When stengthening the external body the internal ie; breathing and endurance should be balanced. If conventional body building is used the result could hinder your flexability and striking power. That type of development is good for lifting and tearing stength but hinders striking. To enhance internal energy in your strikes the external body must be completely relaxed as in a pitcher throwing a 90 mile an hour fastball. If your muscles are overly developed and your fast twitch muscles contract to easily and for to long your internal energy will get caught inside those muscles and will possibly cramp or fatigue. Going back to the example of the pitcher he is so relaxed on his delivery that his body falls forward. The same concept should apply to a strike which should be fast and expansive till the moment of contact. This is not to say you can't use weighted materials to enhance tendon and ligament strength. At www.buddhapalm.com they discribe the different rings, jars, poles and other strength enhancing devices. The idea is to internally enhance your external power for optimum strength and fexability. Also research Joseph Greenstien the Mighty Atom. His book the Spiritual Journey of Joseph L. Greenstien is very enlightening.