Well i'll try. You have two objects: a head and a heavy thing in front i.e. a "heavy head gear". To move the heavy head gear to reach the head you spent some of your initial energy thus actually impacting with less energy the head itself. Now let's say the two objects are conjoint into a heavier head for example, to cause a concussion you will need yet again more energy to move the now heavier head in enough force. Of course the weight of the headgear is negligible here and the benefits of cautioning the blow and spreading the impact of said blow on a larger surface is greater to its shortcoming. That is why people are making it and people are buying it.
In that case we're talking about two different things.
Originally Posted by erezb