size and weight aren't teh only determining factors (but they do play a part). they're also genetic differences between people. some peopel have more fast twitch muscles and some have more slow twitch muscles. fast twitch muscles move fast, and strong, but can't keep going for long. slow twitch muscles aren't too strong or fast, but they can go for ages (if u wanna know which you've got, if you're good at long distance or endurance sports, it's slow, and if you're good at racket sports or football, it's fast). training and style has a lot to do with it too. bruce lee threw 2000 puncehs a day when training, so he was pretty darn hard. if ja put in that kinda work witout getting any bigger or stronger, his punches would be so fast 50 wouldn't know what hit him. in people that don't train though, it's only really gonna be a contest with the bigger person winning.

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..50 was a ameture boxer..Ja Rule is a bitch...