Kinematic, kinetic and EMG patterns during downward squatting

The aim of this study was to investigate the kinematic, kinetic, and electromyographic pattern before, during and after downward squatting when the trunk movement is restricted in the sagittal plane. Eight healthy subjects performed downward squatting at two different positions, semisquatting (40 degrees knee flexion) and half squatting (70 degrees knee flexion). Electromyographic responses of the vastus medialis oblique, vastus medialis longus, rectus femoris, vastus lateralis, biceps femoris, semitendineous, gastrocnemius lateralis, and tibialis anterior were recorded. The kinematics of the major joints were reconstructed using an optoelectronic system. The center of pressure (COP) was obtained using data collected from one force plate, and the ankle and knee joint torques were calculated using inverse dynamics. In the upright position there were small changes in the COP and in the knee and ankle joint torques. The tibialis anterior provoked the disruption of this upright position initiating the squat. During the acceleration phase of the squat the COP moved posteriorly, the knee joint torque remained in flexion and there was no measurable muscle activation. As the body went into the deceleration phase, the knee joint torque increased towards extension with major muscle activities being observed in the four heads of the quadriceps. Understanding these kinematic, kinetic and EMG strategies before, during and after the squat is expected to be beneficial to practitioners for utilizing squatting as a task for improving motor function. (C) 2006 Elsevier Ltd. All rights reserved.

Preparatory trunk motion accompanies rapid upper limb movement

Evaluation of trunk movements, trunk muscle activation, intra-abdominal pressure and displacement of centres of pressure and mass was undertaken to determine whether trunk orientation is a controlled variable prior to and during rapid bilateral movement of the upper limbs. Standing subjects performed rapid bilateral symmetrical upper limb movements in three directions (flexion, abduction and extension). The results indicated a small (0.4-3.3 degrees) but consistent initial angular displacement between the segments of the trunk in a direction opposite to that produced by the reactive moments resulting from limb movement. Phasic activation of superficial trunk muscles was consistent with this pattern of preparatory motion and with the direction of motion of the centre of mass. In contrast, activation of the deep abdominal muscles was independent of the direction of limb motion, suggesting a non-direction specific contribution to spinal stability. The results support the opinion that feedforward postural responses result in trunk movements, and that orientation of the trunk and centre of mass are both controlled variables in relation to rapid limb movements.

Electromyographic Analysis of Paravertebral Muscles in Patients with Idiopathic Scoliosis

Study Design. Prospective clinical electromyographic study in adolescents with idiopathic scoliosis and control group. Objective. To evaluate electromyographic amplitude from erector spinae muscles of patients with idiopathic scoliosis in comparison with control volunteers without spinal deformities. Summary of Background Data. Previous studies have indicated an increased electromyographic activity in paravertebral muscles in the convex side of the scoliotic curvature. However, in previous studies there is the absence or poor description of methods used, and some studies were conducted before the recording and processing recommendations for surface electromyographic signals had been described. Methods. Thirty individuals, matched by sex, age, and body mass index, were divided into two groups: scoliosis and control. The electric activity of the erector spinae muscles was determined by surface electromyography on both sides of the three levels of spine: T8, L2, and L5. Results. Normalized electromyographic amplitudes of erector spinae muscles, in the convex and concave sides of the apex region of the scoliotic curve in the thoracic and lumbar regions, were not significantly different. Also, there was no significant difference between the muscles of these regions when the scoliosis group was compared with the control group. The erector spinae muscle at the L5 level, representing the lower vertebral limit of the lumbar scoliotic curve, had significantly higher electromyographic activity on the convex side. However, the same alteration was shown in the control group homologous muscle (on the left side). Conclusion. Erector spinae muscles on the convex and concave sides at the curvature apex in patients with idiopathic scoliosis and small magnitude of curves did not show significant differences in electromyographic amplitude. Future studies should evaluate whether intragroup activation differences, at the L5 level in 80% of the maximum voluntary isometric contractions with predominance of the left side of the vertebral column, have any relation to the condition.

Ageing and surface EMG activity patterns of masticatory muscles

P>The purpose of this study was to evaluate the influence of age on the electromyographic activity of masticatory muscles. All volunteers were Brazilian, fully dentate (except for Group I - mixed dentition), Caucasian, aged 7-80, and divided into five groups: I (7-12 years), II (13-20 years), III (21-40 years), IV (41-60 years) and V (61-80 years). Except for Group V, which comprised nine women and eight men, all groups were equally divided with respect to gender (20 M/20 F). Surface electromyographic records of masticatory muscles were obtained at rest and during maximal voluntary contraction, right and left laterality, maximal jaw protrusion and maximal clenching in the intercuspal position. Statistically significant differences (P < 0 center dot 05) were found in all clinical conditions among the different age groups. Considerably different patterns of muscle activation were found across ages, with greater electromyographic activity in children and youth, and decreasing from adults to aged people.

Implant-supported prosthesis following Branemark protocol on electromyography of masticatory muscles

This research evaluated the effects of Branemark protocol on electromyography of the masseter and temporal muscles. The patients were divided into two groups: Group 1: patients who wore an implant-supported prosthesis in the mandibular arch following Branemark protocol, and maxillary removable complete dentures; Group II: dentate individuals (control). Electromyography was carried out at rest, right (RL) and left (LL) laterality, protrusion and maximum voluntary contraction (MVC). Data were compared by t-test. At rest, a higher electromyographic (EMG) activity was observed in Group I, and the values were significant in the right masseter and left temporal muscles. In RL, there were statistically significant differences for right masseter (P < 0.01), left masseter and temporal muscles and for the left temporal muscle in LL (P < 0.05). In protrusion, Group I presented a higher EMG activity, and there was a statistically significant difference for the right masseter muscle (RM) (P < 0.05). In MVC, the EMG values were higher in Group II (control), but significant just for the right temporal muscle (P < 0.05). In conclusion, individuals with mandibular fixed dentures supported according to the Branemark protocol and maxillary removable complete dentures showed a higher activity of masticatory muscles during the mandibular postural clinical conditions examined; however, in the MVC, Group I presented lower values when compared to dentate group. Despite presenting different EMG values in all of the clinical conditions, both groups showed similar EMG patterns of muscle activation which demonstrates that the proposed treatment can be considered as a good option for oral rehabilitation.

Neural influences on sprint running - Training adaptations and acute responses

Performance in sprint exercise is determined by the ability to accelerate, the magnitude of maximal velocity and the ability to maintain velocity against the onset of fatigue. These factors are strongly influenced by metabolic and anthropometric components. Improved temporal sequencing of muscle activation and/or improved fast twitch fibre recruitment may contribute to superior sprint performance. Speed of impulse transmission along the motor axon may also have implications on sprint performance. Nerve conduction velocity (NCV) has been shown to increase in response to a period of sprint training. However, it is difficult to determine if increased NCV is likely to contribute to improved sprint performance. An increase in motoneuron excitability, as measured by the Hoffman reflex (H-reflex), has been reported to produce a more powerful muscular contraction, hence maximising motoneuron excitability would be expected to benefit sprint performance. Motoneuron excitability can be raised acutely by an appropriate stimulus with obvious implications for sprint performance. However, at rest reflex has been reported to be lower in athletes trained for explosive events compared with endurance-trained athletes. This may be caused by the relatively high, fast twitch fibre percentage and the consequent high activation thresholds of such motor units in power-trained populations. In contrast, stretch reflexes appear to be enhanced in sprint athletes possibly because of increased muscle spindle sensitivity as a result of sprint training. With muscle in a contracted state, however, there is evidence to suggest greater reflex potentiation among both sprint and resistance-trained populations compared with controls. Again this may be indicative of the predominant types of motor units in these populations, but may also mean an enhanced reflex contribution to force production during running in sprint-trained athletes. Fatigue of neural origin both during and following sprint exercise has implications with respect to optimising training frequency and volume. Research suggests athletes are unable to maintain maximal firing frequencies for the full duration of, for example, a 100m sprint. Fatigue after a single training session may also have a neural manifestation with some athletes unable to voluntarily fully activate muscle or experiencing stretch reflex inhibition after heavy training. This may occur in conjunction with muscle damage. Research investigating the neural influences on sprint performance is limited. Further longitudinal research is necessary to improve our understanding of neural factors that contribute to training-induced improvements in sprint performance.

Neural compensation for compliant loads during rhythmic movement

An experiment was performed to characterise the movement kinematics and the electromyogram (EMG) during rhythmic voluntary flexion and extension of the wrist against different compliant (elastic-viscous-inertial) loads. Three levels of each type of load, and an unloaded condition, were employed. The movements were paced at a frequency of I Hz by an auditory metronome, and visual feedback of wrist displacement in relation to a target amplitude of 100degrees was provided. Electro-myographic recordings were obtained from flexor carpi radialis (FCR) and extensor carpi radialis brevis (ECR). The movement profiles generated in the ten experimental conditions were indistinguishable, indicating that the CNS was able to compensate completely for the imposed changes in the task dynamics. When the level of viscous load was elevated, this compensation took the form of an increase in the rate of initial rise of the flexor and the extensor EMG burst. In response to increases in inertial load, the flexor and extensor EMG bursts commenced and terminated earlier in the movement cycle, and tended to be of greater duration. When the movements were performed in opposition to an elastic load, both the onset and offset of EMG activity occurred later than in the unloaded condition. There was also a net reduction in extensor burst duration with increases in elastic load, and an increase in the rate of initial rise of the extensor burst. Less pronounced alterations in the rate of initial rise of the flexor EMG burst were also observed. In all instances, increases in the magnitude of the external load led to elevations in the overall level of muscle activation. These data reveal that the elements of the central command that are modified in response to the imposition of a compliant load are contingent, not only upon the magnitude, but also upon the character of the load.

Postural control and movement performance during upper limb tasks in children with developmental co-ordination disorder (DCD)

At least 6% of primary school aged children present with DCD, where co-ordination is substantially below the normal range for the child’s age and intelligence. Motor skill difficulties negatively affect academic achievement, recreation and activities of daily living. Poor upper-limb co-ordination is a common difficulty for children with DCD. A possible cause of this problem is deviant muscle timing in proximal muscle groups, which results in poor postural and movement control. While studies have been published investigating postural control in response to external perturbations, detail about postural muscle activity during voluntary movement is limited even in children with normal motor development. No studies have investigated the relationship between muscle timing, resultant arm motion and upper-limb coordination deficits. Objectives: To investigate the relationship between functional difficulties with upper-limb motor skills and neuromuscular components of postural stability and coordination. Specifically, to investigate onset-timing of muscle activity, timing of arm movement, and resultant three-dimensional (3D) arm co-ordination during rapid, voluntary arm movement and to analyse differences arising due to the presence of DCD. This study is part of a larger research program investigating postural stability and control of upper limb movement in children. Design: A controlled, cross-sectional study of differences between children with and without DCD. Methods: This study included 50 children aged eight to 10 years (25 with DCD and 25 without DCD). Children participated in assessment of motor skills according to the Movement ABC Test and a laboratory study of rapid, voluntary arm movements. Parameters investigated included muscle activation timing of shoulder and trunk muscles (surface electromyography), arm movement timing (light sensor) and resultant 3D arm motion (Fastrak). Results: A MANOVA is being used to analyse between-group differences. Preliminary results indicate children with DCD demonstrate altered muscle timing during a rapid arm raise when compared with the control group of children. Conclusion: Differences in proximal muscle timing in children with DCD support the hypothesis that altered proximal muscle activity may contribute to poor proximal stability and consequently poor arm movement control. This has implications for clinical physiotherapy.

Interaction of directional, neuromuscular and egocentric constraints on the stability of preferred bimanual coordination patterns

We investigated how the relative direction of limb movements in external space (iso- and non-isodirectionality), muscular constraints (the relative timing of homologous muscle activation) and the egocentric frame of reference (moving simultaneously toward/away the longitudinal axis of the body) contribute to the stability of coordinated movements. In the first experiment, we attempted to determine the respective stability of isodirectional and non-isodirectional movements in between-persons coordination. In a second experiment, we determined the effect of the relative direction in external space, and of muscular constraints, on pattern stability during a within-person bimanual coordination task. In the third experiment we dissociated the effects on pattern stability of the muscular constraints, relative direction and egocentric frame of reference. The results showed that (1) simultaneous activation of homologous muscles resulted in more stable performance than simultaneous activation of non-homologous muscles during within-subject coordination, and that (2) isodirectional movements were more stable than non-isodirectional movements during between-persons coordination, confirming the role of the relative direction of the moving limbs in the stability of bimanual coordination. Moreover, the egocentric constraint was to some extent found distinguishable from the effect of the relative direction of the moving limbs in external space, and from the effect of the relative timing of muscle activation. In summary, the present study showed that relative direction of the moving limbs in external space and muscular constraints may interact either to stabilize or destabilize coordination patterns. (C) 2003 Published by Elsevier B.V.

Interface Multimodal com Predição de Movimentos para Uso em Reabilitação de Membros Inferiores

Esta dissertação apresenta o desenvolvimento de uma plataforma multimodal de aquisição e processamento de sinais. O projeto proposto insere-se no contexto do desenvolvimento de interfaces multimodais para aplicação em dispositivos robóticos cujo propósito é a reabilitação motora adaptando o controle destes dispositivos de acordo com a intenção do usuário. A interface desenvolvida adquire, sincroniza e processa sinais eletroencefalográficos (EEG), eletromiográficos (EMG) e sinais provenientes de sensores inerciais (IMUs). A aquisição dos dados é feita em experimentos realizados com sujeitos saudáveis que executam tarefas motoras de membros inferiores. O objetivo é analisar a intenção de movimento, a ativação muscular e o início efetivo dos movimentos realizados, respectivamente, através dos sinais de EEG, EMG e IMUs. Para este fim, uma análise offline foi realizada. Nessa análise, são utilizadas técnicas de processamento dos sinais biológicos e técnicas para processar sinais provenientes de sensores inerciais. A partir destes, os ângulos da articulação do joelho também são aferidos ao longo dos movimentos. Um protocolo experimental de testes foi proposto para as tarefas realizadas. Os resultados demonstraram que o sistema proposto foi capaz de adquirir, sincronizar, processar e classificar os sinais combinadamente. Análises acerca da acurácia dos classificadores utilizados mostraram que a interface foi capaz de identificar intenção de movimento em 76, 0 ± 18, 2% dos movimentos. A maior média de tempo de antecipação ao movimento foi obtida através da análise do sinal de EEG e foi de 716, 0±546, 1 milisegundos. A partir da análise apenas do sinal de EMG, este valor foi de 88, 34 ± 67, 28 milisegundos. Os resultados das etapas de processamento dos sinais biológicos, a medição dos ângulos da articulação, bem como os valores de acurácia e tempo de antecipação ao movimento se mostraram em conformidade com a literatura atual relacionada.

Análise do padrão de ativação muscular de indivíduos hemiparéticos pós-AVC em marcha assistida por andador robótico

O Acidente Vascular Cerebral (AVC) é uma das principais causas de prejuízos ao sistema neuromuscular. Dispositivos Robóticos vêm sendo amplamente desenvolvidos e estudados com a finalidade de serem utilizados na assistência à marcha e para o treinamento da marcha durante a reabilitação. O objetivo deste trabalho é avaliar a marcha assistida pelo AROW (Assistive Robotic Walker) em indivíduos hemiparéticos pós-AVC, através da análise de sinais de acelerometria e sinais mioelétricos de superfície (sEMG) provenientes dos músculos vasto medial (VM), bíceps femoral (BF), tibial anterior (TA) e gastrocnêmio medial (GM), e também utilizando os métodos de avaliação GAS (Goal Attainment Scaling) e SUS (System Usability Scale). Nove indivíduos hemiparéticos participaram dos testes. A velocidade da marcha foi reduzida com o uso do AROW e, consequentemente, houve algumas alterações na duração das fases da marcha, por exemplo, uma maior duração da fase de apoio (p = 0,0174). O padrão de ativação muscular para o grupo analisado não apresentou diferença estatisticamente significativa (início da ativação VM: p= 0,4999; término da ativação VM: p= 0,5647; início BF: p= 0,1186; término BF: p= 0,7823; início TA: p= 0,5833; término TA: p= 0,8393; início GM: p= 0,6077; término GM: p= 0,1429). Entretanto, avaliando o padrão de ativação muscular individualmente, podem-se notar algumas alterações benéficas, por exemplo, redução da coativação dos músculos tibial anterior e gastrocnêmio medial. Os resultados das avaliações através do GAS (54,8) e SUS (81,4) sobre o uso do AROW mostraram boa aceitação pelos usuários, e os objetivos esperados durante o uso do andador foram atingidos. A adaptação rápida, facilidade de utilização e sentimento de segurança ao usar o dispositivo são pontos positivos obtidos com o uso do AROW.

Iniciação da marcha em indivíduos com AVE. Sequência de ativação muscular do tibial anterior e solear

Introdução: A iniciação da marcha, enquanto tarefa motora complexa que consiste na transição de uma postura mantida pelo apoio simultâneo dos dois membros inferiores para um equilíbrio dinâmico, permitindo a progressão anterior do corpo, constitui um exemplo que implica uma correta sequência de ativação muscular. Objetivos: Verificar a modificação da fase de iniciação da marcha face à aplicação de um programa de recuperação funcional, analisando a sequência de ativação dos músculos tibial anterior e solear. Registar as repercussões funcionais na participação nas diferentes atividades da vida diária, em contexto padronizado e social. Metodologia: Nos dois participantes em estudo foi realizada uma avaliação antes e após um programa de intervenção, segundo a abordagem do Conceito de Bobath, através da Classificação Internacional de Funcionalidade, Incapacidade e Saúde, da Fugl Meyer Assessment of Sensorymotor Recovery After Stroke, electromiografia e plataforma de forças. Resultados: Após a aplicação do programa de recuperação funcional, verificaram-se alterações na sequência de ativação do tibial anterior e solear. O músculo tibial anterior passou a ser o primeiro a ser recrutado nesta sequência. Conclusão: Foi possível verificar modificações durante a fase de iniciação da marcha, face a um programa de recuperação funcional, em que a sequência de ativação do tibial anterior e solear, tendencialmente, se assemelharam ao comportamento em indivíduos saudáveis, repercutindo-se numa melhoria funcional na participação nas atividades da vida diária.

Efeito de uma intervenção em crianças com hemiparésia espástica ao nível dos ajustes posturais anticipatórios no início da marcha

Objectivos: Verificar o efeito de uma intervenção baseada na abordagem segundo o Conceito de Bobath nos Ajustes Posturais Anticipatórios no Início da Marcha em duas crianças com hemiparésia espástica. Pretendeu-se ainda, verificar o efeito desta abordagem nas actividades e participação, bem como comparar os aspectos individuais das duas crianças com a capacidade de mudança após a intervenção. Metodologia: A avaliação foi realizada antes e três meses após a intervenção através da Electromiografia, da Plataforma de Forças, de um sistema de Câmaras de Vídeo, de uma Máquina Fotográfica e da Classificação Internacional de Funcionalidade para Crianças e Jovens. Resultados: A sequência de activação muscular alterou-se apenas na criança A. A postura na posição de pé, a actividade muscular, o deslocamento do centro de pressão e as actividades e participação modificaram-se em ambas as crianças, sendo que a criança A apresentou maior capacidade de mudança. Conclusão: A intervenção com base numa abordagem segundo o conceito de Bobath induziu mudanças positivas nos Ajustes Posturais Anticipatórios e nas actividades e participação dos casos em estudo.

Influência da actividade do tronco inferior na sequência de activação muscular proximal durante o passo (fase de apoio) - em crianças com quadro motor diplegia

A marcha assegura uma progressão do corpo, compatível com o equilíbrio dinâmico e adaptada a potenciais factores destabilizadores, de um ponto de vista antecipatório, através de sinergias coordenadas entre os MSs, o tronco e os MIs. O tronco inferior tem um papel preponderante na marcha, sobretudo na estabilização necessária durante a fase de apoio. Esta actividade implica mobilidade pélvica e alongamento activo dos abdominais para conseguir a relação comprimento-tensão muscular óptima entre quadricípite e isquiotibiais, permitindo uma correcta sequência, timing e amplitude de activação. Nas crianças com alterações neuromotoras existem alterações no controlo do movimento e na estrutura do próprio movimento, alterando todo este processo. Como tal, este estudo tem como principal objectivo determinar a influência da actividade do tronco inferior na activação muscular proximal durante a fase de apoio da marcha, em crianças com quadro motor de diplegia, caracterizada por uma dificuldade na relação entre os membros e entre estes e o tronco. Para responder a este objectivo realizou-se um estudo de série de casos, com 2 crianças com quadro motor de diplegia. Efectuou-se EMG dos músculos abdominais, quadricípite e isquiotibiais e análise de imagem (para amplitude da CF) durante a marcha, em ambos os membros e em dois momentos de avaliação, separados por 2 meses, nos quais se realizou um protocolo de intervenção terapêutica adequado a cada caso. Os resultados indicam que a variação de amplitude da CF desde a fase de ataque ao solo à fase média de apoio é aproximadamente igual em M0e M1; concretamente, a amplitude inicial é inferior à de referência (pouca flexão) (melhor em M0) e a amplitude final é superior à de referência (pouca extensão) (melhor em M1). Estes resultados são idênticos em ambos os casos. Na EMG verificou-se uma actividade mais global e sincronizada de todos os músculos, mantendo-se aproximadamente a mesma percentagem de activação em M1, sobretudo no caso 1. No caso 2 verificou-se uma maior eficiência na variação da percentagem de activação dos abdominais, em M1, e dos isquiotibiais, à direita. Em conclusão, pode dizer-se que, em crianças com alterações neuromotoras (quadro motor de diplegia), uma actividade mais eficiente e sincronizada no tempo do tronco inferior, nomeadamente dos abdominais, contribui para uma maior capacidade de extensão da CF, durante a fase de apoio.

EMG of the transverse abdominus and multifidus during pilates exercises

The purpose of this research study was to evaluate the intensity of muscle activation of Transverse Abdominus /Oblique Internal (TrA/OI) and Multifidus (Mu) during the performance of four Pilates exercises (and variations), compared, in order to understand the importance of these exercises in the lumbopelvic stability in healthy subjects. The sample consisted of 8 individuals. Using the surface electromyography (EMG), it was found that there are differences in the intensity of muscle activation in the analyzed exercises and, therefore, “Shoulder bridge” and “ShoulderBridge_extension (right and left legs)“ are the more appropriate exercises for co-activation between TrA/OI and Mu muscles for the reeducation of lumbopelvic stability.