The crew of high speed boats often have to absorb sudden shocks due to the g-forces associated with acceleration. During rapid acceleration, a secondary shock sometimes develops between the body of the crew and the boat's interior structure. The body either absorbs this shock or experiences increased vibration.
Such shocks are caused by resistance to the g-forces, which are distributed throughout the body; the pressure bring dissipated in some places and concentrated in others. Analysis of the g-forces on crew members sitting in seats designed to dissipate the secondary shock revealed the need to protect the body by preventing sudden shocks and increased g-forces.