The length-force relationship of the human genioglossus in patients with obstructive sleep apnea.

During sleep, patients with obstructive sleep apnea (OSA) have repetitive episodes of upper airway collapse, which are terminated by increased activity of upper airway dilator muscles. The repetitive activation of the genioglossus (GG) may result in muscle remodeling. We hypothesized that OSA patients have an altered length-force relationship, increased force generation and/or decreased force maintenance as compared with control subjects. The GG length-force relationship was determined in 12 patients with OSA and 12 normal control subjects. The optimum length of the GG (LO) was at a longer muscle length in OSA patients than in control subjects. At longer muscle lengths, OSA patients produced greater percentages of their maximum protrusion force than control subjects. Force maintenance was not significantly different between the two groups. We conclude that in OSA patients relative to normal controls, the length-force relationship of the GG is altered, specifically at longer muscle lengths. We speculate that the GG is remodeled in OSA patients and that this facilitates airway re-opening to terminate obstructive events.