what happens to the rib muscles and the diaphragm when you inhale and hold your breath
When you breathe in, or inhale, your diaphragm contracts (tightens) and moves downward. This increases the space in your chest cavity, into which your lungs expand. The intercostal muscles between your ribs also help enlarge the chest cavity. They contract to pull your rib cage both upward and outward when you inhale. As your lungs expand, air is sucked in through your nose or mouth.