Seleção de características para identificação de diferentes proporções de tipos de fibras musculares por meio da eletromiografia de superfície

Skeletal muscle consists of muscle fiber types that have different physiological and biochemical characteristics. Basically, the muscle fiber can be classified into type I and type II, presenting, among other features, contraction speed and sensitivity to fatigue different for each type of muscle fiber. These fibers coexist in the skeletal muscles and their relative proportions are modulated according to the muscle functionality and the stimulus that is submitted. To identify the different proportions of fiber types in the muscle composition, many studies use biopsy as standard procedure. As the surface electromyography (EMGs) allows to extract information about the recruitment of different motor units, this study is based on the assumption that it is possible to use the EMG to identify different proportions of fiber types in a muscle. The goal of this study was to identify the characteristics of the EMG signals which are able to distinguish, more precisely, different proportions of fiber types. Also was investigated the combination of characteristics using appropriate mathematical models. To achieve the proposed objective, simulated signals were developed with different proportions of motor units recruited and with different signal-to-noise ratios. Thirteen characteristics in function of time and the frequency were extracted from emulated signals. The results for each extracted feature of the signals were submitted to the clustering algorithm k-means to separate the different proportions of motor units recruited on the emulated signals. Mathematical techniques (confusion matrix and analysis of capability) were implemented to select the characteristics able to identify different proportions of muscle fiber types. As a result, the average frequency and median frequency were selected as able to distinguish, with more precision, the proportions of different muscle fiber types. Posteriorly, the features considered most able were analyzed in an associated way through principal component analysis. Were found two principal components of the signals emulated without noise (CP1 and CP2) and two principal components of the noisy signals (CP1 and CP2 ). The first principal components (CP1 and CP1 ) were identified as being able to distinguish different proportions of muscle fiber types. The selected characteristics (median frequency, mean frequency, CP1 and CP1 ) were used to analyze real EMGs signals, comparing sedentary people with physically active people who practice strength training (weight training). The results obtained with the different groups of volunteers show that the physically active people obtained higher values of mean frequency, median frequency and principal components compared with the sedentary people. Moreover, these values decreased with increasing power level for both groups, however, the decline was more accented for the group of physically active people. Based on these results, it is assumed that the volunteers of the physically active group have higher proportions of type II fibers than sedentary people. Finally, based on these results, we can conclude that the selected characteristics were able to distinguish different proportions of muscle fiber types, both for the emulated signals as to the real signals. These characteristics can be used in several studies, for example, to evaluate the progress of people with myopathy and neuromyopathy due to the physiotherapy, and also to analyze the development of athletes to improve their muscle capacity according to their sport. In both cases, the extraction of these characteristics from the surface electromyography signals provides a feedback to the physiotherapist and the coach physical, who can analyze the increase in the proportion of a given type of fiber, as desired in each case.

Intervenção mediacional e hábitos alimentares: um estudo de crianças com síndrome de Down

The inadequacy about eating habits have been established as a serious problem nowadays. It is a multifactorial and difficult to handle, given their different nuances and causes. A population particularly exposed to the bad eating habits arising harm are individuals with Down syndrome, both with regard to the aspects inherent to the individual's own condition, regarding eating misfits, making it the weight control a necessary measure for a proper development. Thus, this study aimed to develop and evaluate a proposal based nutrition education from the assumptions of mediated learning, with children three to four years with Down syndrome. The participants were five children, four girls and a boy. Also included his parents and / or guardians. The data collection procedure involved the use of eight playful workshops with children and nutritional evaluation of those five meetings with parents and three home visits with each participating family. We tried to build with these children and their families a nutritional education to contribute to their daily choices of eating. Using listening, observation and questionnaire, besides playful interventions, it was observed that the first meaning of the act of eating is built in the family and reinforced by their social life. Overall, our sample characteristics seem to agree with the literature. During the intervention, the children showed attention, but little understanding of the content. With mothers, the results were different, with reflections on the inadequate power both the type of food offered, and quantity and so this offer is performed, conducted along the interventions changes in your lifestyle, such as perception of influence they had on their children in the formation of their eating habits, as well as less frequent intake of soft drinks and sweets. Nutritional interventions and mediations conducted with the mothers is that they seem to be effective strategies to combat obesity. Face of what was discussed, we see the importance of implementing intervention measures in combating and preventing overweight or obese since childhood, particularly with children with Down syndrome. One should prevent childhood obesity with educational and informative measures from birth, with family and with each child, through the primary health care and schools.