Athletes who lock their knees prior to the Jerk may suffer from a stuttered ‘dip & drive’, primarily caused by a lag in quad tension. A lag in quad tension can also lead to contact issues with the bar, causing it to bounce on the shoulders during the attempt.
Coaches should cue their athletes to unlock their knees slightly. Unlocking the knees places tension on the quads making the movement smoother creating a controlled jerk. It is possible to maintain a straight upright stance while keeping the knees slightly unlocked.