Investigating the modulation of brain activity associated with handgrip force and fatigue.

<bold>Objective: </bold>To investigate the effect of force level and fatigue on brain activity during handgrip tasks.<bold>Methods: </bold>Electroencephalography (EEG) signals were recorded from eleven healthy male subjects when they performed 25%, 50% and 75% maximal voluntary contraction (MVC), and were in fatigue state. EEG powers in different handgrip tasks were analyzed in the frequency domain and time domain respectively.<bold>Results: </bold>The EEG power at 25%MVC was significantly lower than that at 75%MVC in gamma band (p< 0.05) for electrode C3, C4, Cz, Pz and Fz. EEG power at 25%MVC was also significantly lower than that at 75%MVC in beta band (p< 0.05) for electrode C3. However, the handgrip force level and fatigue did not affect the EEG powers for the other frequencies and electrodes (p> 0.05).<bold>Conclusion: </bold>The results suggest that handgrip force level may modulate the brain activity in certain frequency bands and cortical regions. EEG power is a useful tool to characterize the motor state. [ABSTRACT FROM AUTHOR]