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Background: Since nasal respiration is physiologically important, many studies have been conducted to find factors necessitating a change from nasal breathing into oronasal breathing during exercise. The present study tried to understand the role of anterior nasal resistance in this switching. Methods: Twelve young, healthy, non-athletic and non-smoker male volunteers with normal body mass index (BMI) were selected after medical examinations. Following anterior rhinomanometry at rest, the subjects participated in an exercise protocol during which ventilation, workload and oronasal switching point (OSP) were measured. The protocol involved a 25 watt increase in workload per minute until the OSP was reached. Findings: There were significant correlations between anterior nasal resistance and OSP, workload, and ventilation difference to OSP ratio (P < 0.05).   Conclusion: Anterior nasal resistance can be considered as an effective factor on OSP occurrence. In addition, by reducing nasal resistance, one can tolerate longer periods of nasal respiration during exercise.