Q — I notice some worshipers genuflect in church while others bow. What are the origins of these two forms of reverence and are they interchangeable in Catholic worship?
A — The General Instruction of the Roman Missal governs through its rubrics the actions of clergy in the sanctuary. So, I am answering this question not in terms of what the priest/deacon does in the sanctuary during the celebration of the Eucharist, but, as the questioner asks, in terms of what worshipers do when in church.
The central issue concerning genuflection or bowing is simply this: showing respect both to the altar symbolizing Christ, and to the reserved Sacrament in the tabernacle. In other words, the custom of genuflecting or bowing is the external-ritual-bodily expression of acknowledging the presence of Christ. The important thing is that such an expression takes place. It is important not least because we are not Gnostics.
Our religious faith especially in liturgical assembly is expressed through material things and gestures. We are material beings.
Archbishop William Temple once said and rightly that “Christianity is the most material of the religions of the world.” Having acknowledged this principle, when it comes to a decision about whether to genuflect or to bow, the key factor should be the comfort of the individual person. If a person can easily genuflect, then that makes sense.
If a person cannot easily do so, a bow is in place. A gesture of reverence ought always to occur.