Evaluation of an inspiratory muscle trainer in healthy humans

The Powerbreathe (R) is an inspiratory muscle trainer promoted as improving inspiratory muscle strength (and consequently exercise performance) in ath letes and patients with respiratory disease. No published evidence supports its efficacy. We performed a prospective randomized controlled study in wh ich 12 normal subjects received either Powerbreathe (R) training or sham tr aining for a 6-week period. The primary outcome measure was diaphragm stren gth evaluated as twitch transdiaphragmatic pressure (Tw Pdi) but secondary outcome measures were provided by full respiratory muscle assessment and ca rdiopulmonary exercise testing. An advantage to training was observed when outcome was assessed by maximal static inspiratory mouth pressure (mean adv antage 14.5cm H2O, 95% CI 2.2-26.9cm H2O, P=0.025). However, no significant difference was observed between the groups in any other parameter. In part icular the Delta Tw Pdi was not different between groups (mean 'advantage' -0.7 cmH(2)O, 95% CI-70-+/-5.5 cmH(2)O, P=0.8). The continued sale and use of the Powerbreathe (R) device is not justified by our data. A sample size calculation showed that 234 subjects would need to be randomized to definit ively refute the hypothesis that Powerbreathe (R) improves Tw Pdi and we ar gue that such a study is required.