עבודת הגוף בתפילה

GEMARA: Since the mishna deals with the fundamental obligation to recite the Amida prayer, the Gemara seeks to resolve fundamental problems pertaining to this prayer. Corresponding to what were these eighteen blessings instituted? When the Shemoneh Esreh was instituted by the Sages, on what did they base the number of blessings? Rabbi Hillel, son of Rabbi Shmuel bar Naḥmani, said: Corresponding to the eighteen mentions of God’s name that King David said in the psalm: “Give unto the Lord, O you sons of might” (Psalms 29). Rav Yosef said: Corresponding to the eighteen mentions of God’s name in Shema. Rabbi Tanḥum said that Rabbi Yehoshua ben Levi said: Corresponding to the eighteen vertebrae in the spine beneath the ribs. Since Rabbi Yehoshua ben Levi’s opinion based the Amida prayer on the spinal vertebrae, the Gemara cites another statement of his that connects the two: Rabbi Tanḥum said that Rabbi Yehoshua ben Levi said: In those blessings where one is required to bow, one who prays must bow until all the vertebrae in the spine protrude. Establishing a different indicator to determine when he has bowed sufficiently, Ulla said: Until he can see a small coin [issar], on the ground before him opposite his heart (Rav Hai Gaon). Rabbi Ḥanina said: There is room for leniency; once he moves his head forward, he need not bow any further. Rava said: But that applies only if he is exerting himself when doing so, and he appears like one who is bowing. However, if he is able, he should bow further.