Forearm Posture Affects the Corticospinal Excitability of Intrinsic and Extrinsic Hand Muscles in Dominant and Nondominant Sides.

Different forearm postures can modulate corticospinal excitability. However, there is no consensus on whether handedness plays a role in such a mechanism. This study investigated the effects of 3 forearm postures (pronation, neutral, and supination) on the corticospinal excitability of muscles from the dominant and nondominant upper limbs. Surface electromyography was recorded from the abductor digiti minimi, flexor pollicis brevis, and flexor carpi radialis from both sides of 12 right-handed volunteers. Transcranial magnetic stimulation pulses were applied to each muscle's hotspot in both cerebral hemispheres. Motor-evoked potential peak-to-peak amplitude and latency and resting motor threshold were measured. The data were evaluated by analysis of variance. The level of significance was set at 5%. The resting motor threshold was similar for the 3 muscles and both sides. Motor-evoked potential peak-to-peak amplitude from flexor pollicis brevis was lower during supination, and the dominant upper limb latency was longer. The flexor carpi radialis presented lower motor-evoked potential peak-to-peak amplitudes for neutral and shorter latencies during supination. Abductor digiti minimi seemed not to be affected by posture or side. Different muscles from dominant and nondominant sides may undergo corticospinal modulation, even distally localized from a particular joint and under rest.

Response of masticatory muscles to treatment with orthodontic aligners: a preliminary prospective longitudinal study.

INTRODUCTION: The emergence of orthodontic aligners has provided an aesthetic and comfortable option for orthodontic treatment. However, the encapsulated design of the aligners can influence the masticatory muscles, and might compromise safe treatment. OBJECTIVE: This preliminary longitudinal study aimed to investigate whether the use of orthodontic aligners affects the biting force and myoelectric activity of the superficial masseter and anterior temporal muscles. METHODS: Ten subjects participated in the study and underwent treatment during an 8-month follow-up period. The root mean square (RMS), the median power frequency (MPF) of the surface electromyography (sEMG) signals, and the biting force (kgf) were recorded and normalized relative to the pretreatment condition. The data were analyzed by repeated-measure analysis of variance (ANOVA), with the significance level set at 5%. RESULTS: Both the superficial masseter and the anterior temporal muscles presented an increase in sEMG signal activity during the treatment, with a marked increase in the latter compared to the former (p<0.05). Moreover, a significant decrease in bite force was evidenced (p<0.05). CONCLUSIONS: This preliminary study observed that the orthodontic aligners affected the muscle recruitment pattern of masticatory muscles, and reduced biting performance during the 8-month follow-up period.

Cardiorespiratory and Emotional Responses During Balance Exercises.

Purpose: Physical exercises on unstable surfaces have been largely applied for clinical practice as well as in sports training. Although the unsteadiness can lead to physiological and psychological adaptations, little is known about the autonomic and emotional acute responses during the practice of balance exercises. This study aimed to evaluate both cardiorespiratory and emotional responses while standing on different unstable surfaces. Methods: Eighty-eight healthy participants performed postural balance tasks in three experimental conditions: (1) a rigid surface (control); (2) balance pad; and (3) the Both Sides Up (BOSU) ball. Respiratory activity was recorded through the thoracic movement and the heart rate variability by the electrocardiographic signal during the balance tasks. After the participants evaluated the level of perceived stability and emotional aspects related to each experimental condition. Results: The main results showed that BOSU condition was perceived as more unstable, unpleasant, with higher arousal and lower dominance levels (p < .05). Accordingly, participants had also an increase in the mean respiratory frequency and heart rate (p < .05). Conclusion: These results showed that the postural task with greater instability prompted congruent physiological adjustments to ensure the homeostasis in the more challenging condition. Therefore, the cardiorespiratory and emotional responses should be considered to ensure the safety and benefits in rehabilitation programs in which the exercise progression is based on unstable surfaces.

Response of masticatory muscles to treatment with orthodontic aligners: a preliminary prospective longitudinal study

ABSTRACT Introduction: The emergence of orthodontic aligners has provided an aesthetic and comfortable option for orthodontic treatment. However, the encapsulated design of the aligners can influence the masticatory muscles, and might compromise safe treatment. Objective: This preliminary longitudinal study aimed to investigate whether the use of orthodontic aligners affects the biting force and myoelectric activity of the superficial masseter and anterior temporal muscles. Methods: Ten subjects participated in the study and underwent treatment during an 8-month follow-up period. The root mean square (RMS), the median power frequency (MPF) of the surface electromyography (sEMG) signals, and the biting force (kgf) were recorded and normalized relative to the pretreatment condition. The data were analyzed by repeated-measure analysis of variance (ANOVA), with the significance level set at 5%. Results: Both the superficial masseter and the anterior temporal muscles presented an increase in sEMG signal activity during the treatment, with a marked increase in the latter compared to the former (p<0.05). Moreover, a significant decrease in bite force was evidenced (p<0.05). Conclusions: This preliminary study observed that the orthodontic aligners affected the muscle recruitment pattern of masticatory muscles, and reduced biting performance during the 8-month follow-up period.

RESUMO Introdução: O surgimento dos alinhadores ortodônticos tem proporcionado uma opção estética e confortável para o tratamento ortodôntico. No entanto, o design encapsulado dos alinhadores pode influenciar os músculos mastigatórios e comprometer a segurança do tratamento. Objetivo: Este estudo longitudinal preliminar teve como objetivo investigar se o uso de alinhadores ortodônticos afeta a força de mordida e a atividade mioelétrica dos músculos masseter superficial e temporal anterior. Métodos: Dez indivíduos participaram do estudo e foram submetidos a tratamento durante um período de acompanhamento de 8 meses. A raiz quadrada média (RMS), a frequência mediana de potência (FMP) dos sinais de superfície da eletromiografia (sEMG) e a força de mordida (kgf) foram registradas e normalizadas em relação à condição de pré-tratamento. Os dados foram analisados por análise de variância para medidas repetidas (ANOVA), com nível de significância estabelecido em 5%. Resultados: Tanto o masseter superficial quanto o temporal anterior apresentaram aumento da atividade do sinal sEMG durante o tratamento, com aumento acentuado desse último em comparação ao primeiro (p<0,05). Além disso, foi evidenciada uma diminuição significativa da força de mordida (p<0,05). Conclusões: Esse estudo preliminar observou que os alinhadores ortodônticos afetaram o padrão de recrutamento muscular dos músculos mastigatórios e reduziram o desempenho da mordida durante o período de acompanhamento de oito meses.

The impact of Chikungunya chronic arthralgia on women's upper limbs motor function: a cross-sectional study / O impacto da artralgia crônica pós-Chikungunya na função motora dos membros superiores de mulheres: um estudo transversal / El impacto de la artralgia crónica poschikunguña en la función motora del miembro superior de mujeres: un estudio transversal

ABSTRACT Post-Chikungunya chronic arthralgia (PCCA) may lead to musculoskeletal repercussions and functional loss. The objective was to assess the upper limb physical disability and symptoms during daily, work, and leisure activities of women presenting PCCA compared to healthy controls (HC). This was a cross-sectional study conducted with 52 women. The participants were divided into PCCA (37) and HC (15) groups. Handgrip strength, range of motion, level of pain (numerical rating scale), and participants' physical disability and symptoms (Disabilities of the Arm, Shoulder, and Hand Questionnaire - DASH) were evaluated. Differences between groups were evaluated using the Students t-test and Pearson's correlations. The chi-square test was applied for categorical variables. The significance was set at α=0.05. The disease duration was 19.5±13.1 months. We found no differences between groups for peak force (PCAA:23.6±7.4kgf; HC: 24.5±6.2kgf; p=0.676). The results showed a significant difference between groups regarding range of motion (PCCA: 63.5±17.3o; HC: 77.2±9.6o), level of hand pain (PCCA: 5.8±2.2; HC: 0.4±1.5), and upper limbs functional levels (PCCA: 44.5±17.4; HC: 16.2±20.5). Participants related severe difficulty or inability to perform tasks such as opening a jar (78.4%), placing objects above head height (48.7%), doing heavy household chores (56.8%), and gardening (51.4%). Impairment in the upper limb physical function in daily, work, and leisure activities shows the higher prevalence in the long-term.

RESUMO A artralgia crônica pós-Chikungunya (ACPC) pode gerar repercussões musculoesqueléticas e perda funcional. Nesse sentido, o objetivo deste estudo foi avaliar a incapacidade física e os sintomas de membros superiores de mulheres com ACPC durante atividades diárias, laborais e de lazer comparadas aos controles saudáveis (CS). Para tanto, realizou-se um estudo transversal conduzido com 52 mulheres. As participantes foram divididas entre os grupos com ACPC (37) e CS (15). Foram avaliados força de preensão, amplitude de movimento (ADM), nível de dor (escala numérica de dor) e incapacidade física e sintomas por meio do Disabilities of the Arm, Shoulder and Hand Questionnaire (Dash). Diferenças entre os grupos foram avaliadas pelo teste t de Student e correlações de Pearson. O teste qui-quadrado foi utilizado para variáveis categóricas e α=0,05 foi estabelecido como nível de significância. Verificou-se que a duração da ACPC foi de 19,5±13,1 meses. Não houve diferença entre os grupos para a força pico (ACPC: 23,6±7,4kgf; CS: 24,5±6,2kgf; p=0,676). Os resultados demonstraram diferença significativa entre os grupos em termos de ADM (ACPC: 63,5±17,3o; CS: 77,2±9,6o), nível de dor nas mãos (ACPC: 5,8±2,2; CS: 0,4±1,5) e níveis funcionais dos membros superiores (ACPC: 44,5±17,4; CS: 16,2±20,5). As participantes relataram extrema dificuldade ou incapacidade para realizar tarefas como abrir um pote (78,4%), colocar objetos em um local acima da cabeça (48,7%), realizar atividades domésticas pesadas (56,8%) e atividades de jardinagem (51,4%). Conclui-se que a função física dos membros superiores durante as atividades diárias, laborais e de lazer constitui o maior comprometimento apresentado a longo prazo.

RESUMEN La artralgia crónica poschikunguña (ACPC) puede tener como efecto repercusiones musculoesqueléticas y pérdida funcional. En este sentido, el objetivo de este estudio fue evaluar la discapacidad física y los síntomas de miembros superiores de mujeres con ACPC durante las actividades diarias, laborales y de ocio en comparación con controles sanos (CS). Por ello, se realizó un estudio transversal con 52 mujeres. Las participantes se dividieron en los grupos ACPC (37) y CS (15). La fuerza de agarre, el rango de movimiento (ROM), el nivel de dolor (escala numérica de dolor), la discapacidad física y los síntomas se evaluaron mediante el Disabilities of the Arm, Shoulder and Hand Questionnaire (Dash). Las diferencias entre los grupos se evaluaron con la aplicación de la prueba t de Student y las correlaciones de Pearson. Se utilizó la prueba de chi-cuadrado para las variables categóricas y se estableció como nivel de significación α=0,05. Se encontró que la duración de la ACPC fue de 19,5±13,1 meses. No hubo diferencia entre los grupos para la fuerza máxima (ACPC: 23,6±7,4kgf; CS: 24,5±6,2kgf; p=0,676). Los resultados mostraron una diferencia significativa entre los grupos respecto al ROM (ACPC: 63,5±17,3o; CS: 77,2±9,6o), el nivel de dolor en la mano (ACPC: 5,8±2,2; CS: 0,4±1,5) y los niveles funcionales de miembros superiores (ACPC: 44,5±17,4; CS: 16,2±20,5). Las participantes informaron una extrema dificultad o incapacidad para realizar tareas como abrir un frasco (78,4%), poner objetos en un lugar más alto (48,7%), realizar actividades domésticas pesadas (56,8%) y actividades de jardinería (51,4%). Se concluyó que la función física de los miembros superiores durante las actividades diarias, laborales y de ocio constituye el mayor compromiso a largo plazo.

Perceived exertion, postural control, and muscle recruitment in three different quadruped exercises performed by healthy women.

Although quadruped exercises (QE) have been a part of rehabilitation and sports programs, there is no clarity on how these exercises challenge the musculoskeletal system. Therefore, this cross-sectional study investigated the perceived exertion, postural demands, and muscle recruitment profiles imposed by three QE postures. Surface electromyographic (sEMG) signals were recorded from transverse abdominis, longissimus dorsi, multifidus, and iliocostalis lumborum from 30 sedentary healthy women, bilaterally. They performed the classic quadruped exercise (CQ), a variation with shoulder flexion (FQ), and the homolateral quadruped (HQ). Borg scores (BS) and the center of pressure (CoP) from the palmar statokinesiogram were also recorded. Surface EMG signals were normalized using the myoelectric activity recorded from two other postures while performing isometric voluntary contractions (IVC). Results were analyzed using one- (CoP) and three-way (sEMG data) ANOVA with Bonferroni post hoc tests (α = 0.05). The Borg scale was analyzed using the Friedman test. The CQ provided lower BS and CoP than HQ (p < 0.05), followed by a higher sEMG activity (∼51% of IVC) than FQ (∼47% of IVC; p = 0.53) and HQ (∼44% of IVC; p = 0.01). In turn, HQ provided greater BS (p > 0.05) than CQ and FQ. The results suggested that the HQ was the most challenging exercise regarding CoP and BS, although CQ presented a higher symmetrical sEMG activity. Since QE are often prescribed in exercise programs, specific knowledge of the characteristics of each QE makes prescribing safer and more efficient.

Therapeutic effects of botulinum toxin type A in subjects with gummy smile: A longitudinal sEMG approach.

OBJECTIVE: To evaluate the response of the myoelectric activity of levator labii superioris (LLS), levator labii superioris alaeque nasi (LLSAN), and minor zygomatic (Zm) muscles in individuals with gummy smile, volunteers to botulinum toxin type A (BTX-A) application, with a follow-up of 6 months. MATERIALS AND METHODS: Thirteen individuals were submitted to clinical evaluation and photographic records to monitor the variations of the gingival display (GD) during posed smile. The recording of the surface electromyography (sEMG) signal of muscles studied was performed in three tasks: posed smile (PS), upper lip elevation (ULE) and nose wing elevation (NWE). The root-mean-square value, an amplitude sEMG signal parameter, was extracted from the sEMG signals. One and three-way ANOVA were applied, and the level of significance set at 5%. RESULTS: There were significant differences (P<0.05) in the sEMG signal activity from the control condition (before BTX-A application - T0) to the 8th week of follow up, which was accompanied by clinical evaluation for the gingival display (P<0.05). The peak of the reduction in sEMG signals occurred 2 weeks after T0 for all the studied tasks, with the exception of the left hemiface in the PS, which showed a peak of reduction 4 weeks after T0. CONCLUSIONS: BTX-A led to a decrease in the sEMG signal amplitude over 2 to 4 weeks after application in the muscles, although differently concerning each hemiface when recruited to perform other mouth tasks. During the PS, the recruitment level of the upper lip elevator muscles was compatible with the clinical response obtained in the follow-up period in this study, which corroborates the sEMG assessment to clinical data.

Motor potential evoked by transcranial magnetic stimulation depends on the placement protocol of recording electrodes: a pilot study.

OBJECTIVE: There seems to be no consensus in the literature regarding the protocol of surface electromyography (sEMG) electrode placement for recording motor evoked potentials (MEP) in transcranial magnetic stimulation (TMS) applications. Thus, the aim of this study was to investigate the effect on the MEP amplitude bytwo different protocols for electrode placement. METHODS: sEMG electrodes were placed on three upper arm muscles (biceps brachii, flexor carpi radialis, and flexor pollicis brevis) of six right-handed subjects following two different protocols (1 and 2), which varied according to the interelectrode distance and location relative to the muscle. TMS pulses were applied to the hotspot of biceps brachii, while sEMGwas recorded from the two protocols and for each muscle simultaneously. MAIN RESULTS: Greater MEP amplitudes were obtained for Protocol 1 compared to Protocol 2 (P < 0.05). SIGNIFICANCE: Different electrode placement protocols may result in distinct MEP amplitudes, which should be taken into account when adjusting the intensity on single and repetitive TMS sessions.

Is somatosensory electrical stimulation effective in relieving spasticity? A systematic review.

Spasticity is a sensorimotor disorder widely recognized as one of the features that contribute to patients' disability. Transcutaneous electric neural stimulation (TENS/SES) has been adopted in spasticity rehabilitation as an alternative to pharmacological agents. Although previous studies have reported clinical benefits of TENS/SES in relieving spasticity, there is no clarity on how and whether this therapeutic modality affects specific neural circuitries. Thus, this systematic review aimed to verify the efficacy of TENS/SES in the control of spasticity and its consequences in spinal and corticospinal excitability. This study was carried out according to PRISMA recommendations using SCOPUS, PubMed, BVS, Google Scholar and BASE databases screening, which provided 483 references. Six additional records were found from other sources. All these records were submitted to a filtering process following the eligibility criteria, and 44 studies were selected for further analysis. Ten were replicas. Consequently, 34 studies were read in full with the aim of checking their eligibility criterion, which resulted in 10 manuscripts for qualitative synthesis. Even though they evaluated the effects of TENS/SES both at the spinal and/or corticospinal levels, the electrophysiological results seem to be inconsistent, corroborating the lack of agreement between them and with clinical outcomes.

Ajustes cinemáticos do complexo articular do tornozelo sobre diferentes superfícies instáveis / Kinematic adjustments of the ankle joint complex on different unstable surfaces

INTRODUÇÃO: Poucos estudos discutem as reações corporais de indivíduos saudáveis no momento em que os exercícios em superfícies instáveis estão sendo executados, embora os efeitos do treinamento ­ efeitos crônicos do exercício- sejam bastante estudados. OBJETIVO: Descrever a cinemática articular do tornozelo e retropé durante essa interação. MÉTODOS: Dezoito voluntários participaram do estudo. A posição articular da região do tornozelo foi estudada em três superfícies: Airex® Balance-pad, BOSU® e chão (controle). Para análise estatística, utilizou-se ANOVA e Pós-teste de Tuckey, considerando um nível de significância menor que 0,05. RESULTADOS: A posição articular da região tornozelo no plano sagital foi diferente no BOSU® em relação ao Airex® (p < 0.001) e ao chão (p < 0.001). O tornozelo ficou em posição mais próxima à neutra no AIREX® e no chão. Com o BOSU, a dorsiflexão foi acentuada. Não houve diferença da posição média no no plano frontal. A variabilidade da posição da região do tornozelo foi maior no BOSU® que no Airex® (p < 0.001) e no chão (p < 0.001), tanto no plano sagital, quanto no plano frontal. A frequência média de deslocamento da posição articular na região do tornozelo no plano sagital foi maior no BOSU® que no chão (p < 0.001); e no plano frontal, para o retropé, foi maior no BOSU® que no Airex® (p < 0.001) e chão (p < 0.001). CONCLUSÃO: Houve diferença no comportamento articular da região do tornozelo na condição BOSU® em relação às demais nas superfícies utilizadas, havendo um aumento das oscilações articulares no processo de controle postural em condições mais instáveis e maior dosiflexão no BOSU®. [AU]

INTRODUCTION: There are few studies approaching the bodily reactions of healthy individuals while performing exercises on unstable surfaces, although the training effects ­ exercise chronic effects - are well studied. OBJECTIVE: The goal of this study is to describe the ankle and rear foot region osteoarticular kinematic during this interaction. METHODS: Eighteen volunteers participated in the study. The ankle region osteoarticular displacement was studied in three different surfaces: AIREX® Balance-pad, BOSU® and Ground (control). Statistical analysis was performed using ANOVA and Tukey test, considering a significance level of 0.05. RESULTS: The position of the ankle joint in the sagittal plane was greater in the BOSU® than in the AIREX® (p < 0.001) and ground (p < 0.001). The ankle was close to the neutral position in the AIREX® and on the ground. With BOSU, the dorsiflexion was accentuated. Considering the frontal plane, there was no difference in the rear foot position. Moreover, the variability in the ankle region position in sagittal and frontal planes was higher in BOSU® than AIREX® (p < 0.001) and ground (p < 0.001). The mean frequency of the ankle position in the sagittal plane was greater in the BOSU® than on the ground (p < 0.001), and, in frontal plane, the rear foot frequency displacement was largest in the BOSU® than in the AIREX® (p < 0.001) and on the ground (p < 0.001). CONCLUSION: There were observed differences in ankle region postural control strategies in the BOSU® condition when compared with the other surfaces tested. The ankle and rear foot oscillations increase and there is a greater dorsiflexion for the postural control under the most unstable condition - BOSU. [AU]

Can somatosensory electrical stimulation relieve spasticity in post-stroke patients? A TMS pilot study.

Evidence suggests that somatosensory electrical stimulation (SES) may decrease the degree of spasticity from neural drives, although there is no agreement between corticospinal modulation and the level of spasticity. Thus, stroke patients and healthy subjects were submitted to SES (3 Hz) for 30' on the impaired and dominant forearms, respectively. Motor evoked potentials induced by single-pulse transcranial magnetic stimulation were collected from two forearm muscles before and after SES. The passive resistance of the wrist joint was measured with an isokinetic system. We found no evidence of an acute carry-over effect of SES on the degree of spasticity.

Effect of TMS coil orientation on the spatial distribution of motor evoked potentials in an intrinsic hand muscle.

Previous reports on the relationship between coil orientation and amplitude of motor evoked potential (MEP) in transcranial magnetic stimulation (TMS) did not consider the effect of electrode arrangement. Here we explore this open issue by investigating whether TMS coil orientation affects the amplitude distribution of MEPs recorded from the abductor pollicis brevis (APB) muscle with a bi-dimensional grid of 61 electrodes. Moreover, we test whether conventional mono- and bipolar montages provide representative MEPs compared to those from the grid of electrodes. Our results show that MEPs with the greatest amplitudes were elicited for 45° and 90° coil orientations, i.e. perpendicular to the central sulcus, for all electrode montages. Stimulation with the coil oriented at 135° and 315°, i.e. parallel to the central sulcus, elicited the smallest MEP amplitudes. Additionally, changes in coil orientation did not affect the spatial distribution of MEPs over the muscle extent. It has been shown that conventional electrodes with detection volume encompassing the APB belly may detect representative MEPs for optimal coil orientations. In turn, non-optimal orientations were identified only with the grid of electrodes. High-density electromyography may therefore provide new insights into the effect of coil orientation on MEPs from the APB muscle.

Proposal of surface electromyography signal acquisition protocols for masseter and temporalis muscles

Abstract Introduction The aim of this study was to propose a method of electrodes positioning on the superficial masseter and anterior temporalis muscles for surface electromyographic (sEMG) recordings in order to overcome some known methodological constraints. Methods Fifteen volunteers with normal occlusion participated in two experimental sessions within a 7 day-period. Surface electrodes were placed on two different locations that were based on palpable and individual anatomical references. Surface EMG signals (2000 Hz per channel; A/D: 16 bits; gain: 2000 X; band-pass filter: 20-500 Hz) were recorded under three conditions: mandibular rest position, 30% and 100% of maximum voluntary bite force. Three measurements of maximal bite force were taken by using a force transducer positioned over the lower right first molar region and the highest record was taken into account. The root mean square value was considered for analysis. Intraclass correlation coefficients (ICCs), paired t test, and the Bland-Altman method comprised the statistical analyses. The level of significance was set at 0.05. Results ICC records for right and left masseter and anterior temporalis muscles at T0 (first sEMG record) and T7 (second sEMG record) intervals were significantly different (p<0.05). The results showed satisfactory to excellent reproducibility of RMS values at rest, MVBF and 30% MVBF, as well as for MVBF in kgf. Conclusion The results showed reliable reproducibility for the sEMG signal recording in masseter and anterior temporalis muscles from the protocols presented and under the three conditions investigated.

Is the Frequency in Somatosensory Electrical Stimulation the Key Parameter in Modulating the Corticospinal Excitability of Healthy Volunteers and Stroke Patients with Spasticity?

Somatosensory electrical stimulation (SES) has been proposed as an approach to treat patients with sensory-motor impairment such as spasticity. However, there is still no consensus regarding which would be the adequate SES parameters to treat those deficits. Therefore, the aim of this study was to evaluate the effects of applying SES over the forearm muscles at four different frequencies of stimulation (3, 30, 150, and 300 Hz) and in two intervals of time (5' and 30') by means of transcranial magnetic stimulation and Hoffmann's reflex (H-reflex) in healthy volunteers (Experiments I and II). A group of stroke patients (Experiment III) was also preliminary evaluated to ascertain SES effects at a low frequency (3 Hz) applied for 30' over the forearm spastic flexors muscles by measuring the wrist joint passive torque. Motor evoked potentials and the H-reflex were collected from different forearm and hand muscles immediately before and after SES and up to 5' (Experiment I) and 10' (Experiments I and II) later. None of the investigated frequencies of SES was able to operate as a key in switching modulatory effects in the central nervous system of healthy volunteers and stroke patients with spasticity.

Perspective-taking in blindness: electrophysiological evidence of altered action representations.

It is well established that the mental simulation of actions involves visual and/or somatomotor representations of those imagined actions. To investigate whether the total absence of vision affects the brain activity associated with the retrieval of motor representations, we recorded the readiness potential (RP), a marker of motor preparation preceding the execution, as well as the motor imagery of the right middle-finger extension in the first-person (1P; imagining oneself performing the movement) and in the third-person (3P; imagining the experimenter performing the movement) modes in 19 sighted and 10 congenitally blind subjects. Our main result was found for the single RP slope values at the Cz channel (likely corresponding to the supplementary motor area). No difference in RP slope was found between 1P and 3P in the sighted group, suggesting that similar motor preparation networks are recruited to simulate our own and other people's actions in spite of explicit instructions to perform the task in 1P or 3P. Conversely, reduced RP slopes in 3P compared with 1P found in the blind group indicated that they might have used an alternative, nonmotor strategy to perform the task in 3P. Moreover, movement imagery ability, assessed both by means of mental chronometry and a modified version of the Movement Imagery Questionnaire-Revised, indicated that blind and sighted individuals had similar motor imagery performance. Taken together, these results suggest that complete visual loss early in life modifies the brain networks that associate with others' action representations.

Influência da distância intereletrodos e da cadência de movimento no domínio da frequência do sinal de EMG de superfície / Influence of the inter-electrodes distance and cadence of movement in the surface EMG signal frequency domain

A eletromiografia de superfície (sEMG), apesar de amplamente utilizada em investigações biomecânicas, ainda apresenta inúmeros questionamentos sobre a influência das distâncias intereletrodos (DIE) na morfologia do sinal, principalmente em contrações isotônicas. Logo, muitos dos trabalhos desenvolvidos ainda se limitam ao âmbito do laboratório de pesquisa, onde é possível estabelecer maior controle nos protocolos de registro e análise, o que não é comumente observado na prática clínico-desportiva. Dessa forma, o objetivo do estudo foi examinar os efeitos de dois protocolos de colocação de eletrodos e a realização de contrações isotônicas no domínio da frequência do sinal de sEMG. Quinze sujeitos do sexo masculino (idade: 22,8 ± 3,5 anos), todos destros, realizaram contrações dinâmicas do bíceps braquial direito com carga estimada em 20 por cento da contração voluntária máxima em três diferentes cadências (30, 45, 60bpm). Os sinais de sEMG foram registrados por meio de dois canais, cujas DIEs foram de 4,2 e 13cm, respectivamente. A avaliação dos sinais de sEMG foi baseada na frequência mediana do espectro de potencial do sinal, calculado via transformada rápida de Fourier. A DIE e a cadência foram definidas como fatores (ANOVA two-way; α = 0,05). Não foram observadas diferenças estatísticas e qualquer interação entre ambos os fatores nas três cadências (P > 0,05). Sugere-se que, independentemente da distância utilizada entre os eletrodos, uma investigação no domínio da frequência do sinal de sEMG em tarefas dinâmicas seja evitada, mesmo a partir de DIEs reduzidas, como é sugerido pela literatura, dado que variações no torque e no comprimento muscular podem corromper o sinal e, portanto, sua interpretação.

Surface electromyography (SEMG), despite being widely used in biomechanical investigations, still presents massive questioning about the influence of the distance of the inter-electrodes (DIE) in the signal morphology, especially in isotonic contractions. Thus, much of the research developed is still limited to the laboratory, where it is possible to establish better control over the recording and analysis protocols, which is not commonly observed in the clinical-sportive practice. Therefore, the aim of this study was to examine the effects of two electrodes placement protocols and the performance of isotonic contractions in the SEMG sign frequency domain. Fifteen right-handed male subjects (aged 22.8 ± 3.5 years) performed dynamic contractions of the right brachial biceps with load estimated in 20 percent of the maximum voluntary contraction in three different cadences (30, 45 and 60 bpm). The SEMG signals were registered by two channels with DIEs of 4.2 and 13 cm, respectively. The SEMG signals assessment was based on the median frequency of the potential spectrum of the signal, calculated via fast Fourier transform. DIE and cadence were defined as factors (two-way ANOVA; α = 0.05). No statistical differences or any interaction between both factors were observed in the three cadences (P> 0.05). Regardless of the distance used between electrodes, an investigation in the SEMG signal frequency domain in dynamic tasks should be avoided, even from reduced DIEs, as suggested in the literature, since variations in the torque and muscular length may disrupt the signal and hence its interpretation.