I read some years back some 10 metre Olympic tower divers were exhibiting what were in effect low - level concussions after long practice sessions, which is why they now bubble the water to reduce the impact.

While clearly sports like football, hockey and rugby are the most obvious to look at, I have also read that some researchers are wanting to look at sports like long distance running where the hours and hours of very low level shocks to the body which are transferred to the brain can eventually cause similar brain problems.