Liliam Fernandes de Oliveira

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EMG-driven models can be used to estimate muscle force in biomechanical systems. Collected and processed EMG readings are used as the input of a dynamic system, which is integrated numerically. This approach requires the definition of a reasonably large set of parameters. Some of these vary widely among subjects, and slight inaccuracies in such parameters(More)
This paper uses a EMG-driven Hill-type muscle model to estimate individual muscle forces of the triceps surae in isometric plantar flexion contractions. A uniform group of 20 young physical-active adult males was instructed to follow a specific contraction protocol with low (20%MVC) and medium-high (60%MVC) contractions, separated by relaxing intervals. The(More)
This work aims at testing the influence of peripheral and central fatigue, after maximal oxygen uptake test (Test1) and prolonged (Test2) cycle ergometer exercises, respectively, on sway density curve (SDC) parameters of postural control. Sixteen healthy male subjects were submitted to stabilometric tests, before and after the exercises. The Test1 was(More)
A methodology is proposed for estimating Achilles tendon tangent modulus in vivo, to account for its large deformations and non-linear behavior. True stress is found dividing the axial force by the tendon true cross-sectional area (CSA), whose shrinking caused by axial tension is estimated with Poisson׳s coefficient. The true strain is calculated as the(More)
This study used ultrasound biomicroscopy (UBM) to quantify the pennation angle (PA) and muscle thickness (MT) of rat skeletal muscle and evaluated the reliability and reproducibility of the method by statistical analysis, determining the coefficient of variation (CV), intraclass correlation coefficient (ICC) and typical error of measurement. A UBM system(More)
BACKGROUND This paper describes the "EMG Driven Force Estimator (EMGD-FE)", a Matlab® graphical user interface (GUI) application that estimates skeletal muscle forces from electromyography (EMG) signals. Muscle forces are obtained by numerically integrating a system of ordinary differential equations (ODEs) that simulates Hill-type muscle dynamics and that(More)
This study aims at investigating the effect of removing the negative values of Choi-Wiliams distribution (CWD) related to the electromyogram (EMG) for visualization and instantaneous median frequency (IMF) estimation. Beyond the EMG signals from triceps surae and biceps brachialis, the CWD was applied in a simulated sinusoidal signal as like in stationary(More)
The occurrence of fatigue in triceps surae (TS) muscles during sustained plantar flexion contraction is investigated by means of the RMS electromyogram (EMG) and the instantaneous median frequency (IMF) of the short time Fourier transform (STFT). Six male subjects realized a 40% maximal plantar flexion isometric voluntary contraction until fatigue in two(More)
Age-related changes in postural control during quiet standing likely result from underlying pathological conditions or from the low specificity of classical stabilometric parameters, which are vulnerable to base of support configurations and anthropometric differences. This study focuses on the identification of changes in postural control with natural(More)
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