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The use of electromyography (EMG) signals to characterize muscle fatigue has been widely accepted. Initial work on characterizing muscle fatigue during isometric contractions demonstrated that its frequency decreases while its amplitude increases with the onset of fatigue. More recent work concentrated on developing techniques to characterize dynamic contractions for use

The use of electromyography (EMG) signals to characterize muscle fatigue has been widely accepted. Initial work on characterizing muscle fatigue during isometric contractions demonstrated that its frequency decreases while its amplitude increases with the onset of fatigue. More recent work concentrated on developing techniques to characterize dynamic contractions for use in clinical and training applications. Studies demonstrated that as fatigue progresses, the EMG signal undergoes a shift in frequency, and different physiological mechanisms on the possible cause of the shift were considered. Time-frequency processing, using the Wigner distribution or spectrogram, is one of the techniques used to estimate the instantaneous mean frequency and instantaneous median frequency of the EMG signal using a variety of techniques. However, these time-frequency methods suffer either from cross-term interference when processing signals with multiple components or time-frequency resolution due to the use of windowing. This study proposes the use of the matching pursuit decomposition (MPD) with a Gaussian dictionary to process EMG signals produced during both isometric and dynamic contractions. In particular, the MPD obtains unique time-frequency features that represent the EMG signal time-frequency dependence without suffering from cross-terms or loss in time-frequency resolution. As the MPD does not depend on an analysis window like the spectrogram, it is more robust in applying the timefrequency features to identify the spectral time-variation of the EGM signal.
ContributorsAustin, Hiroko (Author) / Papandreou-Suppappola, Antonia (Thesis advisor) / Kovvali, Narayan (Committee member) / Muthuswamy, Jitendran (Committee member) / Arizona State University (Publisher)
Created2012
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Description
Piloerection (known as goosebumps) is mediated by activation of alpha-adrenergic receptors within the sympathetic branch of the autonomic nervous system. The study of piloerection is important in multiple fields, from emotion studies to nervous system pathology. This makes piloerection particularly relevant to emotions research. Despite wide-ranging applications, current methods for

Piloerection (known as goosebumps) is mediated by activation of alpha-adrenergic receptors within the sympathetic branch of the autonomic nervous system. The study of piloerection is important in multiple fields, from emotion studies to nervous system pathology. This makes piloerection particularly relevant to emotions research. Despite wide-ranging applications, current methods for measuring piloerection are laborious and qualitative. The goal of this study is to build a wearable piloerection sensor through the use of straight-line lasers and photoresistors. The study analyzed methods of detecting and measuring goosebumps, and applied the method of laser scattering as a detection method. This device was designed and tested against a population of seven Arizona State University students. Goosebumps were elicited through conditions of cold, and video clips meant to elicit emotions of awe and sadness. Piloerection was then quantified through two controls of self-identification and camera recording, as well as the new detection method. These were then compared together, and it was found that subjective methods of determining goosebumps did not correlate well with objective measurements, but that the two objective measurements correlated well with one another. This shows that the technique of laser scattering can be used to detect goosebumps and further developments on this new detection method will be made. Moreover, the presence of uncorrelated subjective measurements further shows the need for an objective measurement of piloerection, while also bringing into question other factors that may be confused with the feeling of piloerection, such as chills or shivers. This study further reaffirmed previous studies showing a positive correlation between intense emotions.
ContributorsHemesath, Angela (Author) / Muthuswamy, Jitendran (Thesis director) / Shiota, Michelle (Lani) (Committee member) / Harrington Bioengineering Program (Contributor, Contributor) / School of Molecular Sciences (Contributor) / Barrett, The Honors College (Contributor)
Created2019-05