[Jim Noble]

Multiple deaths from cardiac arrest (commotio cordis) in HS football every year.

Here's a paper that reviews 243 deaths in high school athletes, mostly football, from 1990-2013.

Here's a review of cardiac arrest after blunt force trauma to the chest (commotio cordis), which has been well known and well understood for many years.

[E. Pluribus Unum]

Safe. Effective. Mandatory. Shut up.