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

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 (R-aw), exhaled nitric oxide output (V) over dot(NO), and respiratory duty cycle (T-l/T-TOt) were determined before and after four weeks of RRMT. RRMT decreased T-l/T-TOt (-10% at rest at 1 ATA), (V) over doto(2), (-17% at 2.7 ATA during submersed exercise), (V) over dot(E) (-6% at 2.7 ATA during submersed exercise), and R-aw (-34% inspiratory at 4.6 ATA submersed, 38% expiratory at 2.7 ATA dry), independent of changes in (V) over dot(NO). Most importantly, respiratory muscle efficiency increased (+83% at 2.7 ATA submersed). (C) 2014 Elsevier B.V. All rights reserved.