Both inhalation and exhalation always requires the expenditure of energy?

Inhalation typically requires energy because it involves the contraction of muscles, such as the diaphragm and intercostal muscles, to expand the thoracic cavity and draw air into the lungs. Exhalation can be passive during normal breathing, relying on the elastic recoil of lung tissues, but it can also require energy during forced exhalation, where muscles contract to push air out. Therefore, while inhalation always requires energy, exhalation may or may not, depending on the breathing context.