Push/Pull?

The passage mentions PUSHING & PULLING in the context of there being a certain threshold for injury causing compression. And that threshold of compression being in dangerous levels by the PUSHING of the S curve. And those dangerous levels can cause injury to the spine. But since PULLING was mentioned as a factor to be measured, is it unreasonable to conclude that PULLING could be found to be in a dangerous levels, thereby also being a potential cause for spine injury. And if that's true, would that contradict a premise that specifies PUSHING as the only cause of spinal injury?