The kettlebell jerk is a movement that utilizes the momentum generated by the legs to bring the bells from the rack position to the overhead position. While your arms and shoulders are working to stabilize, they should not be pushing the bells into the overhead position (or the timing will be off). The quicker the launch and the more relaxed the triceps are, the faster the lifter will be able to jerk without feeling muscular fatigue of the upper body.
Interested in trying out Kettlebell Sport as a training methodology? This video incorporates one of the fundamental sport lifts, the kettlebell jerk, into a workout that will challenge the coordination and power of the legs, core, and upper body.
The purpose of the kettlebell Jerk is to move the kettlebell from the rack position to overhead using the legs and hips. While the shoulder and arm stabilize the bell in the overhead position, all the force to lift the kettlebell should be generated from the lower body.
Timing is of the essence in the Jerk. The lifter must powerfully launch the bell from the hips, then quickly squat underneath to let the legs take the load of the bells as they land overhead.