The concept of the power naps divides opinion: some people firmly stand by them, while others think they offer no tangible benefit at all. If you're a doubter, this video may be enough to convince you that they really do work.
The problem is, of course, getting the timings right: don't sleep long enough and you'll feel no benefit, sleep too long and you'll feel worse than ever. Fortunately, practice makes perfect. [YouTube]