What is the relationship between bowing down and prayer?

St. Isaac the Syrian says:

“Bow down at the beginning of your prayers and beseech God with contrition and humility to grant you patience in prayer and control over thoughts.”

“Compel yourself to bow down before God [i.e., to perform metanoias ], for it is this which enlivens the spirit of prayer.”

“Give yourself to prayer and you shall attain the sweetness of metanoias and continue in them with joy.”

32 Eusebius Pamphili, Life of Constantine 4:22 (NPNF II/1:545).

33 St. Basil of Caesarea, On The Holy Spirit 27.66 (PP 42:106).