How is normal breathing accomplished?

Normal breathing, or tidal breathing, relies heavily on the diaphragm, which is the primary muscle used in the process. During inspiration, the diaphragm contracts and flattens, increasing the volume of the thoracic cavity and allowing air to flow into the lungs. This contraction accounts for a significant majority of the work done during normal breathing — approximately 70%.

Tidal volume refers to the amount of air that is inhaled or exhaled during a normal breath, and while it does change with each breath, it is not the primary driver of the process. Instead, the contraction of the diaphragm provides the necessary force to increase lung capacity and facilitate airflow, making it essential for efficient breathing. In a typical breathing cycle, accessory muscles, including those in the intercostal area, may assist in expanding the chest, but their contribution is minimal compared to the primary function of the diaphragm.

Therefore, the notion that normal breathing is accomplished predominantly via the contraction of the diaphragm, which allows the tidal volume to fluctuate as needed, aligns with physiological understanding of respiratory mechanics in healthy individuals. This solidifies the response that highlights the substantial role of diaphragm contraction in any normal breathing pattern.