Activity of the Ryanodine Receptor (RyR2) (aka cardiac Ca2+ release channel) plays a pivotal role in contraction of the heart. S-adenosyl-l-methionine (SAM) is a biological methyl group donor that has close structural similarity to ATP, an important physiological regulator of RyR2. This work provides evidence that SAM can act as a RyR2 regulatory ligand in a manner independent from its recognized role as a biological methyl group donor. RyR2 activation appears to arise from the direct interaction of SAM, via its adenosyl moiety, with the RyR2 adenine nucleotide binding sites. Because uncertainty remains regarding the structural motifs involved in RyR2 modulation by ATP and its metabolites, this finding has important implications for clarifying the structural basis of ATP regulation of RyR2. During the course of this project, direct measurements of single RyR2 activity revealed that SAM has distinct effects on RyR2 conductance. From the cytosolic side of the channel, SAM produced a single clearly resolved subconductance state. The effects of SAM on channel conductance were dependent on SAM concentration and membrane holding potential. A second goal of this work was to distinguish between the two possible mechanisms by which SAM could reduce RyR2 conductance: i) SAM interfering directly with ion permeation via binding within the conduction pathway (pore block), or ii) SAM binding a regulatory (or allosteric) site thereby stabilizing or inducing a reduced conductance conformation of the channel. It was determined that SAM does not directly interact with the RyR2 conduction pathway. To account for these observations an allosteric model for the effect of SAM on RyR2 conductance is proposed. According to this model, SAM binding stabilizes an inherent RyR2 subconductance conformation. The voltage dependence of the SAM related subconductance state is accounted for by direct effects of voltage on channel conformation which indirectly alter the affinity of RyR2 for SAM. Patterns in the transitions between RyR2 conductance states in the presence of SAM may provide insight into the structure-activity relationship of RyR2 which can aid in the development of therapeutic strategies targeting this channel.

The majority of physiological processes and various other processes taking place in the body are closely related to changes in body temperature (Shellock & Prentince, 1985; Bennett, 1990). The temperature of the human body is constant throughout one’s life. It is approximately 37ºC and it constantly adjusts itself to changes in environment, relative air humidity, the level of radiation, atmosphere pressure and thermo isolation. During long-term physical load, in case of illness or in conditions of extreme body temperature may be in the range from 32ºC to 40ºC or even more (Wilmore & Costill, 2004). It could be hypothesized therefore that the muscle warmed prior to the load to be undertaken, when the leg is extended and flexed in the knee joint at high (500, 450o / s) and average (180o / s) speed depending on gender will increase muscle force and muscle capacity to a greater extent than the cooled muscle, but after lowering the temperature muscle resistance to fatigue will increase. Though considerable research has been done already certain questions still remain to be cleared up, namely: 1. how warming affects muscle fatigue and recovery of female knee extensors and flexors when the leg is being flexed and extended in the knee joint at the fixed 500o / s speed; 2. how muscle contraction function of female and male knee extensors and flexors depends on temperature when the leg is being flexed and extended in the knee joint at the fixed 450o / s and 180o / s peed. Though there... [to full text]

Optimal management of fractures, post-traumatic arthritis and instability of the distal radioulnar joint (DRUJ) requires an understanding of the forces existing across this joint as a function of the activities of daily living. However, such knowledge is currently incomplete. The goal of this research was to quantify the loads that occur at the DRUJ during forearm rotation and to determine the effect that individual muscles have on those loads. Human and cadaver studies were used to analyze the shear (A-P), transverse (M-L) and resultant forces at the DRUJ and to determine the role that 15 individual muscles had on those forces. Data for scaling the muscles forces came from EMG analysis measuring muscle activity at nine positions of forearm rotation in volunteers during isometric pronation and supination. Muscle orientations were determined from the marked muscle origin and insertion locations of nine cadaveric arms at various stages of forearm rotation. The roles that individual muscles played in DRUJ loading were analyzed by removing the muscle of interest from the analysis and comparing the results. The EMG portion of this study found that the pronator quadratus, pronator teres, brachioradialis, flexor carpi radialis and palmaris longus contribute significantly to forearm pronation. The supinator, biceps brachii, and abductor pollicis longus were found to contribute significantly to supination. The results of the DRUJ analysis affirm that large transverse forces pass from the radius to the ulnar head at all positions of forearm rotation during pronation and supination (57.5N-181.4N). Shear forces exist at the DRUJ that act to pull the radius away from the ulna in the AP direction and are large enough to merit consideration when examining potential treatment options (7.9N-99.5N). Individual muscle analysis found that the extensor carpi radialis brevis, extensor pollicis longus, extensor carpi ulnaris, extensor indicis and palmaris longus had minimal effect on DRUJ loading. Other than the primary forearm rotators (pronator quadratus, pronator teres, supinator, biceps brachii), the muscles that exhibited the largest influence on DRUJ loading were the abductor pollicis longus, brachialis, brachioradialis, extensor carpi ulnaris, flexor carpi radialis, and flexor carpi ulnaris.

From animal experimentation, and studies using in vitro models, there was evidence in the literature to suggest that dietary fibre may influence contractility and motility of the gastrointestinal tract and long chain (LC) n-3 polyunsaturated fatty acids (PUFAs) from marine sources may influence contractility of smooth muscle cells in blood vessels. The hypothesis of this thesis was that dietary fish oil and/or fibre influence the contractility of isolated intact sections of gut smooth muscle tissue from small animal models. Methodology was established to measure in vitro contractility of intact pieces of guinea pig ileum with the serosal side isolated from the lumen. It was demonstrated that four amino acid peptides from κ-casein (casoxins) applied to the lumen overcame morphine-induced inhibition of contraction. Using this established technology, the guinea pig was used to investigate the effects of dietary fibre and fish oil supplementation on gut in vitro contractility. In separate experiments, changes in sensitivity to electrically-driven and 8-iso-prostanglandin (PG)E₂-induced contractility were demonstrated for dietary fibre and fish oil. A modified, isolated gut super-perfusion system was then established for the rat to validate these findings. It was subsequently shown that LC n-3 PUFA from dietary fish oil significantly increased maximal contraction in response to the G-protein coupled receptor modulators, acetylcholine and the eicosanoids PGE₂, PGF₂α, 8-iso-PGE₂ and U-46619 in ileum but not colon, without changes in sensitivity (EC₅₀), when n-3 PUFA as eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) had been incorporated to a similar degree into the gut total phospholipid membrane pool. It was further established that the spontaneously hypertensive rat (SHR) had a depressed prostanoid (PGE₂and PGF₂α) response in the gut that could be restored by dietary fish oil supplementation (5% w/w of total diet) in the ileum but not the colon. Importantly, the muscarinic response in the colon of the SHR was increased by fish oil supplementation with DHA likely to be the active agent. Dietary fish oil dose experiments deduced differential increases in response occurred at fish oil concentrations of 1% for muscarinic and 2.5% (w/w) for prostanoid stimulators of the ileum with no difference in receptor-independent KCl-induced depolarization-driven contractility. Studies combining high amylose resistant starch (HAMS, 10% w/w) and fish oil (10% w/w) fed to young rats demonstrated a low prostanoid response that was enhanced by dietary fish oil but not resistant starch. There was however, an interactive effect of the HAMS and fish oil noted for the muscarinic-mimetic, carbachol. Generally, resistant starch increased the large bowel short chain fatty acid pool with a subsequent lower pH. Binding studies determined that while the total muscarinic receptor binding properties of an isolated ileal membrane fraction were not affected in mature rats by dietary fish oil, young rats had a different order of muscarinic receptor subtype response with a rank order potency of M₃ > M₁ > M₂ compared to mature animals of M₃ > M₂ > M₁ with fish oil altering the sensitivity of the M₁ receptor subtype in isolated carbachol-precontracted ileal tissue. In conclusion, experiments using the guinea pig and rat gut models demonstrated that dietary fish oil supplementation, and to a lesser degree fibre, increased receptor-driven contractility in normal and compromised SHR ileum and colon. Further, changes in responsiveness were demonstrated in the developing rat gut prostanoid and muscarinic receptor populations that could be altered by dietary fish oil. Preliminary evidence suggested that fish oil as DHA may alter receptor-driven gut contractility by mechanisms involving smooth muscle calcium modulation. Defining the role that dietary fibre and fish oil, and other nutrients, play in normal and diseased states of bowel health such as inflammatory bowel disease (IBD), where contractility is compromised, are among the ongoing challenges. / http://proxy.library.adelaide.edu.au/login?url= http://library.adelaide.edu.au/cgi-bin/Pwebrecon.cgi?BBID=1316907 / Thesis (Ph.D.) -- University of Adelaide, School of Molecular and Biomedical Science, 2008

Diss. (sammanfattning) Umeå : Univ., 2004. / Härtill 6 uppsatser.

Diss. (sammanfattning) Stockholm : Karolinska institutet, 2007. / Härtill 5 uppsatser.

Thesis (Ph. D.)--University of Virginia, 2008. / Includes bibliographical references. Also available in electronic form as viewed 2/16/2009.

Made available in DSpace on 2016-12-06T17:07:12Z (GMT). No. of bitstreams: 1 DISSERTACAO-Affonso Celso Kulevicz da Silva.pdf: 4394417 bytes, checksum: dd5b9db49311f3dcab96792448947fa2 (MD5) Previous issue date: 2006-08-31 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Handgrip can be decisive for certain sports in specific situations. This work constitutes an analysis of handgrip biomechanic variables in tests for maintaining continuous isometric and maximum interval strength in athletes that use this movement in their sport and in non-athletes. The intention is to compare the differences in characteristics among the groups, between dominant hand (DH) and non-dominant hand (NDH) in each test, in a way that identifies parameters that supply quantitative information concerning performance and training methodology, in the different kinds of sports. Participants in the study included fifty male subjects: 29 athletes that practice aikido (AI), jujutsu (JJ), judo (JU) and rowing (RO), and 21 non-athletes. The test for continuous handgrip (CT) consisted of maintaining maximum isometric force for 2 minutes, and the interval test (IT), maximum muscle contractions every 1 second (1Hz) for 4 minutes. The analysis was of maximum strength, strength measured at determined moments, final strength, percentage of normalized strength decrease and stabilization point of the strength curve. The highest levels of strength were observed in the JJ group, regardless of which test was carried out. In the tests comparing the different sports, significant statistical differences had the variables of: Fmax, F15s, F30s (DH, CT); F6s, F9s, F12s, F15s, F30s, F60s, F90s, F114,330s, F150s, F180, F210s (DH, IT) and Fmax, F3s, F6s, F9s, F12s, F15s, F180s, F210s (NDH, IT) between the NA and JJ, as well as the variables Fmax, F3s, F6s, F9s, F12s, F15s (NDH, CT) among NA, AI and JJ. In addition, significant statistical differences were observed between DH and NDH having the variables: F6s, F9s, F12s, F15s (CT, JJ); F3s, F6s, F9s, F12s, F15s, F30s, %F9s, %F30s, %F60s (CT, JU); %F9s (CT, RO); Fmax, F3s, F6s, F9s, F12s, F90, Ffinal (CT, AI); F3s, F6s, F9s, F12s, F15s, F30s, F60s, %F6s, %F9s, %F12s, %F15s, %F30s, Pestab. (IT, JJ); F114,330s, F150s, F180s, F210s, Ffinal, %F3s, %F6s, %F9s, Pestab (IT, JU); F210s, Ffinal, (IT, RO). Comparing the NA group to all the athletes in just one group (AA) significant statistical differences were found in all the strength variables for DH (regardless of the type of test) and with the variables: Fmax., F3s, F6s, F9s, F12s, F15s e F30s (NDH, CT); Fmax., F3s, F6s, F9s, F12s, F15s, F30s, F60s e F90s (NDH, IT); %F6s, %F9s, %F12s, %F15s, %F30s, %F60s (DH, CT); %F3s, %F6s (NDH, CT), %F90s, %F150s, %F180s (DH, IT); %F210s (NDH, IT). These two groups showed differences between DH and NDH with the variables: Fmax., F3s, F6s, F9s, F12s, F15s, F30s, F60s, %F9s, %F12s, %F15s, %F30s, %F60s (CT, AA); %Ftotal, Fmax, F3s, F6s, F9s, F12s, F15s, Ffinal (CT, NA); Fmax., F3s, F6s, F9s, F12s, F15s, F30s, F60s, F90s, F114,330s, F150s, F180s, F210s, Ffinal, %F3s, %F6s, %F9s, %F12s, %F15s (IT, AA); Fmax., F3s, F6s, F9s, F12s, F15s, F30s, F60s, %F114,330s, %F150s (IT, NA). The suitability for the interval muscular contraction was demonstrated by the athletes superior performance in strength. The difference found between the athletes hands in both tests indicates the necessity for work with muscular compensation. Strength decrease values can determine the time of muscular fatigue in handgrip and be part of the athlete s competition strategy. / A força de preensão manual pode ser determinante em situações específicas de certas modalidades esportivas. O presente trabalho consistiu em analisar variáveis biomecânicas da preensão manual em testes de manutenção da força isométrica contínua e intervalar máximas, em atletas que utilizam este movimento na prática esportiva e em indivíduos não atletas. Pretendeu se comparar as diferenças nas características entre os grupos, entre mão dominante (MD) e não dominante (MND) e em cada teste, de forma a identificar parâmetros que fornecessem informações quantitativas em relação ao desempenho e metodologia de treino, nas diferentes modalidades esportivas. Cinqüenta sujeitos do sexo masculino, 29 atletas das modalidades de aikidô (AI), jiu-jitsu (JJ), judô (JU) e remo (RE) e 21 não atletas (NA) participaram do estudo. O teste de preensão contínuo (TC) consistiu na manutenção da força isométrica máxima durante 2 minutos, e o teste intervalar (TI), na realização de contrações musculares máximas a cada 1 segundo (1Hz), durante 4 minutos. Analisaram-se: força máxima; força medida em instantes determinados, força final, percentual do decréscimo normalizado da força e ponto de estabilização da curva de força. Os maiores valores de força foram observados no grupo JJ, independentemente do teste realizado. Nos testes de comparação entre grupos de diferentes modalidades esportivas, foram encontradas diferenças estatisticamente significativas nas variáveis: Fmáx, F15s, F30s (MD, TC); F6s, F9s, F12s, F15s, F30s, F60s, F90s, F114,330s, F150s, F180, F210s (MD, TI) e Fmáx, F3s, F6s, F9s, F12s, F15s, F180s, F210s (MND, TI) entre os NA e JJ, bem como nas variáveis Fmáx., F3s, F6s, F9s, F12s, F15s (MND, TC) entre NA, AI e JJ. Adicionalmente, observaram se diferenças estatisticamente significativas entre MD e MND nas variáveis: F6s, F9s, F12s, F15s (TC, JJ); F3s, F6s, F9s, F12s, F15s, F30s, %F9s, %F30s, %F60s (TC, JU); %F9s (TC, RE); Fmáx, F3s, F6s, F9s, F12s, F90, Ffinal (TC, AI); F3s, F6s, F9s, F12s, F15s, F30s, F60s, %F6s, %F9s, %F12s, %F15s, %F30s, Pestab. (TI, JJ); F114,330s, F150s, F180s, F210s, Ffinal, %F3s, %F6s, %F9s, Pestab (TI, JU); F210s, Ffinal, (TI, RE). Comparando-se o grupo NA e todos os atletas juntos em um grupo (AT) foram encontradas diferenças estatisticamente significativas em todas as variáveis de força para a MD (independentemente do tipo de teste) e nas variáveis: Fmáx., F3s, F6s, F9s, F12s, F15s e F30s (MND, TC); Fmáx., F3s, F6s, F9s, F12s, F15s, F30s, F60s e F90s (MND, TI); %F6s, %F9s, %F12s, %F15s, %F30s, %F60s (MD, TC); %F3s, %F6s (MND, TC), %F90s, %F150s, %F180s (MD, TI); %F210s (MND, TI). Nestes dois grupos, constataram-se diferenças entre MD e MND nas variáveis: Fmáx., F3s, F6s, F9s, F12s, F15s, F30s, F60s, %F9s, %F12s, %F15s, %F30s, %F60s (TC, AT); %Ftotal, Fmáx, F3s, F6s, F9s, F12s, F15s, Ffinal (TC, NA); Fmáx., F3s, F6s, F9s, F12s, F15s, F30s, F60s, F90s, F114,330s, F150s, F180s, F210s, Ffinal, %F3s, %F6s, %F9s, %F12s, %F15s (TI, AT); Fmáx., F3s, F6s, F9s, F12s, F15s, F30s, F60s, %F114,330s, %F150s (TI, NA). Foi observado um melhor desempenho de força dos atletas na contração muscular intervalar, mostrando ser mais adequada aos esportes avaliados. As diferenças encontradas entre mãos nos atletas em ambos os testes indicam ser necessário um trabalho de compensação muscular. Os valores de decréscimo de força podem determinar o tempo de fadiga muscular na preensão e fazer parte da estratégia de competição dos atletas

A motricidade orofacial é a especialidade da Fonoaudiologia, que tem como objetivo a prevenção, diagnóstico e tratamento das alterações miofuncionais do sistema estomatognático. Atualmente, muitos pesquisadores desta área, nacional e internacionalmente, têm buscado metodologias mais objetivas de avaliação e conduta. Dentre tais aparatos está a eletromiografia de superfície (EMG). A EMG é a medida da atividade elétrica de um músculo. Os objetivos deste trabalho foram o de identificar, por meio da EMG, a atividade elétrica dos músculos faciais de adultos saudáveis durante movimentos faciais normalmente utilizados terapeuticamente na clínica fonoaudiológica, para identificar o papel de cada músculo durante os movimentos e para diferenciar a atividade elétrica destes músculos nestes mesmos movimentos, bem como avaliar a validade da EMG na clínica fonoaudiológica. Foram avaliadas 31 pessoas (18 mulheres) com média de idade de 29,48 anos e sem queixas fonoaudiológicas ou odontológicas. Os eletrodos de superfície bipolares foram aderidos aos músculos masseteres, bucinadores e supra-hióides bilateralmente e aos músculos orbicular da boca superior e inferior. Os eletrodos foram conectados a um eletromiógrafo EMG 1000 da Lynx Tecnologia Eletrônica de oito canais, e foi pedido que cada participante realizasse os seguintes movimentos: Protrusão Labial (PL), Protrusão Lingual (L), Inflar Bochechas (IB), Sorriso Aberto (SA), Sorriso Fechado (SF), Lateralização Labial Direita (LD) e Esquerda (LE) e Pressão de um lábio contra o outro (AL). Os dados eletromiográficos foram registrados em microvolts (RMS) e foi considerada a média dos movimentos para a realização da análise dos dados, que foram normalizados utilizando como base o registro da EMG no repouso e os resultados demonstram que os músculos orbiculares da boca inferior e superior apresentam maior atividade elétrica que os outros músculos na maior parte dos movimentos, com exceção dos movimentos de L e SF, Nos movimentos de LD e LE, os orbiculares da boca também estavam mais ativos, mas os músculos bucinadores demonstraram participação importante, especialmente o bucinador direito em LD A Protrusão Lingual não demonstrou diferenças significativas entre os músculos estudados. O SA teve maior participação do orbicular da boca Inferior que o superior, e demonstrou ser o movimento que mais movimenta os músculos da face como um todo e o músculo com maior atividade durante o SF foi o bucinador. Concluímos que o aparato da EMG é eficiente não só para a avaliação dos músculos mastigatórios, mas também dos da mímica, a não ser no movimento de Protrusão lingual, onde o EMG de superfície não foi eficiente. Os músculos orbiculares foram mais ativos durante os movimentos testados, portanto, são também os mais exercitados durante os exercícios de motricidade oral. O movimento que envolve a maior atividade dos músculos da face como um todo foi o Sorriso Aberto / Speech Therapy has been considered subjective during many years due to its manual and visual methods. Many researchers have been searching for more objective methodology of evaluation, based on electronics devises. One of them is the EMG- Surface Electromyography, which is the electric unit measure of a muscle. Literature presents many works in TMJ and Orthodontics areas, special attention to the chewing muscles- temporal and masseter- for been bigger muscles, presenting more evident results in EMG. Less attention is paid for mimic muscles. The objective of our work is to identify, by means of EMG, the electrical activity of facial muscles of healthy adults during facial movements normally used in speech therapy clinic, to identify the role of each muscle during movements and to differentiate the electrical activity of these muscles during this movements. 31 volunteers have been evaluated (18 women) with mean age of 29,84 years, no speech therapy or odontological complains. Bipolar surface electrodes have been adhered to masseter, buccinator and suprahyoid muscles bilaterally and to superior and inferior orbicular oris muscles. Electrodes were connected to a EMG 1000 from Lynx Tecnologia Eletrônica of 8 channels, and it was asked each participant to carry out the following movements: Labial Protrusion (PL), Lingual Protrusion (L), Cheek Inflating (CI), Opened Smile (OS), Closed Smile (CS), Labial Lateralization (LL) and pressure of one lip against the other (LP). EMG data was registered in microvolts (RMS) and the movement media was considered for data analyses, which were normalized using as bases the rest EMG and results show that orbicular oris are more electric activity than other muscles in PL, CI, OS, LL and LP. In LL movements, orbicularis oris also showed greater activity, but buccinator muscles showed effective participation in movement, especially in right LL. L didnt show any differences between evaluated muscles. Buccinator was the most active muscle during CS. We concluded that Orbicularis Ores were the most active muscles during the tasks, exception made to L and CS. In L no muscle was significantly higher and in CS Buccinators were the most active. Opened Smile is the movement where the muscles are more activated in a role. This results shows that EMG is of great use for mimic muscles evaluation, but should be used carefully in specific tongue assessment

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