Objective: To determine the relationship between respiratory muscle strength and age, sex, height and weight.
Material and Method: Maximal inspiratory mouth pressure (MIP) and maximal expiratory mouth pressure (MEP) were
assessed in 249 subjects aged 30-70 years using a mouth pressure meter. MIP was performed 10 times at residual volume,
whereas MEP was performed 12 times at total lung capacity. Pearson’s correlation was used to assess the association
between respiratory muscle strength and characteristics data. Multiple linear regressions were used to establish the prediction
equation of respiratory muscle strength.
Results: MIP decreased at ages beyond 60 years (p<0.05) but age had no effect on MEP in both sexes. MIP was correlated with age, weight and height in males, and with age and weight only in females; whereas, MEP was not correlated with age, height and weight in either sex. Predicted MIP regression equations are MIPfemale = 77.57-0.59 age+0.62 weight (r2 = 0.164, p = 0.004), MIPmale = 124.39-0.91 age+0.63 weight (r2 = 0.175, p = 0.08).
Conclusion: Sex, age and weight factors should be considered for MIP measurement.

Keywords: Maximal inspiratory mouth pressure (MIP), Maximal expiratory mouth pressure (MEP), Age, Sex, Height, Weight