When we move the hips forward at the start of the press, we do so for a couple of reasons. First, it gets the head out of the way to clear a path for the bar to travel vertically, and second, it initiates a stretch reflex out of the bottom of the press to help propel the bar upward.
A common problem, however, with this “reach-and-bounce” or “reach-and-press” movement at the start of the press is that of winding up the press. When you use the hips at the start of the press, the hips should begin by moving forward and then back to their starting position. You absolutely should NOT initiate the press by moving the hips backward first, then forward - this is winding up the press. It creates unnecessary horizontal movement of the bar - a forward-and-backward motion of the bar that is a waste of time and energy, and what is more, this horizontal movement has to be managed, which becomes very difficult indeed at heavy weights. We are trying to move the bar vertically upward, so any unnecessary horizontal motion makes our job that much harder.
To fix this problem, let’s first focus on the start position. Simply put, you stand as tall as possible before initiating the movement. You may find that you tend to lower the previous, finished rep to a position wherein your hips are already reaching forward of neutral; in other words, you look like you’re about to perform the limbo at a birthday party (but with straight knees, which is a terrible way to perform the limbo anyway) instead of returning to a normal, upright, standing position. This will either reduce the effectiveness of a correct hips movement as your hips are already in a “pre-reached” position, or you will start the next rep by yanking your hips backward first - the winding up motion that we are trying so diligently to avoid. If you find that you tend to start your press in this pre-reached position, then at the completion of each rep, after lowering the bar, simply cue yourself to “stand up” or even “stand up tall.”
