The work done by the respiratory muscles during inspiration and expiration. Respiratory work consists mainly of overcoming the elastic resistance and flow-resistive forces of the thorax and lungs. At rest, the respiratory muscles require about 0.5–1.0 ml of oxygen l−1 ventilation. With increasing ventilation, the oxygen cost per unit of ventilation becomes progressively greater. It has been estimated that respiratory work uses as much as 10% or more of the total oxygen uptake during heavy exercise. However, under normal conditions, respiratory work is not a limiting factor of exercise unless the oxygen delivered to the circulation by the additional ventilation is the corresponding increment in oxygen consumption by respiratory muscles. Under most circumstances, ventilation is well-adapted to ensure maximum uptake.
Subjects: Sports and Exercise Medicine.