Why do the inter coastal muscles contract during inspiration?

The intercostal muscles contract during inspiration to elevate the rib cage and expand the thoracic cavity, which decreases the pressure inside the lungs. This pressure change allows air to flow into the lungs, facilitating gas exchange. The external intercostal muscles are primarily responsible for this upward movement, while the internal intercostals assist during forced expiration. Overall, their contraction plays a crucial role in the mechanics of breathing.