Motionless Jab is a jab having no shoulder movement, making it impossible to predict. It is most prominently used by Mexican boxers throughout the series such as Ricardo Martinez and Alfredo Gonzales. The only known Japanese boxer who used it is Date Eiji.
Application
Known for being an extremely high-level Jab compared to the others seen in the series such as the Flicker Jab and the Bullet, the Motionless Jab has no build-up in the user's shoulder or elbow. This is accomplished by keeping one's fist and shoulder completely lined up with the target's eyes, which of course is hard to do consistently. This does wonders both for speed, since it gives a smaller window to react, and range, since the opponent can't gauge if they're in striking distance. The end result is a punch that flies straight out of the user's stance, which looks as if the glove got larger out of nowhere.
Strength & Weakness
Due to the sharpness of the angle of which the Motionless Jab is thrown, the punch can come out fast and unexpectedly, which can catch most opponents off guard. In addition, because the punch has no shoulder motion, hooks and uppercuts can be included from the position of the Motionless Jab and can switch from short to long-range (In other cases like Alfredo Gonzales, the Motionless Jab can change directions such as going underneath an opponent's guard to become a Short Uppercut).
However, the Motionless Jab can still be dodged just like any other punch if properly prepared for such as Ippo using Headslips to get pass the punch.