We do it everyday, repeatedly. In fact, it’s virtually impossible not to do it. Of course, I’m talking about breathing, specifically, breathing in.
Our bodies need a constant supply of oxygen for our cells to produce energy in a process called cellular respiration. Luckily, our atmosphere is 21% oxygen. All we have to do is get it into our lungs.
Inspiration begins in our gut. The diaphragm muscle contracts in a downward direction, which makes the thoracic cavity bigger. At the same time, the intercostal muscles contract and elevate the rib cage. The net effect of making the thoracic cavity bigger is a drop in air pressure in the lungs (the pressure of a gas varies inversely with its volume.) Because air flows from areas of high pressure to areas of low pressure, when the thoracic cavity expands, air rushes into the lungs through either the nose or the mouth. We have just experienced inspiration!
During the course of normal breathing, approximately 500 mL or air moves in and out of our lungs. This is called our “tidal volume”. Our lungs can handle more air than this. Depending on the size of the lungs, we can forcibly inhale between 1500 -3000mL more air. This comes in handy when we are active.
Inspiration comprises half of each day. Sometimes when we are feeling a little less than or best, a deep breath is the best inspiration!