The Indians called controlled breathing, Prana. Prana was the essence of life, vitality. Some compare it to Chi, the energy. I will not go down that spiritual road, I will just point out how in almost every culture, breathing is related to life, even at times where they didn't know anything about oxygen molecules.
The goal here, is to increase that capacity, the exchanges and to permit your lungs to work better, and be stronger.
So now, we will add another exercise to your routine.
You will hold your breath for as long as you can, and time it.
The next day, add from one to five seconds.
The next day, the same. The goal is for you to increase your capacity and train yourself to hold your breath longer.
Remember to exhale completely all the air you have in your lungs.
See you in a week!