INSPIRATORY MUSCLE TRAINING AND ENDURANCE PERFORMANCE IN HYPOXIA
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2017-04
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Abstract
Ventilation is higher at any submaximal workload in hypoxia as compared to normoxia. Whether or not training the respiratory muscles helps to improve exercise performance in hypoxia is unclear. Purpose: To determine if improvements in ventilatory strength with chronic inspiratory muscle training (IMT) improves 20km cycling time trial (TT) performance in hypoxia (FIO2 = 16.1%). Methods: Thirteen highly-trained men were pair-matched based on pre-exercise values of maximal inspiratory pressure (MIP) and randomly placed into either a sham (n = 5, V̇O2max = 61.7 ± 2.0 ml∙kg-1∙min-1) or an IMT (n = 8, V̇O2max = 63.5 ± 3.4 ml∙kg-1∙min-1) group. Subjects completed 6 weeks of flow resistive IMT (80% of MIP) or a sham protocol (30% of MIP), with each session consisting of up to 6 sets of 6 MIP maneuvers performed to failure with descending rest intervals 3 times per week. Pre- and post-training, subjects performed tests of pulmonary function, lung volume, MIP, maximal expiratory pressure (MEP), lung diffusion capacity (DLCO), and a 20km cycling TT in hypoxia (FIO2 = 16.1%). Results: After 6 weeks of IMT or sham, the IMT group significantly improved MIP (127.6 ± 13.4 cmH2O vs 159.0 ± 15.3 cmH2O, p < 0.05), while MIP in the sham group remained unchanged. MEP, DLCO, lung volumes, and pulmonary function values remained unchanged in both groups post-training. 20km TT mean ventilation was significantly higher post-IMT (99.6 ± 5.5 l∙min-1 vs 110.4 ± 6.8 l∙min-1, p < 0.05) and unchanged in sham. 20km TT mean breathing frequency was also significantly increased post-IMT (41.4 ± 2.8 b∙min-1 vs 45.1 ± 2.9 b∙min-1, p < 0.05) and unchanged in sham. 20km TT mean V̇O2 was significantly increased post-IMT (3.41 ± 0.19 L∙min-1 vs 3.61 ± 0.21 L∙min-1) and unchanged in sham. In the IMT group, 20km TT performance time pre-training was 36.77 ± 1.40 (min) and post-training was 36.28 ± 1.24 (min) (-1.4 ± 1.9%, p = 0.06). 20km TT performance time was unchanged in the sham group. 20km TT heart rate and SpO2 were unchanged in both groups post-training. Conclusion: In a small cohort, IMT-induced improvements in respiratory muscle strength which resulted in greater ventilation and oxygen uptake during a 20km time trial in hypoxia. IMT should be explored as a useful strategy for improving the quality of cycle exercise training and/or endurance exercise performance at altitude.
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