some good advice in this thread
but what is being underestimated is the legs
do alot of squats, do alot of jumping, do ALOT of running up and down stairs
the guy above me already stated "Look at Tyson, his power came from his legs"
that's the problem with heavyweights nowadays
they all rely on arm strength, that's why they can't hit as hard as tyson
his legs were humungous