A instabilidade articular é responsável pelo desenvolvimento de lesões degenerativas incapacitantes que comprometem o desempenho funcional. Compreender os processos desenvolvidos para estabilização dinâmica articular é um desafio para pesquisadores das mais diversas áreas. O presente estudo propõe o uso da abordagem Biomecânica para reconhecer os mecanismos relacionadas ao processo de estabilização dinâmica articular, por meio de três diferentes condições experimentais. No experimento 1 foi analisada a Força de Reação do Solo (FRS) e a cinemática 3-D no andar, correr e saltar de portadores (n=10) e não portadores de instabilidade crônica (n=10) do tornozelo. No experimento 2 foi analisada a Eletromiografia dos músculos tibial anterior, fibular longo, fibular curto e gastrocnêmio lateral de portadores (n=14) e não portadores de instabilidade crônica (n=14) do tornozelo antes e após um protocolo de indução à fadiga muscular. No experimento 3 (n=20) foi analisado o efeito do exercício de alongamento muscular estático passivo dos músculos fibular longo e fibular curto na simulação da entorse do tornozelo. Nos protocolos de locomoção foram encontrados no lado acometido picos tardios e aumento dos Impulsos da FRS. No início da fase de apoio o tornozelo instável no andar aumentou a dorsiflexão, no correr aumentou a eversão e no saltar diminuiu a inversão e aumentou a dorsiflexão. Tais estratégias representam a tentativa de melhorar a estabilidade dinâmica articular. No entanto, a variação angular da articulação no plano sagital e frontal aumentaram, sugerindo que há mais amplitude de movimento no tornozelo acometido e maior estresse sobre os estabilizadores passivos locais. Em condições de fadiga muscular, após simulação da entorse, indivíduos com articulações saudáveis aumentam a rigidez articular e a intensidade de contração dos eversores do tornozelo, antecipadamente a perturbação, diferente de portadores de instabilidade crônica. A execução do exercício de alongamento dos músculos fibulares longo e curto, seguido da simulação da entorse, gerou o retardo da resposta motora e diminuição da intensidade de ativação. Desta forma, as estratégias desenvolvidas por portadores de instabilidade crônica podem ser relacionadas à causa e/ou consequência do quadro, a fadiga muscular altera o desenvolvimento de estratégias de proteção e o exercício de alongamento pode prejudicar a estabilização dinâmica articular / Joint instability is associated with degenerating injuries that lead to functional incapacitation. Knowing the process involved in joint dynamic stabilization is a challenge to researchers in many fields. This study proposes the use of a biomechanical approach to recognize the mechanisms involved in joint stabilization through three different experimental conditions. The first experiment analyzed the Ground Reaction Force (GRF) and the 3D kinematics in participants with (n=10) and without (n=10) chronic ankle instability during walking, running and jumping. The second experiment analyzed the Electromyography signal of tibialis anterior, peroneus longus, peroneus brevis e gastrocnemius lateralis in participants with (n=14) and without (n=14) chronic ankle instability before and after a muscle fatigue protocol. The third experiment (n=20) analyzed the effect of static passive stretching of peroneus longus and peroneus brevis muscles on the ankle sprain simulation. During the locomotion protocols the injured side showed late peaks and an increase of the GRF impulses. The instable ankle showed an increase of dorsiflexion during the initial phase of gait and an increase of eversion during running. The instable ankle also showed a decrease of inversion and an increase of dorsiflexion during jumping. These strategies represent an attempt to improve the joint dynamic stability. There was an increase in sagittal and frontal angular displacement, suggesting more range of motion as well as more stress in the passive structures that are responsible for stabilization in the injured ankle. During muscular fatigue, after an ankle sprain simulation, subjects with healthy joints increase the joint stiffness and the intensity of the ankle eversion muscles activation, before the intervention, differently from subjects with chronic instability. The peroneus longus and brevis stretching exercise followed by the ankle sprain simulation caused a delay on the motor response and a decrease in the activation intensity. The strategies developed by the subjects with chronic instability can be related to the cause and/or the consequence of the dysfunction. The muscular fatigue changes the development of strategies of protection and the stretching exercise can weaken the dynamic stability of the joint

Submitted by Nadir Basilio (nadirsb@uninove.br) on 2018-06-21T18:49:26Z No. of bitstreams: 1 Leandro Lauriti.pdf: 1122104 bytes, checksum: 723249c6bdf2f01f0de75515602a5180 (MD5) / Made available in DSpace on 2018-06-21T18:49:26Z (GMT). No. of bitstreams: 1 Leandro Lauriti.pdf: 1122104 bytes, checksum: 723249c6bdf2f01f0de75515602a5180 (MD5) Previous issue date: 2015-12-04 / The aim of the present study was to perform an evaluation of the effect of low-level laser therapy (LLLT) on bite force, facial swelling, mandibular movements and pain in patients having undergone surgical treatment for mandibular fracture. The patients were divided into two groups: Group 1 – active LLLT; and Group 2 – sham LLLT. Both groups took anti-inflammatory agents postoperatively. Group 2 underwent the surgical reduction and rigid internal fixation, the use of postoperative an anti-inflammatory agent and sham LLLT with the equipment switched off. Fifteen sessions were performed using the point application methods and wavelength: 660 nm; power; 108 mW; radiant energy: 21.6 J; fluence: 21.6 J/cm2; radiance: 38197 mW/cm2; exposure time: 200 seconds per point. The active laser group received LLLT in the region of the incision and over the masseter (3 points: superior, medial and inferior) and temporal (anterior region) muscles, with five application points on each side, totaling 10 points bilaterally. The Shapiro-Wilk test was used for the analysis of the results and normal distribution was demonstrated. Thus, the Student’s t-test was used to determine inter-group differences and repeated-measures ANOVA was used to determine whether significant differences occurred at different times. The level of significance was set to 5% ( = 0.05). The findings we can see considerable improvement in the group submitted to active LLLT with regard to mandibular dynamics, a reduction in postoperative facial swelling, a reduction in pain and an increase in bite force in comparison to the sham group, which only used postoperative corticosteroids. / O objetivo deste estudo foi avaliar o efeito da LBI (laserterapia em baixa intensidade) sobre a força de mordida, edema, movimentos mandibulares e presença de dor em pacientes acometidos por fraturas mandibulares. Os pacientes foram divididos em dois grupos: Grupo 1 (LBI) e Grupo 2 (Placebo). No grupo experimental (Grupo 1), além de anti-inflamatórios no pós operatório foi aplicada a LBI. No grupo Placebo (Grupo 2) foi realizado somente o tratamento cirúrgico de redução e fixação interna rígida, o uso de anti-inflamatórios no pós-operatório e aplicação do equipamento de laser desligado. Foram realizadas um total de 15 sessões pelo método de aplicação pontual com comprimento de onda de 660nm, potência de 108 mW, energia radiante de 21,6 J, fluência de 21,6 J/cm2, irradiância de 38197 mW/cm2, durante 200 segundos por ponto. Receberam o tratamento com laser os grupos com fraturas de mandíbula, na área da incisão e nos músculos masseteres (3 pontos: superior, médio e inferior) e temporais (região anterior) em um total de 5 pontos de aplicação em cada lado, totalizando 10 pontos bilateralmente. Para análise dos resultados foi empregado o teste de Shapiro-Wilk. Como os dados apresentaram distribuição normal foi utilizado o teste t de Student para determinar as diferenças entre os grupos e o teste de ANOVA para medidas repetidas e verificar se houve diferença significante nos diferentes tempos. Adotou-se o nível de significância de 5% (=0,05). Com base nos resultados apresentados podemos verificar uma melhora considerável no grupo experimental tratado com LBI em relação a dinâmica mandibular, redução do edema facial pós-operatório, menor sintomotalogia dolorosa e aumento da força de mordida em relação aos pacientes que utilizaram apenas corticosteróides no pós cirúrgico.

<p>Током учесталог вежбања, нарочито професионалних спортиста, мишићи се привремено замарају, услед чега може доћи до пада функционалних способности. Замор мишића услед физичког вежбања постао је један од најважнијих предмета спортске науке. Циљ ове студије био је да се праћењем биохемијских параметара замора и оштећења мишића и оксидативног стреса у току једне појединачне тренажне епизоде утврди замор мишића и антиоксидативни статус кошаркашица након оптерећења изазваног са три различита врсте аеробног тренинга: континуирано ниско интензивни (НИК), континуирано високо интензивни (ВИК) и интервални аеробни тренинг (HIIT). У склопу укрштеног (crossover) дизајна изабран је узорак од 12 кошаркашица које су биле подвргнуте тестирању у предтакмичарској фази. Узорци крви узети су пре и одмах након тренажне епизоде у три наврата у размаку од по седам дана између сваког типа тренинга. Осим узимања узорака крви, проверан је пулс пре тренинга, одмах након тренинга, потом након првог, трећег и петог минута опоравка, затим, испитанице су радиле субјективну процену замора по Борговој скали одмах након тренинга, па затим у првом, трећем и петом минуту опоравка. Биохемијски параметри које смо анализирали били су маркери оштећења мишића, маркери целуларне биоенергетике, параметри оксидативно/антиоксидативног статуса. Резултати истраживања указују на то да маркери замора и оштећења мишића бележе варијабилност у резултатима с обзиром на врсту тренинга. Евидентиране су разлике у маркерима лактати, миоглобин и креатин киназа између НИК и HIIT. У мерењима срчане фреквенције у више временских тачака, статистички значајне разлике појавиле су се између ВИК и HIIT, што је у корелацији са добијеним налазима маркера оштећења мишића. Такође, субјективна процена замора прати добијене налазе и бележи значајно повећање после иста два тренинга одмах после, у првом и трећем минуту опоравка. Од маркера целуларне биоенергетике евидентиране су разлике у креатинину после НИК и HIIT тренинга. Индекс липидне пероксидације (TBARS), као један од параметара оксидативног стреса, бележи промене после НИК. Концентрација нитрита (NO2-) бележи такође статистички значајно повећање код НИК, али и код HIIT. Од испитиваних параметара антиоксидативне заштите једино каталаза (CAT) бележи значајно повећање код НИК. У процени стања замора мишића и деловања ензима оксидативно/антиоксидатине статуса, према добијеним резултатима, најсензитивнији маркери који су реаговали на различите тренажне епизоде, односно на различита аеробна оптерећења јесу миоглобин, лактати, креатин киназа и креатинин, а каталаза је показала могућност дискриминације различитих врста аеробног оптерећења.</p> / <p>Tokom učestalog vežbanja, naročito profesionalnih sportista, mišići se privremeno zamaraju, usled čega može doći do pada funkcionalnih sposobnosti. Zamor mišića usled fizičkog vežbanja postao je jedan od najvažnijih predmeta sportske nauke. Cilj ove studije bio je da se praćenjem biohemijskih parametara zamora i oštećenja mišića i oksidativnog stresa u toku jedne pojedinačne trenažne epizode utvrdi zamor mišića i antioksidativni status košarkašica nakon opterećenja izazvanog sa tri različita vrste aerobnog treninga: kontinuirano nisko intenzivni (NIK), kontinuirano visoko intenzivni (VIK) i intervalni aerobni trening (HIIT). U sklopu ukrštenog (crossover) dizajna izabran je uzorak od 12 košarkašica koje su bile podvrgnute testiranju u predtakmičarskoj fazi. Uzorci krvi uzeti su pre i odmah nakon trenažne epizode u tri navrata u razmaku od po sedam dana između svakog tipa treninga. Osim uzimanja uzoraka krvi, proveran je puls pre treninga, odmah nakon treninga, potom nakon prvog, trećeg i petog minuta oporavka, zatim, ispitanice su radile subjektivnu procenu zamora po Borgovoj skali odmah nakon treninga, pa zatim u prvom, trećem i petom minutu oporavka. Biohemijski parametri koje smo analizirali bili su markeri oštećenja mišića, markeri celularne bioenergetike, parametri oksidativno/antioksidativnog statusa. Rezultati istraživanja ukazuju na to da markeri zamora i oštećenja mišića beleže varijabilnost u rezultatima s obzirom na vrstu treninga. Evidentirane su razlike u markerima laktati, mioglobin i kreatin kinaza između NIK i HIIT. U merenjima srčane frekvencije u više vremenskih tačaka, statistički značajne razlike pojavile su se između VIK i HIIT, što je u korelaciji sa dobijenim nalazima markera oštećenja mišića. Takođe, subjektivna procena zamora prati dobijene nalaze i beleži značajno povećanje posle ista dva treninga odmah posle, u prvom i trećem minutu oporavka. Od markera celularne bioenergetike evidentirane su razlike u kreatininu posle NIK i HIIT treninga. Indeks lipidne peroksidacije (TBARS), kao jedan od parametara oksidativnog stresa, beleži promene posle NIK. Koncentracija nitrita (NO2-) beleži takođe statistički značajno povećanje kod NIK, ali i kod HIIT. Od ispitivanih parametara antioksidativne zaštite jedino katalaza (CAT) beleži značajno povećanje kod NIK. U proceni stanja zamora mišića i delovanja enzima oksidativno/antioksidatine statusa, prema dobijenim rezultatima, najsenzitivniji markeri koji su reagovali na različite trenažne epizode, odnosno na različita aerobna opterećenja jesu mioglobin, laktati, kreatin kinaza i kreatinin, a katalaza je pokazala mogućnost diskriminacije različitih vrsta aerobnog opterećenja.</p> / <p>During intense exercise, especially professional athletes, muscles are temporarily tired, resulting in a decline in functional abilities. Damage caused by muscle stiffness due to physical exercise has become one of the most important subjects of sports science. The aim of this study was to determine the muscle fatigue and the antioxidative status of basketball players following a load caused by three different types of aerobic training: continuous low intensity (LIC), continuous high intensity (HIC) and intermittent aerobic training (HIIT). As part of the crossover design, a sample of 12 basketball players that were tested at the pre-match phase was selected. Blood samples were taken before and immediately after the training episode on three occasions at intervals of seven days between each type of training. In addition to taking blood samples, pulse testing was performed before training, immediately after training, then after the first, third and fifth minutes of recovery, then the subjects were subjective assessment of fatigue on the Bragg scale immediately after the training, then in the first, third and fifth minutes recovery. The biochemical parameters we analyzed were markers of muscle damage, markers of cellular bioenergetics, parameters of oxidative stress and the activity of enzymes of protection against oxidative damage. The results of the study indicate that the markers of muscle damage record the variability in the results compared to the type of training. Differences in markers of lactates, myoglobin and creatine kinase were recorded between LIC and HIIT. In relation to the heart rate measured at several time points, statistically significant differences have occurred between HIC and HIIT, which is correlated with the findings of the markers of muscle damage. Also, a subjective estimate of fatigue follows the findings obtained and shows a significant increase after the same two trainings immediately after, in the first and third minutes of recovery. Differences in creatinine from LIC and HIIT training were recorded from cellular bioenergetic markers. The lipid peroxidation index (TBARS), as one of the parameters of oxidative stress, records changes after LIC. The concentration of nitrite (NO2-) also recorded a statistically significant increase in LIC, but also in HIIT. From the tested parameters of antioxidant protection, only catalase (CAT) showed a significant increase in NIK. In the assessment of muscular fatigue and oxidative / antioxidant status, according to the obtained results, the most sensitive markers that responded to different training episodes or different aerobic loads were myoglobin, lactates, creatine kinase and creatinine, while the catalase showed the possibility of discrimination of different species aerobic load.</p>

Les troubles musculo-squelettiques liés au travail causent des maladies physiques et mentales chez les travailleurs, réduisent leur productivité et causent de grandes pertes aux industries et à la société. Cette thèse porte sur l'évaluation du risque physique de troubles musculo-squelettiques liés au travail, pour laquelle quatre points clés sont identifiés : la mesure de la charge de travail, l'évaluation de l'effet de l'accumulation de la charge de travail, la quantification des caractéristiques individuelles et l'intégration de l'évaluation des risques dans les outils de modélisation numérique humaine. Dans l'état de l'art, les études épidémiologiques des désordres musculo-squelettiques et les méthodes actuelles utilisées pour l'évaluation des risques physiques sont présentées, ainsi que les études concernant les quatre points clés. La deuxième partie présente une étude expérimentale portant sur 17 sujets afin d'explorer un nouvel indicateur de la fatigue musculaire avec EMG de surface. Dans la partie suivante, des développements sont faits pour intégrer un modèle de fatigue musculaire dans OpenSim, un logiciel de modélisation humaine numérique, avec lequel la diminution de capacité de chaque muscle est prévisible pour une tâche donnée. Les valeurs prévues peuvent s'appliquer à l'évaluation des risques physiques. La quatrième partie présente le travail de construction d'un modèle musculosquelettique à chaîne complète dans OpenSim, étant donné qu'aucun modèle actuel ne couvre les muscles du torse et tous les membres. Une attention particulière est portée à la méthode utilisée par OpenSim pour adapter les propriétés inertielles du modèle aux individus. Les erreurs de la méthode sont évaluées à l'aide des données de référence provenant du scanner 3D du corps entier. Dans la dernière partie, le nouveau modèle de la chaîne complète est appliqué à l'analyse de la posture d'une tâche de perçage en hauteur. L'activité musculaire varie en fonction des postures, ce qui est suggéré comme indicateur des charges posturales. / Work-related musculoskeletal disorders cause physical and mental illnesses in workers, reduce their productivity and cause great losses to industries and society. This thesis focuses on the assessment of the physical risk of work-related musculoskeletal disorders in industry, for which four key points are identified: measuring workloads, assessing the effect of workload accumulation, quantifying individual characteristics and integrating the risk assessment into digital human modeling tools. In the state of the art, the epidemiologic studies of musculoskeletal disoders and the current methods used for its physical risk assessment are reviewed, as well as the studies concerning the four key points. The second part presents an experimental study involving 17 subjects to explore a new indicator to muscle fatigue with surface EMG. In the next part, efforts are made to integrate a muscle fatigue model into OpenSim, a digital human modeling software, with which the capacity decrease of each muscle is predictable for a given task. The predicted values could be applicable to the physical risk assessment. The fourth part introduce the work to build up a Fullchain musculoskeletal model in OpenSim in view that no current model covers muscles of the torso and all the limbs. Special attention is paid to the method used by OpenSim to adapt the model inertial properties to individuals. Errors of the method is evaluated with reference data coming from the whole-body 3D scan. In the last part, the newly built Full-chain model is applied on the posture analysis of an overhead drilling task. The muscle activition varies as a function of postures, which is suggested as the indicator of posture loads.

Introduction: Muscle fatigue can contribute to acute flare-ups of lower back pain with associated consequences such as pain, disability, lost work time, increased healthcare utilization, and increased opioid use and potential abuse. The SPINE Sense system is a wearable device with 16 high deflection nanocomposite strain gauge sensors on kinesiology tape which is adhered to the skin of the lower back. This device is used to correlate lumbar skin strains with the motion of the lumbar vertebrae and to phenotype lumbar spine motion. In this work it was hypothesized that the SPINE Sense device can be used to detect differences in biomechanical movements consequent to muscle fatigue. A human subject study was completed with 30 subjects who performed 14 functional movements before and after fatiguing their back muscles through the Biering-Sørensen endurance test with the SPINE Sense device on their lower back collecting skin strain data. Various features from the strain gauge sensors were extracted from these data and were used as inputs to a random forest classification machine learning model. The accuracy of the model was assessed under two training/validation conditions, namely a hold-out method and a leave-one-out method. The random forest classification models were able to achieve up to 84.22% and 78.37% accuracies for the hold-out and leave-one-out methods respectively. Additionally, a system usability study was performed by presenting the device to 32 potential users (clinicians and individuals with lower back pain) of their device. They received a scripted explanation of the use of the device and were then instructed to score it with the validated System Usability Score. In addition they were given the opportunity to voice concerns, questions, and offer any other additional feedback about the design and use of the device. The average System Usability Score from all participants from the system usability study was 72.03 with suggestions of improving the robustness of electrical connections and smaller profiles of accompanying electronics. Feedback from the potential users of the device was used to make more robust electrical connections and smaller wires and electronics modules. These improvements were achieved by making a two-piece design: one piece contains the sensors on kinesiology tape that is directly attached to the patient and the other one contains the wires sewn into stretch fabric to create stretchable electronic connections to the device. It is concluded that a machine-learning model of the data from the SPINE Sense device can classify lumbar motion with sufficient accuracy for clinical utility. It is also concluded that the device is usable and intuitive to use.

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L’objectif général de ce travail doctoral était de comparer les effets de la fatigue musculaire des quadriceps femoris après un exercice musculaire volontaire (VOL) et un exercice musculaire électroinduit (ES) sur le contrôle postural bipodal, ainsi que sur la fatigue centrale. Les résultats montrent qu’à l’issue d’une tâche fatigante unilatérale ou bilatérale, l’exercice ES dégrade davantage la force usculaire que l’exercice VOL. Cependant, le contrôle postural bipodal est indifféremment perturbépar les deux exercices. En outre, les vitesses de récupération des capacités posturales et de force musculaire ne diffèrent pas à l’issue des exercices. Par ailleurs, l'exercice VOL altère davantage la commande centrale que l'exercice ES (immédiatement à l’issue de l’effort), tandis que celui-ci retarde l’apparition de la fatigue centrale et la maintient plus longuement. Etant donné que l'exercice VOL estinduit par la commande centrale et que l'exercice ES est généré par une stimulation artificielle externe, on peut émettre l’hypothèse que l'exercice VOL produit essentiellement une fatigue supraspinale, tandis que l'exercice ES engendre surtout une fatigue spinale. / The overall objective of this thesis was to compare the effect of fatigue of the quadriceps femoris after fatiguing voluntary contractions (VOL) and fatiguing neuromuscular electrical stimulation (ES) on bipedal postural control, and central fatigue. The results show that after unilateral or bilateral muscle fatigue, the ES exercise affected the muscle strength more than the VOL exercise. However, bipedal postural control was similarly deteriorated for both exercises. Moreover, the recovery speeds of postural control and muscle strength abilities did not differ for the both exercises. In addition, the VOL exercise alters central drive quicker than the ES exercise immediately after their completion while the ES exercise delays and prolongs the central fatigue. As the VOL exercise is induced by central command and the ES exercise is generated by artificial external stimulation, one can hypothesize that the VOL exercise especially produces supraspinal fatigue, while the ES exercise especially engenders spinal fatigue.

L’objectif général de ce travail doctoral était d’étudier les effets de la fatigue (physique et mentale) sur le contrôle postural. Tout d’abord, les effets de la fatigue musculaire du quadriceps fémoral induite par des contractions volontaires et des contractions électro-induites ont été comparés. Les résultats ont montré que des contractions volontaires altéraient davantage le contrôle postural que des contractions électro-induites pour une perte de force musculaire équivalente. Ceci s’expliquerait par la présence d’une fatigue centrale après les contractions volontaires, ainsi qu’une sollicitation différente des fibres musculaires entre les deux modalités de contraction. Des mécanismes compensatoires seraient mis en œuvre après ces deux modalités de contractions fatigantes, mais de façon plus prononcée pour les contractions volontaires. Concernant la fatigue mentale, les effets d’une tâche cognitive exigeante et prolongée sur ordinateur (induisant un état de fatigue mentale) et d’un visionnage de documentaire (tâche contrôle) sur le contrôle postural ont été comparés. De prime abord, la fatigue mentale affecterait le contrôle postural en condition de privation visuelle, en réduisant l’efficacité des stratégies d’attention associatives. De façon surprenante, visionner un documentaire conduirait également à une altération du contrôle postural, potentiellement en raison du maintien prolongé d’une posture assise affaissée. La posture assise pourrait ainsi constituer un facteur confondant dans les protocoles expérimentaux comportant une évaluation posturale. Une analyse statistique de classification en cluster hiérarchique a permis de mettre en évidence des sensibilités différentes au sein des individus à l’égard de la tâche mentalement fatigante. Le niveau de fatigue mentale serait associé au niveau de dégradation du contrôle postural sur un support stable avec les yeux ouverts. La réalisation d’une tâche cognitive prolongée exigeant une attention visuelle soutenue face à un écran d’ordinateur provoquerait une fatigue visuelle. Cette fatigue visuelle affecterait différemment les individus. Elle toucherait plus particulièrement les sujets les plus dépendants des informations visuelles, pour lesquels le contrôle postural se dégraderait davantage que les autres individus. / The overall objective of this doctoral work was to study the effects of fatigue (physical and mental) on postural control. First, the effects of femoral quadriceps muscle fatigue induced by voluntary contractions and electro-induced contractions were compared. The results showed that voluntary contractions affected postural control more than electro-induced contractions for an equivalent loss of muscle strength. This could be explained by the presence of central fatigue after voluntary contractions, as well as a different strain on muscle fibres between the two modes of contraction. Compensatory mechanisms would be implemented after these two modes of tiresome contractions, but more pronounced for voluntary contractions. With regard to mental fatigue, the effects of demanding and prolonged cognitive computer work (inducing mental fatigue) and documentary viewing (task control) on postural control were compared. At first glance, mental fatigue would affect postural control in conditions of visual deprivation, reducing the effectiveness of associative attention strategies. Surprisingly, viewing a documentary would also lead to an alteration in postural control, potentially due to the prolonged maintenance of a collapsed sitting posture. Sitting posture could thus be a confounding factor in experimental protocols involving postural evaluation. A statistical analysis of hierarchical cluster classification revealed different sensitivities within individuals towards the mentally demanding task. The level of mental fatigue would be associated with the level of degradation of postural control on a stable support with eyes open. Performing a prolonged cognitive task requiring sustained visual attention to a computer screen would cause visual fatigue. This visual fatigue would affect individuals differently. It would particularly affect the subjects most dependent on visual information, for which postural control would be more degraded than other individuals.

La stimulation éléctrique fonctionnelle (SEF) peut améliorer de manière significative la mobilité des blessés médullaires ainsi que la stabilité et la prévention des effets secondaires. Dans le domaine de la SEF pour les membres inférieurs, le couple articulaire doit être fournie de façon appropriée pour effectuer le mouvement prévu afin de maintenir l'équilibre postural. Toutefois, les changements d'état du muscle telle que la fatigue musculaire est une cause majeure qui dégrade ses performances. En outre, la plupart des patients, dont la blessure médulaire est complète, n'ont pas le retour sensorielle qui permet de détecter la fatigue. De plus, et les capteurs de couples in-vivo ne sont pas disponibles à l'heure actuelle. Les systèmes conventionnels de commande SEF sont soit en boucle ouverte ou en boucle fermée mais cependant pas assez robustes aux changements d'état du muscle. L'objectif de cette thèse est le développement de la prédiction du couple articulaire et de la commande en boucle fermée afin d'améliorer les performances de la commande SEF en termes de précision, de robustesse et de sécurité pour les patients. Afin de prédire le couple articliare induit de la SEF, l'électromyographie (EMG) induit est utilisée pour corréler l'activité musculaire éléctrique et mécanique. Bien que la fatigue musculaire représente une variation dans le temps, une dépendance aux sujets et aux protocoles, la méthode proposée d'identification adaptative, basée sur le filtre de Kalman, est capable de prédire le couple articlaire variant dans le temps de manière systématique. La robustesse de la prédiction du couple articulaire a été evaluée lors d'une tâche de suivi de la fatigue en expérimentation chez des sujets blessés médullaires. Les résultats montrent une bonne performance de suivi des variations d'état des muscles en présence de fatigue et face à d'autres perturbations. Basée sur les performances de precision de la méthode prédictive proposée, une nouvelle stratégie de commande utilisant le retour EMG, "EMG-Feedback Predictive Control (EFPC)", est proposée afin de contrôler de manière adaptative les séquences de stimulation en compensant la variation dans le temps de l'état du muscle. De plus, cette stratégie de commande permet explicitement d'éviter d'appliquer une stimulation excessive aux patients, et de générer les séquences de stimulation appropriées pour obtenir la trajectoire désirée des couples articulaires.

Made available in DSpace on 2015-07-22T20:49:20Z (GMT). No. of bitstreams: 0 Previous issue date: 2008-04-30. Added 1 bitstream(s) on 2015-08-11T03:25:48Z : No. of bitstreams: 1 Publico-10870.pdf: 69580 bytes, checksum: 9aba33341c44980cac0fc8ab7561d008 (MD5) / Embora a análise no domínio da freqüência do sinal Eletromiográfico (EMG) seja empregada na caracterização do processo de fadiga muscular localizada, sua aplicação, especificamente a da Freqüência Mediana (Fmed), é pouco explorada no âmbito esportivo. O objetivo do presente estudo foi verificar a viabilidade da aplicação do sinal EMG, através de sua análise no domínio da freqüência, como parâmetro para determinação e diferenciação no comportamento da fadiga muscular localizada. Dois grupos de sujeitos um caracterizado como atletas (n=12) e outro como sedentários (n=12), foram submetidos a análises baseadas em procedimentos executados em três diferentes situações experimentais, todos envolvendo a modalidade de exercício isométrico: i) teste máximo para determinação da Contração Isométrica Voluntária Máxima (CIVM); ii) teste de fadiga, sustentado por 35 seg. a 80% da CIVM; iii) teste de recuperação, sustentado por 10 seg. a 80% da CIVM; neste ultimo foi monitorado o comportamento da Fmed nos três primeiros (Fmedi) e três últimos segundos (Fmedf) do sinal EMG no músculo tibial anterior durante o teste de fadiga. Durante os 10 segundos do teste de recuperação foi calculada a Fmed referente a todo o período (Fmedr).parâmetro utilizado no cálculo do Índice de Recuperação Muscular (IRM). Os resultados apontam que a Fmedf apresentou valor menor em relação à Fmedi em ambos os grupos (p<0.05). Quando comparado ao grupo de sedentários, o grupo de atletas apresentou valores maiores de Fmedi e Fmedf (p<0.05). O valor médio e desvio padrão do IRM para o grupo de atletas foi de 62.1% ±28.7 e para o grupo de sedentários foi de 55.2% ±27.8 (p>0.05). Desta forma, os resultados apresentados neste estudo permitem inferir a viabilidade na aplicação de parâmetros no domínio da freqüência do sinal EMG para a determinação e diferenciação do comportamento da fadiga muscular localizada. / Though the analysis in the frequency domain of the Electromyographic Signal (EMG) was used in the characterization of the localized muscular fatigue process their application, specifically the Median Frequency (MF), is rarely explored in the sports. The objective of this study was to verify the viability in the application of the EMG signal, through of the frequency domain analysis, as parameter for determination and differentiation of the behavior of located muscle fatigue. Two groups of subjects one characterized as athletes (n=12) and other as sedentary (n=12), were submitted to analysis based in procedures executed in three different experimental situations, all involving the isometric exercise modality: i) maximum test for determination of the Maximum Voluntary Isometric Contraction (MVIC); ii) fatigue test, 35 sec. sustained load of 80% of MVIC; iii) recovery test, 10 sec. sustained load of 80% of MVIC; where was monitored the behavior of MF in the first three (Fmedi) and last three seconds (Fmedf) of the EMG signal of anterior tibial muscle during the fatigue test. During the 10 seconds of the recovery test MF was calculated regarding the whole period (Fmedr) this parameter was used to calculate the Recuperation Muscle Index (RMI). The results showed that Fmedf presented a low value in relation to Fmedi in both groups (p <0.05). Also the value of Fmedi and Fmedf for the athlete group presented larger higher value in comparison with the sedentary group (p <0.05). The mean value and standard deviation of RMI for the athlete group were 62.1% ±28.7 and for sedentary group was 55.2% ±27.8 (p>0.05). In general terms the results presented in this study allow inferring the viability in the application of the frequency domain parameters of the EMG signal for the determination and differentiation of the located muscle fatigue behavior. / TEDE / BV UNIFESP: Teses e dissertações