Question: At what points of the Amida should one bow and what is the correct method of bowing?
Answer: Our Sages that one should bow several times during the Amida prayer.
The blessings during which one must bow within the Amida are as follows: At the beginning and end of the “Magen Avraham” blessing (the first blessing of the Amida) and at the beginning and end of the “Modim” blessing. One should not bow at the beginning or end of any other blessing of the Amida prayer.
How much must one bow? One should not suffice with a small bow; rather, one must bow to the extent that all of the vertebrae in one’s spine protrude. One should not keep one’s head straight while bowing; rather, one should bend one’s head while bowing as well, as the Rambam (Chapter 5 of Hilchot Tefillah) states that while bowing, one must resemble and arc, meaning that besides for bowing until one’s vertebrae protrude from one’s back, one must likewise bend one’s head.
Nevertheless, one should not bow so excessively that one’s mouth is directly across one’s belt. Rather, one should bow as prescribed by Halacha, i.e. that all of one’s vertebrae be protruding from one’s back.
If one is elderly or ill and cannot bow until one’s vertebrae protrude, one need not bow to such an extent and it is sufficient to nod one’s head slightly, for this shows that one wishes to bow fully and one is not doing so merely because of the pain or discomfort involved.
Some have the custom to bend their knees while bowing, as we shall discuss in the following Halacha.