Gait initiation (GI) is an important locomotor transition task that includes anticipatory postural adjustments and the joint propulsion necessary for the first step of walking. Metrics associated with this task are known to change across the lifespan and may provide valuable information for fall risk indication, as falls often occur during transitional tasks. Assessments of discrete variables between fallers and non-fallers at GI have provided insight into differences between groups. However, more complex approaches such as time-series principal component analysis (PCA) may allow the examination of changes in magnitude, pattern, and timing not detectable using discrete comparisons alone. Therefore, this thesis aims to characterize differences between fallers and non-fallers by examining the kinematics and kinetics of gait initiation using time-series PCA. A sample of 56 community-dwelling older adults was recruited for this study and completed five walking trials where GI was measured by two force platforms. PCA of centre of pressure kinematics and kinetics time-series data were used to identify the critical features of the signal, and multivariate analysis of covariance was used to compare the individual loading scores of each principal component for each phase between groups. It was revealed that fallers demonstrated differences in the range of mediolateral movement during weight transfer and forward progression, a greater range of anteroposterior movement in forward progression, and a more gradual rise in vertical forces in the first step, associated with a shorter first step length. These findings point to a tendency for fallers to prioritize stability over forward progression performance, and differences in postural control strategies, compared to non-fallers. Further, the use of time-series PCA helped to highlight differences not detectable using discrete analysis alone. / Graduate

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No. of bitstreams: 1 pestana_mb_me_rcla.pdf: 1594577 bytes, checksum: ba17e6e3e3d9467b6639bffcea05350f (MD5) Previous issue date: 2017-12-14 / Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) / A doença de Parkinson (DP) é a segunda doença neurodegenerativa mais comum, que acomete aproximadamente 0,3% da população mundial. A morte dos neurônios dopaminérgicos na substância negra leva aos seus sinais/sintomas motores característicos da DP. Além dos sinais/sintomas motores destacam-se também os não motores como alterações de humor, cognição, ansiedade e depressão. As alterações cognitivas incluem comprometimentos das funções executivas e da memória de trabalho (MT) verbal e visuoespacial. Déficits na MT visuoespacial parecem estar associados aos comprometimentos do andar em pacientes com DP, principalmente no início do andar, porém esta relação ainda é pouco conhecida. O objetivo deste estudo foi analisar o impacto da MT no posicionamento do pé em alvos com diferentes tempos para iniciar o andar em pacientes com DP e idosos neurologicamente sadios (NS). Participaram do estudo 20 idosos com DP e 18 NS avaliados quanto à função cognitiva geral, capacidade de armazenamento na MT e central executiva da MT por meio dos testes Digit Span, Blocos de Corsi e Clox I e II. A tarefa foi realizada sob condições que combinaram o tempo para início do andar (250ms, 500ms, 1s ou 2s) após a exposição inicial do alvo (5s) e a localização do alvo (direita, esquerda e central). Para a análise cinemática, o sistema optoeletrônico capturou as trajetórias dos emissores infravermelhos que foram fixados no pé direito dos participantes. A estatística descritiva (média ± desvio ou erro padrão) foi empregada para a apresentação das variáveis de caracterização dos grupos e das variáveis dependentes. Na análise estatística foram utilizados os testes de Shapiro-Wilk e de Levene para verificar a normalidade e a homogeneidade dos dados. Para a comparação entre os grupos, testes t para amostras independentes (idade, massa corporal e estatura) e o teste U de Mann-Whitney (variáveis cognitivas) foram empregados. Para o erro absoluto, erro variável e erro constante foram realizadas ANOVAS two-way (grupo X condição), com medidas repetidas para condição. O teste de Bonferroni foi empregado para localizar possíveis diferenças significativas. Os grupos não apresentaram diferença significativa para idade, peso e altura. Nas variáveis cognitivas apenas encontrou-se diferença no MEEM. Para variáveis de posicionamento do pé sobre o alvo, ausência de efeito principal de grupo (GDP X GC) e de interação entre grupo e os fatores de tempo e posição do alvo para os três erros. No sentido médio-lateral, os participantes apresentaram menor erro absoluto e maior erro variável para o alvo posicionado à esquerda, nas condições de 250ms e 2s. Ainda, para o alvo posicionado à direita, observou-se maior erro constante anteroposterior e médio-lateral comparados aos outros alvos. Na condição de maior tempo, 2s, os participantes posicionaram o pé antes do alvo em comparação ao tempo de 500ms, indicado pelo maior erro constante nesta condição. Os participantes apresentaram menor erro absoluto médio-lateral na condição de tempo de 1s e erro absoluto anteroposterior na condição de tempo de 2s para o alvo posicionado no centro nas condições com maior tempo. Finalmente, não houve correlação entre as variáveis de (erro absoluto, constante e variável) com a capacidade de armazenamento de informações verbais e visuoespaciais e os processos de controle executivo da MT. Concluindo-se que pacientes com DP e idosos NS apresentam desempenho semelhante ao posicionar o pé sobre o alvo. Quando os alvos estão posicionados lateralmente, o desempenho da tarefa é prejudicado, principalmente no alvo da esquerda, diminuindo a acurácia e a precisão. Ainda, tempos muito longos (2s) ou curtos (250ms) parecem influenciar negativamente no desempenho da tarefa devido ao longo tempo de armazenamento da informação visual e curto tempo para a realização da ação motora, respectivamente. / Parkinson's disease (PD) is the second most common neurodegenerative disease, affecting approximately 0.3% of the world's population. The death of dopaminergic neurons in the substantia nigra leads to the characteristic motor signals/symptoms in PD. Additionally, patients also show non-motor signs/symptoms such as impairments in mood, cognition, anxiety and depression. The cognitive changes are dependent on executive functions and among them are a verbal and visuospatial (WM) working memory. Deficits in visuospatial WM seem to be associated with gait impairment in patients with PD, especially in gait initiation, but this relationship is still poorly understood. The aim of this study was to analyze the impact of visuospatial WM on foot positioning on targets with different intervals to star walking after target exposure in patients with PD (PDG) and neurologically healthy (NH) older adults. Participants were 20 older adults with PD and 18 NH older adults (CG) who were assessed in regard to general cognitive function, storage capacity in WM and central executive of WM by means of the Span Digit, Corsi Blocks and Clox I and II tests. The experimental task was performed under conditions that combined the time to start walking (250ms, 500ms, 1s or 2s) after the initial target exposure target location (right, left and center). For kinematic analysis, the optoelectronic system captured trajectories of the infrared emitters that were fixed in the right foot of the participants. Descriptive statistic (mean ± standard deviation or error) was used to present variables for characterization of groups and dependent variables. In the statistical analysis of the Shapiro-Wilk and Levene test instruments to verify the normality and the homogeneity of the data. For a comparison between groups, testis for independent samples (age, body mass and stature) and Mann-Whitney test (cognitive variables) and employed. For absolute error, variable error and constant error, we performed two-way ANOVAs (group X condition), with repeated measures for the condition. The Bonferroni test was used to find possible significant differences. The groups did not present significant differences for age, weight and height. For the cognitive variables, we found significant difference for MEEM only, with PDG presenting lower score than the CG. For foot positioning variables, absence of main group effect (PGD X CG) and interaction between group and time and target position factors for the three errors. In the mid-lateral direction, the participants presented lower absolute error and greater variable error for the target positioned to the left, in the conditions of 250ms and 2s. Also, for the right-positioned target, greater anteroposterior and mid-lateral constant error were observed compared to the others targets. For longer time condition, 2s, participants positioned the foot before the target compared to the time of 500ms, indicated by the largest constant error in this condition. The participants presented lower absolute mid-lateral error in the 1s time condition and anteroposterior absolute error in the time condition of 2s for the target positioned in the center in the conditions with greater time. Finally, there was no correlation between the variables (absolute, constant and variable error) with the storage capacity of verbal and visuospatial information and the processes of executive control of WM. It was concluded that patients with PD and NH older people present similar performance for foot positioning. When the targets are positioned laterally, the performance of the task is impaired, especially in the left target, decreasing the precision and accuracy. Also, very long (2s) or short times (250ms) seem to negatively influence the performance of the task due to the long storage time of the visual information and short time to perform the motor action, respectively. / CNPq: 134414/2015-2

Of all children in the US born with Cerebral Palsy (CP), 30-40% of them will be diagnosed with Hemiplegic CP (HCP), presenting with one side of the body weaker than the other. The resulting asymmetries impede the ability of children with HCP to distribute weight evenly between their lower limbs. This often contributes to poor postural control and 'favoring' of their uninvolved side for stability during balance and gait. Much is still unknown about the biomechanical characteristics of asymmetry in the lower limbs. There are a few previous research studies completed in biomechanics labs that highlight some gaps in knowledge regarding our understanding of posture and balance in this population of children, but the availability of clinical assessments that help inform the implementation and impact of treatment targets for posture and balance are sparse. This dissertation showcases two independent studies aimed at some of the gaps in knowledge for posture and balance in children with HCP. The first study in this dissertation presents and tests the reliability when a clinical measure, the Posture and Postural Ability Scale (PPAS) was modified for use in children with HCP going through a therapeutic process. The PPAS was originally developed and tested with adults in controlled settings, often with individuals being placed in postures for examination. For the study presented here, modifications focused on scoring postures when children with HCP naturally assumed various sitting and standing postures during treatment. Researchers and an experienced therapist video-coded the modified PPAS. Intrarater and interrater reliability was calculated via Cohen's kappa, percent agreement and Intraclass Correlation Coefficients. Although reliability amongst and between researchers were weak (kappas < 0.7), videos were successfully scored, demonstrating the tool is feasible. In addition, some high levels of intrarater reliability was obtained by a more experienced clinician. Suggestive that this modified PPAS could serve as a potential tool for qualified clinicians to collect meaningful posture and postural control data. The second study addressed a specific gap in knowledge about the characteristics of gait anticipation (GA, i.e., expectation of initiating a step) in children with HCP on balance. Balance and limb symmetry metrics were compared during standing in three children with HCP and typically developing (TD) peers that were matched by age and sex, alongside a third (independent) sample of 12 unmatched TD children. Motion capture analysis and force plate technology were utilized to record and follow how center of pressure (COP) and center of mass (COM) move during quiet standing (without anticipating gait) and standing with GA. This study applied a Symmetry Index (SI) to COP displacement and COP velocity allowing for quantification of asymmetries between the lower limbs during standing with and without the anticipation of gait. Children completed multiple standing trials where they were ask to stand for 35 seconds (5 seconds to obtain balance and 30 seconds of data collection). Standing trials, involved sets where children were instructed that they would not walk forward and GA trials where they were asked to stand knowing that a light would indicate they should walk forward. The light also indicated which limb (i.e. right or left) the child should step forward with first. Limb designation for stepping forward was randomly generated. Data was examined across and within (15 second blocks) 30 seconds of standing. We had the following hypotheses: 1) GA would increase COP displacement and COP velocity for children with HCP greater than TD peers who would have no change; 2) children with HCP would have different levels of symmetry between the lower limbs when expecting to walk than TD peers; and 3) children with HCP would have different reaction times based on the limb (i.e., involved versus uninvolved) they were asked to start walking with. The HCP group showed the largest increase in COP displacement when comparing standing with no expectation of walking where they had an average of 22.0 ± 10.0 mm over 30 seconds of standing to an average of 24.5 ±9.90mm during GA. The matched group average was 11.3 ±8.87mm with no expectation of walking and 4.6 ±12.6mm with GA. The TD group's COP displacement remained relatively similar with an average of 8.04 ±6.40mm during when not expecting to walk and an average of 8.29 ±6.70mm with GA. Similar increases were seen for COP velocity. Comparisons for symmetry between limbs showed that COP was displaced more underneath the uninvolved side (first 15s was 79.52%) for children with HCP, and that COP displacement asymmetry switched to become larger underneath the involved side over time (the latter 15s was -82.81%) when there was no expectation for walking. This was inverted during GA, where children with HCP initially had more COP displacement on the involved side (-72.68%) and transitioned to higher levels on the uninvolved side (99.66%) as they prepared for gait initiation. Children with HCP took 0.2 seconds longer to initiate gait with their uninvolved (not preferred) side and also took twice as long to initiate gait overall in comparison to TD peers. Our data suggests that our listed hypotheses may be correct. However, this study has limitations to sample size, demographics and biomechanical metrics. Future studies should replicate these findings and include larger, more diverse samples with further metrics such as load. If findings are confirmed, this data suggests that therapies should consider that children with HCP might change postural strategies during standing when they are anticipating walking forward in comparison to simply standing in place. This dissertation seeks to set a foundation for collaborations between biomechanists and therapists alike, potentially highlighting novel opportunities to develop more innovative treatment options for children with HCP. / Doctor of Philosophy / Children with hemiplegic cerebral palsy (HCP) show limitations in coordination and activation of muscles on one side of their body; additionally, clinicians report an asymmetrical distribution of weight in their legs during standing and walking based on observation. This lower limb asymmetry is often paired with poor coordination and is believed to negatively impact posture and balance. Children with HCP often have difficulty starting and stopping walking, altered balance during sitting and standing, and challenges completing everyday activities such as navigating around or across obstacles and climbing up steps. I have worked together with my committee members to complete two independent projects measuring posture and postural control. The first project is a reliability study where researchers tested the utility of a modified measurement tool that could be used to score postures and postural control of children assuming natural postures during therapy sessions. The modified tool was based on a previously developed tool called the Posture and Postural Ability Scale (PPAS). The study had multiple researchers and a therapist score previously recorded treatment videos. Outcomes suggest that our modified PPAS could be used to score postures from video recordings of therapy session, but that increased modifications in the tool and scoring protocol are needed to improve the reliability of the tool. The second project funded by the Eunice Kennedy Shriver National Institute of Child Health and Human Development involved children with HCP and typically developing (TD) peers. The goal of the project was to understand if children with HCP change characteristics of standing when they know they will begin to walk. We also wanted to better understand issues surrounding how symmetrical (or not) children with HCP were with the use of both their involved and uninvolved legs. We found that children with HCP do alter characteristics of standing when they anticipate walking much more that TD peers. We also found asymmetries between the two limbs during standing that differed based on children with HCP's anticipation of walking.

No / Unilateral lower-limb amputees lead with their intact limb when stepping up and with their prosthesis when stepping down; the gait initiation process for the different stepping directions has not previously been investigated. Ten unilateral amputees (5 transfemoral and 5 transtibial) and 8 able-bodied controls performed single steps up and single steps down to a new level (73 and 219 mm). Duration, a-p and m-l centre of mass and centre of pressure peak displacements and centre of mass peak velocity of the anticipatory postural adjustment and step execution phase were evaluated for each stepping direction by analysing data collected using a Vicon 3D motion analysis system. There were significant differences (in the phase duration, peak a-p and m-l centre of pressure displacement and peak a-p and m-l centre of mass velocity at heel-off and at foot-contact) between both amputee sub-groups and controls (P<0.05), but not between amputee sub-groups. These group differences were mainly a result of amputees adopting a different gait initiation strategy for each stepping direction. Findings indicate the gait initiation process utilised by lower-limb amputees was dependent on the direction of stepping and more particularly by which limb the amputee led with; this suggests that the balance and postural control of gait initiation is not governed by a fixed motor program, and thus that becoming an amputee will require time and training to develop alternative neuromuscular control and coordination strategies. These findings should be considered when developing training/rehabilitation programs.

Les paradigmes expérimentaux de l'initiation de la marche (IM) et du rattrapage de l'équilibre (RE) consécutif à une chute-avant ont été choisis pour identifier les adaptations motrices éventuelles chez les enfants souffrant de lésions cérébrales (PC) bilatérales et unilatérales vs. les enfants avec un développement normal (DN). Les enfants PC et DN étaient âgés entre 5 et 16 ans. Les enfants PC avaient une marche autonome sans aide technique. Les résultats montraient que, dans l'IM, les différents groupes d'enfants présentent des patterns biomécaniques et d'activités EMG comparables lorsque l'appui est sain. Plus particulièrement, la présence d'un freinage de la chute pendant la phase pendulaire, qui est l'indice qui caractérise la maturation du processus de la marche, chez les plus jeunes PC indique l'absence de retard. Lorsque l'appui est sur le côté lésé, le freinage est absent voire faible. Cette absence de freinage peut être imputée à la modification de l'appui en équin. De même, les tracés biomécaniques et EMG dans RE montraient des patterns comparables entre les différents groupes d'enfants. Toutefois une différence remarquable peut être distinguée par rapport à l'activité EMG des muscles fléchisseurs plantaires et dorsaux des adultes. Chez les adultes, la chute provoque une réponse précoce bilatérale des Soleus accompagnée parallèlement d'une activité de faible amplitude des TA. Chez les enfants, les TA montraient une importante bouffée EMG en même temps que la bouffée du Soleus. La suppression de cette bouffée précoce lorsque la chute est rapidement arrêtée annihilant l'exécution du pas suggère que les enfants DN et PC déclencheraient en même temps la réaction à la chute et le programme d'initiation du pas. Si les enfants PC pouvaient réalisés les deux tâches motrices, exécution du pas normal et exécution du pas provoqué, c'est semble-t-il grâce à la toxine botulique qui avait permis à l'enfant PC de se mettre debout libre, apprendre à contrôler son équilibre postural et la marche. / Experimental paradigms of gait initiation (GI) and balance recovery (BR) following a forward-fall were chosen to study motor adaptation in cerebral palsy (CP) children as compared to typical development children (TD). Children age ranged between 5 and 16 y.o. PC children walked independently. Results in GI showed that biomechanical and EMG pattern are comparable between the different groups when stance foot was on sound side. More particularly, the presence of fall braking during swing phase, which is a maturation index of gait process, in young CP indicates that there is no delay. When stance foot is on affected side, fall braking is absent that can be explained by equines foot. In BR, biomechanical and EMG traces are comparable between the different groups. However, if compare to adults, there is a striking difference in the EMG patterns. In adults, the fall elicited a bilateral burst of EMG in Soleus muscle, in parallel Tibialis anterior (TA) showed concomitant EMG activity but with lower amplitude. In children, TA showed a burst of EMG activity in parallel to SOL. This TA EMG burst was suppressed whether the fall was arrested annihilating the stepping. This result suggests that children trigger at the time the fall reaction program and the stepping program. If CP children can carry out both motor tasks, normal stepping and provoked stepping, this was thanks to use of botulinum toxin which help children standing up. Then, the mechanism of balance control can operate, and supporting gait acquisition.

No description available.

Made available in DSpace on 2016-06-02T20:19:14Z (GMT). No. of bitstreams: 1 3062.pdf: 2064067 bytes, checksum: 9736110404bad178c5bdecf3fbb8c52a (MD5) Previous issue date: 2010-02-14 / Financiadora de Estudos e Projetos / The gait initiation is set to transition from standing posture to the first step to reversing cyclical, and involves a motor program mediated by adjustments preparations necessary to propel the body forward (MELOUIN ET AL, 2000). Studies that approach the initialization mostly in the adult population have aimed to understand the limitations in postural disorders, aging and what little is in the child population also has a focus on disease and how this process occurs not because of the development of walking independent. This study aimed to describe how the gait initiation process occurs and how it changes as occurs the development of independent walking. We evaluated 29 subjects into three groups: G1 (15 months - 10 subjects), G2 (3 years - 9 subjects) and GA (Adult - 10 subjects). The variables were analyzed: amplitude of oscillation of the center of force toward the average side (COFML) and anterior posterior (COFAP) and average speed and VELAP VELML. The nonparametric Kruskal Wallis test was used to detect differences between groups; the significance level was p &#8804; 0.05%. Results of gait initiation: COFAP (cm) there was no statistically significant differences between groups. However, both groups showed significant differences in the COFML behavior (7.79cm = G1, G3 = 7.46cm, GA = 3.25cm, p = 0.01). Furthermore the variable VELAP (cm / s), showed no statistically significant difference between groups, as well as the variable VLML. Results of gait termination: variables results COFAP (G1 = 11.15 cm, G3 = GA = 8.69 cm and 5.17 cm) and COFML (G1 = 7.83 cm, G3 = 8 cm and 4.86 cm = GA) showed no statistically significant differences when purchased between the three groups proposed both as a platform to platform 2. VELAP (G1 = 4.13 cm / s, G3 = 3.16 cm / GA = 3.26 cm / s) and VELML (G1 = 9.74 cm / s, G3 = 5.72 cm / s and GA = 2, 49 cm / s) were not statistically different during the completion of the gait termination, the results indicated the importance that the strength center behavior and the ability to deal with the gravitational field during the gait initiation and how this process changes with the experience of walking independently. / A inicialização de marcha é definida como transição da postura em pé ao primeiro passo a marcha cíclica, e envolve um programa motor mediado por ajustes preparatórios necessários para propulsionar o corpo para frente (MELOUIN ET AL,2000). Os estudos que abordam a inicialização em sua maioria em população adulta têm como objetivo compreender as limitações posturais em patologias e no envelhecimento e o pouco que se encontra em população infantil também tem o foco em patologias e não como este processo ocorre em função do desenvolvimento do andar independente. Este estudo teve por objetivo descrever como ocorre o processo de inicialização da marcha e como este muda à medida que ocorre o desenvolvimento do andar independente. Foram avaliados 29 sujeitos em três grupos G1 ( 15 meses 10 sujeitos), G2 ( 3 anos 9 sujeitos) e GA (adulto 10 sujeitos). As variáveis analisadas foram: amplitude de oscilação do centro de força na direção médio lateral (COFML) e antero posterior (COFAP) e velocidade média VELAP e VELML. O teste não paramétrico de Kruskal Wallis foi utilizado para detectar diferenças entre os grupos, o nível de significância foi de p &#8804; 0,05%. Resultados Inicialização da marcha: COFAP (cm) não houve diferenças estatisticamente significativas entre os grupos. Porém, ambos os grupos apresentaram diferenças significativas para o comportamento da COFML (G1 = 7.79cm, G3 = 7.46cm, GA= 3.25cm e p= 0.01). Por outro lado a variável VELAP (cm/s), não apresentou diferença estatisticamente significativa entre os grupos,assim como a variável VLML. Resultados Finalização da marcha os resultados das variáveis COFAP (G1 = 11,15cm, G3 = 8,69 cm e GA = 5,17 cm) e COFML (G1 = 7,83cm , G3 = 8cm e GA = 4,86 cm) não apresentaram diferenças estatisticamente significativas quando compradas entre os três grupos propostos tanto para a plataforma 1 quanto para a plataforma 2. VELAP (G1 = 4,13cm/s, G3 = 3,16cm/s e GA = 3,26cm/s) e VELML(G1 = 9,74 cm/s, G3 = 5,72 cm/se e GA = 2,49 cm/s), não foram estatisticamente diferentes durante a finalização do marcha Como conclusão, os resultados indicaram importância que o comportamento do centro de força e a capacidade de lidar com o campo gravitacional durante a inicialização da marcha e como este processo muda de acordo com a experiência do andar independente.

L'instabilité posturale est souvent observée chez les patients atteints de la sclérose latérale amyotrophique (SLA). Cependant, les mécanismes neuronaux impliqués dans cette instabilité posturale demeurent largement inconnus. Comparés aux patients SLA sans instabilité postural, les patients atteints de SLA avec instabilité posturale présentent des APA altérés avec un déplacement postérieur du centre de pression du pied diminué (CP) et une durée des APA augmentée, la longueur et la vitesse du premier pas sont réduites, enfin, le contrôle postural dynamique est déficitaire avec une diminution spectaculaire de l'indice de freinage. A l'inverse, nous n’observons aucune modification des phases d’anticipation et d’exécution du pas chez les patients SLA sans instabilité posturale comparés aux sujets témoins. Le faible recul du CP au cours de la phase d’anticipation est corrélé positivement de façon significative à l’atrophie de la substance grise du PCC, SPL, PPN et le CN ; et la durée augmentée de la phase d’anticipation est corrélée négativement de façon significative à l’atrophie de la matière grise du AMS et du cervelet. Les réductions de la vitesse et de la longueur du premier pas sont liées de façon significative à l’atrophie de la matière grise dans le PMC, le PPN et le vermis cérébelleux, enfin, l’absence de freinage actif est corrélée à une diminution du volume de la matière grise du CUN. Ces résultats suggèrent que l'instabilité posturale des patients atteints de SLA est causée, au moins en partie, par le dysfonctionnement des régions et des réseaux connus pour être impliqués dans l'initiation de la marche et dans le contrôle de l’équilibre. / Postural instability is frequently reported in Amyotrophic Lateral Sclerosis (SLA) patients. However, the neural mechanisms that contribute to postural instability in SLA patients remain largely unknown. In comparison to both SLA patients without postural instability and controls, SLA patients with postural instability presented an altered anticipatory postural adjustment (APA) phase with a decreased posterior displacement of the center of foot pressure (CP) and a increased APA duration, decreased length and velocity of the first step and deficit of the dynamic postural control with a dramatic decreased braking index. Conversely, the gait initiation was not significantly modified in SLA patients without postural instability in comparison to controls. The reduced posterior CP displacement during the APA was significantly related to reduced grey matter volume of the left PCC, left SPL, right PPN and caudate nucleus, and the increased APA duration to the reduced grey matter volume of the left AMS and right cerebellum. The reduced velocity of the first step was significantly related to a decreased grey matter volume within the left PMC, right PPN and cerebellar vermis and the reduced braking index to decreased grey matter volume of the right CUN. These results suggest that postural instability of SLA patients result, at least partly, from dysfunction of brain regions and networks known to be involved in gait initiation and balance controls in human.

Orientador: Lilian Teresa Bucken Gobbi / Resumo: O treinamento resistido tem sido estudado no contexto do envelhecimento e da doença de Parkinson, mas há falta de exploração das características deste tipo de treinamento que contribuem na melhora da locomoção e da funcionalidade. A pergunta central desta tese é: Quais características do treinamento resistido no contexto do envelhecimento saudável e da doença de Parkinson permitem potenciar seus efeitos no desempenho locomotor? Para responder este questionamento foram desenvolvidos dois estudos. ESTUDO 1. Novos modelos de periodização do treinamento, como a periodização ondulatória e a periodização inversa, têm sido desenvolvidos, mas não há evidências sobre as vantagens da periodização ondulatória quando comparada com a periodização linear em idosos. Por outro lado, a periodização inversa não tem sido testada em idosos. Assim, o objetivo do presente estudo foi analisar os efeitos de dois treinamentos de força com periodizações diferentes na locomoção de idosos saudáveis. Participaram 69 idosos (70,23±6,81 anos, 72,58±5,51 Kg, 162,26±5,92 cm), cognitivamente preservados (27,40±1,20 pontos Mini-Exame de Estado Mental) e fisicamente ativos (12,64±3,15 pontos Baecke). A amostra foi distribuída em três grupos, grupo de treinamento de força com periodização inversa ondulatória (GPIO n=25), grupo de treinamento de força com periodização linear (GPL n=25) e grupo controle (GC n=19). Foram realizadas 20 semanas de treinamento resistido, 2 dias na semana, mais 1 dia de treinamento loc... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: Resistance training has been studied in the context of aging and Parkinson's disease, but there is a lack of exploration of the characteristics of this type of training that contribute to the improvement of locomotion and functionality. The central question of this thesis is: What characteristics of resistance training in the context of healthy aging and Parkinson's disease allow to enhance its effects on locomotor performance? To answer this question two studies were developed. STUDY 1. New models of training periodization, such as undulating periodization and inverse periodization, have been developed, but there is no evidence about the advantages of wave periodization compared to linear periodization in the elderly. On the other hand, inverse periodization has not been tested in the elderly. Thus, the aim of the present study was to analyze the effects of two strength training with different periodizations on the mobility of healthy elderly. Participants were 69 elderly (70.23 ± 6.81 years, 72.58 ± 5.51 Kg, 162.26 ± 5.92 cm), cognitively preserved (27.40 ± 1.20 points Mini Mental State Examination) and physically active (12.64 ± 3.15 Baecke points). The sample was divided into three groups, strength training group with inverse undulating periodization (IUPG n = 25), force training group with linear periodization (LPG n = 25) and control group (CG n = 19). We performed 20 weeks of resistance training, 2 days a week, plus 1 day of locomotor training. GPIO performed a decreas... (Complete abstract click electronic access below) / Doutor

L’objectif général de cette thèse était d’analyser les effets d’une modification expérimentale de la capacité-posturo-cinétique (CPC) sur l’organisation biomécanique de l’initiation de la marche (IM) chez le jeune adulte. L’hypothèse générale était qu’une altération de la CPC a un effet négatif sur la stabilité et/ou la performance motrice et, qu’à l’inverse, une amélioration de la CPC a un effet positif. Pour tester cette hypothèse, trois expérimentations ont été réalisées, chacune ayant pour objet de modifier une composante spécifique de la CPC en lien avec le contexte clinique. Dans une première expérimentation, les effets d’une fatigue bilatérale aigue des Tibialis Anterior, muscles impliqués dans les ajustements posturaux anticipateurs (APA) de l’IM, étaient analysés. Les résultats ont montré que lorsque l’IM était réalisée en condition de fatigue, le recul anticipateur du centre des pressions et la vitesse du centre de gravité lors du décollement du pied étaient réduits, malgré une augmentation de la durée des APA. En conséquence, la performance motrice (vitesse maximale du centre de gravité/longueur du pas) était réduite. Les résultats d’une étude complémentaire ont montré que les sujets restaient cependant capables d’atteindre le même niveau de performance qu’en condition « sans fatigue » lorsque la consigne expérimentale l’exigeait. Dans une deuxième expérimentation, les effets d’une hypomobilité unilatérale du genou induite par un port d’attelle ont été investigués. En condition de port d’attelle, l'amplitude des APA médio-latéraux, ainsi que la stabilité étaient augmentées comparativement à la condition contrôle (IM sans port d’attelle). En revanche, la performance motrice était réduite. Là encore, lorsque la consigne expérimentale l’exigeait, les sujets étaient capables d’atteindre le même niveau de performance motrice qu’en condition contrôle, mais au détriment de la stabilité. Enfin, dans une troisième expérimentation, les effets d’une augmentation de la mobilité de la chaîne posturale, induite par une manipulation vertébrale de type HVLA étaient analysés. Les participants étaient répartis dans groupe expérimental (subissant la manipulation HVLA) et un groupe témoin (subissant une manipulation neutre). Les résultats ont mis en évidence un gain de mobilité du rachis de 20% suite à ce type de manipulation, suggérant une amélioration de la CPC. De façon surprenante, l’amplitude des APA et la performance motrices étaient réduites dans le groupe expérimental uniquement. En conclusion, l’ensemble de ces résultats suggère que lorsque la CPC est modifiée expérimentalement, le SNC priorise la protection corporelle, le maintien de la stabilité posturale ou le maintien de la performance motrice, en fonction de la consigne expérimentale et de la contrainte appliquée au niveau du système musculo-squelettique. / The main objective of this thesis was to assess the effects of an experimental modification of the posturo-kinetic capacity (PKC) on the biomechanical organization of gait initiation (GI) in young adults. The general hypothesis was that an alteration of PKC has a negative effect on stability and / or motor performance and that conversely, an improvement in PKC has a positive effect. To test this hypothesis, three experimentations were conducted. Each of them aimed at modifying a specific component of the PKC related to the clinical context. In a first experimentation, the effects of acute bilateral fatigue of Tibialis Anterior, muscles involved in the anticipatory postural adjustments (APA) of GI, were analyzed. Results showed that when the GI was performed in fatigue condition, the anticipatory backward of the center of pressure as well as the speed of the center of gravity during the detachment of the foot were reduced, despite an increase in the duration of APA. As a consequence, the driving performance (maximum center of gravity speed / step length) was reduced. Results of a complementary study showed that the subjects were nevertheless able to reach the same level of performance as in "no fatigue" condition when the experimental set point required it. In a second experimentation, the effects of unilateral hypomobility of the knee induced by orthosis were investigated. In orthosis condition, both mediolateral APA amplitude and stability were increased, compared to control condition (GI without orthosis). However, motor performance was reduced. Again, when the experimental set point required it, the subjects were able to achieve the same level of motor performance as under control conditions, but to the detriment of stability. Finally, in a third experimentation, the effects of an increase of postural chain mobility induced by HVLA-type (High-Velocity, Low-Amplidude) vertebral manipulation were assessed. The participants were divided into experimental group (with HVLA manipulation) and a sham group (with neutral manipulation). The results showed a spinal mobility gain of 20% following this type of manipulation, suggesting an improvement of the PKC. Surprisingly, APA amplitude and motor performance were reduced in the experimental group only. To conclude, all these results suggest that when PKC is experimentally modified, the CNS prioritizes body protection, maintenance of the postural stability or maintenance of the motor performance, depending on experimental conditions and constraints applied on musculoskeletal system.