I am often asked to whom or what we are bowing ... Is it to some thing, god, person or effigy?
I answer by saying that there is nothing that's true that is omitted from our bow. We might consider that we're simply bowing to the whole universe, and to ourself and the other people around us ... after all, 'All is One'! The hands, palms upwards, are raised in a gesture traditionally symbolic of lifting the Buddha's feet over one's head, but that truly means lifting all things of the universe over one's head (and that all things are, in turn, lifting and supporting us when seen from another angle). It's appropriate to cultivate an attitude of emptying, letting go, receptivity and gratitude in our bows.
If there is some physical or personal reason not to prostrate, a simple Gassho can be substituted.
However, there is greatness in the humility of the prostration.