The General Instruction of the Roman Missal (GIRM) specifies three times during the Mass when the celebrant must genuflect: after showing the host (1) and chalice (2) at the consecration, and before Communion (3). The text adds, “If, however, the tabernacle with the … Blessed Sacrament is situated in the sanctuary, the priest…and the other ministers genuflect when they approach the altar and when they depart from it, but not during the celebration of Mass itself” (No. 274).
The GIRM also prescribes appropriate devotional posture for the faithful who wish to receive communion, “When receiving Holy Communion, the communicant bows his or her head before the Sacrament as a gesture of reverence and receives the Body of the Lord from the minister” (No. 160).
What response should we give a communicant — or a celebrant — who feels these gestures are insufficient? We might remark that the GIRM establishes minimum requirements. Should we wish to do more, only the practical limitations of the worship space limit us.
Thus if a celebrant wishes to genuflect before returning consecrated Hosts to the tabernacle, nothing prohibits him. Likewise, a communicant might genuflect or even kneel to receive Communion if this does not impede the progress of others wishing to receive the Eucharist.