Fibrotic diseases account for an estimated 45% of the total number of deaths in the developed world (Wynn 2007). Tendons are an excellent model for studying the dysregulated response which leads to fibrosis, as tendons have an organized, parallel matrix, in which tissue defects could easily be distinguished. Wong et al. (2006b) demonstrated the presence of a bell-shaped region around sutures in tendons that was devoid of cells in histological sections. The mechanisms of the formation of this acellular zone, that was also noted in cornea and cartilage (Matsuda et al. 1999; Hunziker and Stähli 2008), were unknown. It was hypothesized that the acellular zone was formed by cell death and that suturing caused alterations to the extracellular matrix of sutured regions of tendon, which made the acellular zone refractory to cellular re-population. The acellular zone was tracked in sutured tendons for up to a year to determine the temporal properties of the acellular zone. Electron microscopic and time lapse studies were carried out to determine if the acellular zone formed by cell migration or cell death. Microarray analysis was conduced to confirm this and to reveal potential molecular targets for future studies. The extracellular matrix of sutured tendons was studied by electron, atomic, scanning and polarized light microscopy and mechanical measurements were obtained using nanoindentation. It was concluded that the acellular zone formed within 24 hours and persisted for up to a year. Tension and size of the suture's grasp were also shown to be important for acellular zone formation. Cell death was the main effector of acellular zone formation. Microarray analysis showed evidence of upregulation of inflammatory mediators and programmed necrosis pathways. The sutured extracellular matrix was denser, more disorganized and had a lower Young's modulus than unsutured regions of the same tendon. These differences in the properties of the extracellular matrix of sutured tendons may be the cause of the persistence of the acellular zone.

A espécie asinina (E. asinus) teve sua origem há milhares de anos, se desenvolvendo a partir de um tronco comum ao do eqüino doméstico que conhecemos. Vem passando por um processo adaptativo, apresentando características distintas, quando os observamos em diversas partes do planeta. Na região nordeste do Brasil, desenvolve um papel fundamental, influenciando diretamente na renda das famílias locais. Tendo em vista o grande número de afecções locomotoras e a falta de cuidados a que estão submetidos, realizou-se um estudo anatômico e radiográfico da região distal de seus membros torácicos, buscando-se subsídios a prática clínica e cirúrgica dedicada a esses animais, bem como a compreensão de sua maior resistência a lesões locomotoras, quando comparado ao eqüino. A avaliação anatômica revelou características musculares semelhantes as já descritas para eqüinos. O exame radiográfico evidenciou lesões severas, caracterizadas por osteíte podal e áreas de reabsorção óssea e remodelamento na margem solear, associadas à rotação da falange distal. Ainda na avaliação radiográfica, caracterizaram-se os principais vasos arteriais dessa região através de técnica angiográfica. Não se observou correlação entre o ângulo de inclinação da muralha do casco e falange distal, com a área de secção transversal dos tendões dos músculos flexores. As maiores secções transversais para o tendão flexor digital superficial, profundo e interósseo, mostraram coincidência com os pontos de maior estresse articular, caracterizando, assim, a resistência dos asininos à lesões nestas estruturas em seu aparelho locomotor. / The asinine species was originated thousands of years ago from the same branch of the domestic equine. The asinine have been undergoing to a great adaptation resulting in different characteristics of each population of asinine around the world. In the northeast region of Brazil, they play an essential role in the income of the local families. Due to a large number of locomotor disorders and a lack of professional care, an anatomic and radiographic study of the distal forelimb region of the asinine was carried out in order to gather information to improve the clinical and surgical practice in this species, and to explain the less susceptibility to locomotor disorders compared to equines. The anatomical study showed that asinine have similar muscular characteristics already described for equines. The radiographic exam showed severe lesions, characterized by pedal osteitis, bone reabsorption areas and remodelling of sole margin associated to the distal phalanx rotation. The radiographic study also showed the characterization of the main arterial vessels. No significant correlation was observed between the angle of the hoof wall and the angle of the distal phalanx with the cross section area of the flexor tendons. The larger cross section areas of the superficial digital flexor tendon, deep digital flexor tendon and interosseus tendon were coincidental with the great articular stress, explaining the greater resistance of the asinines to lesions in those structures of their locomotor apparatus.

Collagenous tissues such as ligaments and tendons are viscoelastic materials. They exhibit a slow continuous increase in strain over time, or creep, when subjected to a constant stress and a slow continuous decrease in stress over time, or stress relaxation, when subjected to a constant strain. Moreover, the loading and unloading stress-strain curves are different when the tissues are subjected to cyclic loading, showing hysteresis and softening phenomena. The micro-structural origin of the viscoelasticity of these tissues is still unknown and the subject of debate among experts in biomechanics. Therefore, formulating viscoelastic models by accounting for the mechanical contributions of the structural components of these tissues can help in understanding the genesis of viscoelasticity. A nonlinear viscoelastic modeling framework has been developed to describe the elastic and viscoelastic properties of ligaments and tendons by considering their main structural components, the collagen fibers and proteoglycan-rich matrix. The mathematical models derived within this framework can illustrate the tensile behavior, stress relaxation and creep by as suming that the collagen fibers are elastic and the surrounding proteoglycan-rich matrix is viscoelastic. The collagen fibers are represented by linear elastic springs that are engaged to support load at different values of the tissue's strain according to a Weibull distribution function. The mechanical contribution of the matrix is introduced via a Maxwell-type viscoelastic element arranged in parallel with the collagen fibers. According to the proposed mathematical framework, both the collagen fibers and the proteoglycan-rich matrix are responsible for resisting tensile loads. However, the collagen fibers play a significant role in creep while the proteoglycan-rich matrix has a dominant role in stress relaxation. The model parameters that define the stress relaxation and strain stiffening phenomena are estimated by using published experimental on rabbit medial collateral ligaments and are then used to predict creep. The above modeling framework has been also extended to capture the in uence of preconditioning on the mechanical properties of ligaments and tendons. The stress softening and decrease in hysteresis that are observed during successive loading cycles in preconditioning are assumed to be determined by a decrease in the elastic properties of the collagen fibers and proteoglycan-rich matrix. Preliminary data collected on stress relaxation and preconditioning on rat medial collateral ligaments by collaborators are used to evaluate the model parameters and analyze its predictions. The elastic and viscoelastic properties of single collagen fibers are studied by formulating a nonlinear viscoelastic framework by accounting for their main components: microfibrils, cross-links and proteoglycan-rich matrix. The model illustrates tensile behavior and stress relaxation of a single collagen fiber by assuming that the microfibrils and the cross-links are elastic and the surrounding proteoglycan-rich matrix is viscoelastic. The mechanical contribution of the microfibrils is included via a linear elastic spring while the cross-links are represented by linear elastic springs that progressively fail at different values of the tissue's strain according to an exponential distribution function. The matrix is defined by linear dashpots arranged in parallel with each single spring that represents an individual cross-link. The viscous properties of the matrix associated with the unbroken and broken cross-links are assumed to have different values. In the model formulation, the microfibrils and the cross-links are assumed to determine the elastic response of the fibers while the proteoglycan-rich matrix determines the stress relaxation. Microfibrils, cross-links and the proteoglycan-rich matrix are responsible for resisting the loading force during tensile behavior. Experimental data collected by performing incremental stress relaxation tests by other investigators on reconstituted rat tail tendons are used to estimate the parameters in the model and evaluate its performance. / Ph. D.

Tendon pathologies, including both chronic injuries and acute tendon tears, are some of the most common musculoskeletal injuries. Chronic tendon injury, or tendinopathy, occurs both in athletes and in the general population, and can interfere with quality of life and ability to work. Overuse of the tendon during exercise plays a role in up to 50% of injuries in athletes, and affects multiple parts of the body including the supraspinatus tendon in the shoulder, and the Achilles tendon in the ankle. Acute tears of tendons and ligaments, on the other hand, add substantially to the socioeconomic burden of tendon disease as a whole. These injuries also affect both upper and lower extremities, including the shoulder, ankle, hand, and wrist. Historically, inflammatory processes have been thought to be of little importance in tendon pathology, due to the largely avascular nature of the healthy tissue. However, more recent literature has identified the presence of inflammation in both acute and chronic tendon injury. Because the literature on inflammation in tendon is in its relatively nascent stages, there remain gaps in knowledge that hinder progress in the development of therapeutics to improve healing. A more complete characterization of the inflammatory response in tendon is needed, by defining the relative roles of different molecular pathways, and determining how these pathways interact with tendon mechanobiology. To investigate these questions, an in vitro model was developed, wherein the complexity of the in vivo healing environment was simulated by applying M1 macrophage conditioned media (M1-CM) to tendon fibroblasts (TFs). This was motivated by the well-established role of macrophages in driving tendon inflammatory responses. Characterization of the M1-CM and its effect on TFs revealed a robust inflammatory response, including upregulation of over 500 genes and increased secretion of several cytokines in TFs. Next, multiple immune-related pathways were manipulated in TFs in order to identify those necessary for inflammatory responses. Both the NF-kB pathway and the JAK/STAT signaling pathway were inhibited, to determine their respective roles in propagating inflammation. It was determined that both JAK/STAT and NF-kB were necessary for the response to M1-CM, and each pathway was responsible for different downstream responses to inflammation in TFs. Finally, the role of mechanical loading in tendon responses to inflammation was assessed, as mechanical stimulation is crucial for proper tendon function in homeostasis and in healing. We found that the TF response to loading was altered by the presence of an inflammatory stimulus, with more genes being downregulated by loading under inflammatory conditions. Analysis of the genes that responded differently to loading with inflammation present suggested changes in pathways involving extracellular matrix organization and G protein signaling. In summary, this work served to more completely characterize the tendon inflammatory response. The results of these studies indicate that inflammation in tendon is mediated by both NF-kB and JAK/STAT signaling. Additionally, the application of loading may serve to reduce ECM degradation processes, and calm the inflammatory response in tendon, without suppressing it entirely.

La dysfonction du tendon tibial postérieur (DTTP) affecte 3,3% des femmes de plus de 40 ans. Elle se caractérise par une dégénérescence du tendon tibial postérieur (tendinose). La biomécanique de cette population est marquée par une augmentation de l’éversion de l’arrière-pied et du moment de force en inversion à la cheville. L’orthèse plantaire (OP) diminue ces déficits biomécaniques chez la population asymptomatique. Cependant, aucune étude n’a isolé l’effet de l’OP sur la biomécanique du membre inférieur chez cette population. L’objectif de ce projet de recherche était de faire l’état des connaissances sur la DTTP et de mesurer l’effet de trois types d’OP sur la biomécanique de quatorze individus atteints de la DTTP ; OP préfabriquée, OP sur mesure et OP sur mesure varisée avec un biseau médial de 5° et un biseau calcanéen médial de 4 mm. La principale hypothèse était que l’OP sur mesure diminuerait les déficits retrouvés chez la population DTTP comparativement à l’OP préfabriquée. Pour ce faire, une analyse de la cinétique, de la cinématique et de l’activité musculaire à la marche du membre inférieur atteint ont été effectuées. Une diminution de l’angle d'éversion de l'arrière-pied, une diminution du moment d'inversion à la cheville et une augmentation du moment d’abduction du genou ont été observées avec des OP sur mesure par rapport au port de la chaussure et de l’OP préfabriquée (p <0.001). Les OP sur mesures pourraient être plus adaptées que les OP préfabriquées pour optimiser la biomécanique observée à l’articulation de la cheville chez la population DTTP. Cependant, les résultats montrent des effets se répercutant à l’articulation du genou qui pourraient être bénéfiques pour cette population. Une étude clinique, telle qu’un essai contrôlé randomisé, est requise afin de savoir si ces effets biomécaniques se traduiront en bénéfices cliniques pour les individus atteints d’une DTTP. / Posterior tibial tendon dysfunction (PTTD) affects 3.3% of women over the age of 40. It is characterized by the degeneration of the posterior tibial tendon (tendinosis). The biomechanics of this population is marked by an increased eversion of the hindfoot andankle inversion joint moment. Foot orthoses (FO) are more efficient to reduce those biomechanical features in the asymptomatic population. Also, FO reduce the pain associated with PTTD. However, no study has isolated the biomechanical effect of OP on this population. The aim of this research project was to synthesize knowledge on PTTD and determine the effect of three types of FO; prefabricated FO, custom FO and custom-varus FO with a 5 ° medial wedge and a 4 mm medial heel skive on the biomechanics of fourteen individuals with PTTD. The first hypothesis was that both custom FO will reduce the biomechanical deficits observed in PTTD population compared to prefabricated FO. To do so, a quantitative analysis of the gait on the affected lower limb of the kinematic, kinetic and muscular activity was conducted. A decreased in the angles of eversion of the hindfoot,a decreased ankle inversion moment and an increased knee abduction moment wereobserved with both custom FO compared to wearing shoes and prefabricated FO (p<0.001). Custom FO could be more appropriate than prefabricated FO to optimize the biomechanics of the lower limb observed at the ankle joint in PTTD population. However,clinicians should be careful when prescribing custom FO for PTTD since unwanted collateral biomechanical effects can be observed at the knee. A clinical study, such as arandomized controlled trial, is required to find out the clinical impact of those biomechanical effects.

INTRODUCTION: La tendinopathie de la coiffe des rotateurs (TCR) entraine au quotidien des douleurs et faiblesses musculaires et une diminution du contrôle moteur à l'épaule. OBJECTIFS: Les objectifs de cette étude étaient i) d'effectuer une revue de littérature pour identifier les méthodes de quantification de la proprioception de l'épaule utilisées en laboratoire et en clinique et d’en présenter les qualités métrologiques, ii) d'évaluer l'efficacité d’un programme d’entrainement neuro-musculaire en comparant son efficacité à réduire la douleur à l’épaule et en améliorer la fonction à celle obtenue par des soins usuels de physiothérapie. MÉTHODES: i) Une revue de 5 bases de données a été conduite d’octobre 2015 à juillet 2016 pour documenter les propriétés métrologiques de protocoles d’évaluation de la proprioception à l'épaule. Les études incluses ont été évaluées à l'aide de l’outil de contrôle QualSyst et de l'échelle COSMIN à 4 points. ii) Trente-trois soldats en service actif au sein des Forces armées canadiennes ont été assignés au hasard à 1) programme standardisé supervisé d’entrainement neuromusculaire et contrôle moteur (Exp) ou à 2) soins usuels de physiothérapie (Ctl). Les variables principales étaient les symptômes, la capacité fonctionnelle et les limitations physiques évalués avec le questionnaire Disabilities of the Arm, Shoulder and Hand (DASH) et la variable secondaire était l'indice Western Ontario Rotator Cuff (WORC). Toutes les variables ont été mesurées au départ (T0) et à 6 (T6) et 12 (T12) semaines après l'intervention. La comparaison des effets des interventions a été évaluée à l'aide d’une analyse per protocole (APP), analyse intention-traitement (AIT) et avec une analyse de variance à mesures répétées à 2 voies. RÉSULTATS: i) Vingt et une études (n = 407 participants, 553 épaules) ont été retenues. Les études analysées confirment d'excellents scores méthodologiques avec l’outil QualSyst (88,1 ± 9,9%) et de bons scores avec le COSMIN pour la fidélité (71,1%) et un score de qualité modérée à faible (50%) pour la validité de critère. Les coefficients de corrélation intraclasse (CCI) pondérés pour la fidélité intraévaluateur étaient les plus élevés pour le sens du positionnement articulaire passif et la kinesthésie soit 0,92 ± 0,07 (n = 214) et 0,92 ± 0,04 (n = 74), respectivement. Le mouvement et l'outil les plus fidèles sont la rotation interne à 90 ° d'abduction (CCI = 0,88 ± 0,01 (n = 53)) et le dynamomètre (CCI = 0,92 ± 0,88 (n = 225)). Aucune étude n’a rapporté d’indices de sensibilité au changement. ii) Aucune interaction significative (p ≥ 0,101) de groupe × temps (p ≥ 0,101) n'a été démontrée. Par contre, nous avons observé un effet de temps significatif (p <0,001) pour le questionnaire DASH et l'indice WORC. CONCLUSION: Ces données préliminaires suggèrent que les deux approches proposées conduisent à des améliorations comparables. L'utilisation d'une intervention de groupe axée sur l'exercice a le potentiel d'être aussi efficace qu'une approche un à un plus exigeante en terme de temps de traitement. Ces résultats permettront de fournir aux cliniciens des lignes directrices pour la mesure de la proprioception à l'épaule et l’utilisation d’une approche novatrice de traitement en groupe pour la TCR. Mots clés : Épaule, tendinopathie, contrôle moteur, proprioception, programme d'exercices, soins en physiothérapie / INTRODUCTION: The shoulder is the most mobile joint of the body which means that it heavily relies of an important level of neuromuscular control at all times. A rotator cuff (RC) complex provides stability to the shoulder and often times falls victim to injury, which can produce functional limitations during activities of daily living and work tasks. Individuals affected by an RC tendinopathy often have neuromuscular and proprioceptive deficits. OBJECTIVES: The objectives of this study are to (i) conduct a systematic review to identify methods of quantifying shoulder proprioception in a laboratory and clinical setting and to present the associated psychometric properties. (ii) To evaluate the effectiveness of a novel neuromuscular training program for the upper extremities versus one-on-one physiotherapy care (manual therapy, range of motion exercises, strengthening) for the reduction of shoulder pain and improvement in function with soldiers affected by an RC tendinopathy. METHODS: (i) A review of five databases was conducted from conception to July 2016 to identify studies that reported at least one psychometric property of a shoulder proprioception protocol. The included studies were evaluated using the QualSyst checklist and the 4-point COSMIN scale. (ii) Thirty-three military personnel with the Canadian Armed Forces were randomly assigned to one of the following interventions: 1) Upper Extremity Neuromuscular Training Program; (2) usual physiotherapy care. The main outcomes included symptoms and functional capacity assessed using the Disability of the Arm, Shoulder, and Hand (DASH) questionnaire. A secondary outcome included the Western Ontario Rotator Cuff (WORC) Index. Outcome measures were evaluated at baseline (T0) and 6 (T6) and 12 (T12) weeks post-intervention. The effects of the interventions were evaluated using repeated 2-way variance measures (ANOVAs) for a per-protocol analysis and intention-to-treat. RESULTS: i) Twenty-one studies were included, resulting in 407 participants and 553 evaluated shoulders (n). The weighed intraclass correlation coefficients (ICC) for intra-rater reliability were highest for passive joint position sense and kinesthesia, ICC = 0.92 ± 0.07 (n = 214) and ICC = 0.92 ± 0.04 (n = 74), respectively. The most reliable direction of movement and equipment used were internal rotation at 90° abduction, ICC = 0.88 ± 0.01 (n = 53), and the dynamometer, ICC = 0.92 ± 0.88 (N = 225). ii) No significant group (p ≥ 0.1) or group × time interactions (p ≥ 0.1) were found; though a statistically significant time effect (p < 0.001) was established for the DASH questionnaire and WORC Index. Our preliminary data suggests a marginally better improvement with the control group with all outcomes over 12 weeks. CONCLUSION: The evaluation of shoulder proprioception is most reliable when using a passive protocol with an isokinetic dynamometer for internal rotation at 90° shoulder abduction. The preliminary results of our pilot RCT suggest that both groups statistically improved with a time effect, but that the usual care group further demonstrated clinically significant gains. The results of this study will provide clinicians with potential guidelines for measuring shoulder proprioception in a clinical setting, as well as an innovative approach to group therapy that is potentially less costly and equally as effective as conventional one-on-one physiotherapy. Key words (4-6) : Shoulder, tendinopathy, motor control, proprioception, exercise program, physiotherapy care

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Les étirements sont aujourd'hui une pratique courante dans les milieux sportifs et de réadaptation. Ils sont habituellement recommandés dans le but de contribuer à la prévention des blessures (Willson et al. 1991 ;Pope et al. 2000), à l’amélioration de la performance sportive lorsque celle-ci nécessite une amplitude articulaire importante (Heyters, 1985 ;Hortobagyi et al. 1985) et à la récupération de la mobilité articulaire dans le cadre d’un programme de réadaptation (Magnusson et al. 1996b). Ces méthodes, qui se sont développées ces dernières années, font classiquement appel à l’étirement passif et aux étirements neurofacilités (PNF), présentés initialement par Kabat (1958). Plus récemment, un intérêt particulier a été porté au travail musculaire excentrique. Des études ont montré que celui-ci permettait également d’augmenter l’amplitude articulaire (Willson et al. 1991 ;Nelson et Bandy, 2004). <p><p>Dans une première partie de ce travail, il nous a semblé intéressant de comparer les effets de l’étirement passif à ceux des étirements PNF par "contracté-relâché" et "contracté de l’antagoniste". Si les modalités d'application de chaque étirement sont différentes, elles présentent un intérêt majeur. De fait, elles permettent de faire varier les conditions d'allongement des différentes structures du système myotendineux, en modulant l'activité volontaire des musculatures agoniste ou antagoniste. En effet, si l’étirement passif s'effectue sans activation volontaire, l’étirement par "contracté-relâché" consiste à faire précéder l'étirement passif, d'une contraction volontaire maximale isométrique de la musculature agoniste. L’étirement par "contracté de l’antagoniste" associe à l'allongement de la musculature agoniste, une contraction volontaire maximale de la musculature antagoniste. Si de nombreuses études s'intéressent encore actuellement à caractériser leurs effets respectifs, elles ont déjà permis de montrer que ceux-ci avaient au moins deux origines distinctes, l'une neurophysiologique et l'autre mécanique (Taylor et al. 1990 ;Hutton, 1993). Au plan neurophysiologique, il est bien accepté que ces méthodes induisent une modulation de l'activité réflexe tonique facilitant le relâchement musculaire et par conséquent l’amplitude articulaire (Guissard et al. 1988 ;2001). Il est également bien admis que l’importance de ces effets sur la musculature est variable selon la méthode employée (Guissard et Duchateau, 2006). Au plan mécanique, des études menées chez l’animal ont montré que l’étirement passif modifie les caractéristiques viscoélastiques des tissus (Taylor et al. 1990), et de fait favorise l’allongement des tissus myotendineux (McHugh et al. 1992). Chez le sujet humain, plusieurs expérimentations ont montré que l’étirement par "contracté-relâché" permet d’obtenir un allongement myotendineux et un gain d’amplitude articulaire plus important que par étirement passif (Moore et Hutton, 1980). D’autres études ont montré que l’étirement par "contracté de l’antagoniste" permet de majorer encore les gains obtenus par l’étirement "contracté-relâché" (Osternig et al. 1990). Une première question posée dans ce travail est de savoir si la contribution des processus neurophysiologiques et mécaniques se traduit d’une manière spécifique sur le rapport de compliance des tissus de l’unité myotendineuse. Le développement de techniques d’investigation, telles que l’échographie, permet désormais d’observer le comportement de l’unité myotendineuse, d’une manière non invasive (Fukunaga et al. 1992 ;Herbert et Gandevia, 1995 ;Kuno et Fukunaga, 1995 ;Maganaris et al. 1998). Elle permet ainsi d’étudier les effets d’un étirement ou d’une contraction (Fukunaga et al. 1996) sur le rapport de compliance des structures musculaires et des tissus tendineux. <p> <p>S’il était intéressant d’étudier la spécificité de ces trois méthodes d’étirement classiques par rapport à leurs effets sur les tissus myotendineux, il nous paraissait pertinent d’observer celle d’un travail musculaire excentrique. En effet, la particularité de celui-ci est de soumettre l’unité myotendineuse préalablement activée, à un allongement. En réadaptation, le travail excentrique est généralement proposé dans le but d’améliorer plus rapidement la symptomatologie d’une tendinopathie (Stanish et al. 1986 ;Alfredson et al. 1998). Des études récentes ont indiqué qu’il peut également être proposé pour augmenter l'amplitude articulaire (Nelson et Bandy, 2004). Toutefois, ses effets sur les tissus myotendineux ne sont pas clairement définis dans la littérature. Chez l’animal, Heinemeier et al. (2007) ont comparé les effets d’un entraînement en contractions concentriques et excentriques sur les tissus de l’unité myotendineuse. Leurs résultats indiquent que si les tissus tendineux sont sensibles aux deux modes de contraction pour leurs effets favorisant la synthèse de collagène, les structures musculaires sont spécifiquement sensibles au mode excentrique. Chez le sujet humain, Crameri et al. (2004) ont observé une série de contractions excentriques d’intensité maximale augmente la synthèse de collagène au sein de l’ensemble des tissus de l’unité myotendineuse. Ces résultats montrent que les effets de ce travail ne se limitent pas aux tissus tendineux, tels que certains protocoles thérapeutiques le suggéraient, et que le tissu musculaire doit désormais être associé à la discussion des effets de ce travail musculaire. Dans ce contexte, la deuxième question que nous avons posée est de savoir si l’étirement de l’unité myotendineuse préalablement activée, telle que se caractérise une contraction excentrique, modifie le rapport de compliance des tissus myotendineux par rapport aux méthodes classiques. Autrement dit, si l’étirement de l’unité myotendineuse activée favorise spécifiquement l’allongement de l’un des tissus de l’unité myotendineuse. <p><p>Dans une troisième partie, il nous a paru intéressant d'étudier le comportement à l’étirement de l’unité myotendineuse, dont la compliance était modifiée suite à une désadaptation à long terme. L’hypertonie spastique, qui caractérise une majorité de sujets parétiques spastiques, est généralement caractérisée par une augmentation anormale des résistances opposées à l'étirement passif (Carey et Burghart, 1993). L’origine de ces résistances peut être attribuée à des adaptations tant neurophysiologiques (Pierrot-Deseilligny et Mazières, 1985) que mécaniques et structurelles des tissus de l'unité myotendineuse (Berger et al. 1984 ;Tardieu et al. 1989). Il n’existe pourtant pas encore dans la littérature de consensus les définissant clairement (Fridén et Lieber, 2003). En outre, l’étude récente de Lieber et Fridén (2002) a mis en évidence des modifications de l’architecture des muscles fléchisseurs du carpe. Contrairement à ce qui est généralement proposé au sujet de la longueur des fascicules spastiques (Tardieu et al. 1982), Lieber et Fridén (2002) n’ont pas mis en évidence de raccourcissement de ces derniers. Ainsi, l’hypothèse de Tardieu et al. (1982), selon laquelle le raccourcissement des fascicules est à l’origine de l’augmentation des résistances à l’allongement, ne peut plus être soutenue. Il nous paraissait ainsi intéressant d’associer, à l’observation du comportement des fascicules, celui des tissus tendineux, dans le but de déterminer si l’une de ces deux structures présente des caractéristiques particulières, susceptibles d’expliquer le développement plus important de ces résistances à l’allongement. La troisième question que nous avons posée dans ce travail est de savoir comment se caractérise, à l’étirement, le rapport de compliance des tissus musculaire et tendineux dans un contexte de spasticité. <p><p>Outre le fait que la réponse à ces différentes questions soit fondamentale pour mieux comprendre et spécifier la pratique des méthodes d’étirement, l’objectif de notre travail est non seulement de mettre en évidence le tissu dont l’allongement est spécifiquement favorisé par l’une ou l’autre méthode, mais également de contribuer à différencier celui qui limite l’étirement global du système myotendineux. Dans ce contexte, il sera intéressant de pouvoir recommander la pratique d’une méthode particulière, en fonction des besoins spécifiques de chacun. <p> / Doctorat en Sciences de la motricité / info:eu-repo/semantics/nonPublished

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Bridges with external post-tensioned tendons are considered to be more durable than bridges with internal tendons (tendons within the webs and flanges), because external tendons are easier to inspect. In addition, in the event that extensive corrosion damage is detected, it is possible to replace an external tendon. However, an appropriate inspection for detecting damage needs to be determined for external tendons. This investigation focuses on the vibration technique, which uses the dynamic properties of the external tendon to infer the effective prestress force. Four large-scale external tendons, designed to simulate one section of an external tendon between two deviators in a post-tensioned bridge, were tested. In the study, damage to the tendons was induced in a quantifiable fashion at a specific location and the tensile force was measured directly. In addition, free-vibration tests were conducted periodically. This provided a direct means of measuring the sensitivity of measured natural frequencies and measured tensile force to local damage. The measured data were correlated with an approximation of the stiff string vibration model. In addition to the laboratory specimens, field testing was conducted on a bridge with external post-tensioned tendons. The findings from the study show that a loss in tensile force was not linear with a loss in the cross-sectional area of the strand, which results from stress redistribution within the tendon. Also, the natural frequencies were much less sensitive to the level of induced damage than the tensile force. While the measured data from the laboratory data compared very well with the analytical model, the field measurements exhibited a much greater deviation from the model. Due to several factors, the difference between the laboratory specimens and the bridge tendons are believed to be caused by larger levels of inherent error in the model. The findings from the investigation support the notion that vibration testing is most appropriately used in comparing relative differences between peer tendons. / text