The use of neuromuscular electrical stimulation (NMES) to artificially restore movement in people with complete spinal cord injury (SCI) induces an accelerated process of muscle fatigue. Fatigue increases the time between the beginning of NMES and the onset of muscle force (DelayTOT). Understanding how much muscle fatigue affects the DelayTOT in people with SCI could help in the design of closed‐loop neuroprostheses that compensate for this delay, thus making the control system more stable. The aim of this study was to evaluate the impact of the extent of fatigue on DelayTOT and peak force of the lower limbs in people with complete SCI. Fifteen men—young adults with complete SCI (paraplegia and tetraplegia) and stable health—participated in the experiment. DelayTOT was defined as the time interval between the beginning of NMES application until the onset of muscle force. The electrical intensity of NMES applied was adjusted individually and consisted of the amplitude required to obtain a full extension of the knee (0°), considering the maximum electrically stimulated extension (MESE). Subsequently, 70% of the MESE was applied during the fatigue induction protocol. Significant differences were identified between the moments before and after the fatigue protocol, both for peak force (P ≤ .026) and DelayTOT (P ≤ .001). The medians and interquartile range of the DelayTOT were higher in postfatigue (199.0 ms) when compared to the moment before fatigue (146.5 ms). The medians and interquartile range of the peak force were higher in unfatigued lower limbs (0.43 kgf) when compared to the moment postfatigue (0.27 kgf). The results support the hypothesis that muscle fatigue influences the increase in DelayTOT and decrease in force production in people with SCI. For future applications, the combined evaluation of the delay and force in SCI patients provides valuable feedback for NMES paradigms. The study will provide potentially critical muscle mechanical evidence for the investigation of the evolution of atrophy.

Adaptation of automatic postural responses (APR) to balance perturbations might be thought to be impaired by muscle fatigue, given the associated proprioceptive and effector deficits. In this investigation, we aimed to evaluate the effect of muscular fatigue on APR adaptation over repetitive balance perturbations through support base backward translations. APR adaptation was evaluated in three epochs: (a) pre‐fatigue; (b) post‐fatigue, immediately following fatigue of the plantiflexor muscles through isometric contractions and (c) post‐recovery, 30 min after the end of fatiguing activity. Results showed the following: (a) Decreasing amplitudes of joints' maximum excursion over repetitive perturbations in the three fatigue‐related epochs. (b) Modulation of joints' excursion was observed in the first trial in the post‐fatigue epoch. (c) In the post‐fatigue epoch, we found interjoint rescaling, with greater amplitude of hip rotation associated with reduced amplitude of ankles' rotation. (d) Amplitudes of ankles' rotation were similar between the post‐fatigue and post‐recovery epochs. These findings lead to the conclusions that adaptation of automatic postural responses over repetitive trials was effective under focal muscular fatigue; modulation of the postural response took place in the first perturbation under fatigue, and generalization of response characteristics from post‐fatigue to post‐recovery suggests that feedforward processes in APRs generation are affected by the recent history of postural responses to stance perturbations.

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Muscle fatigue accumulated during a soccer game can be a critical element to athletic performance. The aim of this study was to analyze the feasibility of evaluating the effect of muscle fatigue of the support leg in soccer players postural stability and muscular activation of the stabilizing muscles of the ankle in the performance of a power kick. Six university soccer players were evaluated. Muscular fatigue was induced by means of repeated oscillations of the swing leg. Results indicated that fatigue did not significantly affect velocity of the kicking leg and postural stability while kicking. Electromyographic analysis revealed that fatigue induced decreased activation of the medial gastrocnemius and increased activation of the soleus muscles in the period following foot-ball contact. These results show the feasibility of analyzing the effect of fatigue on dynamic balance and muscular activation in the performance of a power kicking task.

A engenharia tecidual é um campo interdisciplinar voltado para desenvolvimento de estruturas biológicas que restaurem, mantenham ou melhorem funções teciduais. Dentre os componentes necessários para isso, há os arcabouços tridimensionais, estruturas criadas para suporte inicial das células e consequente formação de um tecido. Para avaliação do desempenho do arcabouço, é importante analisar características microestruturais como a porosidade, a interconectividade e o tamanho dos poros. Algumas técnicas como a microscopia eletrônica de varredura (MEV), picnometria e porosimetria de mercúrio, já vem sendo usadas para caracterizar os arcabouços. Todavia, alguns estudos mostraram a microtomografia computadorizada como padrão ouro para extrair informações detalhadas sem danificar a amostra em estudo. A Microtomografia Computadorizada de Raios X (microCT) é uma técnica não invasiva e apresenta uma alta resolução, contribuindo para análise e visualização tridimensional interna de vários tipos de amostras. Devido a essas vantagens, diversos pesquisadores vem estudando a microCT como técnica para caracterização de arcabouços para engenharia tecidual, visando obter informações mais apuradas a respeito da porosidade dessas estruturas, que irão influenciar diversos fatores como o desempenho biológico e as propriedades mecânicas das mesmas. O objetivo do trabalho consiste em apresentar a microCT como ferramenta de caracterização de arcabouços para engenharia tecidual e compará-la com outras técnicas utilizadas atualmente. Verificou-se que a microCT vem sendo utilizada na área para análises qualitativas e quantitativas, principalmente por conseguir visualizar poros cegos e área da seção transversal, sem utilizar elementos tóxicos ou sem destruir a amostra. Existem algumas desvantagens, que seriam pouca capacidade de absorção de raios-x em amostras de baixa densidade radiográfica. No entanto, apesar do crescente interesse em utilizar essa técnica, é possível perceber que muitos pesquisadores não a dominam por não ter relatórios com detalhes importantes sobre vários parâmetros da microestrutura e da utilização correta da microCT. Concluiu-se que a caracterização de arcabouços por microtomografia computadorizada é uma área que ainda está em desenvolvimento e com acesso limitado, porém vem ganhando destaque e tende a se tornar mais procurada e usada entre os pesquisadores para aplicação na engenharia tecidual.

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