As I stated elsewhere, current averages of the scrimmage line for college athletes average forces equal to a 40km/h car crash. How much do you plan on changing the rules here? These kids are already starting a couple feet away from each other.
How is your statistic even evaluated? It's dishonest without context. Are you talking about the forces experiences when a person's head is smashed by a car going 40mph? The whiplash forces experienced by a crash test dummy driving in a certain brand of car when strapped in to a seat belt? The force of a crash test dummy being hit by an inflating brand X airbag in a 40mph crash? Some physics calculation?
Going from any sort of decent running speed to zero in a short period of time is going to produce relatively large accelerations, regardless of the material in the way. They simply stop moving way to fast.
This is really wishywashy without numbers. A study of concussed NFL athletes showed that the average collision resulting in a concussion as reconstructed from video was 98 ± 28 g with a 15-millisecond duration. That corresponds to a change in head velocity of 7.2 ± 1.8 m/s (16.1 ± 4.0 miles/h). All these dudes were wearing standard helmets during 1996 and 2001.
For more routine head smashing of the non-concusive kind, the numbers you want are 22.25 g ± 1.79 g for a collegiate mean, ~25 g for the high school sample and up to ~double for individual impacts. (source).
To give a reference, if you jump straight up 20cm, lock your knees, and land on a hard unyielding surface, that's your average G-force for a typical hit by the linebackers, on your legs. (Assuming 1cm of compression) Don't do this if you have bad knees btw. You can calculate how high you'd have to jump with locked knees for the concussion example, but I'm going to leave that as an exercise to the reader because I don't actually want anyone trying it. It goes without saying that a g-force capable of giving you a concussion could damage your legs or fracture something.
These people are getting tau protein build-up in their CNS and it is damaging them, and there's nothing we can do except remove the contact aspect of the sport.
I agree, especially for teens and young adults. They are too young to be deciding that they want to take the risks associated with banging up their brains. I took the position I did because it is CMV and arguing a side of things you don't necessarily believe is pretty standard, not because it is a topic I am passionate about. You've made good points, and I am out of stuff to say.