Orientador: Eliane Mauerberg de Castro / Banca: José Angelo Barela / Banca: Renato de Moraes / Banca: Maria Luiza de Jesus Miranda / Banca: Sérgio Tosi / Resumo: O número de quedas durante o envelhecimento é alto e as consequencias para o indivíduo podem ser drásticas. O entendimento do funcionamento do sistema de controle postural é importante na medida que pode minimizar a quantidade de quedas nesta fase da vida e com isto melhorar a qualidade de vida destas pessoas. Foram realizados dois estudos com o objetivo de investigar os efeitos do envelhecimento sobre o controle postural com o uso de uma ferramenta não-rígida, denominada de sistema âncora, em contextos que restringem a informação visual. O primeiro estudo investigou a estabilidade postural de 15 adultos jovens (média de idade de 20.20 anos ± 1.61) e 15 idosos (média de idade de 68.13 anos ± 6.09) em uma tarefa postural com restrição da base de suporte (posição semi-tandem) sem restrição da informação visual (fixando o olhar a um ponto fixo), e na ausência da informação visual, com utilização do sistema âncora (125 g) e uma condição controle. As medidas do centro de pressão (Cop) foram obtidas através da plataforma de força e as variáveis dispersão, amplitude e velocidade da oscilação na direção médio-lateral e antero-posterior foram analisadas. Os resultados mostraram que o grupo de idosos apresentou maior oscilação corporal que o grupo de adultos jovens, nas duas condições visuais investigadas; que a ausência da informação visual provocou maior instabilidade postural para ambos os grupos e que o sistema âncora foi útil para estabilizar a postura dos dois grupos estudados, com uma diferença entre os grupos: para o grupo de adultos jovens a efetividade do sistema âncora foi maior para as condições em que a informação visual estava ausente e para o grupo de idosos o uso do sistema âncora foi mais efetivo nas condições em que a informação visual estava presente. A partir destes resultados, concluímos que o sistema âncora... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: There is a lot of falls during aging and the results for the person can be drastic. The understanding of the postural control system is important because it can reduce the amount of falls during this phase and it can improve the quality of life of old adults. Two studies were designed to investigate the effects of the aging on postural control using a non-rigid tool, called anchor system. Two different contexts were presented: with and without visual restriction (blindfolding and visual illusion). The first study investigated the postural stability of 15 old adults (mean age of 20.20 years ± 1.61) and 15 young adults (mean age 68.13 years ± 6.09) in a postural task with the restriction of the base of support (semi-tandem position) while looking at a fixed point, and when visual information was absent. These conditions included the use of the anchor system (125 g) and a baseline condition. The center of pressure (Cop) measures was obtained from the signal of a force plate. Variables included: dispersion, amplitude and velocity of sway in medial-lateral and anterior-posterior direction. The results showed that the older adults swayed more than young adults in both visual conditions. For the conditions with no visual information both groups showed more instability. The anchor system helped to stabilize the posture for both groups, with one difference between the groups: for the young adults the effectiveness of using the anchor system was better for conditions where the visual information was absent; for older adults, the usefulness of the anchor system was superior in conditions where the visual information was present Based on these results we concluded that the anchor system can be used for stabilization of the posture for older and young adults. The second study investigated the postural stability of 15 old adults and 15 young adults in the same postural task... (Complete abstract click electronic access below) / Doutor

Orientador: José Angelo Barela / Resumo: O objetivo deste estudo foi examinar os mecanismos de controle do sistema de controle postural durante a manutenção da postura ereta em participantes de 4, 8 e 12 anos de idade e adultos nas condições com e sem visão. Quarenta e cinco participantes de 4, 8 e 12 anos e 15 adultos jovens permaneceram em pé dentro de uma sala constituída de três paredes, duas laterais e uma frontal, de dimensões 2,2 x 1,2 x 1,2 metros (altura, largura e comprimento). Cada participante se posicionou dentro da sala sobre uma plataforma de força (Kistler, modelo 9286A), com os pés afastados na largura do quadril e realizou 10 tentativas, sorteadas aleatoriamente, sendo 5 com e 5 sem visão com duração de 30 segundos cada uma. A plataforma de força forneceu os dados das forças aplicadas sobre ela, que foram utilizados para cálculo das trajetórias do centro de pressão (CP), perambulação e tremor. Para cada uma das trajetórias foram calculadas a amplitude média e a freqüência predominante de deslocamento para as direções ântero-posterior e médio-lateral. Os resultados revelaram que o deslocamento das trajetórias do CP, perambulação e tremor diminuíram com o aumento da idade para as duas direções. Assim, foi verificado que mesmo aos 12 anos de idade crianças não apresentam a mesma performance que os adultos durante a manutenção da postura ereta. Ainda, na condição sem visão, o deslocamento das três trajetórias aumentou para todos os grupos etários, no entanto, a freqüência de deslocamento das trajetórias foi a mesma para todos os grupos nas duas condições. O maior deslocamento da trajetória de perambulação sugere que mesmo crianças de 12 anos de idade ainda apresentam dificuldades em estimar a posição do corpo no espaço e utilizar essa estimativa para manter a orientação postural desejada. Por outro lado, a similaridade na magnitude de... (Resumo completo, clicar acesso eletrônico abaixo). / Abstract: The purpose of this investigation was to examine the functioning of the postural control system in maintaining the upright stance in 4, 8, and 12 year-old children and adults with and without vision. Forty five participants aging 4, 8, and 12 years and 15 adults stood upright inside a room constituted of three walls, two laterals and one frontal, with 2,2 x 1,2 x 1,2 metros (height, breadth and lengh). Each participants was positioned inside the room standing on a force platform (Kistler, model 9286A) with his/her feet parallel and aligned with hip width and performed 10 trials, randomly defined, 5 with and 5 without vision, lasting 30 seconds each. The force measured the applied forces, used to calculate the trajectories of center of pressure, rambling and trembling. For each trajectory, mean amplitude displacement and predominant frequency were calculated for both anterior-posterior and medial-lateral directions. Results revealed that, the displacement of CP, rambling, and trembling trajectories decreased with age for both directions. Therefore, it was observed that even 12-year-old children did not show adults performance in maintaining the upright stance. In the vision condition, the displacement of CP, rambling, and trembling also increased for all groups, however, the frequency was the same for all groups in both conditions. The larger rambling trajectory displacement suggests that even 12-year-old children still show difficulties in estimating the body position and in using this estimation in order to maintain the desired postural orientation. On the other hand, the similar trembling trajectory displacement suggests that the amount of noise due to the muscular commands send to the muscular system in 12-year-old children is similar to the observed in adults. For 10-year-old and younger children, however, this noise is still larger... (Complete abstract, click electronic address below). / Mestre

A entorse de tornozelo pode ocorrer pela amplitude exagerada de inversão e flexão plantar. Lacuna importante no controle postural é a ação do ajuste postural antecipatório (APA) e compensatório (APC) para estabilizar a articulação do tornozelo. O reflexo de estiramento (M1) e as reações pré-programadas (M2 e M3) foram pouco exploradas em pessoas com instabilidade crônica de tornozelo (CAI). A co-ativação e inibição são fenômenos modulados em nível medular por neurônios excitatórios e inibitórios, mas as informações sobre esses fenômenos atuam na CAI são escassas. A fadiga muscular afeta negativamente as pessoas na condição de CAI. Logo, qual é a relação entre APA e APC no movimento de entorse de tornozelo? A CAI pode alterar as respostas M1, M2 e M3 por lesões osteomioarticulares do tornozelo? A fadiga pode alterar todas estas variáveis em pessoas com CAI? Esta dissertação de mestrado teve por objetivo geral analisar o sinal EMG no movimento simulado da inversão de tornozelo em atletas universitárias de futsal que possuem e que não possuem a CAI. A amostra foi composta por 24 atletas de futsal feminino universitário e foram divididos em dois grupos: controle e instabilidade. A simulação do movimento de entorse do tornozelo foi feita por meio de uma plataforma mecânica que simula o movimento de inversão de tornozelo. Foi utilizado um sistema de aquisição de sinais de 8 canais, onde foram utilizados 4 canais para registro EMG e 3 canais para o registro do sinal do acelerômetro. Para determinar o início e final do movimento da plataforma foi fixado um acelerômetro 3D em uma das bordas da plataforma de inversão. Foram realizar quedas aleatórias na plataforma de inversão antes e depois do protocolo de fadiga. Foram monitorados os músculos tibial anterior, fibular longo e curto e gastrocnêmio lateral. Os períodos analisados foram os APA, APC, reflexo de estiramento muscular e reações pré-programadas. Parece que durante os períodos M1, M2 e M3 há um fator de desproteção no grupo instabilidade, apesar de haver em alguns pares de músculos uma maior coerência, comparado com o grupo controle. Durante o APA os músculos eversores não foram alterados no grupo instabilidade, mas no APC os eversores foram menores comparados com o grupo controle, sugerindo um fator de desproteção. Na correlação cruzada, todos os pares de músculos foram maiores no grupo controle, uma forma de se opor ao movimento de inversão maior que o grupo instabilidade. A co-ativação e inibição recíproca foram alteradas com a fadiga, aumentando após a fadiga, mas a inibição recíproca foi maior somente no grupo controle, podendo mover a articulação do tornozelo de uma forma mais facilitada que o grupo instabilidade. A coerência de pares de músculos foi diferente somente nos grupos, sendo que durante o APC os músculos não sincronizaram de forma satisfatória no grupo instabilidade, somente durante APA e período M / Ankle sprain is an injury associated with sports and exercise and may be used for the exaggerated amplitude of inversion and plantar flexion. An important gap in postural control is the anticipatory (APA) and compensatory (CPA) postural adjustments to stabilize the ankle joint. The stretch reflex (M1) and the pre-programmed reactions (M2 and M3) were poorly explored in people with chronic ankle instability (CAI). Coactivation and recíprocal inhibition are phenomena modulated at the spinal level by excitatory and inhibitory neurons, but the information about these phenomena in CAI is scarce. Negative effects of muscular fatigue affect persons with CAI. Therefore, What is the relationship between APA and CPA in the movement of ankle sprain? Can CAI change the M1, M2 and M3 responses due to osteomyoarticular ankle injuries? Can fatigue change all these variables in people with CAI? This dissertation aimed at analysing the EMG signal in the simulated ankle inversion movement task in female indoor soccer university athletes who have and do not have the CAI. Participants were 24 female indoor soccer college athletes divided in two groups: control and instability. Simulation of ankle sprain was performed with a mechanical platform that simulated the ankle inversion movement. An 8-channel signal acquisition system was used, which 4 channels were used for EMG recording and 3 channels to record accelerometer signal. For determine the beginning and end of the movement of the inversion platform a 3D accelerometer was fixed to one of the edges of the inversion platform. We performed random falls on the inversion platform before and after the fatigue protocol. Muscles monitored were mm. tibialis anterior, fibularis longus, fibularis brevis and gastrocnemius lateralis. Data epochs were APA, CPA, muscle stretching reflex and preprogramed reactions. During M1, M2 and M3 epochs, there was an unprotection factor for instability group, although in some muscle pairs there were more coherence compared to control group. The eversor muscles were not changed in instability group compared with control group during APA epoch, it suggests an unprotect factor. All pair of muscles, the cross correlation were greater in control group to oppose the inversion movement greater in control group than instability group. Coactivation and reciprocal inhibition were changed with fatigue, increasing after fatigue, but reciprocal inhibition was greater only in control group, and could move the ankle joint more easily than for instability group. Coherence of muscle pairs was different only between groups, and during CPA the muscles did not synchronize satisfactorily for instability group, only during APA and M epochs

The purpose of the present thesis was two-fold. First, to evaluate the impact of cognitive demand on postural control in young adults and second, to examine the responsiveness of postural control to cognitive tasks presented in varying modalities. Seventeen young adults stood on a force platform while simultaneously performing cognitive tasks of varying difficulty (easy, moderate and difficult), each presented auditorily and visually. Performing the moderate and difficult tasks precipitated a greater reduction in area of 95% confidence ellipse and medio-lateral (ML) sway variability compared to the easy tasks. Presenting the tasks visually produced lower ML sway variability than presenting the tasks auditorily. Of secondary interest of this thesis was to determine if the duration of inter-stimulus intervals could modify the effectiveness of a cognitive task on postural control. Participants stood on a force platform while simultaneously performing cognitive tasks with five-second inter-stimulus intervals (i.e. discrete) and two-second inter-stimulus intervals (i.e. continuous), each presented auditorily and visually. Results revealed higher anterior-posterior (AP) mean power frequency (MPF) when performing the continuous tasks. In addition, presented the tasks visually resulted in a greater reduction in area of 95% confidence ellipse, AP and ML sway variability.

The objective of the present study was to; 1) determine if the use of a continuous cognitive task demonstrates distinct characteristics of a more automatic control of posture, compared to an external focus (EF) and feet together (FT) postural task, and to 2) examine which condition, if any, exhibits the characteristics of increased ankle stiffness proposed by Winter et al. (1998), as well as displaying increased ankle muscular co-contractions, which are a suggested neuromuscular mechanism that stiffens posture. Fifteen young adults stood on a force platform and performed 4 separate conditions: FT, EF, single number sequence (SNS), and double number sequence (DNS). Throughout the session, surface electromyography (EMG) signals were collected from the tibialis anterior (TA) and medial gastrocnemius (MG) of each leg. Each testing session consisted of 24 trials, with 6 per condition. Results displayed decreased sway area for SNS and DNS compared to FT. Sway variability in the anterior/posterior (AP) direction SNS and DNS were smaller compared to EF and FT. As well sway variability in the medial/lateral (ML) direction was smaller for SNS and DNS compared to FT. ML Mean velocity (MV) did not differ across conditions, though in the AP direction it was larger for SNS and DNS compared to EF and FT. AP Mean power frequency (MPF) was larger for SNS compared to FT. In the ML direction MPF was larger for SNS and DNS compared to FT. Co-Contraction indices revealed no differences across conditions. Conversely the left TA for DNS revealed increased EMG activation compared to EF and SNS.

Rising up from a chair (sit-to-stand; STS) and stair climbing are both activities of daily living (ADLs) done throughout our lives. The ability to complete ADLs is crucial for independent living. The goal of this thesis was to research how two ADLs interact with each other and affect postural control. It was hypothesized that an increased number of flights of stairs climbed would lead to a decline in postural control during/after a STS in older more than younger adults. Fourteen older adults and fourteen young adults were tested by completing three STSs before and after climbing 1, 3 and 5 flights of stairs, chosen at random. Movements of the center of pressure (COP) for each STS were obtained from a force platform. Only an age effect was found for COP velocity (left-right and anterior-posterior directions) during the momentum transfer phase, during stabilization and after stabilization. Therefore, contrary to our hypothesis, stair climbing did not lead to significant changes in COP movements during and following a STS.

Acute stretching increases postural stability in nonbalance trained individuals. J Strength Cond Res 26(11): 3095-3100, 2012-Studies into the relationship between acute stretching and maintenance of postural balance have been inconclusive. It was hypothesized that familiarization with the task and subsequent learning might be involved in the conflicting results. Therefore, this study was to designed determine if a regimen of static stretching exercises after a familiarization period would improve a person's ability to maintain a stabilometer in a neutral position and whether stretching had the same effect on individuals with extensive involvement with balancing tasks. Forty-Two college students (21 male, 21 female) and 10 surfers (all male) performed tests on a stabilometer on 2 separate days after 3 days of familiarization. Testing followed either 30 minutes of quiet sitting (nonstretched) or 30 minutes of stretching activities (stretched). Stretching exercises consisted of various assisted and unassisted static stretches of the muscles around the hip, knee, and ankle joints. Improved flexibility after the stretching exercises was demonstrated by significant (p , 0.05) 6.5 6 2.7 cm (mean 6 SD) increase in the sit and reach. Balance time for the students improved significantly by 11.4% (2.0-second increase), but the surfers had no significant change. Thus, stretching improved maintenance of balance perhaps by helping the subjects to eliminate the gross muscle contractions that caused large stabilometer displacements and to replace them with fine muscle contractions that caused little or no stabilometer displacements. However, it appears that experience doing balance tasks supplants any stretching benefit.

No description available.

Chronic ankle instability (CAI), a pathological condition characterized by repetitive bouts of the ankle giving way, commonly develops following a lateral ankle sprain injury. Individuals with CAI have been shown to exhibit deficits in postural control and alterations in movement dynamics, which have been suggested to be contributing factors to the recurrent injury paradigm. The purpose of this investigation was to conduct a comprehensive biomechanical analyses to examine the influence of CAI on postural control and movement dynamics during a single leg squat, side-cut task, and single leg landing on an inverted surface. Fifteen participants with CAI and fifteen participants without CAI completed the study following a between-subjects design, with limb serving as the repeated measure during the single leg squat. Each participant completed a single leg squat, side-cut task, and unexpected and expected single leg landings on a tilted surface. Results from the single leg squat and single leg landings on the tilted surface were analyzed using a 2 x 2 mixed-model ANOVA, while results from the side-cut task were analyzed using an independent samples t-test. Statistical significance was considered for all dependent variables when p < 0.05. Individuals with CAI demonstrated impaired postural control, as indicated by reduced time-to-boundary, during the single leg squat compared to controls. Altered ankle joint kinetics and increased sagittal plane hip joint stiffness were observed in the CAI group compared to controls. With regards to the single leg landings on the inverted surface, during the unexpected landing condition the CAI group displayed altered neuromuscular control and ankle kinematics. However, when the landing on the inverted surface as expected, the CAI group exhibited similar motor control strategies to the control group. Findings from this study indicate CAI alters postural control and movement dynamics during functional and dynamic movements, which may be used by researchers and clinicians to develop rehabilitation protocols to restore maladaptive movement patterns in individuals that develop CAI.

No description available.