2007 Volume 70 Issue 1 Pages 72-80
In order to clarify the role of stomatognathic function during physical activity, we investigated the occlusal contact and muscle activities of five healthy dentulous individuals during bench press of weights by simultaneously measuring dynamic occlusal contact area, occlusa force distribution, and electromyography. Measurement of muscle activity was conducted for the anterior temporalis, the masseter, and digastric muscles on the dominant-hand side. A custombuilt sensor sheet was used to measure the occlusal contact area and occlusal force distribution. These measurements were taken for each subject as he was instructed to clench as hard as possible and open his mouth as wide as possible. Mean maximum occlusal contact force, occlusal contact area and the mean envelope curve of the maximum electromyography signal were calculated as reference values (100%). After determining the heaviest weight that he could bench press (maximum weight), each subject was instructed to bench press different weights less than the maximum as quickly as possible after a light signal (switch). During each bench press, ratios for the temporalis, masseter, and digastric muscle activities were calculated relative to the maximum activity.
We found that during bench press of approximately 95% the maximum weight, the expression of masseter muscle action potential exceeded 20% in all subjects. During bench press of less than 50% the maximum weight, the expression of temporalis and masseter muscle action potential was less than 10% in all subjects. We found that the muscle activity of the digastric muscle was comparable to that at maximum mouth opening. However, the occlusal contact as- sociated with maximum clenching was not seen in any of the subjects at any time during the study. The above findings suggest that during bench press of weight close to an individual's maximum capacity, the masticatory muscles coordinate to stabilize the mandible irrespective of occlusal contact.
