Objection 1. It would seem that adoration does not denote an act of the body. It is written (John 4:23): "The true adorers shall adore the Father in spirit and in truth." Now what is done in spirit has nothing to do with an act of the body. Therefore adoration does not denote an act of the body.
Objection 2. Further, the word adoration is taken from "oratio" [prayer]. But prayer consists chiefly in an interior act, according to 1 Corinthians 14:15, "I will pray with the spirit, I will pray also with the understanding." Therefore adoration denotes chiefly a spiritual act.
Objection 3. Further, acts of the body pertain to sensible knowledge: whereas we approach God not by bodily but by spiritual sense. Therefore adoration does not denote an act of the body.
On the contrary, A gloss on Exodus 20:5, "Thou shalt not adore them, nor serve them," says: "Thou shalt neither worship them in mind, nor adore them outwardly."
I answer that, As Damascene says (De Fide Orth. iv, 12), since we are composed of a twofold nature, intellectual and sensible, we offer God a twofold adoration; namely, a spiritual adoration, consisting in the internal devotion of the mind; and a bodily adoration, which consists in an exterior humbling of the body. And since in all acts of latria that which is without is referred to that which is within as being of greater import, it follows that exterior adoration is offered on account of interior adoration, in other words we exhibit signs of humility in our bodies in order to incite our affections to submit to God, since it is connatural to us to proceed from the sensible to the intelligible.
Reply to Objection 1. Even bodily adoration is done in spirit, in so far as it proceeds from and is directed to spiritual devotion.
Reply to Objection 2. Just as prayer is primarily in the mind, and secondarily expressed in words, as stated above (Question 83, Article 12), so too adoration consists chiefly in an interior reverence of God, but secondarily in certain bodily signs of humility; thus when we genuflect we signify our weakness in comparison with God, and when we prostrate ourselves we profess that we are nothing of ourselves.
Reply to Objection 3. Though we cannot reach God with the senses, our mind is urged by sensible signs to approach God.
Source: Summa Theologica (New Advent)