Changes in Power Spectral Analysis of EEG-Alpha Bands During a Sustained,Voluntary Contraction to Fatigue :

In this study, we investigated the power spectral changes of EEG-alpha bands and the spectral analysis of EMG during sustained, voluntary contraction to fatigue. We discuss our findings with respect to the voluntary contraction to fatigue in terms of the amplitude values obtained from the power spectral analysis of EEG-alpha bands and the spectral changes on EMG. We confirmed that the EMG frequencies were slowed during the last half of sustained, voluntary contraction. Our results confirmed that the alpha power during the first half of the sustained fatiguing contraction was more decreased than that in the control, but not significantly so. The present experiments showed that the alpha 1 and alpha 2 powers were decreased at CZ, C4, P3, and P4 during the last half of the sustained contraction to fatigue, with the frontal location being increased. We also noted that alpha power was more and more decreased as the voluntary contraction continued. It is conceivable that the increase of demand on attention, concentration or motor performance causes stronger alpha attenuation before and during the execution of a task. Desynchronization of upper alpha components may thus reflect more task-specific processes, while that of low alpha components may be related to the level of expectancy and attention. Therefore, it is considered that an excessive decrease in alpha band power in the respective underlying area is most likely related to the greater effort necessary to maintain the voluntary contraction as instructed. Accordingly, from our results, it may be concluded that muscular fatigue-induced changes are reflected by the decrease in alpha power accompanying sustained, voluntary contraction to fatigue.