(RNS) — In the United States, Catholics kneel during the Eucharistic prayer while Catholics in the rest of the world stand. In 325, the Council of Nicaea forbade kneeling on the Lord’s Day and in the days of Pentecost. The Eucharist, the most important prayer of the church on the Lord’s Day, would be covered by this canon. Catholics began kneeling at Mass in the 12th century at the time that the elevation of the consecrated host was introduced. Today, GIRM calls for Catholics to stand during the Eucharist except during the institutional narrative (aka consecration), when they are to kneel.