A drill too often overlooked, but wholly fundamental to the offensive line is the duck walk. Time and time again linemen stand up during the execution of plays on the field during games; yelling for them to stay low is not enough.
This drill will help with the execution of the "thrusting the hips" because it establishes the hitting position for the lineman; which differs from a linebacker or defensive lineman. Offensive lineman need endurance in their legs above all to maintain low hitting position and to move during pass protection.
Coaching the drill
Position One: Begin with the feet shoulder-width apart and slightly staggered (either one foot slightly further back than the other).
Position Two: Bend the knees, not the back, to a 90-degree angle so that hips are parallel with their knees. This is a weightlifting squatting technique.
Position Three: Bend at the waist setting belly on the thighs. This will naturally bring their hips up slightly. Their back should be as flat as a table.
Position Four: With a flat back, do not let them pick their bellies up from their thighs, roll their neck back so that their eyes are looking forward.
Coaching Point: Necks rolled back and bellies on thighs--try this for five yards.
The lineman's legs should fatigue pretty quickly. Over time lengthen the distance from five yards to 10 yards and so forth.
This drill will help them in the chutes, and get them comfortable with going out on linebackers low and ready to explode up through them. Don't let your lineman go out on linebackers half way cocked; have them stay down.