What Mickjoebill said. This has been known in gliding circles (among others?) for years. From the BGA:
Safety Cushions 11th July 2012
BGA RP38 recommends that all glider cockpits should be equipped with cushions containing energy absorbing materials. These cushions are widely used in club gliders but less so in privately owned ones. The BGA has published a booklet explaining how safety cushions work and how they can reduce injury - not just in a crash but also in heavy landings. You can download the booklet here [
http://www.gliding.co.uk/bgainfo/saf...safetyfoam.pdf ] - if you do not already fly with a safety cushion, we hope that it will encourage you to do so.
The originally recommended safety cushions were rather hard, though there was a “pudgee” version with some compliance in it, but there is now an alternative similar to the “Tempur mattress” deformable material which conforms to one’s shape. All these (at current retail prices) are quite expensive.