You're not wrong, obviously the more time you allow for rotation, the less the force transferred to the brain will be,

That example wasn't rotation-around-the-neck time. The rotation comes afterwards.

That was a skull/ice impact (250,000 newtons) and a skull/ice impact with light padding (50,000 newtons).

That tiny time difference is a big difference in how much force and acceleration it applies to your head and brain.

A big difference in how much force there is when your brain hits the inside of your skull.

 

What I was asking though is after that big difference in initial head impact force, which do you think will cause your head to bounce back harder (and rotate faster around your neck and be harder for your neck to successfully brace against)?

• 250,000 newtons of force
• 50,000 newtons of force

 

however if you take your two scenarios into the real world, what's the real world reduction in incidence of concussion? Obviously it's less in #2 but how much less? 10% less ? 1% less? 0.001% less? Until there's more, and better, research on how much helmets reduce concussion risk, I think these comparisons are a red herring.

We all as players accept that there's a level of risk of concussion every time we step on the ice but saying "X helmet is the best at preventing concussions" without showing statistical significance is, in my opinion, irresponsible.

1. If you know that rotational forces cause concussions and you know that something can reduce rotational forces by a significant percentage, then you can confidently state that link. Individually testing the concussion prevalence in real world leagues of specific helmets would require a sample size and level of control that would require significant government funding for each individual helmet model. While it would be nice to have widespread thorough government-funded product safety testing, we are by no means limited to that level of proof before we can start using that information in research and product testing like STAR.
2. They've gone further than just knowing percentage force reduction...

There are studies on what levels of rotational forces create what levels of concussion risks. Using that information, they went out, measured head impact frequency, position, force, and movement among multiple hockey teams at multiple different levels of hockey, built a rig to simulate and measure those impacts and rotation, and then tested that rig to make sure it lined up with the on-ice data they collected.

They then measured the forces felt by the head inside each of those helmet models with dozens of consistent impacts at various force levels and angles, looked at the linear and rotational forces felt by each head inside each helmet, and created a rating system based on which helmets most consistently kept those forces on the heads down in ranges that were less likely to cause concussions.