American football is one of the dangerous games. The lesson is in the cumulative damages
For two years researchers studied head impacts among 24 high school football players. They compared helmet-sensor data with brain imaging scans, along with cognitive tests. And they found that it’s not just a single blow to the head that causes concussion—it can also be the cumulative effect of multiple blows. The last impact is then the last straw for an already compromised brain. The research is in the Journal of Biomechanics.