La déchirure musculaire est la première cause de blessure chez les athlètes. De nombreuses études décrivent ce traumatisme musculaire sans parvenir à en identifier clairement la chronologie et ses circonstances. L’objectif de la thèse est de décrire le phénomène de déchirure musculaire avec la méthode des éléments discrets, en s’appuyant sur des essais expérimentaux pour valider les modèles numériques. Dans une première partie, une revue de littérature permet d’acquérir les propriétés mécaniques des différents éléments constituant le complexe musculo-tendineux afin de pouvoir en réaliser un modèle macroscopique. Dans une deuxième partie, la modélisation du complexe musculo-tendineux est réalisée. La validation du comportement mécanique en traction passive du modèle proposé est réalisée en comparaison des travaux de L-L. Gras sur le muscle sternocléidomastoïdien humain. L’influence des paramètres morphologiques sur le comportement mécanique global est ensuite étudiée. La rupture fait l’objet de la troisième partie. Une modélisation de l’ensemble {tendon d’Achille/triceps sural} est réalisée et soumise à un test de traction passif jusqu’à rupture. La validation des résultats est faite vis-à-vis des essais expérimentaux réalisés sur cet ensemble musculaire provenant de pièces anatomiques humaines. L’étape suivante s’attache à modéliser la contraction musculaire, implémentée au niveau des fibres musculaires. Une validation du comportement actif du complexe musculo-tendineux est réalisée. Cette dernière étape, combinée à la traction destructive permet d’étudier la faisabilité de modéliser la déchirure par la méthode des éléments discrets, mais également d’étudier les structures endommagées et les mécanismes de rupture. Cela ouvre des possibilités d’utilisation cliniques de ce modèle pour comprendre et prévenir des blessures par déchirure musculaire. / Tearing of the muscle-tendon complex is a common sport-related injury for athletes. Many studies reported description of this traumatism but mechanisms leading to such an injury are still unclear as are the site of mechanical failure and involved structures. The aim of the thesis is to describe the phenomenon of the muscle-tendon-complex’s tear using the discrete element method and validating the numerical model with experimental data. In the first part, a literature review explains the different properties of the muscle-tendon complex main components’ in order to model it at the macroscopic scale. In the second part, the muscle-tendon complex is modeled. Validation of the mechanical behavior in passive tensile test is proposed by comparison with experimental data from L.-L. Gras on human sternocleidomastodeus muscle. Then, the different influences of morphometric parameters on the mechanical behavior of the complex are investigated. The third part focuses on the rupture. A model of the complex set of {Achilles tendon/surae triceps} is built and a tensile test until rupture is applied. Model validity is assessed by comparison with in vitro experiments from human cadavers. The fourth part focuses on the muscular activation, implemented inside fibers’ behavior. Validity of its active behavior is investigated. This fifth and last presents the enrichment with destructive tensile test. This added test allows first to study the feasibility to model the tear with the discrete element method; and second to focus on damaged structures and rupture’s mechanisms. This offers possibilities for clinical applications of this model to understand and prevent injuries caused by a tear of the muscle-tendon complex

Le complexe muscle-tendon est constitué d’une composante élastique série fondamentale à son fonctionnement. Cette composante élastique série est composée d’une fraction active située au sein du sarcomère et d’une fraction passive formée par les tissus tendineux (tendon et aponévrose). Elle a un rôle majeur pour optimiser le mouvement en améliorant le rendement énergétique du muscle et le travail produit.La mise au point d’une nouvelle méthode couplant une technique de détente rapide (Quick release) et un échographe haute fréquence a permis de quantifier les contributions de compliance des structures élastiques séries (tendon, aponévrose et fascicules musculaires) à la compliance globale du complexe muscle-tendon en condition active lors d’un test de détente rapide. Les résultats de la première étude montrent que le tendon a une contribution de compliance majoritaire (environ 72 %) tandis que les fascicules musculaires et l’aponévrose contribuent respectivement à 18 % et 10 %. Le tendon confirme donc son rôle capital dans la compliance de la composante élastique série en condition active. De plus, les contributions constantes du tendon, des fascicules musculaires et de l’aponévrose observées aux différents niveaux de couple pourraient aider à simplifier le mécanisme de régulation de la compliance et à maintenir le rôle majeur du tendon dans l’efficience du mouvement.Cette nouvelle méthode a permis d’étudier les adaptations mécaniques de la composante élastique série à la variation de la demande fonctionnelle, notamment en quantifiant les modifications des contributions relatives de compliance des structures élastiques séries chez des escrimeurs élites dans la deuxième étude puis chez des sujets spastiques dans la troisième étude. Concernant les escrimeurs élite, les résultats montrent que les contributions de compliance des structures élastiques de la jambe dominante du groupe d’escrimeurs sont significativement différentes à celles correspondant à la jambe du groupe contrôle, avec notamment une part plus importante de contribution pour l’aponévrose (21,1 vs 15,9 %) et une part minorée pour les fascicules (9,5 vs 13,8 %) concernant la jambe dominante des escrimeurs. En revanche, la contribution du tendon (environ 70 %) est identique pour les deux jambes. Ces modifications tendent à majorer le rôle des tissus tendineux (tendon et aponévrose) et à minorer le rôle des fascicules musculaires ce qui permettrait une utilisation supérieure des structures élastiques tendineuses pour un meilleur rendement énergétique et une performance accrue. Il est possible que l'aponévrose soit un système complémentaire à l’adaptation du complexe muscle-tendon en cas d'hyperactivité.La troisième étude est devenue une étude de cas en raison de la difficulté à tester les patients spastiques sur le Quick release. Elle s’est portée sur un patient spastique dont l’atteinte motrice était plus faible que les autres et a montré des contributions relatives de compliance du tendon (75,3 %) et de l’aponévrose (15,2 %) supérieures à celle des fascicules (9,5 %) Ce résultat s’expliquerait par une augmentation de la raideur du muscle et une diminution de la raideur des tissus tendineux observées classiquement dans les études menées sur des sujets spastiques. / The muscle-tendon complex contains a serie elastic component which is fundamental to its functioning. This serie elastic component is composed of an active part located within the sarcomere and a passive part located in the tendon and aponeurosis. It has a major role to optimize the movement by improving the muscle energetic efficiency and the produced work.A new method coupling a quick release ergometer and a high frequency ultrasound device was used to quantify the compliance contributions of the series elastic structures (tendon, aponeurosis and muscle fascicles) to the global compliance of the muscle-tendon complex in active conditions. The results of the first study showed that the tendon has a major compliance contribution (about 72%) while the muscle fascicles and aponeurosis contributions are 18% and 10%, respectively. The tendon confirms its key role in the compliance of the serie elastic component in active condition. In addition, the constant contributions of tendon, muscle fascicles and aponeurosis observed at various levels of torque may help simplify the regulation mechanism of compliance and maintain the major role of the tendon in the efficiency of the movement.This new method was also used to study the mechanical adaptations of the serie elastic component to variation of the functional demand. The changes in the relative compliance contributions of series elastic structures were quantified in elite fencers in the second study and in spastic subjects in the third study. Regarding the elite fencers, the results showed that the compliance contributions of the elastic structures in the dominant leg of fencers group were significantly different to those corresponding to the leg of the control group. The aponeurosis compliance contribution was higher for the dominant leg of the fencers groupe (21.1 vs 15.9%) while the muscle fascicles contribution was lower for the fencers group (9.5 vs 13.8%). The tendon contribution (about 70%) was the same for both legs. These changes tend to increase the role of tendon tissue (tendon and aponeurosis) and decrease the role of muscle fascicles which would allow greater use of tendon elastic structures for better energetic efficiency and improved performance. It is possible that aponeurosis is a complementary system to the adaptation of the muscle-tendon complex in the case of hyperactivity.The third study has become a case study because of the difficulty in testing the spastic patients on Quick release. Finally, the study has been done on a spastic patient with minor motor impairment compared to the others patients. The results showed a tendon and aponeurosis compliance contributions (75.3% and 15.2% respectively) higher than the muscle fascicles compliance contribution (9.5%). This result may be explained by an increase in muscle stiffness and a decrease in tendon stiffness, which is classically observed in studies with spastic subjects.

Submitted by Nadir Basilio (nadirsb@uninove.br) on 2018-06-14T20:50:43Z No. of bitstreams: 1 Stella Maris Lins Terena.pdf: 2089344 bytes, checksum: 21a72af34c64206cc3ab2d9b66964a22 (MD5) / Made available in DSpace on 2018-06-14T20:50:43Z (GMT). No. of bitstreams: 1 Stella Maris Lins Terena.pdf: 2089344 bytes, checksum: 21a72af34c64206cc3ab2d9b66964a22 (MD5) Previous issue date: 2016-06-28 / Skeletal muscle is a tissue of great adaptive capacity and is able to change its characteristics to meet various functional demands. This adaptation can be caused by mechanical overloading which results in an increase in the size of the area of muscle fiber and increase muscle mass. This process is known as muscle hypertrophy and during numerous modifications hypertrophy occur in both the muscle tissue and tendons. Studies with low-level laser (LLL) in skeletal muscle have demonstrated that its effects are positive with respect to the reduction process of inflammation, myonecrosis and reduced influence on the collagen fibers during the remodeling process.The present study aimed to analyze the effects of LLL (780nm) during the compensatory hypertrophy process on the muscular aspects and tendon of the plantaris muscle of mice (in vivo) and also evaluate its effects on human endothelial cells (HUVECs) in vitro. They were used for the in vivo experiment 22 Wistar rats were divided into control group, non-irradiated group and irradiated group hypertrophy hypertrophy. The parameters used for the irradiation were λ = 780nm, beam area 0.04 cm2, 40mW output power, energy density of 10 J / cm2. periods of 7 and 14 days were analyzed. To cause hypertrophy model was used for ablation of synergists being taken for this study, the gastrocnemius medial and lateral muscles and the soleus muscle, leaving the plantaris muscle suffered overload. the cross-sectional area were analyzed, collagen area, the number of myonuclei and mature blood vessels in muscle tissue and the organization and arrangement of collagen fibers in the tendon. For the experiment in vitro endothelial cells were used (HUVECs) were divided into control group and the other groups irradiated also with λ = 780nm, 0.04 cm2 beam area, 40mW output power and energy density of 1 J / cm2, 5J / cm2, 10 J / cm2 to 20J / cm2. The different application time was calculated for all groups received the same dose of energy. They assessed cell viability, total protein and vessel formation in Matrigel. The in vivo results showed that there was increased cross-sectional area of the irradiated group after 14 days (26.3%) when compared to non-irradiated group. There was also increased number of myonuclei in the irradiated group after 14 days. The total area of muscle collagen increased (4.2%) in the irradiated group in 7 days and decreased (6.4%) in the irradiated group after 14 days when compared to non-irradiated group in both periods. Analysis by birefringence in the tendons showed better organization of the fibers 7 and 14 days when compared to non-irradiated group. In vitro results have shown decrease in cell viability in all irradiated all groups compared to the control and counting mature vessels was increased number of vessels in the irradiated group even after 14 days. In conclusion laser irradiation increased muscle mass, the number of myonuclei and the number of mature vessels and decreased collagen total area of muscle tissue after 14 days; improved tendon collagen organization for 7 and 14 days and interfere with the viability and total protein concentration in a dose-dependent endothelial cells HUVECs. / O músculo esquelético é um tecido de grande capacidade adaptativa e que é capaz de alterar suas características para atender às diversas demandas funcionais. Essa adaptação pode ser causada por uma sobrecarga mecânica que resulta num aumento do tamanho da área da fibra muscular e aumento de massa muscular. Esse processo é conhecido como hipertrofia muscular e durante a hipertrofia inúmeras modificações ocorrem tanto no tecido muscular quanto nos tendões. Os trabalhos recentes com laser de baixa potência (LBP) no músculo esquelético tem demonstrado que seus efeitos são positivos no que diz respeito ao processo de redução da inflamação, redução da mionecrose e influência sobre as fibras de colágeno durante o processo de remodelamento. Nesse contexto o presente estudo teve por objetivo analisar os efeitos do LBP (780nm) durante o processo de hipertrofia compensatória sobre os aspectos músculares e tendíneos do músculo plantar de ratos (in vivo) e também avaliar seus efeitos em células endoteliais humanas (Huvecs) in vitro. Foram utilizados para o experimento in vivo 22 ratos Wistar, divididos em 3 grupos: controle, não irradiado com hipertrofia e irradiado com hipertrofia. Os parâmetros utilizados para a irradiação foram λ= 780nm, área do feixe 0,04 cm2, potência de saída 40mW, densidade de energia de 10J/cm2. Foram analisados os períodos de 7 e 14 dias. Para causar a hipertrofia foi utilizado o modelo de ablação dos sinergistas sendo retirados para este estudo os músculos gastrocnêmio lateral e medial e o músculo sóleo, restando o músculo plantar que sofreu a sobrecarga. Foram analisados a área de secção transversa, a área do colágeno, o número de mionúcleos e vasos sanguíneos maduros no tecido muscular e organização e disposição das fibras de colágeno no tendão. Para o experimento in vitro foram utilizadas células endoteliais (Huvecs) divididas em grupos controle e os demais grupos irradiados também com λ= 780nm, área do feixe 0,04 cm2, potência de saída 40mW e densidades de energia de 1J/cm2, 5J/cm2, 10J/cm2 e 20J/cm2. O tempo de aplicação foi diferente, calculado para que todos os grupos recebessem a mesma dose de energia. Foram avaliados a viabilidade celular, proteína total e a formação de vasos em matrigel. Os resultados in vivo obtidos demonstraram que houve aumento da área de secção transversa do grupo irradiado após 14 dias (26,3%) quando comparado ao grupo não irradiado. Houve também aumento do número de mionúcleos no grupo irradiado após 14 dias. A área total do colágeno muscular aumentou (4,2%) no grupo irradiado em 7 dias e diminui (6,4%) no grupo irradiado após 14 dias quando comparado ao grupo não irradiado nos dois períodos. A análise por birrefringência nos tendões demonstrou maior organização das fibras em 7 e em 14 dias quando comparadas ao grupo não irradiado. Os resultados in vitro demonstraram que as diferentes fluências do laser interferiram de maneira diferente na viabilidade de células Huvecs em todos os períodos avaliados. Com relação a contagem de vasos maduros houve aumento no grupo irradiado após 14 dias. Em conclusão a irradiação laser aumentou a massa muscular, o número de mionúcleos e o número de vasos maduros e diminuiu a área total de colágeno no tecido muscular após 14 dias; melhorou a organização do colágeno tendíneo em 7 e em 14 dias e interferiu na viabilidade e concentração de proteína total de maneira dose dependente das células endoteliais Huvecs.