The jerk rack support is a simple static exercise to strengthen the jerk rack position and trunk for the jerk dip and drive.
 
Set up a bar in a rack 2-3 inches below the height at which it would be when on your shoulders in a standing position—usually the same height you’d use for front squats. Place yourself under the bar in the jerk rack position and brace your trunk forcefully. Straighten the legs to lift the bar straight up—keep the bar directly above the rack so you can set it down immediately if needed. Note that this can also be done in a power rack or on jerk blocks for greater safety.
 
Hold for 5-10 seconds before returning the bar to the rack. For longer holds, you can release and sip small amounts of air as needed while maintaining your bracing as forcefully as possible.
 
A quick dip at the knees or lift of the shoulders at the start to create some oscillation on the bar can add additional stabilization work.
 
Notes
Make sure you keep the shoulders lifted slightly to prevent compression of the carotid arteries and dizziness. Lift the bar straight up from the rack—don’t step back from it. You can even keep the bar in contact with the backs of the rack cradles to be sure you’re in place. If you begin to get dizzy, immediately rack the bar and step away from the rack. Using the pins inside a power rack or jerk blocks is the safest way to do the exercise.
 
Purpose
The jerk rack support strengthens the jerk rack position and the trunk, and can help with confidence by getting the lifter accustomed to the feel of heavy weights in the rack position.   
 
Programming
This exercise should be placed at or near the end of a workout. Use weights of 100% and above of the lifter’s best jerk for holds of 5-10 seconds.