My personal oppinion? Bruce Lee was a genetic freak :nod:
press ups [many different ways of doing them to hit an insane amount of muscles], sit ups and crunches, pulls ups, chin ups, squats etc can all be done without extra weight put into them.
You can also use weights with your back and abs, but go for more reps than what a lot of people will often suggest. constantly stretch - I expect you've heard of him, a guy called matt fury... some say he's a fake, some say he's the sh!t, either way, flexibilty and strength can be easy if you do it right.
Above all, dont go lifting 190 lbs of whatever, because A) you'll probably move up a weight division anyway, but B) theres more muscle to shift, more muscle to slow you down, more muscle to fight with, and you need to put a whole much more effort into building more stamina in your muscles if you want to go any sort of distance at all.
Good luck with it, if you want advice on this matter, look around
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Ben