For the safety and continuance of swimming, breathing is the most important factor. The purpose of this study is to support instruction of breath control while swimming for beginners. The exhalation airway may change from one`s nose to mouth. This airway change might be an involuntary action, so the most important instruction is how to change airway. We used the nasal and oral pressures to recognize the airway route. Twelve recreational swimmers participated, who were in the prone position at pool side. They immersed their faces into the water. In the first trial, after face immersion, subjects held their breath for five seconds, then continued exhalation for five seconds from the nose and then changed the airway to the mouth. In the second trial, the exhalation order changed from the mouth to the nose. Subjects repeated face immersion for more than four times in each trial. We measured the changing time of exhalation from nose to mouth (CTNM) and mouth to nose (CTMN) on pressure curves. The average of four repetitions of CTNM was 258.1 msec and the CTMN was 307.3 msec. The average nasal pressure decreased 0.25 cm H2O and oral pressure increased 1.07 cm H2O in the first trial. In the second trial, the average nasal pressure increased 0.52 cm H2O and oral pressure decreased 0.86 cm H2O. The changing time and the pressure difference revealed no significant difference in the paired T tests. The results seem to show that airway change from nose to mouth is easier than mouth to nose. From measuring pressure, exhalation from nose is easier than from mouth.
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