We spend a lot of our waking life in spinal flexion or forward folding. Sitting is a state of spinal flexion. Think of how many hours are spend sitting in a car, at a desk, in a comfortable chair, in front of the computer, etc. Without proper support from strong postural muscles or appropriate chairs, the alignment of the spine becomes compromised in this position. During spinal flexion the spine moves upwards, towards the sky and we experience a rounding in the back. This movement is supporting of the exhale.
Conversely, back bending is perhaps the most overlooked movement of the spine. Seldom do we intentionally extend the spine up and out of the pelvis, bringing the torso past vertical. Yet, when done correctly, this movement is extremely healthy and can help the spine become stronger and more flexible. During spinal extension we move the spinal vertebrae into the back. This movement encourages an opening across the chest and is supportive of an inhale.