表面筋電図スペクトル成分と筋活動状態との関連について(1部神経・筋・制御)

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Frequency spectrum of surface EMG is analyzed by applying the autoregressive (AR) model. The method used here is able to extract components of a signal. In order to decompose into components, poles of the AR model of EMG are obtained numerically. Poles which are on the real axis correspond to first-order components, and poles on the complex plane correspond to second-order components. A second-order component has one peak in its power spectrum. From the pole value, resonance frequency and damping time are obtained as indices of the second-order component. The former is peak frequency of the spectrum, and the latter expresses sharpness of the peak. Another index is relative power of the component which is the index of the contribution of the component to total power. In this study, focusing on second-order components, three components are extracted from EMG signal. These are here named first component, second component and third component as the peak frequency increases. Changes in these indices are investigated at different levels of tension, in fatigue from isometric contractions, in fatigue from tracking tasks, in ballistic contractions, and in difference between distance runner and sprint runner. There is a little changes at different levels of tension. Resonance frequencies increase as tension increases. Other indices show little change. Both isometric contractions, and tracking tasks show nearly the same effects of fatigue on indices: 1) resonance frequencies decrease, 2) damping time of the first component increases, and 3) relative power of the first component increases. In ballistic contractions the most remarkable change is shown in relative power. At the first stage of ballistic contraction the powers of second and third components, which are high-frequency components, are high compared to that of the first component. This means that high frequency is dominant in EMG at the beginning of ballistic contraction. Differences between distance and sprint runner are shown in damping time and relative power of first component, which are greater for distance runner than for sprint runner. This implies that a low-frequency component is dominant in EMG of a distant runner and has a regular wave pattern. Referring to electrophysiological findings in motor units of muscle, causes of these changes are discussed.
1988-06-15

表面筋電図スペクトル成分と筋活動状態との関連について(1部神経・筋・制御)

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表面筋電図スペクトル成分と筋活動状態との関連について(1部 神経・筋・制御)

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表面筋電図スペクトル成分と筋活動状態との関連について(1部神経・筋・制御)