Basically the players size and abilities, and training produce energies and collisions that the human body cannot withstand. Somethings gonna give when a 290 lb, body moving at 14 mph hits headon a 200 lb body running at 18mph. If the point of impact is a small bone or some soft connective tissue...somethin’ gonna’ give. The coaches who told us that “you gotta’ put your head in the meat grinder”... weren’t kidding...
I always thought they should have had weight limits in football. No more than 250 pounds.