Ventilatory And Pulmonary Responses At Various Treadmill Speed With Different Breathing Methods

PURPOSE: To examine ventilatory and pulmonary responses at various walking and running speed with different breathing methods. METHODS: Ten healthy adult men (25.3 ± 2.3 yrs, 172.8 ± 7.3 cm, 76.6 ± 3.9 kg) participated in three testing sessions. At each session, they walked or ran on a treadmill at an ordered speed of 5, 7, 9, 10, 11, 12 and 13 kph, for 2 min at each speed, while using one of three different breathing methods; nose-only breathing (NB), mouth-only breathing (MB), and combined nose and mouth breathing (CB). During exercise, heart rate (HR), respiratory frequency (Rf), tidal volume (VT), minute ventilation (VE), VE per volume of CO2 (VE/VCO2), oxygen uptake (VO2), end-tidal CO2 pressure (PeCO2), inspiratory time (Ti), expiratory time (Te), and total respiratory cycle time (Ttot) were measured. RESULTS: VE was lower in NB (98.1 ± 12.3 l/min) compared to MB (114.9 ± 13.5) and CB (113.5 ± 13.9) at 13 kph (p < 0.001). RF was lower at 12 and 13 kph in NB (37.2 ± 5.5 and 39.2 ± 4.7 times, respectively) compared to MB (43.0 ± 7.3 and 47.6 ± 8.4) and CB (44.0 ± 7.4 and 49.1 ± 8.3) (p < 0.05). VT was not different in any treadmill speed. Ti was higher at 11, 12, and 13 kph in NB (1.0 ± 0.2, 0.9 ± 0.2, and 0.8 ± 0.2 sec, respectively) compared to MB (0.7 ± 0.1, 0.7 ± 0.1, and 0.7 ± 0.1) and CB (0.8 ± 0.2, 0.7 ± 0.1, and 0.6 ± 0.1) (p < 0.05), while VT/Ti was lower at 11, 12, and 13 kph in NB (2.7 ± 0.4, 3.0 ± 0.5, and 3.2 ± 0.6 l/sec, respectively) compared to MB (3.1 ± 0.4, 3.5 ± 0.4, and 3.9 ± 0.4) and CB (3.2 ± 0.4, 3.5 ± 0.5, and 3.9 ± 0.5) (p < 0.05). VE/VCO2 was lower at 11, 12, and 13 kph in NB (26.2 ± 3.6, 25.9 ± 3.8, and 25.8 ± 3.5, respectively) compared to MB (29.8 ± 4.0, 30.1 ± 4.0, and 30.8 ± 3.4) and CB (28.7 ± 2.3, 28.9 ± 3.2, and 29.8 ± 2.8) (p < 0.05). PeCO2 was only higher at 12 kph in NB (34 ± 5 mmHg) compared to MB (29 ± 4) (p < 0.05), while a marginal tendency of higher values in NB than MB and CB was noticed, but not significant at 12 and 13 kph (p > 0.05). No differences were noticed at any speed and breathing methods in HR, VO2, Te and Ttot. CONCLUSIONS: When only NB was allowed, VT/Ti and VE/VCO2 were lower than MB and CB from the speed of 11 kph, while Ti increases from the same speed. But VT and VE were still maintained until 11 kph. As RF decreases in NB from 12 kph, the maintenance of VE and PeCO2 was disturbed.