The invention relates to an apparatus for monitoring muscle activity related to bruxism, said apparatus comprising:—an electrode assembly for providing signals indicative of said muscle activity, means for processing said signals in order to detect said bruxism, and means for providing a feedback signal in response to detecting said bruxism wherein said electrode assembly comprises three electrodes in a fixed spatial relationship one to another, each electrode having a contact area for electrical connection with the skin which is spaced from the contact area of each other electrode in the electrode assembly by at least 2 mm, the maximum distance from an edge of one electrode contact area to the furthest edge of the furthest away of the other electrode contact areas being not greater than 60 mm.
