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Smooth physical interaction with our environment, such as when working with tools, requires adaptability to unpredictable perturbations that can be achieved through impedance control of multi-joint limbs. Modulation of arm stiffness can be achieved either increasing co-contraction of antagonistic muscles or by increasing the gain of spinal reflex loops. According to the “automatic gain scaling” principle,...
The aim of this study is to validate the time delay estimators recently developed by our group. We test the estimators with the real data in both case isometric isotonic and isometric anisotonic contraction in order to take into account the stationarity and the non-stationarity of the data. The results indicate that these estimators have coherent behaviors with the law of Henneman up to 60% Maximal...
The objective of this pilot study was to examine alterations in motor unit (MU) control properties, (i.e. MU recruitment and firing rate) after stroke utilizing a recently developed high-yield surface electromyogram (EMG) decomposition technique. Two stroke subjects participated in this study. A sensor array was used to record surface EMG signals from the first dorsal interosseous (FDI) muscle during...
A surface electromyogram model has been implemented with both electrical and mechanical outputs. The model has been populated with parameter values based on random distributions about experimentally observed averages. Motor unit firing rates and recruitment threshold have been defined independently for type I and type II muscle fibres. This has led to non-linear inputs to the sEMG model. The observed...
It is well known that there is a change in the spectrum of surface electromyogram (sEMG) with the onset of muscle fatigue. This change has largely been attributed to the change in muscle conduction velocity. In this paper, this theory has been investigated by studying a sEMG model developed earlier. The change of spectrum of the experimental results has been compared with simulated sEMG in response...
A differential, time-invariant, surface electromyogram (sEMG) model has been implemented. While it is based on existing EMG models, the novelty of this implementation is that it assigns more accurate distributions of variables to create realistic motor unit (MU) characteristics. Variables such as muscle fibre conduction velocity, jitter (the change in the interpulse interval between subsequent action...
The effects of control properties of the motor unit, firing rate and recruitment, of the cat's m. gastrocnemius on the EMG spectral frequencies were experimentally determined. The median frequency (MF) of single-M wave increased following the increment of recruitment level. The variations of firing rate influenced the MF insignificantly.
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