An easy way to comprehend helmet pads is to think of them in relation to the combination of springs and shock absorbers in your car. If wheels were bolted directly to the frame, you’d be punished with each jolt from the road. Soft spring without shock absorbers would get you swaying in all directions. Add shock absorbers and the impact forces are first decreased by them, then the springs further lighten and distribute the impact. Good helmet pads also provide a firm foam component to help ‘absorb’ the first energy of impact or bullet strike, then a more conforming foam layer to further distribute the impact force over the head rather than at a single pad/head connection.
When pad foam layers are too stiff and non-conforming, impact forces are more directly passed through to the underlying skull and brain. Too-hard pads also cause ‘hot spots’ on the scalp with resulting migraine-type headaches. Troops frequently loosen or even take off their helmets to relieve pain and regain concentration on the mission…to the detriment of their safety and survival. The Lawrence Livermore National Research Laboratory has brought this to the attention of the military, only to have it dismissed by the Army’s chief scientist who doesn’t tolerate deviation from his own beliefs, no matter how scientifically sound the data may be .
Hence the current stiff GI helmet pads with all the problems of both pain on prolonged wearing and the danger of transmission of ballistic and non-ballistic (impact) forces to the brain, resulting in TBI needlessly. As of now, the only answer is to utilize the helmet pads initially developed for the Army MICH helmet that have tested out both in the impact labs and in battle as a better pad for protection and wearability.