Risk of hyperextension: Fully locking the elbow puts stress on the joint, tendons, and ligaments. Over time (or even once), that’s how boxers get elbow pain or injury. Slower recovery: A locked arm takes longer to retract. A good jab snaps back fast. Loss of control: If your jab is parried or slips past the target, a locked elbow can pull you off balance. What you want instead... Extension without lockout: Extend the arm to about 95–98%, keeping a slight bend in the elbow.