There are two reasons offered for swaying during prayers (called shuckling, or shockling). The first is that the neshama, the soul, is akin to a flame and in the same way that a flame is never still so too should the neshama be constantly moving and striving to reach upwards to Hashem. The second reason is that when we stand before the King of Kings we should be overcome with awe and trembling. There is an alternative and that is that one should stand stock still, the way that a soldier, guarding the king, stands at attention. Rabbi Moshe Feinstein, one of the foremost halachic authorities of our generation who passed away over twenty ago, was renowned for the fact that, with the exception of bowing, he never moved during his recitation of the Shmona Esrei. He told that once, whilst living in Russia, he was arrested by the authorities for teaching Torah. One of the forms of torture that he experienced during his imprisonment was to stand completely still facing a wall, the threat was that if he were to move he would be shot. It was on one of these occasions that Rabbi Feinstein was struck with the realization that if he could stand with such intense concentration for his captors then he should, at least, afford the King of Kings the same respect.
