The obstructing factor favoring sleep apnea, from a biomechanical point of view, is pharyngeal relaxation and hyoid and tongue withdrawal. Certainly the component related to the force of gravity plays an important role in this phenomenon but it is not the only cause, because the lingual chain is the strongest chain in our body and the tongue also plays a very important role in swallowing as well as being the major articulator . Specifically, during the oral phase of swallowing, i.e. when the front part of the tongue pushes upwards against the palate, leveraging it so that the back part of the tongue can lift, the hyoid bone lifts, which in turn lifts the rib cage and the organs inside it.
This action increases tension in the tracheal fascia, rib cage organs, as well as on the subhyoid muscles. Once the lingual push is finished, the structures return to their rest position.
At the level of tissue and compartmental correlations, the lingual chain, and its pertinent band, are anchored at the base of the skull, include the hyoid (to which the tongue is anchored) and continues into the neck as the pre-tracheal band. From this level it expands downward and internally into the thorax including vessels, heart and lungs. Past the diaphragm muscle which marks the passage between the thorax and abdomen it envelops the irony and viscera of the abdominal cavity ending at the level of the pelvis in the pelvic floor. Inside the fascia, due to a process called tissue tensegrity, i.e. the ability to adapt and respond to traction and compression forces of biological tissues, a mutual tension is created between the bottom-up forces and the top-down forces of the fascial chain itself which will cause this contrast to be triggered which will allow, once swallowing is completed, the structures to be brought back downwards by visceral traction. Of these two force vectors, the stronger one is certainly the one coming from below and this is why when the posterior portion of the tongue is lifted, the tension at the level of the fascia increases in a bottom-up direction up to a reverse level in which the tension from below is predominant and it is no longer possible to keep the hyoid and tongue elevated, thus returning to the rest position.