The aim of this study was to examine the characteristics in duration and amplitude of the submental muscle activities during dry and wet swallowing. We examined the middle suprahyoid muscle activities in 32 normal adult women during three swallowing conditions, that is, dry as well as 5 mL & 10 mL water swallowings, using a surface EMG. From the results, there were significant differences in duration: the longest in dry swallowing and shortest in 5 mL water swallowing. However, the mean amplitude per msec increased as the duration decreased. This may imply motor equivalence in swallowing stating that duration and amplitude are complementary in order to achieve a given swallowing goal.