Abstract
The aim of this study was to analyse the influence of inspiratory muscle training (IMT) on ventilatory efficiency, in normoxia and hypoxia, and to investigate the relationship between ventilatory efficiency and cycling performance. Sixteen sport students (23.05 ± 4.7 years; 175.11 ± 7.1 cm; 67.0 ± 19.4 kg; 46.4 ± 8.7 ml·kg−1·min−1) were randomly assigned to an inspiratory muscle training group (IMTG) and a control group (CG). The IMTG performed two training sessions/day [30 inspiratory breaths, 50% peak inspiratory pressure (Pimax), 5 days/week, 6-weeks]. Before and after the training period subjects carried out an incremental exercise test to exhaustion with gas analysis, lung function testing, and a cycling time trial test in hypoxia and normoxia. Simulated hypoxia (FiO2 = 16.45%), significantly altered the ventilatory efficiency response in all subjects (p < 0.05). Pimax increased significantly in the IMTG whereas no changes occurred in the CG (time × group, p < 0.05). Within group analyses showed that the IMTG improved ventilatory efficiency (VE/VCO2 slope; EqCO2VT2) in hypoxia (p < 0.05) and cycling time trial performance [WTTmax (W); WTTmean (W); PTF(W)] (p < 0.05) in hypoxia and normoxia. Significant correlations were not found in hypoxia nor normoxia found between ventilatory efficiency parameters (VE/VCO2 slope; LEqCO2; EqCO2VT2) and time trial performance. On the contrary the oxygen uptake efficiency slope (OUES) was highly correlated with cycling time trial performance (r = 0.89; r = 0.82; p < 0.001) under both conditions. Even though no interaction effect was found, the within group analysis may suggest that IMT reduces the negative effects of hypoxia on ventilatory efficiency. In addition, the data suggest that OUES plays an important role in submaximal cycling performance.
Highlights
Ventilatory efficiency can be defined as the relationship between carbon dioxide production (VCO2) and ventilation (VE)
No gender effect was identified with regard to the parameters of interest (VE/VCO2 slope, LEqCO2, EqCO2VT2, oxygen uptake efficiency slope (OUES))
Baseline values did not differ between groups (VE/VCO2 slope, LEqCO2, EqCO2VT2, OUES, Pimax, peak power output (PPO), TTW mean)
Summary
Ventilatory efficiency can be defined as the relationship between carbon dioxide production (VCO2) and ventilation (VE). CO2during the incremental test (LEqCO2; Sun et al, 2002), (c) the equivalent of CO2 at the second ventilatory threshold (EqCO2VT2; Sun et al, 2002), and (d) the oxygen uptake efficiency slope (OUES; Baba et al, 1999a). The OUES represents the rate of increase of VO2 in response to a given VE during incremental exercise, indicating how effectively oxygen is extracted and taken into the body (Baba et al, 1996). Brown et al (2013) did not find a relationship between maximum oxygen uptake (VO2max) and OUES in juvenile cyclists. We did not find a relationship between VO2max, peak power output (PPO), and VE/VCO2 slope in world-class cyclists (Salazar-Martínez et al, 2016). A significant correlation was found between OUES and VO2max in young active women (Mourot et al, 2004)
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