Background: The sensation of respiratory effort may increase as expiratory muscles become fatigued during expiratory loading. A study was performed to determine whether expiratory muscle training (EMT) affects the sensation of respiratory effort during exercise in healthy subjects.
Methods: Six subjects performed EMT for 15 minutes twice daily for four weeks using a pressure threshold device; another six subjects served as a control group. The expiratory threshold was set at 30% of the individual's maximum expiratory mouth pressure (PEmax). The sensation of respiratory effort was evaluated during a progressive exercise test using the Borg scale.
Results: After EMT PEmax increased by 25% in the training group. The Borg score increased as exercise grade increased before and after EMT, but scores for each grade were lower after EMT. Minute ventilation during exercise decreased after EMT, as did the breathing frequency during exercise, while the expiratory time increased. Although there was no difference in the relationship between Borg score and minute ventilation before or after EMT, the curve shifted to a lower Borg score after EMT. There were no changes in PEmax, Borg score, minute ventilation, or breathing pattern after the four week study period in the control group.
Conclusion: These findings suggest that EMT increases expiratory muscle strength and reduces the sensation of respiratory effort during exercise, presumably by reducing minute ventilation.