C12 cells as a novel regulator of C2C12 differentiation and 3) to generate a GFP-RCASBP-hYAP1 S127A retrovirus to allow the study of the function of Yap in skeletal muscle differentiation <i>in vivo</i>. The results presented in this thesis show that SB431542 promotes the hypertrophy of C2C12 myotubes and mature <i>Xenopus</i> skeletal muscle fibres. However, SB431542 treatment also results in a reduction in specific force of mature <i>Xenopus</i> muscle fibres suggesting that SB431542 is not suitable as a treatment for skeletal muscle atrophy. These results also show that Yap is expressed in mouse skeletal muscle <i>in vivo</i> and that Yap is a novel regulator of C2C12 differentiation. Finally, these results descried the generation of a GFP-RCASBP-hYAP1 S127A retrovirus that can be used to assess the role of Yap <i>in vivo </i>during skeletal muscle formation in the chick embryo. Together, these results suggest that Yap is a novel regulator of C2C12 differentiation that should be studied as a potential therapeutic target in musculoskeletal diseases.

Differentiation of skeletal muscle fibers into fast and slow twitch appears to be under control of the stimulation pattern imparted by motoneurons innervating these muscle fibers. Fast twitch muscle fibers receive intense stimulation for brief periods of time while slow twitch muscle fibers receive less intense stimulation for much longer periods of time. This study examined thickness of Zlines in dually innervated skeletal muscle fibers of slow twitch soleus muscle following transplantation of the fast extensor digitorum longus (EDL) nerve onto the surface of the soleus. Eight individual dually innervated fibers were dissected from four transplanted mouse soleus muscles and examined with a transmission electron microscope. Z-lines in these dually innervated fibers were thinner (mean = 83 nm) than control soleus (mean = 123 nm) and thicker than control EDL (mean = 57 nm). A significant difference (p< .002) was also found between Z-line thickness near the foreign EDL endplate (mean = 81 nm) versus the original soleus endplate (mean = 85 nm). These results suggest the factors controlling protein synthesis in skeletal muscle fibers have both a global and localized effect.<br>Department of Physiology and Health Science

The use of creative monohydrate (CM) supplementation by athletes to increase strength and lean body mass has great anecdotal support. Therefore, the purpose of this investigation was to document the chronic effects of CM supplementation on resistance trained athletes. Sixteen collegiate football players were randomly separated into a CM and placebo (P) group. Supplementation in capsule form consisted of 5 g CM or P per day throughout a 10 week resistance training program. Pre- and Post-testing consisted of 1) Weight. 2) Body fat estimation. 3) One repetition maximal bench press, squat, and power clean. 4) Cybex testing was also included. Results revealed the CM group was able to significantly increase measures of strength and power, as well as increase body mass without a change in body fat %, while the P group showed no significant changes. Data was analyzed using a paired t-test and ANCOVA (p < 0.05). CM PPrePostPrePostBody Wt (lbs)234.5 + 34.41237.37 + 31.34*215.57 ± 55.12213.0 ± 48.897-site fat %15.37+5.5116.68+6.5813.52 + 10.0913.58+8.33Bench Press (lbs)328.75 + 27.87- 340.0 + 27.65*287.14 + 58.94283.57 + 48.71Squats (lbs)532.86 + 130.92592.14 + 123.86*489.17 + 149.81512.50 ± 161.89Power Cleans271.88 + 47.73288.75 + 45.34*246.00 + 33.99241.00 + 64.65* Denotes significant measureThe data from this study supports the anecdotal claims. Further, contrary to what would be expected with long term resistance training alone, the placebo group failed to increase strength and power measures. This suggests that the resistance program lacked sufficient stimuli or that overtraining might have occurred. However, subjects ingesting CM were able to increase strength and power measures. Thus, it appears that CM may also serve as a buffer to overtraining.<br>School of Physical Education

It has been shown that maximal, bilateral efforts result in both a force and EMG deficit when compared to maximal, unilateral activation of the same musculature. It is unclear whether this deficit is the result of interactions of central or peripheral origin. The first aim study investigated the bilateral performance index (BPI (%) = [100 x bilateral force/(right unilateral + left unilateral forces)] - 100) for maximal, isometric, extensor torques about the knee joint in three groups of subjects: untrained (never lifted weights), cyclists (leg musculature trained reciprocally), and weightlifters (legs trained bilaterally). The BPI for the weightlifters (+7.0 ± 5.0%) was significantly (p < 0.05) greater than the BPI of the cyclists (-4.0 ± 6.3%) or the untrained subjects (-9.7 ± 5.2%). These results indicate that the inhibitory mechanisms previously proposed to act during bilateral efforts are inadequate, and that excitatory factors must be present to achieve a BPI > 0. The second aim study showed that the BPI can be altered as a result of three weeks of bilateral isometric strength training. The BPI's for the control and unilateral training groups were not significantly different pre- to posttraining. However, the BPI of the bilateral training group increased significantly (p < 0.05) from -3.7 ± 6.9% prior to training, to +4.2 ± 4.4% after training. These findings indicate that bilateral strength training can alter the relationship between unilateral and bilateral force output. The third aim study demonstrated that subjects with a positive BPI (+6.8 ± 4.3%) responded differently to an afferent perturbation (electrical stimulation) than subjects with a negative BPI (-10.0 ± 5.2%). The negative BPI group showed a 5.7 ± 3.4% facilitation in force during contralateral electrical stimulation. This was significantly (p < 0.05) less than the 16.5 ± 7.5% facilitation shown by the positive BPI group. These results indicate that afferent feedback can alter the force output in the contralateral limb, and may thereby play a role in unilateral-bilateral force differences.

La fonction principale du muscle étant la contraction, nous avons combiné des évaluations physiologiques, biochimiques et structurelles de la régénération des muscles dans divers modèles de lésions (venin, ischémie et venin). Bien que les critères biochimiques suggèrent une récupération complète, ce n'est pas le cas du point de vue fonctionnel. Nos travaux démontrent donc que l'examen des propriétés contractiles après une lésion est la méthode d'évaluation la plus pertinente pour apprécier le degré de guérison du muscle. De plus, il a été récemment recommandé d'analyser les régulations moléculaires par groupe de gènes fonctionnels ou module (protéines contractiles, mitochondrie, transport ionique, acide gras,. . . ). Dans le but de progresser dans la compréhension des modulations coordonnées survenant dans la plasticité musculaire, nous avons entrepris de caractériser les changements dans les module de gènes correspondant au métabolisme énergétique et aux isoformes des protéines contractiles. Nous avons fait le choix de marqueurs spécifiques des modules dans des modèles animaux où le statut neuromusculaire est modifié soit par une hypodynamie (micro gravité simulée par une suspension) soit par une hyperdynamie (entraînement physique), aussi bien dans des muscles lents que dans de muscles rapides. Pour cela nous avons développé des micro-méthodes pernettant d'obtenir des données sur les changements d'expression de nombreux marqueurs, à partir d'un seul muscle. Nous vaons ainsi développé une analyse des modifications coordonnées par une approche certes globale mais qui reste plus ciblée que les approches protéomiques ou génomiques développées ces dernières années<br>There exists little information on the functional recovery and the relationships between functional parameters, biochemistry and the structural aspect of the recovery. This is why, we have combined physiological, biochemical and structural evaluations of the regenerating skeletal muscles in various models of lesions (venom, ischemia and venom). Although the biochemical criteria suggest a complete recovery, it is not the case from the functional xiewpoint. Our work thus shows that the examination of the contractile properties after a lesion is the most relevant method of evaluation to appreciate the degree of muscle recovery. It was recently recommended to analyze the molecular regulations by group of functional genes or modules (contractile proteins, mitochondria, ionic, fatty acid or glucose transport, etc). With the aim of progressing in understanding the coordinated modulations governing muscle plasticy, we undertook to characterize changes in gene modules corresponding to energy metabolism and to isoforms of contractile proteins. We chose specific markers of these moduls to study animal models of neuromuscular modifications corresponding to either hypodynamy (microgravity simulated by suspension) or hyperdynamy (training), in slow muscles. For that purpose, we developed micromethods allowing to obtain data on expression changes of many markers, starting from only one muscle. We thus developed an analysis of coordinated modifications, bringing a global perspective, although more restricted than the proteomic or genomic approaches developed these past years

Animal experiments indicate that the main form of feedback for jaw-closing muscles is from periodontal mechanoreceptors (PMRs). However, due primarily to limitations on methods, this is yet to be confirmed in humans. The main aim of this thesis was to investigate the reflex contribution of PMRs to the human jaws using vertical (axial) stimulation. To this end the electromyographic and bite force responses of the jaw to a number of different mechanical stimulus conditions, delivered to both the upper central incisors and the upper right first molars, were investigated. The principal hypothesis was that PMRs are responsible for the majority of the reflex responses seen in the human jaw muscles. Furthermore this reflex response is modulated by different characteristics of the stimulus such as: rate of rise, maximum force applied, the amount of constant offset force (preload), the level of muscle contraction and also the physical characteristics of the subject's jaw including: dental health and tooth spacing. These studies have contributed towards the understanding of the neuronal wiring and the receptor systems contained in the jaw. The results indicate that PMRs around the incisors are of fundamental importance for the development of reflex patterns but little if any PMR related reflexes exist around the molar teeth. The reflexes originating from the PMRs around the incisors are modulated by different mechanical characteristics of the stimulus, thus helping to explain how the jaw muscles perform numerous and complex patterns of activation which move the jaw in many different ways and develop forces that are optimum for the task at hand.<br>Thesis (Ph.D.)--School of Molecular & Biomedical Science, 2004.

A typical badminton singles match involves numerous intense and high impact movements. Lunges were accounted for approximately 15% of overall movements and were believed to presumably induce significant muscle damage following a match. However, no previous study has investigated changes in knee extensor muscle function after a badminton match.The present study investigated changes in knee extensor neuromuscular function and muscle soreness after a simulated 1-h badminton singles match in relation to the number of lunges performed in the match. Ten state-level male badminton players were recruited (n=10), with each player played a total of eight simulated 1-h matches under the International Badminton World Federation rules. However, each participant was required to play against the same opponent twice and only one participant was fitted with the equipment at any one session, thus the total number of matches analysed was 40. The number of lunges performed by each player in a game was obtained from video analysis. Heart rate (HR) and core body temperature were recorded during the matches, and blood lactate (BL) was measured before and immediately post match. Both femoral nerve and muscle electrical stimulations were used in the present study. Maximal voluntary isometric contraction (MVC) torque of the knee extensors and flexors, voluntary activation during the knee extension MVC (VA), torque generated by a doublet (DT), and 20 Hz (T20) and 80 Hz stimulation (T80) and the ratio (T20/T80) for the knee extensors, and muscle soreness of knee extensor muscles by a 100-mm visual analog scale (VAS) were measured before, immediately (8 - 10 min post-match), 1-h and 24-h after a match. Pearson product-moment correlations were computed to examine relationships between variables using ANOVA.Average (± SD) match HR was 162.0 ± 11.0 bpm, post-match BL was 7.2 ± 1.3 mM.L-1, and 194 ± 18 lunges were performed per match per player. Core body temperature increased from 36.5 ± 0.5 oC to 39.4 ± 0.5 oC immediately post match. Knee extension MVC torque was lower than baseline (278.4 ± 50.8 Nm) at immediately (-11%) and 1 h (-14%) post match (P Moderate muscle soreness developed after 1-h simulated badminton matches, but muscle function returned to baseline by 24 hour post match, indicating moderate muscle fibre damage. Since VA was decreased without changes in T20/T80, and knee flexion MVC torque also showed similar changes to those of knee extension MVC torque that was thought to be affected by lunges, the decrease in MVC torque appeared to be associated with central rather than peripheral fatigue or muscle damage. With moderate muscle soreness developing after 1-h simulated badminton matches and muscle function returning to baseline by 24 hour post-game, suggesting minimal muscle fibre damage. It was concluded that both central and peripheral factors contributed to alterations in neuromuscular fatigue and that muscle damage was moderate after the singles matches in which the game intensity and physiological characteristics were close to those in competitive tournaments.

Malgré les progrès réalisés par le système de santé, la lombalgie chronique reste la principale cause d'invalidité. Le déficit d'extensibilité des muscles ischio-jambiers (MIJ), combiné à un déficit de contrôle neuromusculaire, contribue à l'invalidité dans la lombalgie chronique. Dans ce travail, nous décrivons d'abord les mécanismes de la douleur, le modèle biopsychosocial et la biomécanique, en se concentrant sur les déficits d'extensibilité des MIJ. Ensuite, nous estimons les propriétés métrologiques des mesures de l'extension active du genou, Active Knee Extension (AKE), et de la levée de jambe tendue, Straight Leg Raise (SLR) obtenues à l'aide d'un nouvel inclinomètre éléctronique chez les patients souffrant d'une lombalgie chronique. Cette analyse a été effectuée sur les 90 patients inclus dans l'étude EFIM1. La reproductibilité intra-évaluateur pour AKE et SLR s'est révélée excellente, avec un coefficient de corrélation intraclasse, Intraclass Correlation Coefficient (ICC) supérieur à 0,9. Les valeurs de différence minimale détectable, Minimal Detectable Change (MDC95) ont été de 9 à 11° pour AKE et de 7 à 10° pour SLR. Des corrélations modérées à fortes, ont également été trouvées entre AKE, SLR et la distance doigt-sol, Fingertip-to-Floor (FTF), ce qui confirme la validité de construit de nos mesures. L'étape suivante concernait l'évaluation de l'effet immédiat de l'étirement passif des MIJ, ainsi que l'analyse de l'impact des facteurs psychosociaux sur le changement résultant de l'étirement (étude EFIM1). Les mesures répétées de l'extensibilité des MIJ (AKE, SLR, FTF) ont été effectuées sur 90 patients atteints de lombalgie chronique avant et immédiatement après l'intervention. Celle-ci consistait en une minute d'étirement passif des MIJ réalisée de manière bilatérale par un kinésithérapeute. Les facteurs psychosociaux ont été évalués avant l'intervention grâce aux questionnaires Fear-Avoidance Belief Questionnaire (FABQ) et Hospital Anxiety and Depression Scale (HADS). L'extensibilité des MIJ s'est améliorée de manière significative après l'étirement; la différence moyenne de l'AKE était de 4° (IC à 95 % : 2,4 à 5,1° ; p &lt; 0,001), la différence moyenne de la SLR était de 7° (IC à 95 % : 5,5 à 8,6°, p &lt; 0,001), la différence moyenne de FTF était de 2 cm (IC à 95 % : 1,7 à 3,0cm, p &lt; 0,001). Aucune corrélation n'a été trouvée entre l'amélioration d'extensibilité des MIJ et les scores des questionnaires FABQ ou HADS (p &gt; 0,05). L'étirement passif des MIJ a entraîné une amélioration immédiate et statistiquement significative de l'extensibilité des MIJ chez les personnes atteintes de lombalgie chronique. Cependant, seul le changement d'amplitude passive de la SLR semble avoir une importance clinique. Cela suggère que le système neuromusculaire nécessite une stimulation active pour générer un mouvement actif dans l'amplitude de mouvement passive nouvellement acquise. Par conséquent, nous présentons un nouveau protocole d'étude randomisée contrôlée, EFIM2 pour vérifier si la combinaison d'étirements actifs et passifs est plus efficace que l'étirement passif seul pour améliorer la flexibilité active chez les patients souffrant d'une lombalgie chronique<br>Progress in healthcare management increased life expectancy globally but disabling consequences of diseases remain the major problem. Despite the progress that has been made in healthcare management, chronic low back pain (CLBP) remains the leading cause of disability. The deficit in hamstring muscles (HM) flexibility, combined with a deficit in neuromuscular control, contributes to disability in CLBP. In this work, we first describe the context that links pain mechanisms, the biopsychosocial model, and biomechanics, with a specific focus on HM flexibility deficits. Then, we estimate the measurement properties of the Active Knee Extension (AKE) and Straight Leg Raise (SLR) measures taken with a new digital inclinometer in CLBP patients. Intrarater reproducibility was found to be acceptable, with a Minimal Detectable Change of 9-11° for AKE and 7-10° for SLR. Following that, we conducted the EFIM1 study to evaluate the immediate effect of passive hamstring (HM) stretching on flexibility and to analyze the impact of psychosocial factors on change following HM stretching in 90 CLBP patients. Hamstrings flexibility improved significantly after stretching; AKE mean difference was 4° (95%CI, 2.4 to 5.1; p&lt;0.001); SLR mean difference was 7° (95%CI, 5.5 to 8.6, p&lt;0.001), Fingertips-to-Floor mean difference was 2 cm (95%CI, 1.7 to 3.0, p&lt;0.001). No correlation was found between improvement in any of the HM flexibility measurements and Fear-Avoidance Belief Questionnaire (FABQ) or Hospital Anxiety and Depression Scale (HADS) scores (p&gt;0.05). Additional group-based analysis showed that the Positive Responders and Non-Responders groups were similar in demographic and clinical characteristics, except for lower Body Mass Index (BMI) values within the Positive Responders group. Passive HM stretching induced an immediate, statistically significant improvement in HM flexibility in people with CLBP. However, only the change in SLR amplitude is likely to be of clinical importance. Psychosocial factors were not related to observed improvements in flexibility. This suggests that the neuromuscular system needs active stimulation to generate active movement in the newly acquired passive range of motion (ROM). Therefore, in response to this conclusion we present a new study protocol, EFIM2. From the patient's perspective, the ultimate goal is to achieve an important improvement in active, pain-free ROM. However, passive stretching did not yield satisfactory improvements in active flexibility. This is why we propose a combination of passive and active stretching exercises, with the expectation that it facilitates improvements in both passive and active ROM. To test our hypothesis that combining active and passive stretching is more effective than passive stretching alone in improving active flexibility, we present a randomized controlled study, EFIM2

Low frequency mechanical vibrations (<100 Hz) are naturally generated by skeletal muscles during voluntary contractions. Recording of these vibrations at the muscle surface are called surface mechanomyograms (S-MMGs). In this study, S-MMGs were recorded over a 3 x 5 grid of skin mounted accelerometers on the biceps brachii muscle during submaximal voluntary isometric contractions with the arm in a pronated position for ten healthy and young male subjects with no overt sign of neuromuscular diseases. For a given pair of accelerometers, the spatial coherence of S-MMG is a measure of the similarity of the S-MMG signals propagating between those two sensors. Two common techniques to estimate the spatial coherence for narrowband S-MMG signals, namely the magnitude squared coherence function and the maximum of the time-domain cross-correlation function, were found to yield similar results. In particular, high spatial coherence values were measured for sensor pairs aligned along the proximal to distal ends of the biceps, i.e. the longitudinal direction. On the other hand, the spatial coherence values for sensor pairs oriented perpendicular to the muscle fiber, i.e. along the transverse direction, were found to be significantly lower. This finding indicates that coherent S-MMGs were mainly propagating along the muscle fibers direction (longitudinal) of the biceps brachii within a frequency band varying between 10Hz to 50Hz. Additionally, the spatial coherence of S-MMGs along the longitudinal direction was found to decrease with increasing frequency and increasing sensor separation distance and to increase with contraction level varying between 20% to 60% of the maximum contraction level.

L’expérience du laboratoire en matière de muscles artificiels pneumatiques pour la robotique est appliquée au développement de mini-actionneurs à muscles artificiels destinés à des systèmes robotiques miniatures. Le domaine de la robotique médicale est tout particulièrement visé. Le but de ce travail est de mettre au point et développer des actionneurs dont les caractéristiques et les performances correspondent à ceux présentés par les muscles naturels. Ces actionneurs seront utilisés dans le domaine de la robotique et dans le domaine médical. Ainsi, dans un premier temps on s’est intéressé au développement et à l’étude du muscle artificiel pneumatique de McKibben. Il s’agit d’un type d’actionneur très performant, présentant des propriétés satisfaisantes, se rapprochant énormément de celles des muscles naturels. De ce fait, leur utilisation dans le domaine de la robotique est très avantageuse. Cependant, la source énergétique qu’ils utilisent - l’air comprimé – présente un sérieux frein vis-à-vis d’une utilisation flexible ou médicale. De ce fait, dans un deuxième temps, on a adapté ces muscles de McKibben au domaine biomédical en remplaçant l’air comprimé par des résines échangeuses d’ions ou des hydrogels. On a ainsi développé et étudié des muscles mécanochimiques basés sur des muscles de McKibben<br>The experience of the laboratory in the matter of pneumatic artificial muscle for the robotics is applied to the development of mini-actuators with artificial muscles intended for miniature robot-like systems. The field of medical robotics is particularly aimed. The goal of this work is to develop actuators whose characteristics and performances correspond to those presented by the natural muscles. These actuators will be used in the field of robotics and the medical field. Thus, initially we were interested in the development and the study of the pneumatic artificial muscle of McKibben. It is a type of very powerful actuator, presenting satisfactory properties, approaching those of the natural muscles enormously. So their use in the field of robotics is very advantageous. However, the energy source that they use - compressed air - presents a serious restraint with respect to a flexible or medical use. So in the second time, we adapted these muscles of McKibben to the biomedical field by replacing the compressed air by exchanging resins of ions or hydrogels. We thus developed and studied muscles mecanochimic based on McKibben’s muscles

Les événements métaboliques associés à la fatigue musculaire ont été étudiés in vivo dans le muscle gastrocnémien de rat au moyen de la spectroscopie par résonance magnétique du phosphore-31. Les muscles ont été stimulés pendant 6 minutes à différentes fréquences afin d'obtenir des niveaux croissants de fatigue. Un protocole non fatigant (0,8 Hz) et cinq protocoles fatigants (2; 3,2; 4; 5,2 et 7,6 Hz) ont été utilisés. Nous avons démontré que l'accumulation du phosphate inorganique (Pi) est corrélée avec la diminution de la force musculaire à la fin des 6 minutes de stimulation mais pas avant qu'il y ait développement de la fatigue, bien que la concentration en Pi ne soit pas significativement différente entre ces deux stades de la stimulation. Le Pi affecterait donc la force musculaire de façon indirecte, probablement en perturbant le couplage excitation-contraction. Nous avons ensuite mis en évidence que le coût en ATP diminue au cours d'une activité musculaire, qu'il y ait ou non développement de la fatigue. Le fait que cette diminution soit maximale quel que soit le niveau de fatigue nous conduit à penser que le développement de la fatigue pourrait s'accompagner d'une optimisation de l'utilisation de l’ATP par le muscle. Nous nous sommes ensuite intéressés aux origines métaboliques de la resynthèse de la PCr pendant un exercice musculaire intense. La comparaison des changements métaboliques survenant au cours du protocole à 7,6 Hz réalisé en condition d'aérobie ou d'ischémie totale prouve que la resynthèse de la PCr pendant l'activité musculaire est un phénomène purement oxydatif se produisant dans des fibres musculaires inactivées. Ces travaux ont permis d'améliorer les connaissances sur le versant métabolique de la fatigue musculaire dans des conditions physiologiques. En particulier, nous avons caractérisé certaines modifications du métabolisme énergétique musculaire associées au développement de la fatigue.

Thesis (Ph. D.)--University of Missouri-Columbia, 2007.<br>The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file (viewed on October 18, 2007) Vita. Includes bibliographical references.