The second myth is that martial artists should have big muscular bodies and practise with weights so as to be able to generate power.
Weightlifting is not bodybuilding.
If weight training can generate explosive power, why don't tennis or badminton players wrap their arms with weights during practice to improve their game? Food for thought isn't it?
I'm not a tennis player, but a quick Google search shows they actually use Olympic Weightlifting routines for the same reasons I suggested it be used for martial arts. Turns out it applies to any power athlete who wants to optimize their energy transfer by developing kinetic chain efficiency...
Oh, look at this! Power Cleans for Tennis:
To achieve external power (as opposed to internal power which uses a totally different method), the method is easy but it is hard work. Get a strong bag, fill it with green beans, place the bag onto a solid table or platform, relax your hand and arm and slam your palm down onto the bag. Do it 1,000 times a day (but be careful not to damage your hands). If the bag is not strong enough it may explode within three months. If so replace it with a better bag. After three years of such practise your single palm strike will generate so much power you cannot begin to imagine. And at this point your arm will look no bigger or different than it is three years ago.
That's just conditioning your hands, not developing power.