The tall power jerk is the isolated movement of the body down under the bar into the power receiving position that trains aggression, timing, precision and balance.
 
There are a few variations of tall jerk—it can be done from flat feet or on the toes, and with the bar starting on the shoulders or pressed partially up. Like the tall snatch and clean, I prefer flat-footed to allow optimal balance and focus on more important aspects of the motion than simply not falling over before you start.
 
The default should be a start of the bar on the shoulders because part of the benefit of the exercise is reinforcing the proper bar, arm and head motion. The partial press variation can be used primarily as an introduction to the exercise.
 
With the bar in the jerk rack position and your feet in your jerk drive stance, brace the trunk and confirm balance slightly more toward the heels but with full foot pressure against the floor.
 
Without any upward drive with the legs, aggressively lift and move your feet into your power receiving stance and squat partially while you push the bar off the shoulders slightly backward to lock it forcefully overhead.
 
Stabilize and ensure the correct overhead position before recovering to standing again with the bar overhead.
 
For the partial-press variation, press the bar to around the top of the forehead and pause. Note that in this position, the head needs to be pulled back out of the way so the bar is above the shoulders rather than pushed forward. From this starting position, complete the exercise as you would otherwise.
 
Purpose
The tall power jerk is a technique exercise that helps with aggressiveness, timing and accuracy in the jerk.  
 
Programming
Sets of 3-5 reps are suggested. The tall power jerk can be used as a technique primer before jerks to train the timing and aggressiveness of the movement under the bar.
 
Variations
The tall power jerk can also be performed as a push jerk (feet fixed on the floor).