Sucking occurs in two pressure phases, positive and negative. The normal rate for nutritive sucking is one cycle per second. The positive pressure phase occurs when the tongue tip and the midblade of the tongue elevate to the hard palate, the jaw elevates, and the lips seal. The negative phase of the suck occurs when the tongue moves away from the hard palate, the jaw drops, the posterior cheeks contract, the soft palate elevates, and the lips remain sealed.
More muscular effort is required for the negative phase of the suck.
If oral motor problems exist, the coordination and efficiency of oral intake is adversely impacted, sometimes to the point that oral intake is not sufficient, and non-oral intake must be implemented. Often, even though the child has mild impairment, health crisis does not occur, weight gain is steady, but slow, and real problems do not emerge until time to transition to new food types and utensils. As more strength, variety and control of the lips, cheeks, jaw and tongue emerge, a greater variety of food textures and consistencies are tolerated, as described below. If an individual has lost skill due to illness or injury, the specific oral motor patterns present must be monitored so that the appropriate food textures and consistencies can be provided. As skills improve, diet progression can be systematically reinstated.