What is meant by "work of breathing" and how does exercise affect the work of breathing?

Answer 1

During each breath there is a relationship between the pressure across the lung and the volume of air in the lung. The force generated by the lung is reflected by the change in pressure, and the distance is the change in volume that occurs in relation to the pressure change. Therefore, the work of breathing can be calculated by the change in pressure times the change in volume. The lung works by contracting and relaxing the muscles of the chest wall to move the chest wall and the lungs to overcome the resistance to the airflow into and out of the lung, and at the same time overcome the elastic recoil of the lung tissue. During exercise, the ventilation volume of each breath increases and the number of breaths per minute increases, which results in increasing the work of the lung and the respiratory muscles in direct relation to the work intensity. These increases in breath volume and rate of breathing are needed to increase the delivery of oxygen to the working muscles. However, the lung regulates its breathing frequency to a minimum rate that is the most economical in terms of energy expended for the mechanical work required to ventilate the lung at a given work intensity.