I do the same thing. Whether or not it works depends on the time of day. If it is just a 4:00 in the afternoon lull in attention span a short walk (or if I have a deadline an espresso at the desk) will usually get me back on track. If it is late in the evening though I can only delay the inevitable need for sleep so much.

I think that inevitable tired point where you aren't going to get anything more out of yourself effectively, no matter what you do, is what this article is about.