Helmets are relied upon in a variety of sporting activities to protect the head. They are used for cycling, horseback riding, rock climbing, rollerblading, riding ATVs, snowmobiling, using a motorcycle, and a huge variety of other sports.
Helmets are designed in a way to provide the maximum amount of protection for the head with the lightest materials possible. Helmet shape varies based on what type of activity the helmet is designed to be used for. For this reason, it is not the best plan to use a bicycle helmet to protect one’s head from being thrown from a horse. The impacts are completely different and would come from a completely different direction.
While user error is one cause of helmets not doing the best job of protecting a person’s head from damage upon impact with a solid object, another common cause of head injuries even when there is a helmet is that the helmet itself is faulty.
Helmets are usually constructed in a way that has a foam or similar component immediately around the head. This is typically covered in plastic of some sort that varies in thickness based on the use of the helmet. If the foam or cushioning material around the head is damaged prior to being used, it may not protect the head adequately. Cracked or damaged plastic can prevent the helmet from functioning properly as well. Some of these errors may be due to previous collisions, but a lot of them are due to manufacturing mistakes.