Respiratory muscle function during a six-week period of normocapnic hyperpnoea training

Abstract

Respiratory muscle endurance training (normocapnic hyperpnoea, RMET) improves maximal volitional ventilation (MVV) and respiratory muscle endurance while volitionally-assessed respiratory muscle strength remains unchanged (prior-to-post comparison). What remains unclear is how respiratory muscle function changes/adapts during a defined period of RMET in highly-trained subjects.This study assessed respiratory muscle function during a six-week period of RMET in 13 highly-trained, healthy subjects.Weekly-assessed twitch mouth pressure (prior/post 2.20±0.41kPa vs. 2.43±0.61kPa; p=0.14); twitch transdiaphragmatic pressure (prior/post 3.04±0.58kPa vs. 3.13±0.48kPa; p=0.58) and maximal inspiratory pressure (prior/post 12.6±3.6kPa vs. 13.9±3.8kPa; p=0.06) did not increase. MVV (prior/post 175±18l/min vs. 207±30l/min; p=0.001), sniff nasal pressure (prior/post 11.8±2.8kPa vs. 14.0±2.9kPa; p=0.003) and maximal expiratory pressure (prior/post 16.9±5.8kPa vs. 20.9±4.9kPa; p=0.006) each increased.In conclusion, non-volitionally assessed diaphragmatic strength does not increase during six weeks of RMET in highly-trained subjects, while expiratory muscle strength and MVV rose. Future studies should clarify if these findings apply when assessed during respiratory muscle strength rather than endurance training.