The rising incidence of injuries, particularly to the neck and spine, is attributed primarily to the tactics, legal and illegal, shown below
Blocking with the forearm, known as "shivering," requires the blocker to smash his elbow and forearm against the helmet or face guard or into the neck or throat of the rushing player. Often the helmet is forced up, back and down against the nape of the neck.
A flagrantly illegal tactic, grabbing the face mask is an effective (and neck-breaking) way of stopping a ballcarrier or a would-be tackier. Linemen are the worst offenders, since outlawed maneuvers can more readily be hidden in the tangled fury of interior line play.
"Spearing" and "goring" describe head-on blocking and tackling, which are legal but frowned on by doctors. In the head-on block, the helmet is driven into the opponent's chest or belly. In the tackle, the ballcarrier is hit with helmet or face guard—in the head or neck or ribs—to induce fumbling.