In normal breathing need to use the nose to inhale and breathe, if in the time of strenuous exercise, you can use the nose to inhale and mouth to breathe, mainly because the nasal vestibule location of a lot of long nasal hair, can be inhaled in the air of the dust blocked in this location, so that dust can not enter the respiratory tract, the nasal cavity and rich blood vessels and mucous membrane can be inhaled air humidification, heating, inhaled into the respiratory tract will not Stimulate the mucous membrane of the respiratory tract, will feel more comfortable. If inhaling with the mouth can not play this role, it will dry the mucous membrane of the mouth, but also stimulate the trachea to cause congestion and edema of the mucous membrane, and can even cause infection. During strenuous exercise, exhaling gas through the mouth will be faster than exhaling through the nose, which is beneficial to breathing.