Handbook of ROCOR Liturgical Practice:

Should the clergy and servers in the Altar ‘half-bow’, or incline their heads / upper body, during the consecration of the Holy Gifts?

A custom has emerged in some places, which is in fact an adoption of heterodox customs from other sources, of clergy and servers in the Altar ‘half bowing’, or inclining their heads or upper bodies forwards, at various moments in the Divine Liturgy (e.g. the ‘words of institution’, the epiclesis, and so on). This is not a practice of our Church and should not be done. In the Altar, we always stand upright and attentive; and at the appointed solemn moments we cross ourselves and make either a bow or prostration (as prescribed).