Efeito de previsibilidade temporal de perturbações posturais e demanda de precisão de tarefa manual no desempenho em tarefa dual

O objetivo deste estudo foi avaliar a integração entre os componentes manual e postural em uma tarefa motora dual em resposta a perturbações que afetam a ambos os componentes. Foram avaliados oito adultos jovens em uma tarefa requisitando resposta reativa a uma perturbação postural causada por liberação de carga, enquanto apontando um laser continuamente para um alvo circular. As comparações foram feitas em função da combinação de dois fatores: (a) previsibilidade do momento da perturbação postural, com dica temporal versus sem dica; e (b) demanda de precisão da tarefa manual, contrastando alvos com diâmetros de 2 cm (alta restrição) versus 20 cm (baixa restrição). Os resultados revelaram que a previsibilidade do tempo de perturbação reduziu a amplitude de oscilação dos movimentos manuais e diminuiu a correlação entre respostas manuais e posturais, enquanto que o a amplitude de excursão do centro de pressão foi reduzida na condição de previsibilidade temporal da perturbação associada à baixa restrição da tarefa manual. Este estudo revela a factibilidade do método aqui empregado para avaliar a integração entre controle postural e de tarefas manuais, na busca de melhor compreender a regulação de ações duais dessa natureza realizadas frequentemente em nosso cotidiano

A quantificação do trabalho mecânico como recurso de avaliação do controle postural

The study aims to propose two methods for calculating the amount of mechanical work (W) as a resource for analysis of postural control in individuals subject to motor disturbances, visual and / or are in the process of physical rehabilitation. This study addresses the W quantification performed by the muscle after the extension of the trunk to the upright position (self-disturbance) in subjects with preserved vision (VP) and temporary deprivation of vision (PMV) by two methods known as: i) Mechanical Work Total (Wtot) and ii) Mechanical Work of the Center of Mass (WCM). The sample consisted of 10 healthy volunteers, males aged 25,6 (± 2,2) years. Five trials were performed for each volunteer in both conditions. An imaging system for tracking optoelectronic three-dimensional it used to collect data, consisting of 8 video cameras, with a frequency of capture of 200 Hz. The linear regression analysis Wtot and WCM show strong correlation between the two conditions (r2 = 0,77 for the VP condition and r2 = 0,84 for condition PMV) and the Student t test was observed statistically significant differences (p<0,10) in the first attempt among the volunteers with VP and PMV for Wtot during the post-interval disturbance, and differences in WCM the intervals [0,80]ms and [0,100]ms. It was concluded that the methods to calculate Wtot and WCM investigate possible postural control after motor and visual disturbances may be used as a resource in physical rehabilitation.O estudo tem por objetivo propor dois métodos de cálculo para a quantificaçao do trabalho mecânico (W) como recurso para análise do controle postural em indivíduos submetidos a perturbaçoes motoras, visuais e/ou que estao em processo de reabilitaçao física. Neste estudo se aborda a quantificaçao do W realizado pelo sistema muscular após a extensao do tronco para postura ereta (auto-perturbaçao) em indivíduos com visao preservada (VP) e privaçao momentânea da visao (PMV) por meio de dois métodos denominados: i) Trabalho mecânico total (Wtot) e ii) Trabalho mecânico do centro de massa (WCM). A amostra constituiu-se de 10 voluntários saudáveis, do sexo masculino com idades de 25,6 (± 2,2) anos. Foram realizadas cinco tentativas para cada voluntário em ambas as condiçoes. Para coleta dos dados foi utilizado um sistema de imagem para rastreamento optoeletrônico tridimensional, composto de 8 câmeras de vídeo, com freqüência de captaçao de 200 Hz. Observou-se pela análise de regressao linear que o Wtot e WCM apresentam forte correlaçao entre as duas condiçoes (r2 = 0,77 para a condiçao VP e r2 = 0,84 para a condiçao PMV) e pelo teste t de Student observou-se diferenças estatisticamente significativas (p<0,10) na primeira tentativa entre os voluntários com VP e PMV para o Wtot durante o intervalo pós-perturbaçao, bem como diferenças no WCM nos intervalos [0,80]ms e [0,100]ms. Concluiu-se que os métodos que calculam o Wtot e o WCM possibilita investigar o controle postural após perturbaçoes motoras e visuais podendo ser utilizado como recurso na reabilitaçao física

Effect of Creatine Supplementation on Functional Capacity and Muscle Oxygen Saturation in Patients with Symptomatic Peripheral Arterial Disease: A Pilot Study of a Randomized, Double-Blind Placebo-Controlled Clinical Trial

The aim of the study was to verify the effects of creatine (Cr) supplementation on functional capacity (walking capacity; primary outcome) and calf muscle oxygen saturation (StO2) (secondary outcome) in symptomatic peripheral arterial disease (PAD) patients. Twenty-nine patients, of both sexes, were randomized (1:1) in a double-blind manner for administration of placebo (PLA, n = 15) or creatine monohydrate (Cr, n = 14). The supplementation protocol consisted of 20 g/day for 1 week divided into four equal doses (loading phase), followed by single daily doses of 5 g in the subsequent 7 weeks (maintenance phase). Functional capacity (total walking distance) was assessed by the 6 min walk test, and calf muscle StO2 was assessed through near infrared spectroscopy. The measurements were collected before and after loading and after the maintenance phase. The level of significance was p < 0.05. No significant differences were found for function capacity (total walking distance (PLA: pre 389 ± 123 m vs. post loading 413 ± 131 m vs. post maintenance 382 ± 99 m; Cr: pre 373 ± 149 m vs. post loading 390 ± 115 m vs. post maintenance 369 ± 115 m, p = 0.170) and the calf muscle StO2 parameters (p > 0.05). Short- and long-term Cr supplementation does not influence functional capacity and calf muscle StO2 parameters in patients with symptomatic PAD

Influence of cognitive processes on automatic postural responses to extrinsic perturbations

A capacidade de adaptação das respostas posturais automáticas de acordo com informações do contexto indica uma interação entre dois níveis de controle, em que o processamento cognitivo de alta ordem das características de uma perturbação iminente seria capaz de modular o controle postural em níveis inferiores do sistema sensoriomotor. Os estudos aqui propostos procuram responder quais informações sobre as características da perturbação são utilizadas pelo central set para modular as respostas posturais automáticas. A tarefa estudada consistiu na recuperação do equilíbrio da postura ereta em resposta à translação da base de suporte. No Experimento 1, foi avaliada a influência de dicas visuais sobre a amplitude de deslocamento da base de suporte em sequências repetitivas ou aleatórias de perturbação. No Experimento 2, a dica de amplitude de deslocamento foi dada por meio da sequência de perturbações, comparando-se tentativas repetidas em bloco, em sequência conhecida e em sequência aleatória. No Experimento 3, foi avaliado o efeito de incerteza tanto da amplitude da perturbação quanto do tempo de aplicação da perturbação. O Experimento 4 teve como propósito avaliar a interação entre dica temporal e tarefa cognitiva concomitante à recuperação do equilíbrio. Os resultados mostram que (a) informações prévias sobre a magnitude da perturbação postural parecem ser incapazes de modular respostas posturais automáticas; (b) modulação de respostas posturais automáticas a partir de uma sequência repetitiva de perturbações aparentemente está associada à adaptação do sistema sensoriomotor e não à participação de processamento cognitivo das características físicas da perturbação iminente; (c) previsibilidade temporal da perturbação postural induz uma otimização das respostas posturais automáticas; e (d) a execução de tarefa cognitiva no momento da perturbação inibe o ganho de estabilidade de respostas posturais automáticas conferido pela dica temporal. Como conclusão, parece haver uma limitação do processamento cognitivo em modular respostas posturais automáticas. Considerando-se que o conceito de central set expressa a noção de que processamento cognitivo de dicas contextuais é capaz de otimizar respostas posturais automáticas, nossos resultados sugerem a necessidade da revisão deste conceito amplamente empregado na literatura de controle posturalAdaptability of automatic postural responses according to context information indicates an interaction between two levels of control, in which the high-order cognitive processing of the perturbation characteristics would be able to modulate postural control in lower levels of the sensorimotor system. The studies proposed here intended to scrutinize what cues about the perturbation characteristics are used by the central set to modulate the automatic postural responses. The task studied consisted in the recovery of postural equilibrium in response to a posterior translation of the support base. In Experiment 1, it was evaluated the effect of precueing the displacement amplitude of the supporting base in repetitive or random perturbation sequences. In Experiment 2, precueing of the support base displacement was provided by the sequence of perturbations, comparing repetitive trials, known sequence and random sequence. In Experiment 3, we evaluated the effect of uncertainty about amplitude and time of perturbation. Experiment 4 aimed to evaluate the interaction of temporal precueing and a concurrent cognitive task on body equilibrium recovery. Results show that (a) previous information about perturbation magnitude seems to be unable to modulate automatic postural responses; (b) modulation of automatic postural responses from a repetitive sequence of perturbations is apparently associated with an adaptation of the sensorimotor system rather than to the participation of cognitive processing of the perturbation characteristics; (c) temporal predictability of the postural perturbation induces optimization of automatic postural responses; and (d) cognitive task execution at the time of the perturbation inhibits the gain of automatic postural responses stability provided by temporal precueing. As a conclusion, there seems to be a limitation of cognitive processing to modulate automatic postural responses. Considering that the concept of central set expresses the notion that cognitive processing of a contextual precue is able to optimize automatic postural responses, our results suggest the need for revision of this conceptualization widely used in the postural control literatur

O trabalho mecânico segmentar como novo instrumento de avaliação do controle postural

Objectie: Calculate the mechanical work (W), applying the total mechanical work (Wtot) and segmental work (Wseg) as a new complementary evaluation resource of the postural control mechanisms in subjects undergoing  motor and visual disturbance. Methods: Ten healthy adult male volunteers were selected with ages 25.6 (±2.26) years, whose height was 1.69 (± 0.25) m and body weight was 68.22 (± 0.25) kg. Kinematic data of trunk extension with eyes open and blindfolded were captured with a frequency of 200 Hz. This way the post perturbation interval has been selected and the  Wseg (i.e. trunk, head, etc) and the total mechanical work (Wtot) calculated, which were obtained by means of total integral mechanical energy. Results: The statistical analyzing of information was done by paired-data Student's t test.  There has been no significant difference  (p<0,08)  for the Wtot during the post perturbation interval. On the other hand, there has been a significant difference (p<0.05) in the post perturbation interval of Wseg. However, there were significant differences in interval (p<0.05). This difference is related to Wseg of head (Whead) and lower limbs (Wleg and Wthigh ) in the post-perturbation interval with early range of [0. 60] ms and [0. 100] ms after the self-perturbation. Conclusion: These differences that were found in Whead between the two conditions can be associated with modulations of the vestibulo-ocular-motor system. On the other hand, the differences that were found in Wleg and Wthigh can be associated with somato-sensory adjustment mechanisms.Objetivo: Calcular o trabalho mecânico (W), aplicando o trabalho mecânico total (Wtot) e o trabalho segmentar (Wseg) como um novo recurso de avaliação complementar dos mecanismos de controle postural em sujeitos submetidos a perturbação motora e visual. Método: Dez voluntários adultos saudáveis do sexo masculino foram selecionados com idade 25,6 (± 2,26) anos, cuja altura era de 1,69 (± 0,25) m e peso corporal de 68,22 (± 0,25) kg.  Os dados cinemáticos da extensão  do tronco com os olhos abertos e vendados foram capturados com frequência de 200 Hz. Dessa forma, foi selecionado o intervalo pós-perturbação e o Wseg (tronco, cabeça, etc) e o trabalho mecânico total (Wtot) calculados, que foram obtidos por meio de energia mecânica  total integral. Resultados: A análise estatística das informações foi feita pelo teste t student para dados emparelhados. Não houve diferença significativa (p<0,08) para a Wtot durante o intervalo pós-perturbação. Por outro lado, houve uma diferença significativa (p<0,05) no intervalo pós-perturbação de Wseg. Entretanto, houve diferenças significativas no intervalo (p<0,05). Esta diferença está relacionada com Wseg de cabeça (Wcabeça) e membros inferiores (Wperna e Wcoxa ) no intervalo pós-perturbação com intervalo inicial de [0. 60] ms e [0. 100] ms após a auto-perturbação. Conclusão: Essas diferenças encontradas em Wcabeça entre as duas condições podem estar associadas a modulações do sistema vestibulo-ocular-motor. Por outro lado, as diferenças encontradas em Wperna e Wcoxa podem ser associadas a mecanismos de ajuste somato-sensorial

Modulation of manual preference induced by lateralized practice diffuses over distinct motor tasks: age-related effects

In this study we investigated the effect of use of the nonpreferred left hand to practice different motor tasks on manual preference in children and adults. Manual preference was evaluated before, immediately after and 20 days following practice. Evaluation was made with tasks of distinct levels of complexity requiring reaching and manipulation of cards at different eccentricities in the workspace. Results showed that left hand use in adults induced increased preference of that hand at the central position when performing the simple task, while left hand use by the children induced increased preference of the left hand at the rightmost positions in the performance of the complex task. These effects were retained over the rest period following practice. Kinematic analysis showed that left hand use during practice did not lead to modification of intermanual performance asymmetry. These results indicate that modulation of manual preference was a consequence of higher frequency of use of the left hand during practice rather than of change in motor performance. Findings presented here support the conceptualization that confidence on successful performance when using a particular limb generates a bias in hand selection, which diffuses over distinct motor tasks

Association of Foot Sole Sensibility with Quiet and Dynamic Body Balance in Morbidly Obese Women

An important health-related problem of obesity is reduced stance stability, leading to increased chance of falling. In the present experiment, we aimed to compare stability in quiet and in dynamic body balance between women with morbid obesity (n = 13, body mass index [BMI] > 40 Kg/m2, mean age = 38.85 years) and with healthy body weight (lean) (n = 13; BMI < 25 Kg/m2, mean age = 37.62 years), evaluating the extent to which quiet and dynamic balance stability are associated with plantar sensibility. Quiet stance was evaluated in different visual and support base conditions. The dynamic task consisted of rhythmic flexion—extension movements at the hip and shoulder, manipulating vision availability. The plantar sensibility threshold was measured through application of monofilaments on the feet soles. The results showed that the morbidly obese, in comparison with the lean women, had higher plantar sensibility thresholds, and a reduced balance stability in quiet standing. Mediolateral stance stability on the malleable surface was strongly correlated with plantar sensibility in the obese women. Analysis of dynamic balance showed no effect of obesity and weaker correlations with plantar sensibility. Our results suggest that reduced plantar sensibility in morbidly obese women may underlie their diminished stance stability, while dynamic balance control seems to be unaffected by their reduced plantar sensibility

Evaluation of balance recovery stability from unpredictable perturbations through the compensatory arm and leg movements (CALM) scale

Following unpredictable large-magnitude stance perturbations diverse patterns of arm and leg movements are performed to recover balance stability. Stability of these compensatory movements could be properly estimated through qualitative evaluation. In the present study, we present a scale for evaluation of compensatory arm and leg movements (CALM) in response to unpredictable displacements of the support base in the mediolateral direction. We tested the CALM scale for intra- and inter-rater reliability, correlation with kinematics of arm and leg movement amplitudes, and sensitivity to mode (rotation, translation and combined) and magnitude (velocity) of support base displacements, and also to perturbation-based balance training. Results showed significant intra- and inter-rater coefficients of agreement, ranging from moderate (0.46-0.53) for inter-rater reliability in the arm and global scores, to very high (0.87-0.99) for inter-rater leg scores and all intra-rater scores. Analysis showed significant correlation values between scale scores and the respective movement amplitudes both for arm and leg movements. Assessment of sensitivity revealed that the scale discriminated the responses between perturbation modes, platform velocities, in addition to higher balance recovery stability as a result of perturbation-based balance training. As a conclusion, the CALM scale was shown to provide adequate integrative evaluation of compensatory arm and leg movements for balance recovery stability after challenging stance perturbations, with potential application in fall risk prediction.status: publishe