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 push-up handles keep your wrist in a more natural position, you can exercise your grip at the same time.
Alternately, perform your push-ups using clenched fists, which will help configure your hands for closed-fist punching.
Today I came across this article in the British Medical Journal. A 23 year 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 my 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.