A trans mucosal neuromuscular electrical stimulation device (1) including a mouthpiece (3, 103) and electrodes (32a, 33a, 132a, 133a) associated with the mouthpiece (3, 103). The device (1) and/or mouthpiece (3, 103) incorporates electrical circuitry operatively connecting the electrodes (32a, 33a, 132a, 133a) to a power source and is configured to provide, in use, electrical stimulation to one or more palate and/or tongue muscles via the electrodes (32a, 33a, 132a, 133a) through the oral mucosa. The treatment regime, including the location of stimulation and the parameters used, is designed to increase resting muscle tone and/or muscle tone during sleep.