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Inspiratory muscle training improves exercise capacity with thoracic load carriage
Ren-Jay Shei1,2, Robert F Chapman2, Allison H Gruber2
1Division of Pulmonary, Allergy, and Critical Care Medicine, Department of Medicine, University of Alabama at Birmingham, Birmingham, Alabama.
Physiological Reports
|February 10, 2018
Summary
Carrying weight during exercise significantly reduces endurance and causes diaphragm fatigue. Inspiratory muscle training improved endurance but did not reduce this specific muscle fatigue.
Area of Science:
- Exercise Physiology
- Respiratory Mechanics
- Sports Science
Background:
- Thoracic load carriage (LC) exercise is known to impair exercise performance compared to unloaded exercise.
- This impairment is partly attributed to compromised respiratory mechanics.
- Diaphragmatic fatigue is a potential contributing factor to reduced exercise capacity during LC.
Purpose of the Study:
- To investigate the effects of load carriage on exercise performance and diaphragmatic fatigue.
- To determine if inspiratory muscle training (IMT) can enhance exercise capacity and mitigate diaphragmatic fatigue during load carriage exercise.
- To compare the effects of true IMT versus placebo-IMT.
Main Methods:
- Twelve recreationally active males performed constant-load running to exhaustion (Tlim) under unloaded (UL) and load carriage (LC) conditions.
- Subjects underwent a 6-week intervention of either true IMT or placebo-IMT.
- Diaphragmatic fatigue was assessed via transdiaphragmatic pressure (Pdi,tw) changes measured by phrenic nerve stimulation before and after exercise.
Main Results:
- Load carriage significantly reduced Tlim by 42.9% compared to unloaded conditions.
- Diaphragmatic fatigue, indicated by a greater decrease in Pdi,tw, was significantly more pronounced during LC compared to UL.
- Six weeks of IMT significantly improved Tlim (+29.3%) compared to pretraining, but did not significantly alter the magnitude of diaphragmatic fatigue post-exercise.
Conclusions:
- Load carriage exercise significantly impairs endurance performance and induces greater diaphragmatic fatigue.
- Inspiratory muscle training effectively enhances exercise capacity during load carriage.
- IMT does not appear to mitigate the diaphragmatic fatigue experienced during prolonged, constant-load exercise with thoracic load carriage.
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