Variability in electromyographic surface recordings of the human masseter muscle.

Serial registrations of integrated unilateral surface masseter EMG were performed in eight healthy subjects in the rest position, during controlled gentle biting and during maximal clenching at five different sessions in order to analyse the variability. The recording conditions were standardised. The EMG activity for the group did not differ significantly between the sessions at any level but individual variations were great in the rest position both within and between days. Good consistency was found at controlled force levels. Temporally stable measurements of masseter activity which permit quantitative comparisons thus seem possible.