I don’t know who started this, or why, but it’s become a thing. At the top of a deadlift, lifters do a very deliberate jarring motion to finish off the movement.
The trouble is, it adds absolutely nothing to the movement. It doesn’t increase glute involvement at all, nor does it improve hip drive. Instead, it sets up a perfect platform for injury, lumbar hyperextension, and acetabular issues.
We have to think about this logically. From a force angles perspective, the deadlift is a vertical pull. Hip drive is horizontal. The majority of our glute involvement will probably come through the first two-thirds of the lift. That’s when the hips are the most flexed, and the glutes serve as a hip extensor.
Aggressively driving through the bar at a million miles per hour at the top of the lift provides no added value. And the reason why people can add that much speed to that segment of the lift in the first place is because the force angle isn’t directly on the glutes anymore. Instead, it’s shifted to the traps, shoulders, and spine.
By the flawed logic that the glutes get more from whipping through the top, you’d see people able to do the same thing while doing a heavy hip thrust, which situates the load directly in line with the force created by the glutes. But they can’t.
Lastly, there’s no real way to guard against compressing your spine when hip whipping. Chances are, if you have issues with your initial setup or keeping good mechanics through the duration of your normal deadlift, adding a little speed, courtesy of the hip whip, will only make matters worse.
There’s nothing wrong with coming up smooth and controlled, and you’ll see better gains by doing so.