Efeitos do dano muscular sobre indicadores neuromusculares e de aptidão aeróbia

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

Relação entre a fadiga muscular e a mudança da técnica de nado durante um exercício exaustivo no nado crawl

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

Discriminant analysis of neuromuscular variables in chronic low back pain

Background: Investigation and discrimination of neuromuscular variables related to the complex aetiology of low back pain could contribute to clarifying the factors associated with symptoms. Objective: Analysing the discriminative power of neuromuscular variables in low back pain. Methods: This study compared muscle endurance, proprioception and isometric trunk assessments between women with low back pain (LBP, n=14) and a control group (CG, n=14). Multivariate analysis of variance and discriminant analysis of the data were performed. Results: The muscle endurance time (s) was shorter in the LBP group than in the CG (p=0.004) with values of 85.81 (37.79) and 134.25 (43.88), respectively. The peak torque (Nm/kg) for trunk extension was 2.48 (0.69) in the LBP group and 3.56 (0.88) in the GG (p=0.001); for trunk flexion, the mean torque was 1.49 (0.40) in the LBP group and 1.85 (0.39) in the CG (p=0.023). The repositioning error (degrees) before the endurance test was 2.66 (1.36) in the LBP group and 2.41 (1.46) in the CG (p=0.664), and after the endurance test, it was 2.95 (1.94) in the LBP group and 2.00 (1.16) in the CG (p=0.06). Furthermore, the variables showed discrimination between the groups (p=0.007), with 78.6% of the individuals with low back pain correctly classified in the LBP group. In turn, variables related to muscle activation showed no difference in discrimination between the groups (p=0.369). Conclusion: Based on these findings, the clinical management of low back pain should consist of both resistance and strength training, particularly in the extensor muscles.

Verbal and visual stimulation effects on rectus femoris and biceps femoris muscles during isometric and concentric

Background: Coactivation may be both desirable (injury prevention) or undesirable (strength measurement). In this context, different styles of muscle strength stimulus have being investigated. In this study we evaluated the effects of verbal and visual stimulation on rectus femoris and biceps femoris muscles contraction during isometric and concentric. Methods: We investigated 13 men (age =23.1 ± 3.8 years old; body mass =75.6 ± 9.1 kg; height =1.8 ± 0.07 m). We used the isokinetic dynamometer BIODEX device and an electromyographic (EMG) system. We evaluated the maximum isometric and isokinetic knee extension and flexion at 60°/s. The following conditions were evaluated: without visual nor verbal command (control); verbal command; visual command and; verbal and visual command. In relation to the concentric contraction, the volunteers performed five reciprocal and continuous contractions at 60°/s. With respect to isometric contractions it was made three contractions of five seconds for flexion and extension in a period of one minute. Results: We found that the peak torque during isometric flexion was higher in the subjects in the VVC condition (p > 0.05). In relation to muscle coactivation, the subjects presented higher values at the control condition (p > 0.05). Conclusion: We suggest that this type of stimulus is effective for the lower limbs.

Postactivation Potentiation Biases Maximal Isometric Strength Assessment

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Efeito protetor após sessões de exercício excêntrico: comparação entre membros superiores e inferiores

The objective of the present study was to compare in which part (lower limb or upper limb) the repeated bout effect has the greatest magnitude. Twelve males individuals with no recent (6 months) experience with resisted training participated in this study. The subjects were randomly divided into two groups (legs and arms) and came to the laboratory 5 times. 1st) adaptation to the dynamometer. 2nd) to perform one bout of eccentric exercise (EE) and provide markers such as isometric peak torque (IPT), delayed onset muscle soreness (DOMS) (both collected before and after the bout) and concentration of the creatine kinase (CK) enzyme in the blood (only before the bout). 3rd) 48 after the first bout the same markers were collected again. After 14 days, the methodologies used in the 2nd and 3rd visits to the laboratory were repeated respectively to determine the repeated bout effect. A significant decrease of IPT and a significant increase of CK and DOMS were found immediately after and 48 hours after the first bout of EE for the arms group. The legs group showed a significant increase in CK (48 hours after the EE) and DOMS (immediately after the EE) resulting from the first bout. In the arms group, the second bout did not cause significant increase in CK or DOMS on any of the situations, however, it provoked a decrease in force production immediately after the EE. The legs group showed a significant increase of DOMS immediately after the second bout of EE, which caused no significant increase in CK. The only marker in which the repeated bout effect happened for both groups was CK. No significant difference was found between the protections for both groups. Taking into account the results, it’s been discussed whether there is a relation between the susceptibility to muscle damage and the repeated bout effect, and also...(Complete abstract click electronic access below)

Comparação dos parâmetros de força e propriocepção entre indivíduos com e sem instabilidade funcional de tornozelo

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

Comparação entre a recuperação da economia de corrida e força muscular medida por diferentes métodos após o dano muscular

The goal of the present study was to investigate possible differences towards strenght recovery measured by different methods and running economy (RE), after one session of downhill running (DR), in order to induce muscle damage (MD). Our hypothesis is that the strenght recovery measured by jumps is more alike RE markers, due to the measures' specificity. Ten male subjects, ages 18 to 30, apparently healthy, without any experience with strenght training at least 6 months before the tests took place in this study. After going to the lab twice (to familiarize themselves with the protocols, and determine their maximum oxygen consumption/running speeds), they went to the lab five times in the following week, in order to collect all the variables before, immediately after, and 24, 48, 72 and 96 hours in. The variables obtained were: stride frequency (SF), stride lenght (SL), oxygen volume (VO2), carbon dioxide volume (VCO2), ventilation (VE), lactate blood concentration ([Lac]), isometric peak torque (IPT), subjective pain perception (SPP), effort perception (EP), medial-portion circumference (CIR), knee movement extent (EXT), torque development rate (TDR), counter movement jump and squat jump height (HCM and HS), strenght development rate of both jumps (SDCM and SDS), and maximum soil strenght reaction (SRCM and SRS). Changes over time in all variables were verified by one way variancy analysis. Differences between the strenght measures were verified by two way variancy analysis. When significant effects were verified, Tuckey's post-hoc were applied. The significancy level taken on this study was p < 0,05. Of all indirect muscle damage markers, IPT, SPP and TDR were the only ones in which ocurred significant changes. We couldn't find the moments where this happened for TDR with the post-hoc used. On RE markers, VO2, [Lac] and VE suffered significant effects over time. About the jumps variables, only SDCM and HCM presented significant...

Influência do método de avaliação no diagnóstico da dor muscular de início tardio após corrida em declive

Several methods are used towards delayed onset muscle soreness appraisal. This study's goal was to investigate, amongst three commonly adopted methods, which one would be the most effective (the one that shows higher values) in the quantification of this phenomenon. 10 male subjects, of age 22.8 ± 3.1 years old, weight 80 ± 12.4 kg, height 174 ± 0.07 cm, without recent experience with strength training (lower limbs) and/or running took place in this study. All subjects carried out a muscle damage induction protocol, which consisted of 30 minute downhill running (-16% or -9.09º) at 80% speed compared to their maximum oxygen consumption. Muscle damage determinants such as isometric peak torque, knee joint range of motion and circumference of the medial portion of the thight were measured before, during, 24, 48, 72 and 96 hours after downhill running. The subjective pain perception was measured simultaneously with the other determinants through three different tests: sitting on and getting up of a chair; climbing and descending from a 45cm step; and self thigh palpation. After going through all subjective pain perception tests, the subjects filled out a visual analog scale with their perception of pain. Muscle damage changes over time were compared through variance analysis (ANOVA) one way for repeated measures. Subjective pain perception values obtained in all three different tests were compared through two way ANOVAs for repeated numbers. The significance level adopted in this study was z ≤ 0.05. The results showed that the step test was the on which better evaluated the delayed onset muscle soreness. No significant differences were found through the ADM and CIR recovery markers. Downhil running determined reduced of PTI (~22.4%). Significant links between pain were obtained for both subjective pain perception tests starting at 24 and 48 hours, where the highest registered average happened in the step test after 48h, with high...

Direct Observation of Tetragonal Distortion in Epitaxial Structures through Secondary Peak Split in a Synchrotron Radiation Renninger Scan

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Neural network based estimation of torque in induction motors for real-time applications

Induction motors are largely used in several industry sectors. The selection of an induction motor has still been inaccurate because in most of the cases the load behavior in its shaft is completely unknown. The proposal of this article is to use artificial neural networks for torque estimation with the purpose of best selecting the induction motors rather than conventional methods, which use classical identification techniques and mechanical load modeling. Since proposed approach estimates the torque behavior from the transient to the steady state, one of its main contributions is the potential to also be implemented in control schemes for real-time applications. Simulation results are also presented to validate the proposed approach.

Line-pack management for producing electric power on peak periods

The distribution of natural gas is carried out by means of long ducts and intermediate compression stations to compensate the pressure drops due to friction. The natural gas compressors are usually driven by an electric motor or a gas turbine system, offering possibilities for energy management, one of these consisting in generating energy for use in-plant or to commercialize as independent power producer. It can be done by matching the natural gas demand, at the minimum pressure allowed in the reception point, and the storage capacity of the feed duct with the maximum compressor capacity, for storing the natural gas at the maximum permitted pressure. This allows the gas turbine to drive an electric generator during the time in which the decreasing pressure in duct is above the minimum acceptable by the sink unit. In this paper, a line-pack management analysis is done for an existing compression station considering its actual demand curve for determining the economic feasibility of maintaining the gas turbine system driver generating electricity in a peak and off-peak tariff structure. The potential of cost reduction from the point of view of energy resources (natural gas and electric costs) is also analyzed. (C) 2010 Elsevier Ltd. All rights reserved.

Spacecraft's attitude prediction: solar radiation torque and the Earth's shadow

A semi-analytical approach is proposed to study the rotational motion of an artificial satellite, under the influence of torque due to the solar radiation pressure, and taking into account the influence of Earth's shadow. Using Andoyer variables the equations for the rotational motion are presented in extended Hamiltonian form. In order to get a solution for the state variables close to an actual motion, the considered model for the shadow function takes into account physical and geometric factors and three specific regions: shadow, penumbra and full light. A mapping for the shadow function is proposed and a semi-analytical process is applied. When the satellite is totally illuminated or it is inside the penumbra, a known analytical solution is used to compute the satellite's attitude. A numerical simulation shows, when the penumbra region is included, the attenuation of the rotational motion during the transition from the shadow to the illuminate region and vice versa. (c) 2005 Published by Elsevier Ltd on behalf of COSPAR.

Analytical attitude prediction of spin stabilized spacecrafts perturbed by magnetic residual torque

An analytical approach for spin-stabilized spacecraft attitude prediction is presented for the influence of the residual magnetic torques. Assuming an inclined dipole model for the Earth's magnetic field, an analytical averaging method is applied to obtain the mean residual torque every orbital period. The orbit mean anomaly is utilized to compute the average components of residual torque in the spacecraft body frame reference system. The theory is developed for time variations in the orbital elements, and non-circular orbits, giving rise to many curvature integrals. It is observed that the residual magnetic torque does not have component along the spin axis. The inclusion of this torque on the rotational motion differential equations of a spin stabilized spacecraft yields conditions to derive an analytical solution. The solution shows that residual torque does not affect the spin velocity magnitude, contributing only for the precession and the drift of the spin axis of the spacecraft. (c) 2005 COSPAR. Published by Elsevier Ltd. All rights reserved.

Attitude stability of artificial satellites subject to gravity gradient torque

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)