Abstract

Respiratory/inspiratory muscle training (RMT/IMT) has been proposed to improve the endurance performance of athletes in normoxia. In recent years, due to the increased use of hypoxic training method among athletes, the RMT applicability has also been tested as a method to minimize adverse effects since hyperventilation may cause respiratory muscle fatigue during prolonged exercise in hypoxia. We performed a review in order to determine factors potentially affecting the change in endurance performance in hypoxia after RMT in healthy subjects. A comprehensive search was done in the electronic databases MEDLINE and Google Scholar including keywords: “RMT/IMT,” and/or “endurance performance,” and/or “altitude” and/or “hypoxia.” Seven appropriate studies were found until April 2018. Analysis of the studies showed that two RMT methods were used in the protocols: respiratory muscle endurance (RME) (isocapnic hyperpnea: commonly 10–30′, 3–5 d/week) in three of the seven studies, and respiratory muscle strength (RMS) (Powerbreathe device: commonly 2 × 30 reps at 50% MIP (maximal inspiratory pressure), 5–7 d/week) in the remaining four studies. The duration of the protocols ranged from 4 to 8 weeks, and it was found in synthesis that during exercise in hypoxia, RMT promoted (1) reduced respiratory muscle fatigue, (2) delayed respiratory muscle metaboreflex activation, (3) better maintenance of SaO2 and blood flow to locomotor muscles. In general, no increases of maximal oxygen uptake (VO2max) were described. Ventilatory function improvements (maximal inspiratory pressure) achieved by using RMT fostered the capacity to adapt to hypoxia and minimized the impact of respiratory stress during the acclimatization stage in comparison with placebo/sham. In conclusion, RMT was found to elicit general positive effects mainly on respiratory efficiency and breathing patterns, lower dyspneic perceptions and improved physical performance in conditions of hypoxia. Thus, this method is recommended to be used as a pre-exposure tool for strengthening respiratory muscles and minimizing the adverse effects caused by hypoxia related hyperventilation. Future studies will assess these effects in elite athletes.

Highlights

  • Studies on the influence of specific respiratory muscle training (RMT) upon exercise in healthy adults in normoxia provide convincing evidence supporting the ergogenic effect on endurance performance (Markov et al, 2001; Stuessi et al, 2001; Volianitis et al, 2001; Romer et al, 2002a,b; Johnson et al, 2007)

  • During recent years it has been postulated that RMT could be able to reduce premature fatigue of respiratory muscles subjected to maximal demand in moderately/highly trained athletes as well as climbers exposed to hypoxia (Verges et al, 2010)

  • Study findings regarding the effects of RMT upon endurance performance in hypoxia remain scarce in comparison with the large number of investigations performed in normoxic conditions (Illi et al, 2012)

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Summary

Introduction

Studies on the influence of specific respiratory muscle training (RMT) upon exercise in healthy adults in normoxia provide convincing evidence supporting the ergogenic effect on endurance performance (Markov et al, 2001; Stuessi et al, 2001; Volianitis et al, 2001; Romer et al, 2002a,b; Johnson et al, 2007). Preliminary results indicate favorable RMT effects in normoxia on endurance and strength of respiratory muscles, and delayed onset of the respiratory metaboreflex (Dempsey et al, 2006), lactate accumulation (Verges et al, 2010), hipoxemia (Downey et al, 2007), and sympathetic activation (McConnell and Romer, 2004) These positive responses would be beneficial as an enhancer procedure of the respiratory muscles prior to exposure or competition in hypoxia or at altitude (Downey et al, 2007; Esposito et al, 2010)

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