An apparatus for and method of improving muscle tone of a patient using chronic sub-tetanic electrical stimulation. For patients suffering from obstructive sleep apnea, for example, the muscles of the upper airway are provided the chronic stimulation to mitigate or prevent the adverse medical condition caused in part by excessively flaccid muscle tissue around and in the airway.A stimulation generator supplies pulses to the muscle to be treated through insulated leads which are coupled to electrodes directly in contact with the appropriate neuro-muscular tissue. The output of the stimulation generator is adjusted to a frequency of sufficiently low level as to prevent fused tetanic contraction of the stimulated muscle. The adjustment may be made manually by attending medical personnel or may be done automatically using electrodes to sense the tension of the stimulated muscle. In the automatic mode, the sensing system insures the stimulation frequency level is decreased below the threshold of muscle tetanus.Stimulation may be accomplished at a particular site or may be multiplexed to a number of sites. Chronic stimulation will enhance muscle tone to an individual degree and then will simply maintain the desired status.