Let me focus on two items to keep this letter brief. The results and interpretation of the results are equally ridiculous. One should note that roller coasters often sustain 4 gs for brief periods. The human spine bears the entire load.
Most people emerge unscathed.
Aircraft ejection seats are designed to impart accelerations of up to 15 gs. A high-frequency vibration in the human spine would be remarkable indeed. The soft discs between each vertebra would prevent a high-frequency vibration from occurring. The species of humans with straight spines might also have rigidly connected vertebrae. Now if you will excuse me, I will get off my soapbox and sit down very gently so as not to injure my spine.