Here we are practicing diaphragmatic breathing. The concentration is on expanding the lower stomach on the inhale and contacting it on the exhale.
This has many physiological benefits such as lowering your heart rate, lowering your blood pressure, and reducing stress. To aide in this practice, the person behind gently pulls in the stomach of the person in front of them on the exhale.
Simultaneously on the exhale, we concentrate on the energy flow from the bottom of our spine up to our pineal gland. This turns our carnal energy, or retas into spiritual energy, or ojas.