The effects of respiratory muscle training on respiratory mechanics and energy cost

• A unique protocol was used to determine the work and energy cost of breathing.
• Testing was done before & after 4 weeks resistance respiratory muscle training (RRMT).
• 8 subjects were tested dry and submersed at 1 ATA, 2.7 ATA, & 4.6 ATA in a chamber.
• Breathing resistance decreased after RRMT, despite of no change in nitric oxide.
• RRMT increased max respiratory pressures and efficiency, decreasing V˙O2 and V˙E.

Resistance respiratory muscle training (RRMT) increases respiratory muscle strength and can increase swimming endurance time by as much as 85%. The purpose of this study was to examine potential mechanisms by which RRMT improves exercise endurance. Eight healthy adult male scuba divers underwent experiments in a hyperbaric chamber at sea level (1 atmosphere absolute (ATA)), 2.7 ATA and 4.6 ATA, both dry and fully submersed. Subjects rested, exercised, and rested while mimicking their own exercise breathing (ISEV). Airway resistance (Raw), exhaled nitric oxide output (V˙NO), and respiratory duty cycle (TI/TTot) were determined before and after four weeks of RRMT. RRMT decreased TI/TTot (−10% at rest at 1 ATA), V˙O2 (−17% at 2.7 ATA during submersed exercise), V˙E (−6% at 2.7 ATA during submersed exercise), and Raw (−34% inspiratory at 4.6 ATA submersed, −38% expiratory at 2.7 ATA dry), independent of changes in V˙NO. Most importantly, respiratory muscle efficiency increased (+83% at 2.7 ATA submersed).