The following is an excerpt from the 7 principles of Russian Breathing according to Vladimir Vasiliev with commentary by Systema SLC. For more information pick up Let Every Breath: the Secrets of the Russian Breath Masters.
2.Leading – Breath leads action (action is delayed slightly behind breath.)
Breath, mind, and body exist in symbiosis with each other. The mind follows the breath, and the body follows the mind. Consider the following: When your body works harder, your breath rate increases. When your breath rate increases, your mind becomes considerably more agitated.The opposite also happens, when your breath rate is calm, your mind and body will reflect that. The mind and body are difficult to control, especially the mind, because we are fairly “disjointed”. Most people have no idea how tense they are because they are not aware of their own body or mind state. You certainly cannot control something that you are not aware of.
Start with the Breath:: The breath is easy to control. You may learn to control the rate of your breath, the continuity, the timing, and intensity. Everything else will follow.
If you desire to squat, your exhale will guide you downwards and your inhale will pull you back up. With practice you will feel your breath initiate the movement, creating the momentum necessary to complete a more relaxed squat or eventaully, a fully relaxed squat. Likewise, you will feel your inhale pull you downward into a squat and your exhale push you back up into standing position (you must practice both variations.)
For example: before you begin to squat, start to exhale, and before you begin to rise, start to inhale. Imagine that the breath pulls you downward or stretches you upward. In some ways, it is very easy to feel the body expanding on inhales and contracting on exhales, however, remember to inhale into a squat and exhale to rise as well (see Independence.) When you practice breathing in both directions, you maintain freedom and control.
Practice squats, pushups, leglifts, and situps in this manner, then move to free work.
When you are practicing free work or movement, we recommend that beginners exhale on every movement and inhale between movements. Exhalations are naturally more relaxed than inhalations.