Maximal static inspiratory (PImax) mouth pressure is a simple measurement of respiratory muscle strength. A study by Tomalak et al. (A-10) examined correlations among the variables with PImax

(measured sitting), forced expiratory volume (FEV), peak expiratory flow (PEF), and maximal inspiratory flow (PIF) in 144 boys and 152 girls ages 7–14. The researchers found PImax was correlated with FEV, PEF, and PIF in boys (p ¼ :001; p ¼ :0055, and p ¼ :002; respectively) and for girls the correlations were also significant (p < :001; p < :001, and p < :001, respectively).