CP9 is just to keep fit and make physical strength reach an unimaginable level. However, in the second gear of Luffy, after taking stimulants, the potential of the body exploded, and the speed and strength rose to a great level. Smoking on the legs will speed up the beating of the heart, the body will release steam and the skin will turn red, just like using stimulants. Ordinary people use this trick to cause blood vessels to burst and die. Luffy can bear it, but it will also shorten its life. It can shoot an air bomb (explain, because the attack process is too short, it looks like shooting an air bomb) to attack, and the speed can be increased several times. So CP9 mistakenly thought Luffy had learned to shave.
PS: one of the "six styles" of "shaving". During the transient period, the ground is trampled 10 times or more, and the explosion speed generated by the reaction force is used to move.