Why had I been so dismissive of this practice? However, classes in pranayama are hard to find and pranayama is often never mentioned in yoga classes. Pranayama is usually translated as control of the breath. Yet "breath" doesn't do justice to such a profound concept: it is the energy permeating the universe. This includes heat, light, gravity, magnetism, electricity, physical, mental, intellectual, sexual, spiritual, and cosmic. Without prana there is no life and it is the prime mover. Power, vitality, life and spirit are all prana.
Mystery Of Breathing
Although science has discovered much about breathing, precise factors controlling breathing are not understood by physiology. The brainstem appears to be the control center for breathing and receives inputs from bodily receptors and other parts of the brain. This control center directs ventilation appropriate for metabolic demand - running or sleeping require vastly different amounts of ventilation; yet minimizing disturbances to internal homeostasis such as chemical composition of the blood, blood pressure and temperature. It must also adapt to effects of injury and disease.
Through the vayus, pranayama increases digestion, cleanses the lungs, neutralizes lactic acid, tones the nerves, brain, spinal cord and cardiac muscles, improves blood and lymph circulation, stimulates peristalsis and cleanses the lungs, liver and other organs.
What Pantajali has to say
The practice of pranayama, or I should say, the art of pranayama, makes it easier to distinguish between the true self and the false self, the observer from the observed. It is an important step in the penetration of the layers of the body/mind toward the soul. This is the core problem of human existence that yoga addresses - instead of observing our bodies, minds and senses, we identify with them and respond to life from that vantage point.
We run from suffering, suppress our awareness, emotions, sensations, distract ourselves with pleasures. The practice of pranayama gives us the opportunity to reach toward the soul.