The objective of this experiment was to determine the relative contributions and patterns of activity of different muscles involved during the oral phase of swallowing. Electromyographic (EMG) signals were recorded from the orbicularis oris inferior, masseter, palatal elevator, anterior and posterior genioglossus, mylohyoid, anterior belly of the digastric, and vocalis muscles of 12 normal adult subjects. Each subject swallowed 15 mL of water, under normal and bite block conditions, 15 to 20 times. The integrated EMG signals for each subject's swallows were ensemble averaged. The results of the analyses showed that swallowing function varies from individual to individual in terms of the specific muscles used and how the various muscle activity patterns are coordinated. These results suggest that swallowing is a highly complex adaptive motor activity which probably relies more on higher-level control mechanisms than previously believed.
