We analysed whether type of movement (brisk vs slow) and active muscle force are encoded in the time course of mu-rhythm desynchronization during self-paced finger movements. Ten subjects performed 100 brisk and slow extensions of the right index finger. The time course of mu-rhythm desynchronization in the contralateral sensorimotor area before movement was identical for both types of movements. Brisk movements accompanied by a stronger extensor muscle contraction were preceded by larger desynchronization. The onset of mu-rhythm recovery was related to the duration of the extensor EMG burst in both types of movement. The results suggest that both amplitude and duration of the extensor muscle contraction are encoded in the time course of murhythm desynchronization.