Inspiratory muscle training with threshold or incentive spirometry: Which is the most effective?

Inspiratory muscular training (IMT) increases the respiratory muscle strength, however, there is no data demonstrating its superiority over the incentive spirometry (IS) in doing so. Values of muscle strength after IMT (Threshold IMT®) and by the IS (Voldyne®) in healthy females was compared. Subjects (n = 40) were randomly divided into control group (CG, n = 14), IS group (ISG, n = 13) and threshold group (TG, n = 13). PImax was measured before (pre-IMT), at 15 and 30 days of IMT. There was an increase in PImax of the TG at 15 days (p < 0.001) and 30 days of IMT (p < 0.001). The same occurred with the ISG, which increased the PImax at 15 days (p < 0.001) and 30 days of training (p < 0.001). After 30 days of IMT, the TG presented a PImax which was significantly higher than ISG and the CG (p = 0.045 and p < 0.001, respectively). It can be concluded that IMT by threshold was more effective in increasing muscle strength than the Voldyne.