It's the chest protector. Chest trauma is the #2 cause of injury and death just after the head. I find it interesting that there have been many studies focusing on head trauma but not chest. When you see that someone died who was wearing a helmet its likely they died from a chest hit.

Yet most MC jackets do not have chest protectors. But there are some options. This video that was just published discusses a few. I wear the Helite air bag vest. But admittedly, it's an expensive option.