['Chair-sitting may allow for more readily activated scalene, sternocleidomastoid, and parasternal intercostal muscles, and may raise and enlarge the upper thoracic cage, thereby allowing the thoracic cage to be more easily compressed.', 'To evaluate the effect of  chair-sitting during exercise training on respiratory muscle function in mechanically ventilated patients.', "We randomized 16 patients to a control group and 18 patients to a chair-sitting group. The patients in the chair-sitting group were transferred by 2 intensive care unit nurses  from bed to armchair and rested for at least 30 min, based on the individual patient's tolerance. We measured heart rate, blood pressure, S(pO(2)), and respiratory rate. In the treatment group, before transferring the patient from bed to armchair, and 30 min after the completion  of chair-sitting we measured respiratory muscle function variables, including the ratio of respiratory rate (f) to tidal volume (V(T)), S(pO(2)), maximum inspiratory pressure (P(Imax)) and maximum expiratory pressure (P(Emax)). In the control patients  we took those same measurements while the patient was in semirecumbent position, before and after treatments, for at least 6 days or until the patient was discharged from the intensive care unit or died.", 'The 2 groups did not significantly differ in age, sex, or clinical outcomes.  Respiratory rate, V(T), f/V(T), S(pO(2)), P(Imax), and P(Emax) were not significantly better in the chair-sitting group. The study period significantly improved respiratory rate, V(T), P(Imax), and P(Emax) (all  P < .001), but not f/V(T).'] Does chair-sitting exercise intervention improve respiratory muscle function in mechanically ventilated intensive care unit patients?