This is not merely concentrating in breathing.  In this meditation form breathing is used to understand body as a separate phenomenon from ones own-self.

Meditation form

Perceiving the body as a phenomenon

• s/he dwells perceiving the body as just the body (not mine, not I, not self, but just a phenomenon) in himself
• s/he dwells perceiving the body as just the body in others
• s/he dwells perceiving the body as just the body in both himself and in others

Perceives cause and the actual appearing of the body

• s/he dwells perceiving the cause and the actual appearing of the body

• s/he dwells perceiving the cause and the actual dissolution of the body
• s/ he dwells perceiving both the actual appearing and dissolution of the body with their causes

Detached from craving and wrong views

• s/he is firmly mindful of the fact that only the body exists (not a soul, a self or I).
• that mindfulness is just for gaining insight (vipassana) and mindfulness progressively.
• being detached from craving and wrong views he dwells without clinging to anything in the world.
• thus, this is a way taught in which a person dwells perceiving again and again the body as just the body.

Similar to Anapana Pabba, here the individual will use hers/his body stance to understand body as a separate phenomenon from ones own-self.

Meditation form

Perceiving the body as a phenomenon

• s/he dwells perceiving repeatedly on the body as just the body (not mine, not I, not self, but just a phenomenon) in himself
• or he dwells perceiving the body as just the body in others
• or he dwells perceiving the body as just the body in both himself and in others.

Perceives cause and the actual appearing of the body

• s/he dwells perceiving the cause and the actual appearing of the body or he dwells perceiving the cause and the actual dissolution of the body

• s/ he dwells perceiving the actual appearing and dissolution of the body with their causes

Detached from craving and wrong views

• s/he is firmly mindful of the fact that only the body exists (not a soul, a self or I).
• that mindfulness is just for gaining insight (vipassana) and mindfulness progressively.
• being detached from craving and wrong views he dwells without clinging to anything in the world.
• thus, this is also a way in which a individual dwells perceiving the body as just the body.

Meditation form

• while going forward or while going back does so with clear understanding
• while looking straight ahead or while looking elsewhere s/he does so with clear understanding
• while bending or stretching her/his limbs s/he does so with clear understanding

• while carrying the alms bowl and while wearing the robes he does so with clear understanding
• while eating, drinking, chewing, and savouring s/he does so with clear understanding
• while urinating or defecating he does so with clear understanding; while walking, standing, sitting, falling asleep, waking, speaking or when remaining silent, he does so with clear understanding.

Meditation form

A person will examine and reflect closely upon the body, from the soles of the feet up and from the tips of the head hair down, enclosed by the skin and full of various kinds of impurities

An individual examines and reflects closely upon this very body enclosed by the skin and full of various kinds of impurities.

Thinking

"There exists in this body: hair of the head, hair of the body, nails, teeth, skin, flesh, sinews, bones, marrow, kidneys, heart, liver, membranes (including the pleura, the diaphragm and other forms of membrane in the body), spleen, lungs, intestines, mesentery, gorge, faeces, brain, bile, phlegm, pus, blood, sweat, solid fat, tears, liquid fat, saliva, mucus, synovic fluid (i.e. lubricating oil of the joints) and urine."