|» Chakra ;
Normally, chakra is required to perform any jutsu. This is done by combining the body's energy as well as the spirit's energy and releasing them. However, one must controlling them equally, otherwise chakra will be wasted. Usually, once a user runs out of chakra, he/she cannot perform any moves for a while. However, this is different with Lee.
Even the simpliest genjutsu or ninjustu moves require chakra. Since Lee cannot use any of these moves, he relies on taijutsu. As explained later, taijutsu's edge over other jutsu is the fact that simplier moves don't require chakra. Therefore, Lee's not entirely helpless if he runs out of chakra. In fact, aside from his forbidden techniques, he seems to release very little amounts of chakra. We may conclude that either he doesn't need much chakra to perform most of his moves, or that he controls chakra very well, releasing the exact amount needed to perform the jutsu, without wasting any. With taijutsu, Lee doesn't focus on his chakra limits, and instead focus on his body's limits.
This is not to say that Lee doesn't rely on chakra at all. His forbidden techniques require much chakra. Increasing his speed will require chakra as well. While Lee's speed is incredible already without his weights and chakra, releasing any of the Eight Gates will further increase his speed to superhuman, as well as giving him power. Plainly, Lee relies on chakra quite a bit. The more gates released, the more chakra flow, and thus the more chakra Lee can release. With the gates opened, Lee's possesses a power surge, giving him immense power in both speed and attack. This is how Lee uses chakra differently from other shinobi. As far as we know, Lee is the only genin capable of releasing any of the gates. He has the ability to control how much chakra flow he has. Consequently, he is also capable of stressing his body to the max and sacrificing his health. But his forbidden techniques require the opening of some of the gates. The technique works by a combination of high speed moves and power, those that can't be obtained without unfastening the gates. I think it's pretty safe to say that Lee can reach his body's limit before he can run out of chakra.
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