The impact is a category that can cover a broad range of different scenarios and types. For example, the impact might be the result of falling, if you should hit your head or torso on a wall or furniture, or if your face or limbs should hit the ground hard.
However, the impact can also include things like projectiles. If something is thrown at you, or if something should fall on you, then this can cause an impact.
Likewise, if you are attacked, then you might experience an impact due to striking force against your body.
Car accidents can also commonly cause heavy impacts. This can be the result of something coming through the windshield or through the doors, or it can be the result of your head or face striking against a steering wheel or the dashboard.