91Ó°ÊÓ

The diaphragm is the primary muscle responsible for breathing. It is a dome-shaped muscle located at the base of the lungs. During inhalation, the diaphragm contracts and flattens out. This contraction increases the space in the thoracic cavity, allowing the lungs to expand and fill with air.
This process of inhalation is automatic and occurs without conscious effort. When the diaphragm relaxes, it returns to its dome shape, decreasing the space in the thoracic cavity and pushing air out of the lungs, leading to exhalation. This cycle of contraction and relaxation enables continuous breathing, providing oxygen to the body and removing carbon dioxide.

While the diaphragm is the main muscle for breathing, additional inspiratory muscles become active during strenuous activities. These muscles help to increase the volume of air taken into the lungs.

• External Intercostal Muscles: These muscles are located between the ribs and help lift the ribcage up and out, further expanding the thoracic cavity.
• Sternocleidomastoid: This is a muscle located in the neck that helps lift the sternum, aiding deeper inhalation.
• Scalene Muscles: Also found in the neck, these muscles elevate the first two ribs, further increasing lung volume.

By utilizing these muscles, the body can efficiently increase the air volume during intense physical activities, ensuring adequate oxygen supply.

Unlike normal breathing, which is mostly passive, forced expiration during exercise involves active muscle contraction.

• Internal Intercostal Muscles: These muscles lie inside the ribcage and work to pull the ribs down and in, reducing the volume of the thoracic cavity and helping push air out of the lungs.
• Abdominal Muscles: These muscles play a significant role during forced expiration. They contract to push the diaphragm upward, expelling air more forcefully from the lungs.

By engaging these muscles, the body can expel air more rapidly and efficiently during intense physical exertion, making room for a new breath.

During exercise, the body's demand for oxygen increases, and so does the need to expel carbon dioxide. This requires the activation of additional inspiratory and expiratory muscles.
When you exercise, your breathing rate and volume (tidal volume) increase. To meet the increased oxygen demand, inspiratory muscles such as the external intercostal muscles, sternocleidomastoid, and scalene muscles come into play.
Simultaneously, for effective removal of carbon dioxide, expiratory muscles, including the internal intercostal muscles and abdominal muscles, become active. These extra efforts ensure that your body receives enough oxygen and efficiently removes excess carbon dioxide to keep up with the heightened metabolic demands of exercise.