Estudo do sinal eletromiográfico em exercícios isométricos em diferentes velocidades de contração

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Parâmetros do sinal eletromiográfico aplicados ao estudo da fadiga muscular localizada: caracterização do processo; análise de reprodutibilidade e multivariada

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Efeito do treinamento de força e potência na curva força-tempo isométrica e na ativação muscular em idosos com doença de Parkinson

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Velocidade de movimento no desempenho muscular em mulheres jovens e idosas treinadas

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

O controle de preensão em pinça em adultos jovens: efeito da posição do punho

The human hand is the focus of inumerous research studies. Human individuals are capable of performing manual tasks beyond the ability of any other animal. Such large motor ability is due in part to contact surface of the pulp thumb in opposition to the other fingers. Evidences in the literature show that the position of the upper limb influences the ability of hand strength and control. Specifically, the position of the wrist has great influence on the production of pinch strength. The main objective of this study was to investigate the influence of wrist position on the pinch grip with the thumb in opposition to the index finger. Participants of the present study were 21 undergraduate students, 10 men and 11 women. Participants performed a pinch grip task in three wrist positions - maximum flexion, maximum extension and neutral - on two force conditions - 20% and 40% of maximum voluntary contraction (MVC). MVC was measured in two attempts in each of the three positions of the wrist for a period of three seconds, and the trial of the best result was used as the parameter for task performance. In each trial participants maintained the force production at position for 10 seconds. All participants performed each test condition four times, and the first was used as a familiarization trial and discarded from further analysis. In all trials visual feedback online was provided. Results of both group gender showed variability was similar for force production. Men were stronger than women, but this difference was not significant and both produced on the average more strength in the neutral wrist position than in flexion or extension. In the extended position participants were significantly less variable than in the flexion and neutral positions. We obtained a significant positive correlation between weight and pinch force...(Complete abstracts click electronic access below)

Efeito agudo de diferentes intensidades de exercícios com pesos sobre o volume e a contração voluntária máxima isométrica, em idosas treinadas

The prescription of strength training intensity (ST) by maximum repetition (RM) is characterized by a decrease in the number of repetitions in multiple series. Some studies have shown that reductions in the intensity of exercise can optimize the volume of training with similar acute neuromuscular behaviors. The objective of the study was to investigate the acute effect of two different ST intensities on the training volume, maximum voluntary contraction (MVC) and rate of force development (RFD) in elderly women. The study included eight trained women (66.7 ± 6.7 years; 7.6 ± 17.8 kg; 159 cm; 29.33 ± 5.80 kg/m²). They underwent to three experimental conditions: two different intensities of ST (100% and 80% of 15-RM) on a chair for Leg Extension and a control condition. In the condition to 100% of 15 RM, all participants performed three sets to the concentric muscle fatigue, whereas in the condition to 80% involved the use of two sets of 15 repetitions and only the third to the concentric muscle fatigue. The order of experimental conditions was randomized. The MVC and RFD were determined on the basis of the isometric forcetime curve analysis which was obtained by a force transducer fixed on the unit Bonnet Chair, in the pre and after four and ten minutes for each experimental conditions. The total volume was calculated by multiplying the number of repetitions in three sets by the load in kg. Descriptive statistical analysis procedures were employed (mean ± standard deviation) in addition to two-way ANOVA. The level of significance was set at p <0.05. It was neither main effect of moment or condition, nor condition x moment interaction for MVC and RFD. For the total volume, no significant difference was noted between the conditions (100 and 80% of 15-RM). For sustainability of ...(Complete abstract click electronic access below)

The effects of a water-based exercise program on strength and functionality of older adults

Objective: To analyze the effects of a water-based exercise program on peak torque (PT) and rate of torque development (RTD) during maximal voluntary ballistic isometric contractions of the lower limb muscles and the performance of a number of functional tests in the elderly. Method: Thirty-seven elderly were randomly assigned to water-based training (3 d/wk for 12 wk) or a control group. Extensor and flexor PT and RTD of the ankle, knee, and hip joints and functional tests were evaluated before and after training. Results: PT increased after training for the hip flexors (18%) and extensors (40%) and the plantar-flexor (42%) muscles in the water-based group. RTD increased after training for the hip-extensor (10%), knee-extensor (11%), and ankle plantar-flexor (27%) muscles in the water-based group. Functional tests also improved after training in the water-based group (p < .05). Conclusion: The water-based program improved PT and RTD and functional performance in the elderly.

Effects of leucine supplementation and resistance exercise on dexamethasone-induced muscle atrophy and insulin resistance in rats

Objective: We aimed to evaluate the effects of resistance exercise (RE) and leucine (LEU) supplementation on dexamethasone (DEXA)-induced muscle atrophy and insulin resistance. Methods: Male Wistar rats were randomly divided into DEXA(DEX), DEXA + RE (DEX-RE), DEXA + LEU (DEX-LEU), and DEXA + RE + LEU (DEX-RE-LEU) groups. Each group received DEXA 5 mg . kg(-1) . d(-1) for 7 d from drinking water and were pair-fed to the DEX group; LEU-supplemented groups received 0.135 g . kg(-1) . d(-1) through gavage for 7 d; the RE protocol was based on three sessions of squat-type exercise composed by three sets of 10 repetitions at 70% of maximal voluntary strength capacity. Results: The plantaris mass was significantly greater in both trained groups compared with the non-trained groups. Muscle cross-sectional area and fiber areas did not differ between groups. Both trained groups displayed significant increases in the number of intermediated fibers (IIa/IIx), a decreased number of fast-twitch fibers (IIb), an increased ratio of the proteins phospho(Ser2448)/ total mammalian target of rapamycin and phospho(Thr389)/total 70-kDa ribosomal protein S6 kinase. and a decreased ratio of phospho(Ser253)/total Forkhead box protein-3a. Plasma glucose was significantly increased in the DEX-LEU group compared with the DEX group and RE significantly decreased hyperglycemia. The DEX-LEU group displayed decreased glucose transporter-4 translocation compared with the DEX group and RE restored this response. LEU supplementation worsened insulin sensitivity and did not attenuate muscle wasting in rats treated with DEXA. Conversely, RE modulated glucose homeostasis and fiber type transition in the plantaris muscle. Conclusion: Resistance exercise but not LEU supplementation promoted fiber type transition and improved glucose homeostasis in DEXA-treated rats. (C) 2012 Elsevier Inc. All rights reserved.

Atividade muscular da mastigação na anquilose temporomandibular

Purpose: due to the presence of major masticatory dysfunction in patients with temporomandibular joint (TMJ) ankylosis, this study analyzed mouth opening and EMG activity of masticatory muscles in order to detect changes in these parameters after surgical release of mandible ankylosis. Method: in 7 patients with temporomandibular ankylosis, between 7 and 30 years (median = 9 years), the distance was measured as interincisal maximum active (DIMA) and we recorded the electromyographic activity (EMG) of masseter and temporal muscles during voluntary isometric contraction (VIC) and chewing, comparing the data before and after surgery using the Wilcoxon test. Results: higher values were observed for DIMA after surgery (p=0.0277), the asymmetry index showed no difference between the two evaluated periods for both studied muscles, the values of the EMG during VIC decreased after surgery for the right (p=0.0179) and left (p=0.0179) masseter but not for the temporal muscle, there were no changes in EMG values for the studied muscles during mastication. Conclusion: the surgical release of TMJ ankylosis resulted in an increase of mouth opening and decreased amplitude of action potentials generated during maximum isometric voluntary contraction of the masseter muscle on both sides, this did not change the asymmetry index of the masseter and temporal as well as the electromyographic activity of the temporal muscle bilaterally during isometric contraction and masseter and temporal muscles during mastication.

Quantitative motor unit action potential analysis in 2 paraspinal neck muscles in adult Royal Dutch Sport horses

BACKGROUND: Reference values for quantitative electromyography (QEMG) in neck muscles of Royal Dutch Sport horses are lacking. OBJECTIVE: Determine normative data on quantitative motor unit action potential (QMUP) analysis of serratus ventralis cervicis (SV) and brachiocephalicus (BC) muscle. ANIMALS: Seven adult normal horses (mean age 9.5 standard deviation [SD] +/- 2.3 years, mean height 1.64 SD +/- 4.5 cm, and mean rectal temperature 37.6 SD +/- 0.3 degrees C). METHODS: An observational study on QMUP analysis in 6 segments of each muscle was performed with commercial electromyography equipment. Measurements were made according to formerly published methods. Natural logarithm transformed data were tested with ANOVA and posthoc testing according to Bonferroni. RESULTS: Mean duration, amplitude, phases, turns, area, and size index (SI) did not differ significantly among the 6 segments in each muscle. Mean amplitude, number of phases, and SI were significantly (P < .002) higher in SV than BC, 520 versus 448 muV, 3.0 versus 2.8 muV, and 0.48 versus 0.30 muV, respectively. In SV 95% confidence intervals (CI) for amplitude, duration, number of phases, turns, polyphasia area, and SI were 488-551 muV, 4.3-4.6 ms, 2.9-3.0, 2.4-2.6, 7-12%, 382-448, and 0.26-0.70, respectively; in BC this was 412-483 muV, 4.3-4.7 ms, 2.7-2.8, 2.4-2.6, 4-7%, 393-469, and 0.27-0.34, respectively. Maximal voluntary activity expressed by turns/second did not differ significantly between SV and BC with a 95% CI of 132-173 and 137-198, respectively. CONCLUSIONS AND CLINICAL IMPORTANCE: The establishment of normative data makes objective QEMG of paraspinal muscles in horses suspected of cervical neurogenic disorders possible. Differences between muscles should be taken into account.

ANKLE IMPEDANCE AND ANKLE ANGLES DURING STEP TURN AND STRAIGHT WALK: IMPLICATIONS FOR THE DESIGN OF A STEERABLE ANKLE-FOOT PROSTHETIC ROBOT

During locomotion, turning is a common and recurring event which is largely neglected in the current state-of-the-art ankle-foot prostheses, forcing amputees to use different steering mechanisms for turning, compared to non-amputees. A better understanding of the complexities surrounding lower limb prostheses will lead to increased health and well-being of amputees. The aim of this research is to develop a steerable ankle-foot prosthesis that mimics the human ankle mechanical properties. Experiments were developed to estimate the mechanical impedance of the ankle and the ankles angles during straight walk and step turn. Next, this information was used in the design of a prototype, powered steerable ankle-foot prosthesis with two controllable degrees of freedom. One of the possible approaches in design of the prosthetic robots is to use the human joints’ parameters, especially their impedance. A series of experiments were conducted to estimate the stochastic mechanical impedance of the human ankle when muscles were fully relaxed and co-contracting antagonistically. A rehabilitation robot for the ankle, Anklebot, was employed to provide torque perturbations to the ankle. The experiments were performed in two different configurations, one with relaxed muscles, and one with 10% of maximum voluntary contraction (MVC). Surface electromyography (sEMG) was used to monitor muscle activation levels and these sEMG signals were displayed to subjects who attempted to maintain them constant. Time histories of ankle torques and angles in the lateral/medial (LM) directions, inversion-eversion (IE), and dorsiflexionplantarflexion (DP) were recorded. Linear time-invariant transfer functions between the measured torques and angles were estimated providing an estimate of ankle mechanical impedance. High coherence was observed over a frequency range up to 30 Hz. The main effect of muscle activation was to increase the magnitude of ankle mechanical impedance in all degrees of freedom of the ankle. Another experiment compared the three-dimensional angles of the ankle during step turn and straight walking. These angles were measured to be used for developing the control strategy of the ankle-foot prosthesis. An infrared camera system was used to track the trajectories and angles of the foot and leg. The combined phases of heel strike and loading response, mid stance, and terminal stance and pre-swing were determined and used to measure the average angles at each combined phase. The Range of motion (ROM) in IE increased during turning while ML rotation decreased and DP changed the least. During the turning step, ankle displacement in DP started with similar angles to straight walk and progressively showed less plantarflexion. In IE, the ankle showed increased inversion leaning the body toward the inside of the turn. ML rotation initiated with an increased medial rotation during the step turn relative to the straight walk transitioning to increased lateral rotation at the toe off. A prototype ankle-foot prosthesis capable of controlling both DP and IE using a cable driven mechanism was developed and assessed as part of a feasibility study. The design is capable of reproducing the angles required for straight walk and step turn; generates 712N of lifting force in plantarflexion, and shows passive stiffness comparable to a nonload bearing ankle impedance. To evaluate the performance of the ankle-foot prosthesis, a circular treadmill was developed to mimic human gait during steering. Preliminary results show that the device can appropriately simulate human gait with loading and unloading the ankle joint during the gait in circular paths.

Pelvic floor stimulation: what are the good vibrations?

OBJECTIVE: The aim of this study was to determine if two different whole body vibration, sinusoidal vibration (SV) and stochastic resonance vibration (SRV), using various intensities lead to a reactive activation of pelvic floor muscles. STUDY DESIGN: We compared the pelvic floor muscle response of a healthy control group with that of a post partum group with weakened pelvic floor contraction. Activation effects of stochastic resonance vibration and sinusoidal vibration with six increasing vibration intensities were investigated using pelvic floor EMG and compared to activity during rest and maximum voluntary contraction. RESULTS: Both whole body vibration systems were able to activate pelvic floor muscles significantly depending on vibration intensity. Generally, the SRV achieved a significantly higher activation than maximum voluntary contraction, especially in women post partum and using a frequency of 6-12 Hz. CONCLUSION: SRV, compared to SV, leads to higher pelvic floor muscle activation in subjects with weakened pelvic floor muscles and achieves higher pelvic floor activation than maximum voluntary contraction alone. Neurourol. Urodynam. 28:405-410, 2009. (c) 2009 Wiley-Liss, Inc.

Effects of intensive arm training with the rehabilitation robot ARMin II in chronic stroke patients: four single-cases

BACKGROUND: Robot-assisted therapy offers a promising approach to neurorehabilitation, particularly for severely to moderately impaired stroke patients. The objective of this study was to investigate the effects of intensive arm training on motor performance in four chronic stroke patients using the robot ARMin II. METHODS: ARMin II is an exoskeleton robot with six degrees of freedom (DOF) moving shoulder, elbow and wrist joints. Four volunteers with chronic (>or= 12 months post-stroke) left side hemi-paresis and different levels of motor severity were enrolled in the study. They received robot-assisted therapy over a period of eight weeks, three to four therapy sessions per week, each session of one hour.Patients 1 and 4 had four one-hour training sessions per week and patients 2 and 3 had three one-hour training sessions per week. Primary outcome variable was the Fugl-Meyer Score of the upper extremity Assessment (FMA), secondary outcomes were the Wolf Motor Function Test (WMFT), the Catherine Bergego Scale (CBS), the Maximal Voluntary Torques (MVTs) and a questionnaire about ADL-tasks, progress, changes, motivation etc. RESULTS: Three out of four patients showed significant improvements (p < 0.05) in the main outcome. The improvements in the FMA scores were aligned with the objective results of MVTs. Most improvements were maintained or even increased from discharge to the six-month follow-up. CONCLUSION: Data clearly indicate that intensive arm therapy with the robot ARMin II can significantly improve motor function of the paretic arm in some stroke patients, even those in a chronic state. The findings of the study provide a basis for a subsequent controlled randomized clinical trial.

Electromyographic activity of back muscles during stochastic whole body vibration

OBJECTIVES: Stochastic resonance whole body vibrations (SR-WBV) may reduce and prevent musculoskeletal problems (MSP). The aim of this study was to evaluate how activities of the lumbar erector spinae (ES) and of the ascending and descending trapezius (TA, TD) change in upright standing position during SR-WBV. METHODS: Nineteen female subjects completed 12 series of 10 seconds of SR-WBV at six different frequencies (2, 4, 6, 8, 10, 12Hz) and two types of "noise"-applications. An assessment at rest had been executed beforehand. Muscle activities were measured with EMG and normalized to the maximum voluntary contraction (MVC%). For statistical testing a three-factorial analysis of variation (ANOVA) was applied. RESULTS: The maximum activity of the respective muscles was 14.5 MVC% for the ES, 4.6 MVC% for the TA (12Hz with "noise" both), and 7.4 MVC% for the TD (10Hz without "noise"). Furthermore, all muscles varied significantly at 6Hz and above (p⋜0.047) compared to the situation at rest. No significant differences were found at SR-WBV with or without "noise". CONCLUSIONS: In general, muscle activity during SR-WBV is reasonably low and comparable to core strength stability exercises, sensorimotor training and "abdominal hollowing" in water. SR-WBV may be a therapeutic option for the relief of MSP.

Response of myocardial oxygenation to breathing manoeuvres and adenosine infusion

AIMS: Testing for inducible myocardial ischaemia is one of the most important diagnostic procedures and has a strong impact on clinical decision-making. Current standard protocols are typically limited by the required infusion of vasodilatory substances. Recent data indicate that changes of myocardial oxygenation induced by hyperventilation and breath-holds can be monitored by oxygenation-sensitive (OS) cardiovascular magnetic resonance (CMR) and may be useful for assessing coronary vascular function. As tests using breathing manoeuvres may be safer, easier, and more comfortable than vasodilator stress agent infusion, we compared its impact on myocardial oxygenation with that of a standard adenosine infusion protocol. METHODS AND RESULTS: In 20 healthy volunteers, we assessed changes of myocardial oxygenation using OS-CMR at 3 T during adenosine infusion (140 µg/kg/min, i.v.) and during voluntary breathing manoeuvres: a maximal breath-hold following normal breathing and a maximal breath-hold following 60 s of hyperventilation. The study was successfully completed in 19 subjects. There was a significantly stronger myocardial response for hyperventilation (decrease of -10.6 ± 7.8%) and the following breath-hold (increase of 14.8 ± 6.6%) than adenosine (3.9 ± 6.5%), whereas a simple maximal voluntary breath-hold yielded a similar signal intensity increase (3.1 ± 3.9%). Subjective side effects occurred significantly more often with adenosine, especially in females. CONCLUSIONS: Hyperventilation combined with a subsequent long breath-hold and hyperventilation alone both have a greater impact on myocardial oxygenation changes than an intravenous administration of a standard dose of adenosine, as assessed by OS-CMR. Breathing manoeuvres may be more efficient, safer, and more comfortable than adenosine for the assessment of the coronary vasomotor response.