Effect of respiratory muscle endurance training on respiratory sensations, respiratory control and exercise performance: A 15-year experience

Respiratory muscle endurance training (RMET) can improve respiratory muscle endurance as well as cycling and swimming endurance. Whether these improvements are caused by reduced perception of adverse respiratory sensations and/or a change in ventilatory output remains unclear. We re-analysed nine (five randomized controlled) RMET studies performed in our laboratory. One hundred and thirty-five healthy subjects completed either RMET [i.e. an average of 12.4 ± 4.9 h (median 10; range 10–25) of normocapnic hyperpnoea at 60–85% of maximal voluntary ventilation achieved during 27 ± 11 sessions (median 20; range 20–50) of 29 ± 4 min (median 30; range 15–30) duration over 6.5 ± 4.2 weeks (median 4; range 4–15), n = 90] or no RMET (CON, n = 45). Before and after RMET/CON, respiratory (≈70% MVV) and cycling (70–85% maximal power) endurance were tested. RMET increased both respiratory and cycling endurance, reduced perception of breathlessness and respiratory exertion during volitional and exercise-induced hyperpnoea, and slightly increased ventilation at identical workloads. Decreased respiratory sensations did not correlate with improved cycling endurance. Changes in ventilation correlated with changes in cycling endurance in both groups. We conclude that reduced adverse respiratory sensations after RMET are unlikely to cause the improvements in cycling endurance, that the level of ventilation seems to affect cycling endurance and that additional factors must contribute to the improvements in cycling endurance after RMET.