Control of masseter muscle tension during sleep.

This study evaluated whether muscle tension could be controlled during sleep. Twelve volunteers were assigned to an experimental condition or to a no treatment control group. Experimental subjects were instructed to reduce the tension in their masseter (jaw) muscle when signalled with an auditory tone. These subjects demonstrated cue-controlled tension reductions during awake training sessions. Although both groups evidenced muscle tension increases in response to the tones presented during sleep, experimental subjects produced significantly smaller increases in response to tone stimuli than did control subjects. More importantly, experimental subjects sustained lower tonic levels of muscle tension throughout the sleep sessions than did control subjects. Sleep was moderately disrupted for subjects in both groups. However, experimental subjects evidenced the greatest tension reductions during those responses in which they shifted to a lighter stage of sleep rather than fully awakening. These data suggest that muscle tension can be moderated during sleep.