The 2nd Principle of Yoga

The second principle of Yoga is breath with movement.

Being aware of the breath with each movement in Yoga brings awareness into the body. There is a vital flow of energy in the body. This enables movement to be more conscious and allows us to be in the moment. Coordinating the breath with each movement during Yoga practice soon becomes a subltle, natural habit.
Exhalations are especially important. When you focus on exhalation, the body relaxes and moves deeper into poses. Exhaling, the body becomes grounded allowing the spine freedom to move and lengthen.

Inhalation, while resting or lifting the body, brings a fresh supply of oxygen to hard working muscles and organs. To try an example of moving with the breath, stand in
Tadasana and begin focusing on the breath:

As you exhale, become grounded to the earth.

Inhale bringing in energy.

Exhale and lengthen up the spine.

Inhale.

Exhale and relax the shoulders down.

Inhale and raise the arms up.

Exhale and fold forward, bringing the arms behind you. (Bend the knees as you fold forward.)
Inhale raising the arms and body back up.

Exhale and lower the arms to the sides.

This flow of breath and movement can be continued for several rounds. Keep the rhythm slow and smooth.

On completion, stand in Tadasana with eyes closed and experience the subtle changes in the body and mind.