Symptoms of hyperactivity and inattention can mediate deficits of postural stability in developmental dyslexia

DDevelopmental dyslexia is a reading disorder associated with impaired postural control. However, such deficits are also found in attention deficit hyperactivity disorder (ADHD), which is present in a substantial subset of dyslexia diagnoses. Very few studies of balance in dyslexia have assessed ADHD symptoms, thereby motivating the hypothesis that such measures can account for the group differences observed. In this study, we assessed adults with dyslexia and similarly aged controls on a battery of cognitive, literacy and attention measures, alongside tasks of postural stability. Displacements of centre of mass to perturbations of posture were measured in four experimental conditions using digital optical motion capture. The largest group differences were obtained in conditions where cues to the support surface were reduced. Between-group differences in postural sway and in sway variability were largely accounted for by co-varying hyperactivity and inattention ratings, however. These results therefore suggest that postural instability in dyslexia is more strongly associated with symptoms of ADHD than to those specific to reading impairment.

Efeito de exercícios de pilates clínico no controlo postural de jovens adultos com dor lombar não específica

Introdução: Os efeitos a longo prazo de exercícios de Pilates têm sido bem documentados, não entanto os seus efeitos imediatos no controlo postural estático e dinâmico de jovens adultos com dor lombar não específica permanecem por desvendar. Objetivo: Avaliar os efeitos imediatos de uma sessão composta por 4 exercícios de Pilates Clínico no controlo postural estático e dinâmico de jovens adultos com dor lombar não específica. Métodos: 46 estudantes universitários com dor lombar não específica participaram no estudo randomizado e controlado. Os participantes foram randomizados para um grupo de Pilates (n = 23, 10 do sexo masculino, idade: 21,8 ± 3,2 anos; peso: 64,5 ± 11,5 kg; altura: 1,70 ± 0,1 m) e um grupo controlo (n = 23, 9 do sexo masculino; idade: 22,8 ± 3,6 anos; peso: 62,5 ± 9,9 kg; altura: 1,68 ± 0,1 m). O controlo postural estático foi avaliado com uma plataforma de forças e o controlo postural dinâmico com o Star Excursion Balance Test, antes e depois da intervenção ou período de repouso. Para avaliar o controlo postural estático, os participantes estavam em posição ortostática, o mais quietos possível durante 90s, com os olhos fechados em superfície instável. A intervenção durou 20 minutos e consistiu em 4 exercícios de Pilates Clínico: single leg stretch (nível 1), pelvic press (nível 1), swimming (nível 1) e kneeling opposite arm and leg reach. Resultados: No momento de avaliação inicial, não foram encontradas diferenças estatisticamente significativas entre os grupos em nenhuma das variáveis. Após a intervenção, o grupo Pilates melhorou em todos as variáveis do controlo postural estático (COPx: 5,7 ± 1,0 para 5,1 ± 0,7 cm, p = 0,005; COPy: 4,4 ± 1,0 para 3,8 ± 0,7 cm, p < 0,001; comprimento total: 255,2 ± 55,9 para 210,5 ± 42,7 cm, p < 0,001 ; área: 11,5 ± 3,4 para 9,7 ± 2,7 cm2, p = 0,002 e velocidade : 2,8 ± 0,6 para 2,3 ± 0,5 cm/s, p < 0,001) e no Star Excursion Balance Test (anterior: 65,3 ± 8,3 para 68,6 ± 6,4%, p = 0,001; póstero-medial: 82,6 ± 11,7 para 89,5 ± 9,7%, p < 0,001; póstero-lateral: 83,9 ± 11,0 para 87,6 ± 10,2%, p < 0,001 e composite: 86,2 ± 12,4 para 91,1 ± 11,0%, p < 0,001). O grupo de controlo só melhorou na velocidade (2,8 ± 0,5 para 2,6 ± 0,5 cm/s, p = 0,009) e comprimento total (248,5 ± 45,3 para 237,3 ± 47,2 cm, p = 0,009) no controlo postural estático. No entanto, as melhorias no grupo Pilates foram significativamente maiores do que as do grupo de controlo. Conclusão: Os exercícios de Pilates Clínico melhoraram, no imediato, o controlo postural estático e dinâmico em jovens adultos com dor lombar não específica.

O efeito agudo da terapia Bowen no limiar de dor e controlo postural em indivíduos saudáveis

Introdução: A fáscia é tecido conjuntivo inervado por terminações nervosas livres e por mecanoretores, tendo um papel importante na dor e na proprioceção. Acredita-se que a Terapia Bowen estimule os mecanorecetores e as terminações nervosas livres presentes na fáscia. Objetivos: Determinar o efeito imediato da Terapia Bowen no limiar de dor à pressão mecânica e no controlo postural em indivíduos saudáveis. Métodos: Este foi um estudo cruzado de amostras emparelhadas, duplamente cego, constituído por duas sessões para cada indivíduo: numa foi aplicado Terapia Bowen e noutra placebo. Em ambas as sessões, cada indivíduo foi avaliado quanto ao controlo postural, com plataforma de forças, e ao limiar de dor à pressão mecânica, com algómetro de pressão eletrónico, antes e depois da aplicação da intervenção/placebo. Resultados: A amostra foi constituída por 34 participantes, 17 receberam Bowen na primeira sessão e os restantes receberam placebo, distribuídos aleatoriamente. Os resultados mostraram uma diferença significativa para a deslocação ântero-posterior e velocidade de excursão do centro de pressão e limiar de dor à pressão mecânica em C1 bilateralmente (p <0,05). Discussão/Conclusão: A diferença significativa entre Terapia Bowen e placebo para apenas 4 de 14 variáveis sugere que a primeira tenha um efeito imediato reduzido no controlo postural e limiar de dor em indivíduos saudáveis. Estes resultados estão em consonância com estudos anteriores sobre o efeito imediato da terapia manual em indivíduos saudáveis.

Quantification of the human postural control system to perturbations

Human standing posture is inherently unstable. The postural control system (PCS), which maintains standing posture, is composed of the sensory, musculoskeletal, and central nervous systems. Together these systems integrate sensory afferents and generate appropriate motor efferents to adjust posture. The PCS maintains the body center of mass (COM) with respect to the base of support while constantly resisting destabilizing forces from internal and external perturbations. To assess the human PCS, postural sway during quiet standing or in response to external perturbation have frequently been examined descriptively. Minimal work has been done to understand and quantify the robustness of the PCS to perturbations. Further, there have been some previous attempts to assess the dynamical systems aspects of the PCS or time evolutionary properties of postural sway. However those techniques can only provide summary information about the PCS characteristics; they cannot provide specific information about or recreate the actual sway behavior. This dissertation consists of two parts: part I, the development of two novel methods to assess the human PCS and, part II, the application of these methods. In study 1, a systematic method for analyzing the human PCS during perturbed stance was developed. A mild impulsive perturbation that subjects can easily experience in their daily lives was used. A measure of robustness of the PCS, 1/MaxSens that was based on the inverse of the sensitivity of the system, was introduced. 1/MaxSens successfully quantified the reduced robustness to external perturbations due to age-related degradation of the PCS. In study 2, a stochastic model was used to better understand the human PCS in terms of dynamical systems aspect. This methodology also has the advantage over previous methods in that the sway behavior is captured in a model that can be used to recreate the random oscillatory properties of the PCS. The invariant density which describes the long-term stationary behavior of the center of pressure (COP) was computed from a Markov chain model that was applied to postural sway data during quiet stance. In order to validate the Invariant Density Analysis (IDA), we applied the technique to COP data from different age groups. We found that older adults swayed farther from the centroid and in more stochastic and random manner than young adults. In part II, the tools developed in part I were applied to both occupational and clinical situations. In study 3, 1/MaxSens and IDA were applied to a population of firefighters to investigate the effects of air bottle configuration (weight and size) and vision on the postural stability of firefighters. We found that both air bottle weight and loss of vision, but not size of air bottle, significantly decreased balance performance and increased fall risk. In study 4, IDA was applied to data collected on 444 community-dwelling elderly adults from the MOBILIZE Boston Study. Four out of five IDA parameters were able to successfully differentiate recurrent fallers from non-fallers, while only five out of 30 more common descriptive and stochastic COP measures could distinguish the two groups. Fall history and the IDA parameter of entropy were found to be significant risk factors for falls. This research proposed a new measure for the PCS robustness (1/MaxSens) and a new technique for quantifying the dynamical systems aspect of the PCS (IDA). These new PCS analysis techniques provide easy and effective ways to assess the PCS in occupational and clinical environments.

Effects of joint immobilization on standing balance

We investigated the effect of joint immobilization on the postural sway during quiet standing. We hypothesized that the center of pressure (COP), rambling, and trembling trajectories would be affected by joint immobilization. Ten young adults stood on a force plate during 60 s without and with immobilized joints (only knees constrained, CK; knees and hips, CH; and knees, hips, and trunk, CT). with their eyes open (OE) or closed (CE). The root mean square deviation (RMS, the standard deviation from the mean) and mean speed of COP, rambling, and trembling trajectories in the anterior-posterior and medial-lateral directions were analyzed. Similar effects of vision were observed for both directions: larger amplitudes for all variables were observed in the CE condition. In the anterior-posterior direction, postural sway increased only when the knees, hips, and trunk were immobilized. For the medial-lateral direction, the RMS and the mean speed of the COP, rambling, and trembling displacements decreased after immobilization of knees and hips and knees, hips, and trunk. These findings indicate that the single inverted pendulum model is unable to completely explain the processes involved in the control of the quiet upright stance in the anterior-posterior and medial-lateral directions. (C) 2009 Elsevier B.V. All rights reserved.

Vibratory noise to the fingertip enhances balance improvement associated with light touch

Light touch of a fingertip on an external stable surface greatly improves the postural stability of standing subjects. The hypothesis of the present work was that a vibrating surface could increase the effectiveness of fingertip signaling to the central nervous system (e.g., by a stochastic resonance mechanism) and hence improve postural stability beyond that achieved by light touch. Subjects stood quietly over a force plate while touching with their right index fingertip a surface that could be either quiescent or randomly vibrated at two low-level noise intensities. The vibratory noise of the contact surface caused a significant decrease in postural sway, as assessed by center of pressure measures in both time and frequency domains. Complementary experiments were designed to test whether postural control improvements were associated with a stochastic resonance mechanism or whether attentional mechanisms could be contributing. A full curve relating body sway parameters and different levels of vibratory noise resulted in a U-like function, suggesting that the improvement in sway relied on a stochastic resonance mechanism. Additionally, no decrease in postural sway was observed when the vibrating contact surface was attached to the subject`s body, suggesting that no attentional mechanisms were involved. These results indicate that sensory cues obtained from the fingertip need not necessarily be associated with static contact surfaces to cause improvement in postural stability. A low-level noisy vibration applied to the contact surface could lead to a better performance of the postural control system.

Bodyweight and migration-related differences in motor abilities in preschool children "Ballabeina"

Introduction: Motor abilities in schoolchildren have been decreasing in the last two decades (Bös, 2003, Tomkinson et al., 2003). This may be related to the dramatic increase in overweight and adiposity during the same time period. Children of migrant background are especially affected (Lasserre et al., 2007). But little is known about the relationship between BMI and migration background and motor abilities in preschool children. Methods/Design We carried out a cross-sectional analysis with 665 children (age 5.1 ± 0.6 years; 49.8 % female) of 40 randomly selected kindergarten classes from German and French speaking regions in Switzerland with a high migrant background. We investigated BMI, cardiorespiratory fitness (20 m shuttle run), static (displacement of center of pressure (COP)) and dynamic (balancing forward on a beam) postural control and overall fitness (obstacle course). Results: Of the children, 9.6 % were overweight, 10.5 % were obese (Swiss national percentiles) and 72.8 % were of migrant background (at least one parent born outside of Switzerland). Mean BMI from children of non-migrant background was 15.5 ± 1.1 kg/m2, while migrant children had a mean BMI of 15.8 ± 1.7 kg/m2 (p=0.08). Normal-weight children performed better in cardiorespiratory fitness (3.1 ± 1.4 vs. 2.6 ± 1.1 stages, p<0.001), overall fitness (18.9 ± 4.4 vs. 20.8 ± 4.6 sec, p<0.001) and in dynamic balance (4.9 ± 3.5 vs. 3.8 ± 2.5 steps, p<0.001) compared to overweight and obese children, while the latter had less postural sway (COP: 956 ± 302 vs. 1021 ± 212 mm, p=0.008). There was a clear inverse dose-response relationship between weight status and dynamic motor abilities. There were no significant differences in most tested motor abilities between non-migrant and migrant. The latter performed less well in only one motor test (overall fitness: 20.2 ± 5.2 vs. 18.3 ± 3.5 sec, p<0.001). These findings persisted after adjustment for BMI. Conclusion In preschool children, differences in motor abilities are already present between normal weight and overweight/obese children. However, migrant children demonstrate similar motor abilities compared to non-migrant children for almost all tests, despite their slightly higher BMI.

Effects of Instruction on Walking and Turning Performance in Individuals with Parkinson's Disease

Parkinson’s disease (PD) is characterized by postural instability and gait impairment. Verbal instructions can reduce postural sway and improve gait performance in PD. For gait, this evidence is limited to unobstructed straight-path walking. As falls in PD often occur when turning, the purpose of this thesis was to determine if instructions can benefit turning performance in this population. Twelve individuals with PD performed two walking tasks (normal walking, walking with a 180 degree turn) under four instruction conditions (no instruction, take big steps, make larger trunk movements, focus on end and/or turn point). Task duration and trunk yaw and roll sway were calculated. In general, the results demonstrated that the instruction to take big steps improved performance for both tasks compared to providing no instruction or externally based instruction. These results suggest that instructions related to step amplitude may facilitate walking and turning performance in PD.

Pathomechanics of posterior ankle impingement syndrome in female ballet dancers

A dança é uma actividade de grande exigência atlética, que pode conduzir a um elevado número de lesões, particularmente na região do tornozelo, possivelmente devido à amplitude extrema do movimento articular de flexão plantar do mesmo, que os bailarinos, especialmente do sexo feminino possuem, para realizar a ponta e meia ponta tão características do ballet clássico (Kadel, 2006; Motta-Valencia, 2006; Russel, Kruse, Koutedakis, McEwan, Wyon, 2010). Estas posições de flexão plantar extrema produzem força excessiva na região posterior do tornozelo, o que muitas vezes pode resultar em conflito, dor e incapacidade, representando na maioria das vezes um desafio de diagnóstico. O síndrome do conflito posterior do tornozelo refere-se a um grupo de entidades patológicas que resultam da flexão plantar forçada do tornozelo, de forma repetitiva ou traumática, causando um conflito das estruturas ósseas e/ou de tecidos moles (Hamilton, Geppert, Thompson, 1996; Hamilton, 2008) . Os objectivos deste projecto são compreender os quais os factores de risco, mecânicos e funcionais que contribuem para a mecânica patológica da lesão descritos na literatura, e proceder a uma avaliação biomecânica do movimento de flexão plantar do tornozelo. Método. Realizar uma revisão sistemática de literatura dirigida á mecânica patológica do síndrome do conflito posterior do tornozelo em bailarinas e conduzir um estudo caso-controlo, cujo objectivo é avaliar, comparar e descrever o movimento da flexão plantar do tornozelo realizado ao efectuar os movimentos de ponta e meia-ponta, em bailarinas pré-profissionais com e sem lesão recorrente resultante do conflito posterior do tornozelo. Resultados. Não foram encontrados estudos relacionados especificamente com a mecânica patológica do tornozelo, no entanto vários estudos foram encontrados considerando as características clínicas e anatómicas assim como os procedimentos de tratamento, indicando que os principais factores de risco relacionados com a lesão se dividem em factores mecânicos e funcionais que quando combinados entre si e associados ao sobre-uso podem resultar no conflito posterior do tornozelo. Na avaliação do movimento foram observadas diferenças na actividade muscular entre os sujeitos com lesão e controlos, tendo sido possível a observação de um padrão na sequência de activação para um dos movimentos testados. Na oscilação postural e na rigidez do tornozelo foram também observadas diferenças entre os sujeitos bem como entre as posições realizadas. Conclusão. Concluiu-se que não sendo possível alterar a anatomia do bailarino, por vezes é possível intervir a nível funcional melhorando a capacidade técnica de forma obter um melhor desempenho e a actuar preventivamente em relação às lesões, uma vez que estas podem apresentar padrões cinéticos próprios, relacionados com a função muscular, a estabilidade postural e a rigidez articular.

Disruption of sitting balance after stroke: influence of spoken output

Objectives: To identify the extent of dual task interference between cognitive and motor tasks, (cognitive motor interference (CMI)) in sitting balance during recovery from stroke; to compare CMI in sitting balance between stroke and non-stroke groups; and to record any changes to CMI during sitting that correlate with functional recovery. Method: 36 patients from stroke rehabilitation settings in three NHS trusts. Healthy control group: 21 older volunteers. Measures of seated postural sway were taken in unsupported sitting positions, alone, or concurrently with either a repetitive utterance task or an oral word category generation task. Outcome measures were variability of sway area, path length of sway, and the number of valid words generated. Results: Stroke patients were generally less stable than controls during unsupported sitting tasks. They showed greater sway during repetitive speech compared with quiet sitting, but did not show increased instability to posture between repetitive speech and word category generation. When compared with controls, stroke patients experienced greater dual task interferences during repetitive utterance but not during word generation. Sway during repetitive speech was negatively correlated with concurrent function on the Barthel ADL index. Conclusions: The stroke patients showed postural instability and poor word generation skills. The results of this study show that the effort of verbal utterances alone was sufficient to disturb postural control early after stroke, and the extent of this instability correlated with concomitant Barthel ADL function.

Validade e reprodutibilidade do Wii Balance Board para avaliação do equilíbrio vertical estático: um novo método de avaliação.

The Wii Balance Board (WBB) began to be investigated as a low-cost alternative for assessing static balance in vertical posture. However, studies employed methodological procedures that did not eliminate result variability between the tests and equipment used. Objective: Determine the validity and reproducibility of the WBB as an instrument for assessing static balance in the vertical position, using simultaneous data analysis and superimposed equipment. Methods: This is an accuracy study of 29 healthy young individuals of both sexes aged 18 to 30 years. Subjects were assessed 24h apart (test-retest), using unipodal and bipodal support tests, with eyes closed and open. To that end the WBB was placed on top of a force platform (FP) and data (postural sway) were collected simultaneously on both devices. Validity and reproducibility were analyzed using the interclass correlation coefficient (ICC). Finally, Bland-Altman analysis was applied to assess agreement. Results: The sample was composed of 23 women and 6 men, with mean age of 24.2±6.3 years, 60.7±6.3 kg and 1.64±4.2 m. The validity of the WBB compared to the FP was excellent for all 4 tasks proposed (ICC = 0.93 0.98). The reproducibility analyzed by test-retest was excellent for the bipodal support tasks (ICC = 0.93-0.98) and only moderate for the unipodal support tests (ICC = 0.46 0.70). Graphic analysis exhibited good agreement between the devices, since most of the measures were within the limits of agreement. Conclusion: this study proved the validity and reproducibility of the Wii Balance Board as an instrument for assessing static balance in vertical posture, using simultaneous analysis with superimposed equipment. Thus, the WBB has been increasingly used by physical therapists and other health professionals in their clinical practice, as both a rehabilitation and assessment tool

Avaliação do sincronismo do sinal eletromiográfico com o equilíbrio dinâmico de jogadores de futebol durante o chute

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Efeitos da mobilização miofascial plantar no equilíbrio corporal, mobilidade funcional e ativação muscular em idosas

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Rehabilitation Engineering in Parkinson's disease

Impairment of postural control is a common consequence of Parkinson's disease (PD) that becomes more and more critical with the progression of the disease, in spite of the available medications. Postural instability is one of the most disabling features of PD and induces difficulties with postural transitions, initiation of movements, gait disorders, inability to live independently at home, and is the major cause of falls. Falls are frequent (with over 38% falling each year) and may induce adverse consequences like soft tissue injuries, hip fractures, and immobility due to fear of falling. As the disease progresses, both postural instability and fear of falling worsen, which leads patients with PD to become increasingly immobilized. The main aims of this dissertation are to: 1) detect and assess, in a quantitative way, impairments of postural control in PD subjects, investigate the central mechanisms that control such motor performance, and how these mechanism are affected by levodopa; 2) develop and validate a protocol, using wearable inertial sensors, to measure postural sway and postural transitions prior to step initiation; 3) find quantitative measures sensitive to impairments of postural control in early stages of PD and quantitative biomarkers of disease progression; and 4) test the feasibility and effects of a recently-developed audio-biofeedback system in maintaining balance in subjects with PD. In the first set of studies, we showed how PD reduces functional limits of stability as well as the magnitude and velocity of postural preparation during voluntary, forward and backward leaning while standing. Levodopa improves the limits of stability but not the postural strategies used to achieve the leaning. Further, we found a strong relationship between backward voluntary limits of stability and size of automatic postural response to backward perturbations in control subjects and in PD subjects ON medication. Such relation might suggest that the central nervous system presets postural response parameters based on perceived maximum limits and this presetting is absent in PD patients OFF medication but restored with levodopa replacement. Furthermore, we investigated how the size of preparatory postural adjustments (APAs) prior to step initiation depend on initial stance width. We found that patients with PD did not scale up the size of their APA with stance width as much as control subjects so they had much more difficulty initiating a step from a wide stance than from a narrow stance. This results supports the hypothesis that subjects with PD maintain a narrow stance as a compensation for their inability to sufficiently increase the size of their lateral APA to allow speedy step initiation in wide stance. In the second set of studies, we demonstrated that it is possible to use wearable accelerometers to quantify postural performance during quiet stance and step initiation balance tasks in healthy subjects. We used a model to predict center of pressure displacements associated with accelerations at the upper and lower back and thigh. This approach allows the measurement of balance control without the use of a force platform outside the laboratory environment. We used wearable accelerometers on a population of early, untreated PD patients, and found that postural control in stance and postural preparation prior to a step are impaired early in the disease when the typical balance and gait intiation symptoms are not yet clearly manifested. These novel results suggest that technological measures of postural control can be more sensitive than clinical measures. Furthermore, we assessed spontaneous sway and step initiation longitudinally across 1 year in patients with early, untreated PD. We found that changes in trunk sway, and especially movement smoothness, measured as Jerk, could be used as an objective measure of PD and its progression. In the third set of studies, we studied the feasibility of adapting an existing audio-biofeedback device to improve balance control in patients with PD. Preliminary results showed that PD subjects found the system easy-to-use and helpful, and they were able to correctly follow the audio information when available. Audiobiofeedback improved the properties of trunk sway during quiet stance. Our results have many implications for i) the understanding the central mechanisms that control postural motor performance, and how these mechanisms are affected by levodopa; ii) the design of innovative protocols for measuring and remote monitoring of motor performance in the elderly or subjects with PD; and iii) the development of technologies for improving balance, mobility, and consequently quality of life in patients with balance disorders, such as PD patients with augmented biofeedback paradigms.

From inverted pendulum to N-link chain: inertial sensors-based assessment of movement kinematics and dynamics for functional evaluation and rehabilitation

Despite several clinical tests that have been developed to qualitatively describe complex motor tasks by functional testing, these methods often depend on clinicians' interpretation, experience and training, which make the assessment results inconsistent, without the precision required to objectively assess the effect of the rehabilitative intervention. A more detailed characterization is required to fully capture the various aspects of motor control and performance during complex movements of lower and upper limbs. The need for cost-effective and clinically applicable instrumented tests would enable quantitative assessment of performance on a subject-specific basis, overcoming the limitations due to the lack of objectiveness related to individual judgment, and possibly disclosing subtle alterations that are not clearly visible to the observer. Postural motion measurements at additional locations, such as lower and upper limbs and trunk, may be necessary in order to obtain information about the inter-segmental coordination during different functional tests involved in clinical practice. With these considerations in mind, this Thesis aims: i) to suggest a novel quantitative assessment tool for the kinematics and dynamics evaluation of a multi-link kinematic chain during several functional motor tasks (i.e. squat, sit-to-stand, postural sway), using one single-axis accelerometer per segment, ii) to present a novel quantitative technique for the upper limb joint kinematics estimation, considering a 3-link kinematic chain during the Fugl-Meyer Motor Assessment and using one inertial measurement unit per segment. The suggested methods could have several positive feedbacks from clinical practice. The use of objective biomechanical measurements, provided by inertial sensor-based technique, may help clinicians to: i) objectively track changes in motor ability, ii) provide timely feedback about the effectiveness of administered rehabilitation interventions, iii) enable intervention strategies to be modified or changed if found to be ineffective, and iv) speed up the experimental sessions when several subjects are asked to perform different functional tests.