Which muscle is used for normal breathing and which additional muscles are when performing strenuous exercises?

Normal breathing:

- Diaphragm: The primary muscle responsible for normal breathing is the diaphragm. It is a large, dome-shaped muscle located at the bottom of the ribcage. When the diaphragm contracts, it pulls the ribcage down and increases the volume of the chest cavity. This negative pressure draws air into the lungs through the nose and mouth.

Additional muscles used during strenuous exercises:

When performing strenuous exercises, the body requires more oxygen, and the respiratory rate increases. To meet this demand, additional muscles are recruited to assist in breathing. These include:

- Intercostal muscles: The intercostal muscles are located between the ribs. When they contract, they pull the ribs up and out, further increasing the volume of the chest cavity.

- Accessory muscles: The accessory muscles of respiration include the sternocleidomastoid muscles (located on the sides of the neck), the scalene muscles (located on the front and sides of the neck), and the pectoralis minor muscles (located on the front of the chest). These muscles help to raise the ribcage and expand the chest cavity when the diaphragm is not able to do so sufficiently.

During strenuous exercises, the respiratory rate can increase significantly, reaching up to 30-40 breaths per minute. This allows the body to take in more oxygen and expel more carbon dioxide, which is essential for maintaining aerobic metabolism and preventing fatigue.