Effect of body posture on chewing behaviors in healthy volunteers

Abstract

Mastication is essential to the eating process, and forms an important part of feeding behavior. Many factors related to the food bolus, such as bolus texture and size, are known to influence mastication. The aim of the present study was to determine the effects of body posture on (1) chewing duration prior to the first swallow and (2) patterns of mastication-related EMG activity. We asked 10 healthy adults to chew 8 g of steamed rice with barium sulfate while we recorded masseter, suprahyoid, and infrahyoid muscle activity and simultaneously collected videofluorographic images. Participants chewed in either an upright or reclining position. Chewing duration, which was defined as the time from the start of mastication to the first swallow, was not different between the positions. However, the variability of chewing duration was larger in the upright vs. reclining position, and the chewing duration in the reclining position was distributed around 15 s. Masseter activity gradually decreased in a time dependent manner and was significantly larger at the early vs. late stage of mastication. Suprahyoid activity was significantly larger at the early vs. middle stage of mastication in the upright position only. Finally, masseter activity per second was negatively correlated with changes in chewing duration, i.e., the larger the increase in chewing duration in the reclining position, the more the decrease in masseter activity per second. These results suggest that position-dependent changes in chewing behaviors, as described by chewing duration and EMG activity, may vary among participants.

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