Body position influences the maximum inspiratory and expiratory mouth pressures of young healthy subjects.

Objective: The purpose of this study was to determine the effects of body position on respiratory muscle strength of young healthy subjects.

Methods: Sixty-three (50 female, mean age 19.7±1.5 years) healthy subjects participated in the study. Methods: Participants were measured in the sitting position, semi-upright sitting position, and in the supine position. The order of the three conditions was randomly determined. Methods: Maximal inspiratory and expiratory mouth pressures (PImax, PEmax) and lung function.

Results: A significant effect of body position was observed on PEmax values, controlling for gender. PImax in the sitting position (92.8±20.05 cm H2O) was significantly higher than in the supine (84.1±15.1 cm H2O; mean difference: 8.70, 95% CI [5.95, 12.45], p<0.001) and semi-upright sitting positions (84.4±17.5 cm H2O; mean difference: 8.43, 95% CI [5.78, 11.07], p<0.001). PEmax was also significantly higher in the sitting position (125.4±34.2 cm H2O) than in the supine (115.8±29.0 cm H2O; mean difference: 9.59, 95% CI [4.86, 14.32], p<0.001) and semi-upright sitting positions (120.2±33.9 cm H2O; mean difference: 5.21, 95% CI [0.87, 9.54], p=0.013).

Conclusions: Body position influences respiratory muscle strength of young healthy subjects. PImax and PEmax are higher in the sitting position than in the supine or semi-upright sitting positions.