Massage therapists are all about muscles. New research indicates that two powerful brain chemical systems work together to paralyze skeletal muscles during rapid eye movement (REM) sleep.

During REM sleep—the deep sleep where most recalled dreams occur—muscles that move the eyes and those involved in breathing continue to move, but most of the body’s other muscles are stopped, potentially to prevent injury.

The finding may help scientists better understand and treat sleep disorders, including narcolepsy, tooth grinding, and REM sleep behavior disorder.

“The study’s findings are relevant to anyone who has ever watched a sleeping pet twitch, gotten kicked by a bed partner, or has known someone with the sleep disorder narcolepsy,” said Dennis J. McGinty, PhD, a behavioral neuroscientist and sleep researcher at the University of California, Los Angeles, who was not involved in the study.

“By identifying the neurotransmitters and receptors involved in sleep-related paralysis, this study points us to possible molecular targets for developing treatments for sleep-related motor disorders, which can often be debilitating,” he said.

The research was published in The Journal of Neuroscience.