(notice alignment of heels, knees, hips, shoulders, and hands)
I often get the question in our gym about behind the neck movements. The primary concern/question is always functionality based. i.e. If we are never lifting from behind the neck un the Olympic lifts then why practice from behind the neck?
This is a legitimate question as I am a big proponent that performing the movements from the competition positions best prepares lifters for competition. However, the benefit of behind the neck movements carries great weight in strength gain for optimal overhead positions.
When the bar is overhead, the most secure position for the bar is over the traps, just behind the ears. Obviously the bar can be too far behind your head… ask the Hungarian in the picture below.
However, the best position for the bar is for the head to be through your arms and the bar to be situated over neck. (See picture at top) This allows the traps to engage and stabilize the muscles which works 100x better than the deltoids. Therefore, it benefits your stability overhead and your strength with the bar overhead to work exercises like jerks, push presses, and presses from behind the neck. Generally you can do more weight from this position and you worry less about getting your head through the bar and worry more about building overhead strength.
Yes there is a necessity and a reason for doing overhead movements from a front rack jerk grip. However, mixing in behind the neck movements has its place as well.