Prayer should be easy and joyous. Do your knees hurt during davening? Does your back or neck or shoulders ache? Learn how to pray with poise.
God wants you to be straight with him, not all contorted and pulled down.
Joe* emails: The Shelo Hakadosh advocates for not moving at all during davening, with stillness being the most appropriate meditative position. Add to that the Mishna Brurah’s advocation of Alexander Technique stance during the amidah- he says the ideal position is back straight, head up, eyes downward.