Ventilatory Responses to Progressive Treadmill Speeds in Women: A Comparative Analysis of Nasal, Oral, and Oronasal Breathing Conditions

Background: Breathing conditions influence ventilatory efficiency and exercise performance, but little research has examined how different breathing conditions affect cardiorespiratory responses in women. Despite the growing popularity of nasal-only breathing in fitness culture, its physiological benefits remain unclear. The purpose of the current study is to examine the ventilatory responses to nasal, oral, and oronasal breathing during treadmill exercise at speeds of 5 to 11 km/h in 10 healthy females. Methods: Participants completed sessions under each breathing condition while heart rate (HR), oxygen uptake (VO 2 ), ventilatory equivalent for CO 2 (VE/VCO 2 ), respiratory frequency (Rf), tidal volume (VT), minute ventilation (VE), and respiratory timing variables were measured. Results: Breathing condition had minimal impact at lower speeds (5–7 km/h). However, at higher intensities (10–11 km/h), nasal breathing resulted in lower Rf and VE but elevated VE/VCO 2 , indicating reduced ventilatory efficiency. In contrast, oral and oronasal breathing facilitated greater VE and shorter inspiratory and expiratory times, supporting ventilation under vigorous exercise. Conclusions: While nasal breathing may suffice at low intensities, it is inadequate at higher intensities, potentially leading to carbon dioxide accumulation and early fatigue. These findings support the use of oral or oronasal breathing during higher-intensity activity and highlight the need for individualized breathing strategies.