Researching for my book lead me to discover many interesting things. One of the things that I discovered was that the traditional push-ups we were made to do in school are not very good for your health. If you think about this a little it will soon be obvious why this is true. Bend you hand back as far as it can comfortably go without assistance and you will see that it does not form a 90 degree angle with the forearm. Putting all your body weight on it to make it do so is not a good idea. Push ups are a good way to build upper body strength but if you do them invest in some push-up handles or use some asymmetrical dumbbells that you can grip without them rolling away. Not only do handles keep your wrist in a more natural position, you can exercise your grip at the same time.
Today I came across this article in the British Medical Journal. A 23yr old kickboxer was performing a form of reverse press-up putting pressure on the backs of his hands. Not sure what the intended benefit of this variation is, but the result was he ruined a tendon along the outside of his forearm and needed reconstructive surgery and a transplant.
Very nasty, and his competition days are probably over for a few years if not permanently. In the book I caution against the common but dubious practice of punching with weights. There are a lot of other exercises out there that can cause you more harm than good, so be careful. Good exercise improves your condition, not reduces it.The Books