Different hatha yoga breathing exercises affect respiration in different ways, this article is produced by IYO International Yoga Organization but before we can understand how they do this we need a little more background. We’ll start our discussion with a look at the amount of air found in the lungs and airways at different stages of the breathing cycle. These values—the lung volumes, capacities, and anatomic dead space— vary according to stature, age, sex, and conditioning, so to keep things simple we’ll always use round numbers that are characteristic for a healthy young man. The numbers are generally smaller for women, for older men and women, and for those in poor physical condition. That’s not so relevant to us here. Our main interest is not in how the lung volumes and capacities vary in different individuals; it is in how they vary with different breathing practices and postures. The numerical representations in as well as in all the charts on respiration, are only simulations, but they will be a useful starting point for more rigorous inquiry.