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Purpose: The ability to perform motor imagery (MI) might be impaired by the physical fatigue elicited during training. Interestingly, there is also theoretical support for a more limited influence ...

Purpose: Brazilian jiu-jitsu is a martial art emphasizing ground combat with multiple ramifications to self-defense and military training. Some Brazilian jiu-jitsu athletes prefer fighting on their back (Guardadors), while others preferentially adopt a standing or kneeling position (Passadors). Whether the combat scenario leading to adopt a preferential or nonpreferential combat style influences the combat outcomes remains unexplored. Methods: In a counterbalanced design, 13 athletes performed simulated combats from either a congruent or incongruent scenario with regard to their preferred combat style. We collected combat scores from the official ranking system and measured upper- and lower-limb explosive performance before and after the combats, as well as the rating of perceived exertion and blood lactate concentrations to index fatigability. Results: Passadors had greater grip strength than Guardadors ( = .23, P = .03), whereas Guardadors showed higher lower-limb performance ( = .16, P = .05). When forced to combat as Passadors, Guardadors exhibited greater grip-strength impairment and a greater increase in perceived exertion ( = .12, P = .04; = .15, P = .05, respectively). They also had higher blood lactate concentrations ( = .19, P = .02). Conclusion: Guardadors exhibited greater fatigability after fighting from an incongruent combat situation compared to Passadors, presumably due to greater difficulties to adjust to the loss of initiative when restricted to a primarily defensive role. Future studies should examine how combat style congruency might affect performance and influence recovery strategies during high-level competitive events.

Motor imagery (MI) shares psychological and physiological similarities with the physical practice of the same action. Yet, it remains unclear whether fatigue elicited by exercise impairs MI ability. Fourteen participants performed MI of a self-paced walking sequence of 22 m before and after a resistance exercise eliciting muscle fatigue from upper and lower limbs, selectively. We indexed MI ability using psychometric and behavioral methods. Electromyography of the quadriceps was also recorded during physical practice trials of the walking sequence. For both experimental conditions, we recorded improved temporal congruence between MI and physical practice of the walking sequence (9.89 %, 95 % CI [7.03, 12.75], p0.01). Vividness decreased immediately after the fatiguing exercise (6.35 %, 95 % CI [5.18, 7.51], p0.05), before rapidly returning to pre-fatigue values during recovery trials. The results challenge the hypothesis of an effect of acute fatigue elicited by a resistance exercise on MI ability, i.e. restricted to MI tasks focusing fatigued effectors. The beneficial effects of fatigue conditions on the psychometric and behavioral indexes of MI ability are discussed in the broader context of psychobiological fatigue models linking perceived exertion with the reallocation of attentional resources. The general perception of fatigue, rather than local muscle fatigue, appeared linked to the acute effects of resistance exercise on MI ability.

Action observation (AO) alone or combined with motor imagery (AO + MI) has been shown to engage the motor system. While recent findings support the potential relevance of both techniques to enhance muscle function, this issue has received limited scientific scrutiny. In the present study, we implemented a counterbalanced conditions design where 21 participants performed 10 maximal isometric contractions (12-s duration) of elbow flexor muscles against a force platform. During the inter-trial rest periods, participants completed i) AO of the same task performed by an expert athlete, ii) AO + MI, i.e. observation of an expert athlete while concurrently imagining oneself performing the same task, and iii) watching passively a video documentary about basketball shooting (Control). During force trials, we recorded the total force and integrated electromyograms from the biceps brachii and anterior deltoideus. We also measured skin conductance from two finger electrodes as an index of sympathetic nervous system activity. Both AO and AO + MI outperformed the Control condition in terms of total force (2.79–3.68%, p

International audience; The efficacy of motor imagery (MI) practice to facilitate muscle stretching remains controversial and the underlying neurophysiological mechanisms unexplored. We evaluated the effects of MI practice during a sit-and reach task. Healthy participants were randomly assigned to a MI practice (n = 15) or Control (n = 15) group and completed 2 blocks of 5 sit-and-reach trials. During the first block (B1), participants performed 5 maximal stretching trials of 10s. During the second block (B2), trials were divided into two consecutive parts: i) reproducing the maximum performance of B1 (10s, B2 part 1), and ii) attempting to outperform the maximum performance of B1 (10s, B2 part 2). Participants performed kinesthetic MI of hamstring stretching during B2 trials in the MI practice group. We recorded electromyography from the hamstring and rectos femoris of the dominant leg. We also processed skin conductance as an index of sympathetic activity. We measured greater performance improvements from B1 to B2 part 2 in the MI practice group compared to Control (p < 0.05). Participants in the MI practice group exhibited reduced hamstring activation during both B2 part 1 (p < 0.001) and B2 part 2 (p < 0.001) compared to Control. Skin conductance revealed higher sympathetic activation during B2 part 2 compared to both B1 and B2 part 1 in the two groups. Thus, performing MI during actual movement is likely to improve stretching performance through reduced muscle activation. Such improvement may be grounded in a cortical gain over spinal reflexes.

Frequency domain analyses in electromyographic (EMG) signals are frequently applied to assess muscle fatigue and similar variables. Moreover, Fourier-based approaches are typically used for investigating these procedures. Nonetheless, Fourier analysis assumes the signal as stationary which is unlikely during dynamic contractions. As an alternative method, wavelet-based treatments do not assume this pattern and may be considered as more appropriate for joint time-frequency domain analysis. Based on the previous statements, the purpose of the present study was to compare the application of Short-Time Fourier Transform (STFT) and Continuous Wavelet Transform (CWT) to assess muscle fatigue in dynamic exercise of a 1-km of cycling (time-trial condition). The results of this study indicated that CWT and STFT analyses have provided similar fatigue estimates (slope) (p> 0.05). However, CWT application represents lesser dispersion (pp> 0.05) according to different methods, it is important to note that these responses seem to show greater values for CWT compared to STFT for 2 superficial muscles. Thereby, we are capable of considering CWT as a reliable and useful method to take into consideration when non-stationary or oscillating exercise models are evaluated.

It is becoming ever more common for the difference between winning and losing in sport to be decided by the smallest details. In basketball, free throws can be a differentiating factor between teams and motor imagery (IMA) has been studied as a potential ergogenic agent to improve free throw performance, but little attention as been given to its acute effects, particularly among athletes. The objective of this study was to investigate the effect of a single mental training session on the free throw performance and self-efficacy of young athletes. Eleven young basketball players from the Federação Paulista de Basquete junior league were enrolled on the study. Players were either allocated to an IMA group and watched a 1 minute video before a 3-minute motor imagery session, or to a control group and were rested for 4 minutes, before taking 10 free throw shots in both cases. All participants completed a self-efficacy questionnaire before and after the intervention. Statistical analysis was conducted using the Mann-Whitney U test and the Wilcoxon test, plus measures of Smallest Worthwhile Change (SWC). There were no significant difference between median results for the two groups, but the SWC statistic indicated an 84% likelihood that mental training had a beneficial effect on performance in the first two free throws. It is concluded that motor imagery used in advance has an 84% chance of having a beneficial effect on performance in up to two free throws. O esporte cada vez mais diferencia vencedores e perdedores por mínimos detalhes. No basquetebol um fator diferenciador é o lance livre. Sessões de imagética motora (IMA) vêm sendo estudada como um ergogênico sobre o desempenho de lance livre, porém, pouco se estuda o seu efeito agudo, principalmente, em atletas. O objetivo desse estudo foi verificar o efeito de uma sessão prévia de treinamento mental sobre o desempenho no lance livre e na percepção de autoeficácia de jovens atletas. Participaram do estudo 11 atletas juvenis da Federação Paulista de Basquete. Na condição IMA, foram submetidos a 1 minuto de vídeo + 3 minutos de imagética, seguidos de 10 lances livres, e no controle, 4 minutos de repouso seguidos de 10 lances livres. O questionário de autoeficácia foi preenchido antes e após a intervenção. Para análise estatística, foram utilizados os testes U de Mann-Withney, Wilcoxon e o Smallest Wothwhille Change (SWC). Não foi encontrada diferença entre a mediana dos grupos, porém, o SWC apontou uma possibilidade de 84% de efeito benéfico do treinamento mental sobre o desempenho para até 2 lances livres. Concluiu-se que a imagética motora prévia tem 84% de chance de causar um efeito benéfico sobre o desempenho de lance livre em até 2 arremessos.

The purpose of this study was to compare the prefrontal cortex (PFC) blood flow variation and time on in males and females while performing a motor task and imagery perspectives. Eighteen right handed subjects (11 males and 7 females) were volunteers to this study. All subjects went through three randomly conditions, a motor task condition (MT) in which they had to do a simple finger tap. The other conditions included practicing imagery in first and third views. During all the conditions, the fNIRS device was attached to the subject forehead to obtain the blood flow; the total time in each task which was measured with a chronometer. No difference had been found in any condition for both sexes in the PFC and time, nor for all subjects integrated in the PFC. Therefore, we conclu-de that both imageries can be used to mentally train a motor task, and probably both sexes can be benefited. O objetivo do estudo foi comparar a variação sanguínea do córtex prefrontal (CPF) e o tempo de realização, durante uma tarefa motora e diferentes perspectivas de imagética motora em homens e mulheres. Dezoito sujeitos destros (11 homens e 7 mulheres) foram voluntários. Todos os sujeitos passaram por 3 condições randomicamente, uma tarefa motora que consistia em uma simples batida de dedos. As outras condições fora a prática de imagética motora em primeira e terceira pessoa. Durante todas as condições, um aparelho fNIRS foi acoplado a testa para obtenção do fluxo sanguíneo; e o tempo total de cada tarefa foi obtido com um cronômetro. Nenhuma diferença foi encontrada em nenhuma condição para ambos os gêneros no CPF e no tempo, bem como quanto considerados todos os sujeitos. Concluímos que ambas imagéticas podem ser usadas para treinar mentalmente uma tarefa motora e que, provavelmente, ambos os gêneros podem se beneficiar da técnica. El propósito de este estudio fue comparar la actividad de la corteza frontal (CF) y el tiempo del realización de una tarea motora en diferentes perspectivas del entrenamiento mental. Dieciocho participantes diestros (11 hombres y 7 mujeres) fueron voluntarios en este estudio. Todos los participantes realizaram tres condiciones aleatorias: tarea motora (TM), dónde hicieron golpes con los dedos en una secuencia determinada. Las otras condiciones estaban practicando el entrenamiento mental vistas en primera y tercera persona. Durante todas las condiciones, el dispositivo fNIRS estaba unido a la frente del sujeto para obtener el flujo de sangre; el tiempo total de cada tarea se midió con un cronómetro. Ninguna diferencia se había encontrado en ninguna condición para ambos sexos y el tiempo. Por lo tanto, llegamos a la conclusión de que ambas las formas de imaginación pueden utilizar para entrenar mentalmente una tarea motora, y probablemente ambos géneros pueden ser beneficiados.

There is compelling evidence that motor imagery contributes to improved motor performance, and recent work showed that dynamic motor imagery (dMI) might provide additional benefits by comparison with traditional MI practice. However, the efficacy of motor imagery in different states of physical fatigue remains largely unknown, especially as imagery accuracy may be hampered by the physical fatigue states elicited by training. We investigated the effect of static motor imagery (sMI) and dMI on free-throw accuracy in 10 high-level basketball athletes, both in a non-fatigued state (Experiment 1) and immediately after an incremental running test completed until exhaustion (20 m shuttle run-test-Experiment 2). We collected perceived exhaustion and heart rate to quantify the subjective experience of fatigue and energy expenditure. We found that dMI brought better shooting performance than sMI, except when athletes were physically exhausted. These findings shed light on the conditions eliciting optimal use of sMI and dMI. In particular, considering that the current physical state affects body representation, performing dMI under fatigue may result in mismatches between actual and predicted body states.

The effect of motor imagery (MI) practice on isometric force development is well-documented. However, whether practicing MI during rest periods of physical training improves the forthcoming performance remains unexplored. We involved 18 athletes in a counterbalanced design including three physical training sessions scheduled over five consecutive days. Training involved 10 maximal isometric contractions against a force plate, with the elbow at 90°. During two sessions, we integrated MI practice (focusing on either muscle activation or relaxation) during the inter-trial rest periods. We measured muscle performance from force plate and electromyograms of the biceps brachii and anterior deltoideus. We continuously monitored electrodermal activity (EDA) to control sympathetic nervous system activity. MI of muscle activation resulted in higher isometric force as compared to both MI of muscle relaxation and passive recovery (respectively +2.1% and +3.5%). MI practice of muscle relaxation also outperformed the control condition (+1.9%). Increased activation of the biceps brachii was recorded under both MI practice conditions compared to control. Biceps brachii activation was similar between the two MI practice conditions, but electromyography revealed a marginal trend toward greater activation of the anterior deltoideus during MI practice of muscle activation. EDA and self-reports indicated that these effects were independent from physiological arousal and motivation. These results might account for priming effects of MI practice yielding to higher muscle activation and force performance. Present findings may be of interest for applications in sports training and neurologic rehabilitation.

Este estudo investigou os efeitos agudos da imagética motora (IM) sobre o desempenho de atletas de basquetebol. Para tanto 3 estudos foram elaborados. Inicialmente uma revisão sistemática específica sobre a utilização da imagética motora em atletas levantou os principais achados e lacunas da literatura. Em seguida um estudo piloto envolvendo 11 atletas juniores de basquetebol do sexo masculino, que realizaram a sessão de imagética motora + vídeo, com posterior teste de desempenho envolvendo 10 lances livres seguidos. Também foi avaliado a percepção de autoeficácia, através do questionário EAEGP, antes e após a sessão de imagética. A intervenção foi capaz de causar com 84% de chance, um efeito benéfico sobre os dois primeiros arremessos convertidos, entretanto, a percepção de autoeficácia não sofreu alteração. Por fim, um terceiro estudo envolvendo também atletas juniores de basquete (n=9), utilizou-se de uma intervenção mais ecológica. Os atletas forma submetidos a sessões de imagética tanto estática (IE) quanto dinâmica (ID), em situações de fadiga (F) ou somente aquecidos (C). Para elevar o estado de cansaço dos atletas foi utilizado o teste de Shuttle-run 20 metros. Foram avaliadas a frequência cardíaca, nível de cansaço (escala de OMNI), nível de imagética (Escala likert de 1-6) e desempenho no teste de lance livre (até 5 arremessos), averiguando tanto arremessos convertidos quanto precisão dos arremessos. Todas as condições foram superior a condição C. Quando descansados a ID se mostrou superior a IE, entretanto quando levados a um estado de fadiga a IE causou os maiores efeitos encontrados, enquanto a ID não mais foi efetiva além da própria fadiga, a qual também se mostrou benéfica em relação a condição C. O fator emocional envolvido na imagética ainda se mantém incerto. Assim sendo, a ID e a IE possuem momentos específicos dentro de um jogo para serem utilizadas com maior especificidade. This study investigated the acute effects of motor imagery (MI) on basketball athletes performance. For such 3 studies were conducted. Firstly a systematic review regarding the MI use on athletes rised the main findings and gaps in the literature, the main results were the absence of studies using motor imagery acutely, the new perspective with the dynamic imagery and the MI accuracy lost caused by fatigue. Next, a pilot study with 11 male junior basketball athletes, which performed a motor imagery session + video, with posterior free-throw performance test (10 consecutives free-throws). Still the self-efficacy perception was evaluated before and after the MI session. The intervention were capable of causing, with 84% of chance, a beneficial effect until 2 free-throws, however the self-efficacy perception didn’t sufer modifications. For last, a third study also with junior basketball players (n=9) employed a more ecological approach. The athletes underwent motor imagery sessions, both motionless (IE) and dynamic (ID), in fatigue situation (F) ou only warmed (C). To elevate the fatigue level of the athletes the 20 meters Shuttle-run teste was used until exhaustion. Were measured the heart rate, fatigue level (OMNI scale), imagery level (Likert scale of 1 to 6) and free-throw performance (until 5 shots), ascertaining both converted shots and and shots precision. All conditions were superior to C. When rested the ID was superior to IE, however once the athletes were fatigued the IE caused the biggest effects founded, and the ID was no more effective beyond the fatigue itself, which was also benficial when compared to C. The emoctional effect is still uncertain. Thus, ID and IE are to be used in specific moments inside a game with better specificity.

O objetivo do estudo foi analisar os efeitos da ingestao de cafeina sobre o desempenho fisico e estado de humor de ciclistas em teste contra-relogio de 1 km. Dez ciclistas do sexo masculino realizaram aleatoriamente um teste contra-relogio de 1 km em duas condicoes experimentais: ingestao de cafeina (CAF - 6 mg.kg -1 ) e placebo (PL) 60 min antes do teste. Durante os testes foram obtidas as medidas de tempo total e estado humor pelo questionario de Brunel (BRUMS). Para comparacoes dos parâmetros tempo total e estado de humor foi utilizando-se do teste t de Student pareado e teste Wilcoxon , respectivamente. Nenhuma diferenca estatisticamente significante foi encontrada no tempo total e no estado de humor nas condicoes CAF e PL ( P >0,05). Os resultados sugerem que a cafeina nao melhora o desempenho fisico nem altera o estado de humor dos atletas em um teste contra-relogio de 1 km.

© 2012 Altimari et al., licensee InTech. This is an open access chapter distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Influence of Different Strategies of Treatment Muscle Contraction and Relaxation Phases on EMG Signal Processing and Analysis During Cyclic Exercise