Background: Effect of nasal breathing without and with nostril dilatation on sustainability of moderate exercise (75% VO2max) and selected respiratory variables were examined.
Experimental design: Nine healthy male subjects completed three randomly assigned exhaustive treadmill runnings under three breathing conditions: (i) oronasal breathing (CON), (ii) nasal breathing with external nasal dilator strip (NBENDS), and (iii) nasal breathing with fake nasal strip (NBFNS).
Results: Pre-exercise peak nasal inspiratory flow was increased with NBENDS but not with NBFNS. Pre-exercise nasal 12-sec maximum voluntary ventilation with NBENDS was greater than that with NBFNS while both were less than oronasal value. Exercise time to exhaustion in NBFNS trial, which was 23.6+/-6.7% less than the CON value, increased 31.9+/-12.3% under NBENDS condition. During exercise at exhaustion, although the difference in ventilation among all trials was not significant, lower breathing frequency in NBFNS and NBENDS exercises and higher end-tidal CO2 tension in NBFNS trial were found in comparison to CON values. Ratings of perceived magnitude of breathing effort (RPMBE) and exertion (RPE) at exhaustion were similar among all trials. However, RPMBE at exhaustion during NBFNS exercise was higher than that at the iso-time point during CON and NBENDS exercises. Similar result in RPE was found between NBFNS and CON exercises. After exercise, maximum inspiratory and expiratory pressures reduced. The reduction of each variable was similar among the three trials.
Conclusions: Nasal breathing reduces the sustainability of moderate exercise measured under oronasal breathing condition. Nostril dilatation increases the capacity to sustain moderate exercise under nasal breathing condition.