Kneeling.

"It may well be that kneeling is alien to modern culture–insofar as it is a culture, for this culture has turned away from the faith and no longer knows the One before whom kneeling is the right, indeed the intrinsically necessary gesture. The man who learns to believe learns also to kneel, and a faith or a liturgy no longer familiar with kneeling would be sick at the core. Where it has been lost, kneeling must be rediscovered, so that, in our prayer, we remain in fellowship with the apostles and martyrs, in fellowship with the whole cosmos, indeed in union with Jesus Christ Himself."

Pope Benedict XVI writing in the Spirit of the Liturgy.