
Helmeted heads would have come into contact much sooner and less slowing down of the heads as bodies would not be in contact with each other so that head speed is higher at point of impact than unhelmeted, ergo significantly greater forces put upon the brain/skull, that's not even taking into account risk compensation if one was wearing a helmet. Which as I mentioned I have, playing another collision sport that the opening post links to.
The differential is massive re rugby to gridiron due to the PPE and not just in head injuries but also traumatic injuries to other body parts, my brother who boxed in both eras of non headgear/compulsory head gear agrees, and the facts that there were massively more concussions in boxing during the headgear era proves without a doubt that risk homeostasis occurs and that the headgear was good for superficial wounds only (cuts).
Helmets are next to useless in anything other than genteel incidents were you are very unlikely to hit your head anyway, in cycling particularly, I read with amusement the 'I split my helmet', 'it was in three pieces' etc and then decree it saved their lives, yet they'll continue to spout this utter bunk/false logic!
*no loss of consciousness, no leg wobbling, just a second or so buzzing in head and a bit of blood and fractured teeth socket, the other guy was fine, his cheekbone was fine and he had a sizeable lump underneath his eye, no scars though, shame as chicks dig scars
