There are two broad categories of dip & drive styles: strength and elastic. These are really the two ends of a spectrum; a lifter may fall between the two rather than exhibiting one or the other dramatically.
The strength jerk relies more on absolute strength to accelerate the bar. This requires a deeper dip to allow a longer drive to put enough force into the bar to achieve adequate speed.
We want to maintain a fairly constant back angle through the first pull, although we’ll nearly always see a slight change. It’s important to understand what actually constitutes the starting positionbecause this is a common source of confusion and argument when suggestion the back angle shouldn’t change considerably—the starting position is the posture you’re in the moment the bar begins to separate from the floor. It’s not whatever low-hipped, shoulders-behind-the-bar preparatory position or any given point of a dynamic startyou feel like picking.
The goal is to prevent an excessive and unwanted shift in position. This is a quick shift very quickly after the bar leaves the floor. You’ll recognize it as a sudden rising of the hips while the bar travels relatively little. The hips shooting up dramatically more than the shoulders and bar rise creates a two primary potential problems: It tends to shift balance too far forward, and it tends to force an early second pull, which reduces bar speed and elevation and also disrupts balance.