Open AccessInspiratory muscle training improves exercise capacity with thoracic load carriage
Author(s) -
Shei RenJay,
Chapman Robert F.,
Gruber Allison H.,
Mickleborough Timothy D.
Publication year - 2018
Publication title -
physiological reports
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.918
H-Index - 39
ISSN - 2051-817X
DOI - 10.14814/phy2.13558
Subject(s) - medicine , diaphragmatic breathing , placebo , ventilation (architecture) , backpack , cardiology , diaphragm (acoustics) , anesthesia , physical therapy , respiratory physiology , respiratory system , mechanical engineering , physics , alternative medicine , archaeology , pathology , acoustics , loudspeaker , engineering , history
Thoracic load carriage ( LC ) exercise impairs exercise performance compared to unloaded exercise, partially due to impaired respiratory mechanics. We investigated the effects of LC on exercise and diaphragmatic fatigue in a constant‐load exercise task; and whether inspiratory muscle training ( IMT ) improved exercise capacity and diaphragmatic fatigue with LC . Twelve recreationally active males completed three separate running trials to exhaustion ( T lim ) at a fixed speed eliciting 70% of their V ˙ O 2max . The first two trials were completed either unloaded ( UL ) or while carrying a 10 kg backpack ( LC ). Subjects then completed 6 weeks of either true IMT or placebo‐ IMT . Posttraining, subjects completed an additional LC trial identical to the pretraining LC trial. Exercise metabolic and ventilatory measures were recorded. Diaphragm fatigue was assessed as the difference between preexercise and postexercise twitch diaphragmatic pressure ( P di, tw ), assessed by bilateral stimulation of the phrenic nerve with esophageal balloon‐tipped catheters measuring intrathoracic pressures. T lim was significantly shorter ( P < 0.001) with LC compared with UL by 42.9 (29.1)% (1626.5 (866.7) sec and 2311.6 (1246.5) sec, respectively). The change in P di, tw from pre‐ to postexercise was significantly greater ( P = 0.001) in LC (−13.9 (5.3)%) compared with UL (3.8 (6.5)%). Six weeks of IMT significantly improved T lim compared to pretraining ( P = 0.029, %Δ +29.3 (15.7)% IMT , −8.8 (27.2)% Placebo), but did not alter the magnitude of diaphragmatic fatigue following a run to exhaustion ( P > 0.05). Minute ventilation and breathing mechanics were unchanged post‐ IMT ( P > 0.05). Six weeks of flow‐resistive IMT improved exercise capacity, but did not mitigate diaphragmatic fatigue following submaximal, constant‐load running to volitional exhaustion with LC .