On more than one occasion I've been asked: "Sam, why do you lift your hands when you worship?" My answer is two-fold.
First, I raise my hands when I pray and praise because I have explicit biblical precedent for doing so. I don't know if I've found all biblical instances of it, but consider this smattering of texts. . . .
If someone should object and say that few of these texts speak of worship (see Pss. 63:4; 134:2), but only of prayer (as if a rigid distinction can even be made between the two; indeed, I can't recall ever worshiping God without praying to him!), my question is simply this: Why do you assume that the appropriate place for your hands is at your side and you need an explicit biblical warrant for raising them? Wouldn't it be just as reasonable to assume that the appropriate place for one's hands is raised toward heaven, calling for an explicit biblical warrant (other than gravity or physical exhaustion) to keep them low?