One of my wise colleagues tipped me off about moving toward the piano when playing scales and arpeggios in contrary motion. After trying it, I integrated the leaning forward motion into my own practicing and naturally, it trickled down to my students in the lesson environment.
Here’s a demonstration using the E minor arpeggio in contrary motion through a three octave spread. RH E G B E, etc. ( 1, 2, 3, 1); LH Descends E, B, G, E, etc. (1, 2, 4, 1) Thumbs at Middle E.. LH thumb in front of Right.
Leaning toward the instrument is best done during the last octave in conjunction with a Rotational motion as seen in my video instruction.
Blocking out the arpeggio, is a good preliminary which can include the forward leaning movement at the terminus of the arpeggio figure.